I peered out through the curtain of falling snowflakes, breath condensing on the fabric of my facemask, and eyelashes sticking to one another in the single-digit temperatures. I plodded through the calf-deep snow, making my way up a narrow trail bordered by young aspen trunks and a mixture of Engelman and blue spruce, ponderosa and limber pines. I had already been out for almost two hours and aside from a few dark-eyed juncos, a flock of red crossbills, and four suspicious mule deer, the other animals appeared to have made the wise choice of hunkering down. With a high of 7 degrees Fahrenheit that day, and the mercury dropping, I was second-guessing my decision to venture out in such conditions. It was so cold I had taken the battery out of my camera and had it inside my glove along with an activated Hothands packet.
I tried not to think about the cold, but instead focused on keeping my eyes and ears alert for any signs of life in the white world around me. The reasons I had forsaken the comfort of our toasty house were twofold: one, there were unlikely to be any other people out and about in such conditions, which improved my chances of spotting human-shy wildlife; and two, there was a chance the storm could bring in some interesting bird rarity. As the trail approached a dirt road, the vegetation opened up into a small meadow with a few willow and alder thickets clustered around the edges. I glanced up and saw a plump bird with a long tail atop a tall pine, swaying in the wind. My first thought was northern pygmy owl, which I had been hoping to see for weeks. I quickly realized it was not an owl at all, but another predatory bird—a northern shrike.
Shrikes have an unusual ecology; they are songbirds like thrushes, sparrows, and warblers, but unlike most other songbirds, the 33 species in the shrike family are carnivorous. Shrikes eat a lot of insects, but they also eat vertebrates such as small mammals, birds, reptiles, and amphibians. Shrikes have a wicked hooked beak that they use to immobilize and kill their prey, and then use to tear off bite-sized pieces. These are not your run-of-the-mill backyard songbirds—just imagine watching a robin stalking mice instead of worms, and then piercing the mouse’s neck with its beak. You’d never look at robins the same way again.
But shrike ecology gets even more fascinating. These fearsome predators are not armed with the same suite of tools as their contemporaries, the hawks, eagles, falcons, and owls; shrikes lack talons. Instead of talons, they have normal songbird perching feet which are not well-equipped for predatory duties. One way in which shrikes have gotten around this oversight by natural selection is to use their environment, and they have done so with gruesome efficiency. Shrikes often skewer their prey on sharp objects such as thorns, broken branches, and barbed wire. This stabilizes the prey allowing the bird to tear into the food with its beak. It is this behavior that has earned shrikes the name “butcherbirds” (their family name Laniidae is derived from the Latin word for butcher). Shrikes also store food in this fashion, and a few years ago I got to experience a shrike cache in person.
I was visiting friends in Arkansas who work with another North American shrike species, the loggerhead shrike, and one afternoon we went to the territory of a nesting pair of these birds. Loggerhead and northern shrikes superficially resemble northern mockingbirds-they are about the same size and shape, and the bold gray and white plumage is relatively similar. Shrikes and mockingbirds also like to perch on exposed branches or power lines, but the shrike’s resemblance to the fruit and insect-eating mockingbirds ends there.
All around the shrike nesting area there were little bodies impaled on thorns and barbed wire; frogs, snakes, lizards, grasshoppers, partial remains of small mammals, all serving as a grisly warning to any small animal in the area to watch the skies. This caching behavior allows the shrikes to store food for times when prey is less plentiful, and provides a nice back-up when the nestlings turn into adolescents and begin demanding lots of food.
Back in the high elevation deep freeze of Colorado, I watched the northern shrike surveying its surroundings from the top of the pine. Suddenly it dropped through the falling snow and landed in one of the alder thickets up the trail from me. I lost sight of the bird for a few minutes, and when I had drawn even with the shrike, I could see that it was eating something. I snapped a few photos which revealed that the shrike had caught a small songbird, likely a junco or chickadee, and was hastily gulping it down, feet and all. I was impressed; this was a first-year bird (apparent from its duller mask and browner plumage), and clearly it had already mastered the art of catching avian prey. Northern shrikes eat mostly birds and small mammals in the winter months, and have been known to capture and kill prey substantially larger than themselves, including rock pigeons, mourning doves, American robins, blue jays, and lemmings. They use both sit-and-wait and active pursuit strategies for hunting and are capable of chasing down other birds in flight. It is also possible that a bit of deception is included in their repertoire. They don’t really resemble traditional avian predators like falcons and hawks, and other birds may not be alert to the danger they represent, especially if they’ve never encountered a shrike before.
This was certainly not the case a few weeks past when I came across a Clarke’s nutcracker harassing another young northern shrike. The nutcracker had chased the shrike into a tall aspen and was scolding the young predator from a nearby branch, and occasionally pecking at it with its long beak. The shrike was clearly agitated, and was yelling back at the nutcracker, snapping its bill in agitation. The young shrike finally shed its agitator and flew off to pursue hunting in a more private location. The nutcracker, for its part, winged over to some nearby limber pines, likely feeling a bit of self-satisfaction at having driven off the butcher of the north. At least for the moment.
Our other focal bird this week is the dipper, and like the shrikes, it is a songbird with an unusual ecology; the American dipper is North America’s only aquatic songbird. These rotund birds (also known as “ouzels”) spend their entire lives in and around water, mostly fast-flowing streams and rivers of high-elevation habitats. They are occasionally found along the edges of ponds, lakes, and marine environments, but the quintessential dipper territory is a boulder-strewn stream tumbling down the side of a forested mountain. Here these slate-gray birds can be found bobbing their bodies (hence the name “dipper”) while standing on rocks protruding from the water, or wading through the swift-flowing current, grasping the slick substrate with long, strong claws. And then, suddenly, the bird will be gone, vanished beneath the boiling surface, to reappear nearby a few moments later with a small aquatic invertebrate in its beak.
A little over a week ago, I was following the South Platte River through Waterton Canyon, south of Denver, and I came across an actively bobbing American dipper. Dippers forage almost exclusively underwater and employ a variety of techniques to secure their food. The individual I found was especially accommodating and allowed me to watch it from close quarters, where I could observe many of its foraging tactics. The simplest maneuver is when it would stick just its head underwater and look around for aquatic inverts attached to nearby substrate.
It also frequently plunged into the water and swam to the bottom, where it would then walk around, turning over rocks, leaves and sticks for hidden prey. This sounds straightforward, but it was able to perform this act in the very fast-flowing current by using its strong feet to hold onto the bottom. In addition to walking on the stream floor, it would occasionally swim around underwater, searching the perimeter of submerged rocks, peering into crevices and poking into cracks for attached inverts. Dippers can also pursue mobile prey underwater, chasing after minnows with powerful wing-propelled thrusts.
Like other aquatic birds, dippers have a transparent third eyelid called a nictitating membrane that allows them to see clearly underwater. They also come equipped with an exceptionally warm, feather-lined wetsuit that keeps them dry and warm, even in freezing temperatures, although they have to spend a substantial portion of their day preening to keep their feather-suit functioning properly. Dippers also have low metabolic rates and higher oxygen carrying capacity of their blood relative to similarly sized songbirds, both of which are thought to be adaptations to their cold, aquatic lifestyles.
Those who have seen an American dipper will probably agree that, aside from its tendency to dive under water, the most conspicuous aspect of its behavior is the constant bobbing. The function of the dipper’s dipping isn’t clear but could serve as a form of visual communication to other dippers in the area, or could help mask the dipper’s presence from predators. American dippers also have bold white, feathered eyelids, which really become apparent when the bird blinks. Like the dipping behavior, the purpose of this bold marking is unclear, but it likely serves as some signal to other dippers. On the vocal communication front, dippers produce a loud, musical song, consisting of sweet bell-like tones and harsher staccato notes. John Muir described it this way:
"[H]is music is that of the streams refined and spiritualized. The deep booming notes of the falls are in it, the trills of the rapids, the gurgling of margin eddies, the low whispering of level reaches, and the sweet tinkle of separate drops oozing from the ends of mosses and falling into tranquil ponds." —John Muir, 1894.
Dippers sing year-round, but they ramp up the singing activity prior to and during the breeding period in late winter/early spring. Once dippers have found a mate, they begin building their nests. Dippers build a large, ball-like nest constructed of moss on the outside, and leaves and grass on the inside. They often place their nest behind a waterfall or under a hanging structure along the side of the stream or river.
Once the young hatch, the parents work full-time to keep those hungry mouths fed. These duties continue even after the chicks leave the nest, as the parents continue to provision the fledglings until they are ready to take the plunge and embrace a world no other North American songbird knows; the world under the water’s surface.
Next post: TBD
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There are few animals in North America that have been persecuted for as long, or as intensively, as the coyote, Canis latrans. The coyote has been targeted by wildlife agencies at every level and in every state (excluding Hawaii, which it doesn’t inhabit. Yet…) and an estimated 500,000 coyotes are killed annually. There are competitive coyote-killing events in many states, and almost no state has a limit on the number of coyotes that can be killed. The coyote is reviled by ranchers, hunters, and suburban pet-owners alike.
And yet, in the face of all this loathing, and campaigns to eradicate it, the coyote has thrived and has dramatically expanded its range. Prior to 1700 the coyote was restricted to the deserts and prairies of North America, and now it occupies most of the continent. In addition to this range expansion, the coyote has taken up residence in suburban and urban habitats across North America, including megacities like Chicago, Denver, L.A., and New York. One of my favorite coyote stories comes from 2007, when people were beginning to recognize the urban wildlife phenomenon. One hot spring day, a coyote casually strolled into a downtown Chicago Quiznos sub shop that had its door propped open, and proceeded to climb into an open beverage cooler unit and lie down. The patrons and employees relinquished control of the restaurant to the coyote, and it remained in the cooler until animal control officers collected it and released it elsewhere.
According to coyote expert Dan Flores, there is actually a long history of urban cohabitation between coyotes and humans; 1,000 years ago coyotes lived in large urban areas in the Aztec empire of Mexico, and modern coyotes have been a part of the L.A. scene for at least a century. Despite this shared history, we have only recently begun to understand what coyotes are doing in the cities, and how they’ve managed to flourish in these concrete jungles.
Part of what makes coyotes so successful is their highly flexible nature. Rather than being strict carnivores, coyotes are broad generalists, consuming everything from seeds, fruits, and insects to rodents, rabbits, and deer. When I lived in Santa Barbara, I would often walk at a local suburban park that had a small pack of coyotes living in it. During the olive-fruiting season, the coyote scat would be full of olive pits and skins from fruits they had vacuumed up from the ground. And in spite of their reputation as major predators on cats and dogs, a study of coyotes in the Chicago area found that cat DNA was present in only 1.3% of 1,400 scat examined. The most frequently consumed food items were rodents, which jives with work done in other coyote populations and my own observations. Whenever I have seen coyotes hunting, either singly or in packs, they have been going after rodents. In areas with prairie dogs, these ground squirrels often make up the bulk of the coyotes’ diet. When traveling through Grasslands National Park in Saskatchewan this past June, I repeatedly came across coyote packs loping through the prairie dog colonies, causing the ground squirrels to issue their predator alarm calls. I see the same here in Colorado, although I have only seen one or two individuals hunting in the prairie dog colonies rather than the packs I saw in Grasslands.
The coyote’s ground squirrel strategy seems to be the following: get as low to the ground as possible, keep as much vegetation between you and the prairie dog as you can, creep up on an individual foraging away from its burrow, sprint to catch it before it disappears down the burrow. The further away from a burrow a prairie dog is, the better a coyote’s chances.
Up here in the mountains where there are no prairie dogs, the coyotes appear to target voles and other small mammals. On multiple occasions I have watched coyotes in the area perform the quintessential canid maneuver; standing motionless in a field, head focused intently on the ground, and then raising up on the hind limbs and pouncing down on the ground with the front legs. Just a few days ago, in fact, we had a coyote performing exactly this behavior about 20 meters from the house. We were in the midst of a moderate snowfall, and a lone coyote was repeatedly pouncing in an area with a good covering of dried grasses and flowers under the snow.
The coyote didn’t appear to capture anything, but it seemed to be having a good time trying; every so it would wag its tail in excitement. I don’t know if it was happy about the snow, or if it was simply the thrill of the hunt, but it remained in that area for 10+ minutes, pouncing and wagging. More interesting still was that I was not the only one who noticed the coyote’s efforts. An immature northern goshawk flew in and landed on a branch overlooking the coyote. Goshawks are the larger, more aggressive cousins of Cooper’s hawks and sharp-shinned hawks, and are generally restricted to the wilder areas of North America. These large hawks are renowned bird-predators (they really like a nice, plump grouse), but they also go after small mammals like squirrels, rabbits, and voles.
After the hawk landed, it watched the coyote for a few minutes, and then swooped low over the coyote’s head. The goshawk was almost certainly hoping to profit from the coyote’s actions by picking off any small mammals attempting to escape from the coyote. It wasn’t successful during that hunting episode, but I suspect that bird has used similar tactics in the past with more luck. This avian hunting strategy is clever (and there are many species of bird that cue in on other predators), but it is the coyote that has earned a reputation for cunning, intelligence, and mischief. The coyote features prominently in dozens of Native American and First Nations mythologies, and in many of them the coyote figure is a savvy trickster.
I experienced a little of this cunning firsthand at Grasslands National Park. As I mentioned above, I saw a number of coyotes while I was in the park, and one time when I was out hiking, I saw a pair of adult coyotes just cresting a hill. They were a few hundred meters away, but I was curious to see what they were up to, so I followed along, but at a good distance. They led me to a small valley, and on an east-facing slope in the valley there were four small coyote pups playing on the hillside near their den. They were still a couple hundred meters away, so I went into stealth mode in an attempt to get closer. I shrugged out of my backpack and kept low to the ground as I crept closer, keeping another hill’s ridge in between me and the pups so they would not see me, and hopefully not smell me either. The adult coyotes had disappeared, and I kept looking for them as I made my way closer to the den. When I had made it to within 100 or 150 meters of the den, I slowly climbed to the ridge, and looked across the valley towards the den. The pups were still there, but just as I was getting ready to take some photos, a short howl, followed by a series of yips came from behind me. I turned around and 150 meters away stood one of the adults, howling, barking, and yipping. And from the top of a hill on the other side of the valley another coyote adult emerged, joining the one behind me in a chorus of howls and yips, and then a third from another hilltop. They had triangulated themselves around me.
Apparently while I had been stalking the coyotes, they had been stalking me. Not to hunt, but to determine what I was doing, and to sound the alarm if necessary. I guess they determined that the alarm was necessary. And once the first alarm had sounded, the pups had vanished into their den.
I sat down, thinking perhaps I could wait for the adults to move along, and that the pups might reemerge, but as long as I was in the vicinity of the den, the adults continued to vocalize. I decided I would continue with my hike, and that I would revisit the den on my way back in an hour or two. I hoped that by that point the adults would have gone back to hunting, and that the pups’ curious nature would have lured them back out of the den. When I returned to the coyote den valley, that is exactly what had happened; the adults were gone and two of the pups were out on the hillside. I assumed the other two pups were following the parents’ orders and were still down in the den.
I spent about 45 minutes watching the pups from across the valley, and for most of that time, the two pups napped, or sat and looked around. One attempted to engage in some play with its sibling, but his efforts were mostly met with indifference. A couple of times the pups would lift their noses to the sky, and I wondered if they were catching my scent, or if they were still on alert from earlier.
To my surprise, the other two pups emerged from the grass up-slope and after a quick greeting with their siblings, disappeared into the den. One of the siblings I had been watching followed, and the remaining pup curled up in the grass, and went to sleep. I decided that was a good cue to leave, so I slunk quietly out of sight.
A litter of four pups is on the low to average size, and I suspect the relatively small size had to do with high levels of competition in the park. Coyotes are capable of adjusting their litter size in response to available resources and competition levels. If food is scarce, or home range size is limited by the presence of other coyotes, a breeding pair may have only one or two pups. When food is plentiful and there are few other coyotes around, they can raise upwards of 11 pups. All this flexibility allows coyotes to respond to prevailing conditions relatively rapidly and helps explain why efforts at decreasing coyote populations almost always fail. If a bunch of coyotes are removed from an area, the remaining coyotes simply increase their litter size to take advantage of the now-available resources.
The combination of behavioral, reproductive, and diet flexibility goes a long way towards explaining how and why coyotes have successfully colonized most of the continent. But we have also played a large role in that expansion by removing their predators and competition. Wolves and mountain lions have been extirpated from much of their historical range, especially in the eastern part of the continent, and these predators helped limit coyote numbers. In Yellowstone National Park, for example, coyote numbers have dropped by 50% since wolves were reestablished in the park in the late 1990's, and this pattern is repeated just about everywhere wolves are returning to. But even with wolf and mountain lion numbers increasing, it is unlikely we will see a large drop-off in coyote numbers across the continent. These adaptable canids now occur in almost every available habitat type. There are an estimated 2,000 coyotes in metropolitan Chicago, and aside from the occasional Quiznos encounter, these wraiths go almost completely unnoticed by the 9 million human inhabitants. So whether you love or hate these animals, you have to respect their ability to survive, and flourish, in our human-dominated world.
Next post: TBD
Note: The View Out the Door will be transitioning to an every-other-week schedule for the time being.
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To help set the stage for this series of posts examining different winter-coping strategies, Mother Nature gave us the first taste of winter last week. Air temperatures dropped to 11 degrees Fahrenheit, wind chills plummeted to below 0F, and we received about 4 inches of snow. I ventured out a couple of times in the hopes of collecting images that captured the collision between fall and winter and came away with shots of golden aspen coated in snow, steaming ponds, and frosted moose.
It was breathtakingly beautiful and brutally cold, but it was short-lived. Within two days temperatures rebounded into the 60s and most of the snow had vanished except for patches lurking in the shade of north-facing slopes. I think the foliage season is pretty much done, however, as the extreme cold temperatures really accelerated the leaf senescence process. Many aspen groves now stand naked, and others are dressed in crisp, brown leaves. Despite the loss of their leaves, aspen can continue to photosynthesize using the relatively high levels of chlorophyll in their bark. This is just one of many tricks that organisms at high elevations and latitudes use to deal with the relatively short growing season.
Caching food is a strategy that some animals use to take advantage of temporarily abundant food resources like seeds and nuts. Cachers generally store food in hidden locations across the landscape for consumption at times when other food isn’t available. A few weeks back I wrote about the impressive memory capabilities of some of these food-hiders, but how do these animals accomplish feats such as remembering where they cached 80,000 seeds, or avoid having their stashes raided by hungry thieves? Regarding the first task, animals that store food across the landscape typically have a highly developed hippocampus—this is the region of the brain responsible for spatial memory. In addition, the hippocampus can undergo seasonal changes, increasing in size during periods when the animal relies heavily on recalling where it placed its snacks, and decreasing for the months when it feeds on fresh food. This is handy because the brain eats lots of calories, and downsizing a portion of the brain that isn’t needed for months of the year can save a lot of energy.
In addition to seasonal plasticity, the hippocampus can exhibit neurogenesis of new hippocampal cells in response to certain types of stimulation. Research in birds has found that some forms of memory stimulation result in high levels of neurogenesis, and wild birds typically have much higher levels of neurogenesis than captive birds. Perhaps there’s hope for those of us who have a hard time recalling where they placed their keys, phone, or car. For some memory exercises I suggest hiding 100 M&Ms around your house, and then trying to find them again in a week. You’ll either have a better spatial memory, or your house will be overrun by rodents and/or children.
One thing to keep in mind when you’re hiding your candies is that many cachers use tricks to help reduce the memory load. One widely used tactic is stashing multiple food items in the same area. Clarke’s nutcrackers, for example, often stash four or five seeds together at the base of a given tree. Squirrels do this too. One of my squirrel-friends at the nearby Caribou Ranch Open Space has stashed dozens if not hundreds of pine cones in one 3-meter square area. This little fellow has taken caching to another level; I’ve sat and watched as he stuffed four large pinecones, one after another, into a single hole. Once a hole is full of pinecones, he carefully covers it up, tamps it down, and moves on to the next hole.
An important aspect of caching is that the food item being stashed needs to have a good shelf-life; perishable items that spoil rapidly are not good candidates for caching. Nuts and seeds, which are well-suited to long-term storage, make up the bulk of cached food items. In very cold or very dry areas, however, normally inappropriate food items like meat can be stored long-term without spoilage. In our neck of the woods, the primary cachers are the chickadees, nuthatches, jays, crows, ravens, magpies, red squirrels, and the champion cachers, the Clarke’s nutcracker. Many of these species visit backyard bird feeders, and you may have seen a nuthatch stashing sunflower seeds in bark crevices around your yard. This is caching in action.
Other than trying to remember where you placed your food, cachers have to contend with sneaky cache-thieves who would gladly dig up and eat the buried treasure. In fact, some individuals make a living as thieves, and invest a good portion of their time spying on others. What’s an honest, hard-working squirrel supposed to do when thieving spies are everywhere? Researchers have discovered that caching squirrels will engage in some deception of their own; if they think they are being watched, they will pretend to bury something in the ground. The would-be thief then wastes his time searching for a non-existent food item, while the honest cacher can go hide his food somewhere else. Birds also have to contend with thieves, and some species exhibit exceptional levels of awareness. Western scrub-jays, for example, keep track of which of their colleagues are watching them when they cache food. If an individual that is a known cache-thief was watching, the original bird will return to the cache, dig it up, and move it when they aren’t being watched by the thief. And for good measure, in addition to being able to identify likely thieves, and remember where they stashed hundreds or thousands of food items, scrub-jays keep track of the duration of time a food item has been stored, and if it has passed the “use by” date, they won’t return to dig it up. Not bad for a bird brain.
We all know some hoarders in our lives, but in this case, I’m referring to animals that stuff their larder with food so as to sustain them over the course of the winter. A number of rodents are fervid hoarders; if you’ve ever had a pet hamster or rat, you’re likely familiar with this behavior. I happened to have a trio of pet rats when I was younger, and in one of my more misguided moves, I decided that they could live a free-range life in my room. Things seemed to be working out for the first couple of weeks, and then I noticed one of the rats scurrying along the floor with some dog kibble in his mouth. I followed the rat (named Brownie), and he led me under the dresser to a massive pile of dog food. Turns out that in their spare time, my rats had found the food bin, gnawed a hole in it, and had been stockpiling kibble under my dresser for the impending rat Armageddon. But these rats hadn’t put all their eggs, or kibble, in one basket; they also had stashes in my desk drawers and under the desk. Thus ended the short-lived experiment with free-range rodents in my room.
It also happens that the second largest rodent in the world, the North American beaver, is a hoarder, with a twist. Beavers are well-known ecological engineers, modifying the landscape with the construction of their dams. It has been proposed that one reason beavers build dams is to create deep pockets of water in which they can store a winter’s supply of sticks and branches. Beavers subsist on a delightfully varied diet of twigs, branches, bark, and sticks. I’m kidding, of course; that’s just their winter diet. In the spring and summer they really spice things up by adding leaves and aquatic plants to the mix. Once the ponds freeze over, these industrious hoarders are able reach their larders under the ice via underwater entrances in their lodges. So in essence, beavers drastically alter the landscape in the process of making aquatic tree-branch refrigerators that only they can access during the winter. That’s a pretty neat trick for a rodent.
The term “hyperphagia” really just means elevated levels of food consumption and can be applied to animals that have increased appetites prior to migrating or hibernating. The supermigrants I covered last week experience pronounced periods of hyperphagia because they need to rapidly put on fat reserves before their marathon flights. But birds have to balance energy reserves with flight efficiency, and in case you’ve ever wondered, those fat turkeys that get served up for Thanksgiving meals are not flight capable. Being more earth-bound can free one up to pack on the pounds. Bears eat almost non-stop during the late summer and fall months in preparation for hibernating. Previously I covered some of the incredible statistics regarding caloric intake during the hyperphagia period, and caloric output during hibernation. But I didn’t cover this: Fat Bear Week. Alaska’s Katmai National Park and Preserve puts on a bracket-style competition in which the public votes for the fattest brown bear each October. These bears have been feasting on salmon for the previous month, and the results are impressive. Check out all the images in the link—the champion (Holly) was crowned last week, and it’s a crown well-deserved.
Yellow-bellied marmots also experience significant weight-gain prior to hibernation. These rotund ground-squirrels are close relatives of the woodchuck or groundhog (or better yet, the “whistle-pig”), and spend 7-8 months each year hibernating. Like the hibernating bears, marmots depend on their fat reserves to get them through this 200 day-long snooze. During this period, the marmot’s heart rate dips from 180+ beats/minute to 30 beats/min, their body temperature drops to 41 degrees Fahrenheit, and they take only one or two breaths/min. These physiological changes are crucial to helping them survive until the following spring. At that point they will slowly transition from zombie-marmot to living marmot, and resume their lives of socializing and eating.
Next week: TBD
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Animal migrations capture our attention like few other events in nature. When you picture nature’s greatest spectacles, it is likely that at least one flavor of animal migration is in there; the massive herds of ungulates crossing Africa’s Serengeti in search of high quality forage; the leaping, boiling, churning masses of salmon returning from the ocean to spawn in their natal rivers; the monarch butterflies coating every available inch of leaf and trunk on the oyamel trees in their wintering regions of Mexico; the “arribadas” of sea turtles congregating on tropical beaches to lay their eggs; and the undisputed winner of long distance migration, the Arctic tern, which undertakes a zigzag route between the Arctic and Antarctic each year, a total annual journey of 44,000 miles. And these represent just a few of the flashiest migrations that have made it into the public’s collective awareness over the years. There are dragonfly migrations that exceed 10,000 miles round trip, a flying fox migration in Africa that approaches 10,000,000 animals, and daily vertical migrations for trillions of planktonic organisms that travel up towards the water surface each night to feed, and down into the dark depths each morning to escape predators. As our ability to track animals’ movements has improved, so has our understanding of the physiological and behavioral mechanisms involved in these feats. I’ll touch on a few of North America’s migrations this week to highlight the variety of tactics that animals employ when embarking on these voyages.
I’ll start with something called “partial migration,” and while this category may not be well known, one bird that uses it is: the American robin. The robin holds the title of “America’s favorite worm-eater” although I’m not sure that A) it has much competition, or B) this title actually exists. Nonetheless, the robin is one of the most widespread and abundant birds in North America. Despite their abundance and conspicuous nature, robin migratory movements have been the source of confusion for millions of people over the years. People tend to get excited when they see a robin in their yard in mid-February or early March, and are ready to proclaim winter over, and to heck with Punxsutawney Phil’s dire predictions of 6 more weeks of winter.
The reality is that robins exhibit partial migration; some populations, and some individuals within a given population, migrate for part of, or all, the winter months. Populations in the far north of Alaska, northern Canada, and northern New England all tend to head south for the winter, although where they migrate to is highly variable. Some head down to relatively warmer, but still chilly areas like southern Maine, New York, and Illinois, while others eschew the cold entirely and go off to nice sub-tropical locations like Florida, Cuba, and Mexico. Populations throughout the lower 48 and coastal British Columbia are more variable still; some individuals may remain in their breeding area throughout the year, while others may head a few hundred miles to the south, east or west for the winter. The real driver of these movements is thought to be food availability. When the ground is frozen and delicious invertebrates (i.e. worms!) are hard to come by, robins switch to a berry-based diet. If the area where a bird bred has great berry resources (think honeysuckles, junipers, hawthorns, Pinkberries…) it may remain there as long as there are fruits left to eat. Robins tend to move around a lot during the winter months as they search for reliable food sources, meaning that a noisy flock may be present in your yard one day, gleefully gobbling down freeze-dried berries, and gone the next.
The Cornell Lab of Ornithology has put together this wonderful graphic depicting robin presence across North America over a one-year period using data generated by birdwatchers who import their bird sightings into eBird. You can see the big shifts at the northern and southern edges of the range, and the other, more subtle shifts across the middle portions. I think these graphics are amazing, and a brilliant use of Citizen Science data. So, this winter if you have robins in your yard, try listening to them to distinguish whether they are year-round residents, or visitors from up north in Canada. It’s always easy to tell if they’re friends from the north by their accents, eh?
A related form of migration that is relatively common in mountainous regions of the world, and one that is well-represented here in Colorado, is elevational, or altitudinal, migration. Organisms that undertake elevational migration often don’t need to travel great distances because climatic conditions change rapidly as one ascends or descends. A drop in elevation of 1,000—3,000 feet can be the equivalent of hundreds of miles of latitudinal change. Because of the relatively short-distances involved, elevational migrants often have more flexibility in their migratory movements; rather than initiating their travel based on some indirect cue associated with the changing conditions such as decreasing day-length, these animals often have the luxury of using more direct cues such food availability, to guide their departure. Here in the Colorado High Rockies, there are a number of species that exhibit this sort of migration: mountain chickadees, mountain bluebirds, mountain goats…I guess any animal named after mountains.
That’s really only partly true as there are many other species without the mountain moniker that slide up and down the slopes with the changing seasons. In addition to the above-mentioned species, some populations of elk, red-breasted and white-breasted nuthatches, dark-eyed juncos, and a suite of other species descend to milder elevations in the winter. For many of these species, the occurrence and degree of elevational change can be linked to an individual’s condition, age, and sex, as well as the severity of the winter conditions. Individuals in good condition, and/or those that can claim ownership over a good food resource may not migrate downslope at all, whereas those in poorer condition and/or subordinate in the social hierarchy may drop down early in fall. Conversely, extreme winter conditions may force all individuals down to more moderate elevations. My wife and I could very well turn into elevational migrants if winter conditions force us from our home at 9,000 feet.
In stark contrast to these partial and situational migrants are the long-distance super-migrants. As I mentioned above, the Arctic tern is the undisputed champion of this category, but there are many variants on the theme of super-migrants. Let’s take a look at the ruby-throated hummingbird for starters. These iridescent, nectar-sipping, hovering dynamos breed throughout eastern North America, and are a common backyard inhabitant.
In late summer, these birds begin disappearing from northern regions as they begin their southbound journey. Migrating birds often time their movements to coincide with northerly winds to help provide an extra boost and to conserve resources. Once birds reach the northern edge of the Gulf of Mexico, they pause their journey for a few hours to 15 days. At this point they have a decision to make: continue migrating south in a circuitous route along the edge of the gulf, of fly directly across it. Unlike larger birds, hummingbirds rely entirely upon fast wing-beat propulsion to stay aloft—you won’t find a hummingbird soaring around on a nice pocket of rising warm air.
The decision about which route to take comes down to timing and body condition. Birds that take the long, coastal route can stop and forage as needed, but the journey may take a month or longer, whereas those taking the direct route can do it in less than a day, so long as they don’t become fish-food. The difference in the timing can be important, as those that arrive on their wintering grounds early can lay claim to higher quality territories. Crossing a massive expanse of water with no stopping areas along the way, however, is a substantial undertaking for a bird that typically weighs between 3 and 3.5 grams. For reference, that’s a little heavier than a penny. So picture a penny with some extra baggage flying nonstop for 15+ hours, flapping its wings over 50 times/second, and zipping over the surface of the water at 40mph. Birds that are about to cross the gulf need to load up on energy stores, and often add a third or more of their body weight in fat. These reserves, while critical for making the crossing, come with a cost; they reduce the birds’ flight efficiency. There is thus a tradeoff for a hummingbird between how much extra weight to pack on and how much that extra weight will cost to transport, especially if they encounter a headwind. Nonetheless, many of these fat flying pennies will embark on this flight across the gulf. What percentage of the population uses this route, and how many survive is still unknown, but the fact that at least some of these birds successfully navigate this route is amazing.
The blackpoll warbler is a bit larger than the hummingbird, clocking in around 10 grams, and this denizen of the northern forests has one of the most physically taxing fall migrations of any bird. The blackpoll breeds from northern New England over to western Alaska, and birds winter primarily in South America. To get to their wintering grounds, birds head east to the eastern seaboard of the US, and then from various staging points on the coast they plummet off the map into the ocean.
Well, not exactly. But birds do continue to head east where they hope to catch northwesterly winds that will help propel them to South America. In the process, these birds cross an average of almost 2,000 miles of open ocean. Like the ruby-throated hummingbird, these birds make this crossing in one go, which typically takes 80-90 hours of non-stop flying. To put this in perspective, researchers Tim and Janet Williams came up with some comparable statistics:
“The trip… requires a degree of exertion not matched by any other vertebrate. For a man, the metabolic equivalent would be to run 4-minute miles for 80 hours…If a blackpoll warbler burned gasoline for fuel instead of its reserves of body fat, it could boast of getting 720,000 miles to the gallon!”
This feat is truly an extraordinary example of endurance, but when the Williams wrote that piece in 1978 we did not yet know about some of the migratory journeys undertaken by shorebirds, who are the true ultra-endurance winners.
I wrote above that the Arctic tern is the champion long-distance migrant, but these birds are 1) meant for life on the wing (they can even sleep while flying), and 2) able to stop either on land or on the water during their migration. In comparison, some shorebirds such as the red knot and bar-tailed godwit, undertake preposterous trans-oceanic flights of more than 7,000 miles, lasting upwards of 7 days, during which they do not feed, drink, stop, or sleep.
How do they accomplish this? Imagine for a moment simply not sleeping for 7 days, ignoring the no eating, drinking, sleeping, and constant physical exertion components. The result would be the crankiest person you know, multiplied by a thousand-fold. It’s only natural to wonder if the consequence of this marathon event is a bunch of really foul-tempered (or is it fowl-tempered…) birds jabbing at one another with their bills once they reach their wintering grounds? I don’t think anyone has yet examined shorebird crankiness although my informal observation would suggest that they can be quite crabby.
Researchers have looked into other aspects of the physiological changes birds undergo prior to and during these migratory events. Most obvious are the changes in fat deposition; birds can more than double their weight prior to migration by putting on large fat reserves. Fat is the perfect fuel for these journeys—it provides more energy per unit than carbohydrates or proteins, it can be stored dry without accompanying water or protein, it can be oxidized efficiently and completely by most body tissues, and fat catabolism results in the production of water, which can be used by the bird. Birds also undergo rapid changes in tissue size, in which organs that are not going to be used during the flight (like the stomach and intestines, some immune organs, and leg muscles) are more or less absorbed by the body, whereas others that will be heavily relied upon (such as flight muscles) increase in mass. Upon arriving at their destination, these broadscale changes to muscles, gut, and immune organs occur in reverse and in short-order—typically within just a few days. The ability to undergo these rapid and reversible changes is known as “phenotypic flexibility” and migratory birds exhibit some of the most flexible phenotypes we know. I wonder if they do much yoga…
We have acquired a wealth of information about animal migration in the past few decades, but there are still huge gaps in our understanding of migratory patterns, habitat usage, behavior, and physiology for many if not most migratory species. However, when you consider that historically people thought birds that vanished in the fall and reappeared in the spring spent the winter hibernating under the mud like frogs and turtles, we’ve come a long way.
Next week: Cachers, Hoarders, and Hyperphagists (Super-eaters)
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Autumn is a season defined by change; everything is in flux as the sun slides towards the south and the temperatures slip downwards. In northerly latitudes animals adopt one of three general strategies for coping with the approach of winter; they migrate to warmer areas, enter a state of partial or complete hibernation, or remain active. Plants aren’t really great at migration, so they are left with two principle options; go dormant or continue to photosynthesize. But before we deck the halls and wax the skis, there are a wealth of autumnal events that are worth discussing. This week’s post will be a short introduction to some of these phenomena which I’ll cover in more detail in the coming weeks.
Southward Migration: Birds and Butterflies
I talked about avian spring migration back in March, and the feelings of excitement and anticipation wrapped up with the return of so many colorful birds. Bird migration in the fall is a little different; many of the birds have traded their bright breeding plumage for drabber tones and their boisterous songs for quiet chip notes or silence.
But the absolute number of birds is generally much higher because the young that were produced during the breeding period join the adults on the southward journey. On average, 4.7 billion birds travel from the US into Mexico and beyond in the fall, whereas only 3.5 billion make the return journey in the spring. Much of that difference is a result of mortality that occurs during migration. Many species migrate across the Gulf of Mexico, embarking on a non-stop journey of up to 20 hours. This undertaking requires large energy reserves and favorable weather conditions. Not all individuals survive the crossing, however, and recent research has shown that at least one marine predator takes advantage of this unfortunate windfall. Gut content analyses of young tiger sharks in the gulf showed that 39% of sharks sampled had neotropical migrants in their bellies. Researchers speculate that these birds may provide a critical food resource for baby tiger sharks that are not yet skilled at catching live prey. Most birds crossing the gulf avoid becoming shark food, but that’s not the only peril that these birds face; migrating raptors are looking to catch a snack on the wing.
One of the great natural wonders is the fall migration of raptors in North and Central America. Places such as Hawk Mountain Sanctuary in Pennsylvania, or Cape May in New Jersey provide opportunities to see hundreds or even thousands of these birds passing by on crisp September days with a brisk northerly wind. The real mecca for viewing this migration, however, is in sections of Mexico and Central America where the birds are funneled over narrow swathes of land. At these locales, single day tallies can exceed 1 million birds in what is known as the River of Raptors. I visited a hawk-watching platform in Veracruz, Mexico in 2006 and watched as raptors passed overhead in fantastic numbers. The flow of birds southward happened in many layers; from the small hawks and falcons zipping past at tree-top level to the larger hawks and eagles streaming past at 10,000 feet, too small to see with the naked eye. In the few hours I was there, some 7,000-10,000+ birds crossed through the airspace over us en-route to their wintering destinations.
No less impressive is the migration of monarch butterflies from the eastern US to the mountains of southern Mexico; a journey of 2,500 miles for some populations. During the spring migration, monarchs exhibit a generational pattern of migration. That is, one generation travels from Mexico to the southern US, at which point they eat, mate, lay eggs, and die. These eggs hatch into caterpillars, the caterpillars pupate into butterflies, and the butterflies head north a few hundred miles before they eat, mate, lay eggs, and die. Individuals that migrating southward from the northern US and southern Canada in September and October may be three or four generations removed from the individuals that left that area the preceding fall. These great-great-grandchildren-flies tap into a genetical flight program that guides them to the same region, and possibly even the same stand of trees, their relatives wintered in the previous year.
The Rut: Battle for Dominance
I briefly mentioned the moose rut a few weeks prior, but elk, white-tailed deer, mule deer, bison, mountain goats and bighorn sheep are other species here in Colorado that participate in the breeding spectacle referred to as “the rut.” Essentially, males compete with one another to establish dominance, and high-ranking males acquire harems of females. Much of the male social hierarchy can be determined through visual and chemical cues, but when two evenly matched foes face one another, peaceful negotiations give way to violent confrontations. Sheep, bison, and goats bash their horns together, while moose, deer and elk clash antlers and engage in the equivalent of sumo-wrestling matches; whichever male succeeds in pushing the other around usually emerges the victor. Victorious males get the ultimate prize: the opportunity to pass their genes on to the next generation.
Food Stores: Caches and Winter Weight
Winter is a time of reduced food availability for many animals, but fall provides a rich bounty of dietary options: fruits, nuts and seeds are produced in abundance, and insects and other invertebrates are still active. Small mammals like pikas and squirrels spend the fall collecting and storing foods that they will use during the winter. American pikas are stocky relatives of rabbits and hares and are often found at high elevations, living on talus slopes and other rocky habitats. They spend the fall in a frenzy of food collecting activity as they prepare for winter. Pikas gather grasses, flowers, and forbs, dry them in the sun to prevent rot, and then stash them in their den for leisurely dining once the snows arrive.
Squirrels, in contrast, bury nuts, seeds and pinecones in the ground as a way to store them for later consumption. This behavior is called “caching” and it requires some sophisticated memory, and a good sense of smell, on the part of the squirrels.
More impressive than the squirrel’s memory is that of the Clarke’s nutcracker. These raucous birds cache tens of thousands of seeds in the fall and return to eat them over the course of the winter. The memories of squirrels and nutcrackers are not infallible, however, and many seeds are forgotten. These seeds may then germinate and become part of the next generation of trees. Cachers like the squirrels and nutcrackers are thus thought to play important roles in natural forest regeneration.
A much easier strategy that requires no memory is that of storing food reserves on your body. These reserves exist as something called adipose tissue or “fat” and many people are familiar with the physiological tendency for our bodies to generate some of these fat stores in preparation for winter. But humans are supreme underachievers in this category compared to some other animals like bears. During the autumn fattening period, bears can consume 20,000 calories a day and put on 30+ pounds of fat per week. Bears need to bulk up because they can burn 4000 calories a day during their hibernation, which may last 100 days or more. Bears eat just about anything they can find during the fall; those in areas with rich fish or other marine resources feast on salmon and seafood, while those in interior locations search for fruits, berries, nuts, insects and tubers. Sounds like a good way to spend the fall if you ask me.
Side Note: I have six photos on display in the Nederland Community Center Art Exhibition, which opens this Thursday! I’m thrilled to be showing these images in my community, and hope this is the first of many such shows. If you’re in the Boulder or Nederland area, come on out to the Nederland Community Center this Thursday, October 3rd, from 5-7pm.
Next week: Fall Migration
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If you’ve never seen a bird try to swallow something bigger than its head, it can be hard to imagine how such a feat would be possible. Just think about yourself for a moment; could you swallow something as big as a football? Unlikely. And remember that birds don’t have teeth, so there’s no chewing involved. What they do have (some species anyway) are remarkably elastic jaws and throats, and while in British Columbia, we witnessed the amazing stretch-act performed by the glaucous-winged gull. Gulls will eat just about anything, but they truly adore sea-stars; they almost seem to savor the experience of eating them. In much the same way that a person will let a piece of chocolate melt in their mouth, a gull will often sit on the beach with part (or even most) of a sea-star sticking out of its bill for over an hour. Very slowly, the sea-star disappears down the gull’s gullet until all that remains is a giant bulge in the gull’s throat.
Gulls are notorious for swallowing large items, but one of the most impressive swallowing acts I can recall was performed by an American bittern that showed up in our backyard in Illinois in spring 2018. American bitterns are medium-sized members of the heron family (Ardeidae) and are generally considered to be among the most cryptic of North American birds. These secretive waders usually reside in wetlands where their striped tan and black plumage helps them blend in with long reeds and grasses. When they sense danger, they will often stand erect with their bill pointed upwards so as to more fully mimic the vegetation around them.
It was therefore a bit of a shock when I went onto our balcony on an early-spring morning and noticed one standing at the edge of the retention pond behind our apartment. In and of itself this might not have been unusual as bitterns migrate through that area in the spring, but our pond had no emergent vegetation, which left the bittern without its customary cover. There was a patch of scrubby trees clustered at the edge of the pond, and when a neighbor went out with her dog, the bittern stalked into the patch of trees and vanished into the shadows. The bittern remained in hiding until long after the threat had passed, and then crept back to the water. The pond had a reasonably large population of smallmouth bass and bluegill sunfish, but the spring had been quite cool, and the cold water temperatures meant that most of the fish were still in deeper sections of the pond. I watched the bittern stalk its way around the edge of the pond at a glacial pace before I had to leave for work. I thought that would be the end of our backyard bittern adventures, but to my surprise, the bittern stuck around for days. I would go out onto the balcony to find the bittern in various states of hunting or hiding. Sometimes the bittern would be out in the water up to its belly, frozen in a pre-strike pose, while other times it would simply be standing on the shore looking dour. The bittern attracted a fair bit of attention from the locals while it was there. A belted kingfisher spent part of a morning perched above to the bittern, presumably hoping that the bittern’s activities would spook some fish out of hiding that it would then be able to dive in after. One of the resident Cooper’s hawks seemed to take offense at the bittern’s presence, and gave it a warning fly-by, buzzing right over the bittern’s head.
I wondered at the bittern’s prolonged stay; there didn’t appear to be much in the way of available food, the pond lacked good cover, and the bittern was exposed to semi-frequent disturbances from the neighbors, both human and animal alike. But the bittern’s persistence paid off, and one morning when I went to look for the bird, I found it with an enormous bullfrog in its bill. The frogs had recently emerged from their period of winter estivation under the mud, and on sunny days could be seen basking on the banks of the pond. The continuing cool temps likely made them sluggish, however, and potentially easier targets for a hungry predator like the bittern.
Upon being seized, the bullfrog had employed its best defense against predators that cannot chew; it gulped in air and inflated its body like a balloon. From my vantage point, it looked like a winning strategy. I watched the bittern maneuver the frog-balloon around, trying to get it positioned so that it could swallow the puffed-up amphibian, but every time it attempted to get the frog into its mouth, the inflated air sacs precluded the bittern from getting anything more than the head in. Unfortunately for the frog, the bittern’s hunger had endowed it with an elevated sense of determination, and it began to implement a slow and slightly gruesome plan for overcoming the frog’s defense. Without going into too much detail, the plan consisted of battering the frog around and trying to puncture it with its bill. Occasionally it would dunk the frog in the water to lubricate it before trying to gulp it down, but this didn’t seem to help. After 45 minutes of this tactic, I could see that the frog had deflated somewhat, and looked to be punctured in a couple of places. Still the bittern was having trouble; it would flip the frog’s hind quarters towards the sky to enlist gravity’s help. Finally, it all came together for the bittern, and the large (and now dead) frog disappeared down the bird’s throat. The bird chased the meal with a couple sips of water, and then walked to the edge of the trees to digest its large meal in peace. Within a day or so the bittern had moved on, presumably happy to continue its migration northward with the energy derived from the bullfrog. In the five years we lived at that location, that was the only bittern I had seen or heard, but it was not the only amazing biological phenomenon I was privileged to observe from our balcony.
Despite living in a large development and having a massive interstate highway pass a few hundred feet from our place, our backyard was a constant source of natural wonderment. In those five years, I published three scientific articles based on observations I made from the balcony. In fact, the idea for this blog was born of those experiences and was going to be called The View from the Balcony. While we lived there, I would sit out on the balcony in the morning with my cup of coffee and watch the natural rhythms of the pond unfold below me.
In the last post I mentioned one of the papers that emerged from those observations (the grebes foraging on land), but another balcony publication came together over a much longer time-frame. That paper arose from observations made two years apart and involved another member of the heron family—the green heron. The green heron is the second smallest heron in the US (standing only 17 inches tall), but it has achieved very large stature in the bird world because it is one of the few avian species to routinely demonstrate tool-use. Green herons will use pieces of vegetation or, when available, bread crumbs, to lure fish in to striking distance. I also watched one individual hang practically upside-down from a branch, coiled in a striking pose, and wait for a fish to swim underneath it. When a fish swam close enough, the heron plunged its head into the water, grabbed the fish, and was then able to right itself onto the branch to swallow it.
Green herons were common visitors to our pond, and between May and September one or more of these diminutive waders could be found creeping along the perimeter of the pond or perched in one of the trees overhanging the pond. One particularly hot weekend day in early July I wandered onto the balcony in the glaring light of the late-morning and made a quick appraisal of things around the pond. On the opposite shore stood a green heron exhibiting some classical preening behavior; it was drawing feathers through its bill, fluffing up its body feathers, and scratching its head with its claw. Then it did something I had never seen; the heron opened and extended one wing and held it parallel to the ground. It then cocked its head under the opened wing and looked up at the back-lit feathers. The contorted bird seemed to be carefully inspecting each feather and would occasionally peck at them. I took a couple of pictures, but after a little while the heron closed its wings, walked to the water’s edge and began hunting, and I returned inside. I thought the observation was interesting, but that was extent to which the experience occupied my mind. Until almost exactly two years later, when I observed another (or the same) bird exhibiting the same behavior in almost the same location. As before it was late morning on a hot weekend day in early July, and I had been watching a heron perched in a willow tree preen itself. Then, slowly, it unfurled its wing, held the wing out to the side, and cocked its head underneath, peering up at the wing feathers. As before, it appeared to be carefully scanning the feathers and occasionally pecking at them. My mind returned immediately to the previous episode and I was struck by something; in all my hours watching these herons in the early mornings, and to a lesser extent, in the evenings, I had never seen this behavior. But on two hot, sunny, early July weekend days I had gone out onto the balcony in late morning and witnessed a heron engaging in this unique preening behavior.
After researching the issue in some depth and thinking over the two events at length, I settled on a possible explanation; the heron(s) were using light and heat to help facilitate ectoparasite removal. Most ectoparasites don’t like being exposed to high heat or bright light. It is likely that backlighting the wing allows the bird to more easily locate any ectoparasites attached to the feathers, and exposing the feathers to the hot, bright sun makes any ectoparasites on those feathers uncomfortable enough to move around, which also increases the bird’s chances of seeing and removing them. I (or someone else) would need to conduct some experimental manipulations to verify these ideas, but for now I’m happy to leave things as speculative.
Next week: TBD
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One of the great joys of traveling is happening upon a lovely little location that A) you didn’t know existed, and B) far surpasses your expectations. I realize of course that this may be a bit circular as one typically doesn’t have expectations about a place one doesn’t know exists, but you get the gist of it. One such place for me on my journey from British Columbia to Maine was a small park by the name of Beauvais Lake Provincial Park, located in southern ranching area of Alberta, Canada. I was on my way to Waterton Lakes and Glacier National Parks from the spectacular Peter Lougheed Provincial Park, and I decided en-route that maybe I would break up the drive into two days rather than one long day. I stopped in the nearby town of Pincher Creek to load up on supplies, and then made my way to the park.
I paid a visit to the ranger station to get some maps and information about this mystery park. I was surprised to learn that despite being largely surrounded by ranches, the relatively small park hosts an impressive diversity of large fauna, including moose, elk, mule deer, black and grizzly bears, mountain lions and bobcats, coyotes, foxes and occasionally wolves. In addition, the park is a birding hotspot, and the lake and surrounding wetlands provide breeding habitat for a number of exciting birds such as sandhill cranes, common loons, trumpeter swans, yellow-headed blackbirds, osprey, and red-necked grebes. The ranger wished me good luck in my wildlife-finding ventures, and I continued on to the campground to select a spot for the night.
After I had set-up my tent, I grabbed my camera, binoculars and bear-spray and took-off to do some exploring. It was late afternoon by that point, but I still had hours of daylight ahead of me with the summer solstice only a few weeks away. The wet meadows were brimming with wildflowers; brilliant blue camas and white bog orchids in particular caught my attention with their long, spiky flower stalks. Blue flowers like those of the camas are generally pollinated by bees and butterflies (the flowers often reflect extra brightly in the UV range, which many insects can see), and white flowers like those of the bog orchid are typically pollinated by moths. It may seem counterproductive for a plant to target only one or a few types of pollinators, but having some specificity in who pollinates which flower type can increase the chance that an individual pollinator will transfer pollen between flowers of the same species.
I watched the pollinators fly from flower to flower, carrying with them the makings of the next generation, before resuming my hike. I explored the north side of the lake, but there was a lot of human activity there, so I headed towards the west side, which was decidedly quieter. I had been alerted by the ranger that some areas of the park were closed due to an aggressive black bear that had staked a claim near the outflow of a stream along the west/southwest corner of the lake. White suckers (a type of fish) were spawning there, and the bear had found this bountiful food source to its liking and was defending it against any perceived competition or threats. Apparently one ranger had been charged by the bear and been forced to use her bear spray. I guess it worked, but the park had taken the wise precaution of cordoning off a large section around the spawning site. Most of the west side was still open, however, and a dirt road traversing that side provided access to the lake’s edge and the associated wetlands.
As I began walking down the road, my progress was opposed by a gang of posturing, swaggering, hissing Canada geese. The flock was composed of both adults and juveniles, and the adults were making a great show of how seriously they took their parental responsibilities. The young birds, meanwhile, were much more interested in eating, and were quite content to plop down and pluck at grass mere feet from me. Eventually, the parents succeeded in herding the youngsters off to the side, thereby allowing me to pass with just a few residual hisses aimed in my direction. Soon after navigating the goose gauntlet, I noticed a bird floating low in the water a few meters offshore. A look through my binoculars quickly revealed that the submarine act was being performed by a red-necked grebe. These handsome birds are members of the Podicipedidae (grebe) family, which exhibit several interesting traits. Grebes are primarily underwater foragers (but click here for coverage of a short paper I wrote on pied-billed grebes foraging on land) and they use their feet to propel them after fish and aquatic invertebrates. This foot-propulsion system is facilitated by having the feet located way back on the body (to provide more thrust) and by having broad, flattened toes that fold in when drawn forward through the water (to reduce drag), and that spread out wide like paddles when pushed back against the water. Grebes also consume their own feathers (or those of their parents if they are young), and while the reason for this behavior is not wholly clear, there are a few possible explanations. One is that the feathers provide protection for the stomach and intestine against puncture by fish bones. A related option is that the feathers help collect bones and other indigestible materials into pellets which are then regurgitated. A more recent proposal is that the feathers slow down the passage of food items, enabling the grebes to more fully extract nutrients from their food. These are not mutually exclusive ideas, and it’s very possible that feathers provide all three services.
Grebes are also good at controlling their buoyancy, and the individual I watched was keeping a very low profile as it swam—just like a submarine’s periscope traveling through the water. And I soon realized why; it was swimming with a small fish in its bill that was destined for the mouth of a recently hatched chick. The new chick was perched on the back of the attending parent, who was sitting on the nest. Grebes build floating nests made of mud and aquatic vegetation that are anchored to living reeds or cattails. As the adult with the fish drew close to the nest, the chick wiggled around in anticipation, straining to get closer to the food. The small fish was delivered to the gaping mouth, but in all the excitement of the moment, the chick dropped the fish. The parent patiently picked the fish up and again offered it to the squirming chick, who proceeded to drop it again. This happened a few more times before the chick finally succeeded in gulping down the tiny minnow. Once the food was safely down the hatch, the parent zoomed off in search of more food. I sat down and watched the action at the nest for 30-40 minutes, but the sun was fading by that point, and I decided I would need to return the following evening to capture some images under better lighting conditions. I returned to my campsite, ate a quick dinner, and turned in for the night.
The next day I rose at dawn and got out to explore more of the park. I had seen on the map that there was a small pond located about a mile away, so I headed there in the hopes of seeing some moose. I struck out on the moose, but the birding was fantastic. When I arrived at the pond I was inundated with birdsong; red-winged and yellow-headed blackbirds called from cattails, while soras (a small rail) winnied from unseen haunts. A family of sandhill cranes stalked the far side of the wetland, while blue-winged and green-winged teal dabbled in the pond and quacked softly. A northern harrier soared low over the wetland and ignited an angry plume of blackbirds in its wake. After birding for a few hours, I returned to camp for a late breakfast.
While I sat at the picnic table eating my bagel, a pair of evening grosbeaks materialized from the forest. It was a male and female, and the female quickly dropped to the ground, disappearing from view. The male remained perched about 10-15 feet up and seemed to be keeping watch. Curiosity got the better of me, and I snuck closer to see if I could figure out what the female was doing on the ground. It turns out she was bathing in a pool of water, and when she saw me, she took off and rejoined her mate. I backed away, and after a few moments, the two of them flew down to bathe and drink together. When they had finished their morning ablutions, they returned to the low branches of some nearby aspens, and began preening. This went on for some time, and the male allowed me to get quite close to watch his act of self-maintenance. He drew wing, body, and tail feathers through his massively thick bill, straightening and aligning the barbs and barbules in each one. Feathers work kind of like Velcro, and one of the purposes of preening is to make sure the Velcro is all locked in place. Once the grosbeaks were happy with the state of their feathers they flew off into the forest, uttering a few parting calls as they left.
I too disappeared into the forest for much of the day, emerging in the evening to revisit the grebes. The action continued much as it had the previous day, with one parent hosting the chick on its back while the other searched for food. There were a few additions to the scene, however. A California gull had shown up at the lake that day, and it made a number of low passes over the grebe nest, hoping to catch the parent unawares. With only one chick to watch, the parent at the nest was able to keep its sharp bill squarely between the gull and the nestling. The other parent, meanwhile, was preoccupied with some other intruders. The gaggle of Canada geese from the day before were milling about in the water, and they were too close to the nest for that parent’s comfort. The grebe would sink below the waves, and launch an underwater attack on the geese. Essentially this consisted of the grebe sneaking up on the geese from below and then poking them in the butt with its bill. I may have derived the slightest bit of satisfaction at the geese getting some of their own medicine.
In between sneak-attacks, the grebe diligently hunted for food for the chick. It brought a smorgasbord of food items; many small fish, a large leech, insect larvae, and the occasional digestive aid (feather). At one point, the parent at the nest decided the nest needed some reorganizing. It awkwardly got to its feet and beginning moving bits of vegetation around with its bill. The chick, which was still perched on the adult’s back, was not at all happy at this turn of events, and let the parent know. It pecked at the back of the adult’s head, grabbing some of the feathers and giving them a twist for good measure. This act of belligerence seemed to go unnoticed by the parent, who continued the redecorating for a few more minutes before settling back down on the nest. With the world beneath it stable again, the chick ceased its attack on the back of its parent’s head, and returned to its comfy nook under the wing feathers. I stayed until the sun’s rays were hidden by the reeds, and left the grebe family in peace.
There was one more place on the opposite side of the lake I wanted to explore before it got dark, so I quickly made my way over there and headed out on an overgrown trail as the sun dipped below the horizon. The trail took me onto a small peninsula that jutted into the lake, and I followed the path hoping it might lead me to some interesting animals. The path did not fail in that regard. I had completed half the trail and was on my way back to the car when I noticed movement in the long grass just off to my side. It was something small, and I paused, hoping I might catch a glimpse of it. Then I noticed that there was grass moving in another spot, and another, and another. Then a small shape burst onto the path and before I could register what I was seeing, it had bounded down the trail and vanished into the grass. And when I say bounded, I mean it covered 4-6 feet in a single leap. I looked around me and there was movement everywhere; I felt like I was under attack from a pack of miniature velociraptors. Small shapes darted past me on the trail, while others dangled from branches a few feet off the ground. Finally, I realized what was happening; a squadron of meadow jumping mice had descended upon me and were scouring the area looking for food. Jumping mice are aptly named, but they are also excellent climbers, and use their very long tails to help with balance when off the ground. I watched this merry band of marauding mice for about 10 minutes as they jumped about me, and climbed bushes and grass stalks, and finally, when it was just about too dark to see them, I returned to my car and drove back to my campsite.
I left the next morning, but in the short time I had spent at Beauvais Lake, I had seen over 90 bird species, watched intimate parenting and preening behavior, and spent time with a magical rodent. Not bad for a little park I’d never heard of and only stopped at on a whim. It’s a place that’s now locked in my memory, and one that I hope to return to soon.
Next week: View from the Balcony: A Return to Illinois
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I stood up from the crouch I had been in and removed the canister of bear spray from its holster. For the previous 20 minutes I had been watching a good-sized grizzly bear make his way around the edge of a small lake in Glacier National Park. He dutifully followed the lake’s perimeter, tracing the outline of each inlet and cove. But when he made it to my side of the lake, he had disappeared, obscured by the contours of the shoreline. I waited and watched, searching for any sign of him, and when I saw the ripples in the water, I knew he was headed right for me and the two hikers I had just met.
“Ok—stand next to me, side by side, and have your spray in your hand,” I instructed the young couple, whose morning had just gotten a lot more exciting than they had expected. Or wanted.
“He knows we’re here, but when he appears, I’m just going to talk to him to let him know everything’s cool.”
I was doing my best to sound calm and confident so that the couple wouldn’t lose their composure, but I could feel the adrenaline beginning to kick in. And then, about 25 feet from where we stood, the massive honey-brown head and shoulders of the bear emerged from the vegetation and paused. The bear looked out with his small, dark eyes, scanning the area, and I began talking to him in what I hoped was a soothing, non-threatening tone. The bear took a few moments to assess the situation, and then, without looking at us directly, resumed walking. I quickly realized he was following the hiking trail. The same one, it just so happened, that we were on. And unfortunately, we were situated at a point where the path hugged the lake, meaning there was nowhere for us to go unless we wanted to take a dip.
The distance between us shrank rapidly, and I could feel a few butterflies begin to flit around my stomach. I continued talking to the bear, doing my best rendition of Barry White’s deep-bass voice (which, if we’re being honest, is a terrible rendition of Barry White). Suddenly, and to my relief, the bear detoured off the path, giving us a nice buffer before rejoining the trail about 20 feet further down. He broke into a slow lope and vanished around the corner. I turned to my companions with a big smile on my face. “Can you believe that just happened?!?” The looks on their faces said that they couldn’t, and that perhaps a change of clothes was in order.
We talked about the encounter, and how different it had been from their previous experience with a grizzly the day before. They had been on a trail when the people in front of them saw a grizzly nearby and began freaking out. This scared the young couple, so they started running back the way they had come. They never even saw the bear, but the experience had left them shaken and given them some serious anxiety about encountering another bear (the term “bearanoid” was common parlance for this sentiment in Glacier). Our encounter, in contrast, was a textbook example for how things could go, and I was thrilled that this couple was able to rewrite their bear-story so quickly.
An important point I want to hit on is that I had no preconceived notion for how that bear was going to react to us; I prepared us for a worst-case scenario (although there are very few instances of bear attacks with groups of three of four people, especially when they are spaced side-by-side), but I watched the bear constantly while it was visible to look for clues as to how it would act. My interpretation of the bear’s unwillingness to look at us directly was that this was a subordinate individual who was not interested in challenging us. But we all know what happens when we assume things about bears—“u” and “me” might wind up coming out a bear’s “as-”… well, you get the picture. The point is, every bear encounter is unique, and should be treated as such, with caution and respect.
For me, the encounter marked my (approximately) 125th bear sighting between mid-April and mid-June. Granted, a number of those sightings were from vehicles, and perhaps 20 of them were “Albert” sightings (our resident black bear at Katie and Dennis’s in Bella Coola). But over that short period of time, I had been afforded an opportunity to observe and occasionally interact with a good number of black bears and grizzly bears. Much of the time, the bear would bolt into the woods as soon as it saw me. Bears can move incredibly fast for their size: a grizzly can outrun a horse over short distances, topping 35mph. Moreover, bears are capable of running uphill at almost the same speeds they can attain on the flat. And if you’ve never seen a large grizzly run through a patch of scrubby trees, picture the opening scene in Jurassic Park when the trees are all swaying side to side as the giant machine comes crashing through.
But the next story I want to share doesn’t involve bears running, or trees swaying; just a bear and a barbed wire fence.
This story takes us back to Bella Coola, and a nice cool mid-May morning. I was walking down a former logging road through a section of second growth forest that was very bird-y and very bear-y. The dirt road was bordered on one side by a steep, heavily forested slope, and on the other side by an old barbed wire fence. I was padding along quietly, listening to the forest’s rich repertoire of sounds; the scolding chatter of an angry red squirrel, the crinkle of old leaves getting tossed by robins and varied thrushes in the underbrush, the metallic hum of a rufous hummingbird’s wings as it foraged at a patch of columbine, and the songs of countless birds staking out their territories. I looked up ahead and saw a large black bear grazing on some fresh grass along the road. It was facing away from me and had not yet heard me, so I eased off to the side in an attempt to blend in with the vegetation. I couldn’t go very far, however, because the barbed wire fence was only a few feet back from the road edge. I stood next to the fence, quietly watching the bear eat. It then turned around and began walking in my direction. I didn’t want to disturb the bear’s morning meal, so I thought if I could just slip over the fence, I’d be able to let it eat in peace and remain safely out of its way.
I pressed down on the top line of the barbed wire with one hand and stepped over the fence with one leg. But I was trying to keep an eye on the bear, and keep my camera from banging around, so I failed to give the maneuver the full attention it warranted. As such, I didn’t realize that: A) even when pressed down, the fence was taller than my crotch, and B) I was stepping over the point at which my hand was holding the fence down. What this means is that I pushed my hand into the barbed wire with my thigh. I felt a sting in my palm but held on and managed to get fully over the fence. When I was safely on the other side, I looked down at my palm and the red bead forming in the middle. Then I looked at the barbed wire and the deep coating of rust covering it. I looked back up the road and saw the bear still walking towards me, blissfully unaware of the absurd fiasco I had just created. I tried to recall the timing of my last tetanus shot while also assessing whether I wanted the bear to get any closer. I had a sneaking suspicion that the barbed wire wouldn’t be much of a deterrent for the bear if it wanted to get through it, rust or no rust, so when the bear was within 50 feet, I gave a little whistle to let him know I was there. He looked up sharply, and immediately turned around and walked back the way he had come. I waited until he had rounded the corner, and then I eased myself back over the deathtrap fence. I walked back to the car mentally kicking myself and remembering horror stories of people who had gotten tetanus. My last shot had been 7 years prior, and I had no idea if I would need a booster, or if I would even be able to get one in Bella Coola.
I called the health clinic once I was back home, and they told me I should definitely come in. When I arrived, the nurse administering the shot asked what had happened, so I recounted my misadventure while she jabbed the needle into my arm. She seemed amused by the story and told me to come back if the wound showed any signs of infection. I left thinking that it was fitting that one little puncture had gotten me into trouble, and another had gotten me out of it, and wondering if anyone else had ever needed to get a tetanus shot because they had cut themselves while climbing over a barbed wire fence to avoid a bear. I’m not sure I’ll ever know the answer.
We return to Glacier for the next bear encounter, and a beautiful subalpine mountain setting. I was descending the Grinnell Glacier Trail in the early evening when I caught sight of a light brown blob a little way across and up the slope. I looked through my binoculars and the blob turned into a mother grizzly sleeping with her two yearling cubs. They were lying in a bed of mixed wildflowers located just back from a ledge that overlooked the trail maybe 60 feet below. As I watched the bears snooze, a group of hikers came up the trail. The sounds from the group woke the mom, and she slowly got to her feet and walked to the edge of the rock ledge to look down at the activity below.
When the hikers reached me, I pointed to the bears, and they admired them for a few minutes before continuing. A few more sets of hikers passed by going down the trail, and mom bear decided it was time for her and the cubs to be moving on. She led them across the steep slope, pausing now and again to snack on some greens. During one of these snack stops, the cubs found an overhanging rock that made a perfect grizzly-cub sized back-scratcher. One of the yearlings got really into the action; he stood on his hind limbs and scratched up and down, side to side, and even contorted his body sideways to get all the spots.
After mom had eaten her fill, and the cubs had itched all their scratches, mom led the cubs up slope and over the ridge, vanishing into the maw of the mountain wilderness.
I’ll close this week with one of the more unusual, and frankly disturbing, bear encounters I’ve had. I was in Waterton Lakes National Park, which is located in Alberta just north of the border with Montana. Waterton abuts Glacier National Park, and together they form a massive international parcel of protected land. Waterton suffered devastating wildfires in 2017 which burned 40% of the park. I was stopping in Waterton for a few nights on my way to Glacier, and my first full day in the park I had walked almost 20 miles without seeing much wildlife. The wildflowers were stunning, and it was fascinating to see how some areas of the park were recovering nicely, whereas others (which had presumably burned too hot) were still bereft of plant life. But in terms of large wildlife, I was striking out. I decided I would try one final hike in the evening along a road that was closed to car traffic. I was the only person out at that hour, and I was on alert for any and all activity. After I had hiked about 2 miles, I came over a slight rise and saw a pair of ears and a head—a black bear among the tall grasses. I stopped and waited to see if the bear had noticed me. Nothing happened, so I moved a little bit closer to get a better view of what the bear was doing; it was looking right at me, not moving a muscle. I had seen bears exhibit this sort of behavior before when they were trying to figure out what something was, so I wasn’t too worried at this point. I snapped a couple of photos, and took a few more steps to the side. Still no reaction from the bear. Now I was beginning to get concerned. It was still staring at me and had not moved an inch. I took a few steps back at that point, removed my bear spray, and began talking to the bear in an attempt to diffuse the mounting tension. My talking and slow retreat had no effect; its small beady eyes were still locked on me.
I briefly wondered if maybe this wasn’t a real bear. Could it be that the park had placed a stuffed bear out in the grasslands? A quick look at the images on my camera’s LCD screen convinced me it was real. I decided I should begin making my way back to my car, so I walked backwards away from the bear keeping a close eye on it to see if it would follow. I dropped below the point at which I could see the bear and turned to begin my retreat in full. After 10 steps I came to an abrupt halt and decided I couldn’t walk away from this bizarre situation. I slowly retraced my steps and the bear’s profile appeared in the same spot, still staring right at me. I took another photo, zoomed it in all the way, and finally saw it; the smooth ridges on the bear’s neck. I had been talking to, and retreating from, a bear cut-out.
Now this was no ordinary cut-out; it was an immaculate piece of deception. A con-job for the ages. And I felt like a complete idiot. The bear was clearly meant to give drivers coming over the hill a good start, but it had fooled me for 15 minutes. I blamed the distance (I hadn’t wanted to get too close), the failing light (it was dusk after all), and my lack of having seen any big game all day (I really wanted to see a bear), but my ego lay in ruins. I decided I would delete all the images and never breath a word of this to anyone. But my resolve on that wobbled, and I eventually (weeks later) told my wife the story. She thought it was wonderful and insisted I share the story here. And so now I have.
Next week: Alberta’s Hidden Gem: Beauvais Lake Provincial Park
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Before I jump back into recounting moose adventures, I want to properly introduce you to the central player in these stories—the moose. As the host here, this is something I really should have done in the previous post, so you’ll have to forgive my bad manners.
The moose (scientific name: Alces alces) is the largest living member of the deer family (Cervidae), capable of reaching heights over 7 ft at the shoulder, and weighing more than 1,800 lbs. A male (or “bull”) grows antlers every spring through summer, which he then sheds in the winter. Moose and deer antlers are the fastest growing organs known to science—they can grow up to ½ an inch a day. The largest moose antler spread recorded was close to 7ft wide, and weighed almost 80 lbs. That would be the equivalent of an average-sized person carrying a medium-sized cat around in a giant sombrero on their head. That may not sound too bad, but remember, you’re toting that hat and feline around 24/7. They’re up there for meals, work, weddings, sleep, trips to the dentist, during all of which the hat keeps knocking into nearby objects while the cat swats at everything within reach. After 6-8 months, you’d be happy to dump that cat-in-the-hat into the nearest snow-pile too.
Female moose (or “cows”) are typically smaller than males, and males compete for access to females during the rut in early autumn. Females give birth to one or two calves in May or June, and the calves typically remain with mom until the following spring. Images of mother and calf often make the mom appear very gentle, but don’t let these images (or my story of magical moose in the last post) fool you; cows with calves can be one of the most formidable creatures on land. A mother will charge bears, wolves, humans, and anything else that she thinks poses a threat to her calf, and a moose’s sharply pointed hooves can inflict mortal wounds. According to one source, moose are responsible for more wildlife-related injuries to people (not including parasites and diseases) than any other animal worldwide except hippos. That puts moose into some scary company; hippos are notoriously foul-tempered and have foot-long canines and incisors to back up their attitudes. It’s unclear, however, if the injury statistic includes vehicle collisions. I don’t think there are too many car-hippo accidents in Africa, whereas car-moose accidents are a big problem in areas with lots of moose, and account for many injuries to people. So, while moose may be dangerous, I don’t think we have to begin thinking of them as the hippos of the north.
Speaking of the north, moose are cold-adapted animals, and are found across the mid-northern band of North America, Europe, and Asia, with populations extending into mountainous areas further south. Their long legs allow them to navigate through deep snow, and they are well-insulated with an outer coat composed of hollow guard hairs, and a thick undercoat. It is thought that their preposterously long snout is also an adaptation for cold climates; when they breath in, the frigid air is warmed as it passes through the long nasal passage, thereby protecting the moose’s lungs and core from extreme cold temperatures. In addition to their penchant for cold climates, moose also display a fondness for water, particularly the aquatic vegetation growing in shallow ponds and slow-moving rivers. This vegetation is rich in sodium, and moose have a real weak-spot for salt. Of course based on the typical human diet, I guess we do too. Unlike us, however, the moose will happily dive underwater to get this sodium. Moose are excellent swimmers, capable of speeds up to 6-7 mph (that’s faster than Michael Phelps), and can easily cross large bodies of water. They are not faster than orcas, however, and moose swimming between islands off Alaska are known to have been preyed-upon by orcas. It’s perhaps fitting that one of the primary predators of moose on land is the wolf, and in the water, it’s the sea wolf.
Now that we’ve gotten the introductions out of the way, I want to share some of the more recent encounters I’ve had with moose, beginning with a cow and her relatively new calf in Glacier National Park back in June.
I was camping in the Many Glaciers section of the park and had been waking early to get out on the trails before the hordes of other visitors. The Swiftcurrent Trailhead, located close to my campground, provides excellent moose-viewing opportunities. The trail starts off slowly, winding past a chain of beautiful lakes whose waters are tinted turquoise-blue with glacial sediment, before ascending to the high alpine areas. I had hiked a few miles of the trail my first full day there and had come across a young moose calf hovering at the margins of a willow-thicket along the edge of the first lake in the chain, Fishercap Lake. I had watched the calf for a few minutes hoping its mother would appear, but it soon disappeared into the willows when it heard people approaching.
On this particular morning, I arrived at the lake around 5:30am and looked out onto the gray scene. The air was heavy with fog, and every stem of grass and willow leaf was coated with dew. And there, just about 150 feet away, a large female moose was bedded down in the grass at the edge of the lake, slowly chewing her cud as she dozed. I smiled as I took in the scene; it was beautiful AND I had gotten out before the moose were even awake! This more than made up for the rot-gut instant coffee I had choked down that morning.
I started taking photos of the snoozing moose when I realized she wasn’t alone. Her young calf lay nestled in the grass sleeping next to her, with its head propped up on a small log pillow. I was amazed that the mom would choose this spot to spend the night given how exposed it was, but perhaps she liked the proximity to water.
Grizzly and black bears, coyotes, wolves, and even wolverines pose serious threats to moose calves in Glacier, but a young moose can outswim most of these predators within a few weeks of being born. As I considered the perils a young moose faces, mom’s ears pricked up and she turned away from the water. She quickly rose to her feet and took a few steps towards the wall of willows, with all her senses directed forward. This activity roused the calf from its slumber, and the dazed-looking calf looked around with mild alarm. I thought perhaps mom had heard hikers coming, but I couldn’t hear or see anything coming down the trail. The calf got to its feet, and stared into the willows, mirroring the intensity visible in mom’s demeanor. Mom took a few deliberate steps and vanished into the shrubs, leaving the calf alone on the shore. Mom reappeared a few minutes later, and began browsing on the willows, but she still seemed to be on high alert. I was puzzling over what the perceived threat could have been, when it came prancing out of the vegetation; a pair of white-tailed deer bucks.
The deer emerged about 100 feet from the moose, and after pausing to assess the moose pair, the two deer began to play. They ran through the water, kicking and bucking, and chasing one another in circles. They raced in and out of the shrub thicket, disappearing for up to 10 minutes at a time before reappearing somewhere else. They were totally immersed in their games, fully given over to their pursuit of fun.
Momma moose, meanwhile, was not impressed. To her, these two large animals represented a possible threat to her calf, and she made it clear she did not want them close to her baby. With hackles up, and ears down, she initiated a handful of aborted charges in the direction of the frolicking deer whenever they got too close for her comfort. In between her attempts at keeping the deer away, she would return to her calf to reestablish contact, and do some bonding. These sessions usually consisted of some amount of nuzzling and licking.
The calf, for its part, seemed more curious about the deer than concerned. At one point while mom was busy eating, the calf found itself face to face with the deer, who had emerged only 20 feet away. The deer stared at the calf and I could feel the invitation to play being extended by the deer.
This scenario immediately transported me back to Maine and the encounter between the moose twins and the giant white-tailed deer at Baxter State Park I covered in last week’s post. Only this time, the roles were reversed. When the moose calf took a few tentative steps towards the deer, I thought maybe the young mooseling would engage with the rambunctious duo. But the youngster’s nerves got the better of it, and it retreated to the safety of mom’s side. The deer turned away and went back to their cavorting.
Not long after, the deer again vanished into the willows. But this time, whether by accident or on purpose, they appeared in the shrubs close to mom and the calf. Mom caught wind of them, and charged through the shallows, sending water spraying. This was, by far, the most aggressive action the female moose had exhibited, and the deer retreated rapidly into the thicket. This signaled the end of the play-time, and the deer wandered away. Mom and calf soon followed suit, as did I.
On the surface, this agonistic interaction appears to be the product of an overly-zealous mother protecting her offspring. But the relationship between moose and white-tailed deer is complicated, and the female moose’s aggressive behavior towards the deer could have origins in an unusual form of competition. The two species don’t exhibit extensive geographic overlap, and it has been proposed that part of the reason for the separate distribution is that the deer can have a detrimental effect on the moose via a third player: parasites. This process is known as parasite-mediated competition. White-tailed deer are carriers of a few types of parasites that have minimal impacts on the deer but result in severe pathology and death in moose. In fact, this parasite-mediated competition may be a major source of declining moose populations in the Midwest and Northeastern US. White-tailed deer numbers have been increasing in these areas, likely due to a combination of climate change, habitat alteration, and shifting management practices. White-tailed deer carry a nematode worm (known as the brainworm) that resides in the meningeal tissue adjacent to their brain, but which is not overly detrimental to them. For moose, however, this brainworm is especially pathogenic (it burrows into their brains), and the higher the deer population, the greater the risk of transmission to moose. A coalition composed of researchers from the University of Minnesota and the Grand Portage Band (a Native American band which formerly relied heavily on moose) was recently funded to examine the impact of white-tailed deer and the brainworm on moose populations in Minnesota.
In addition to the diseases associated with the deer, moose in the Midwest and Northeast have been succumbing to a species of tick known as the winter tick. These ticks attach themselves to moose and other large mammals in the fall, and then feed on the mammal through the winter. According to a study conducted by researchers at the University of New Hampshire, the frequency of heavy winter tick infestations has increased, coinciding with the trend for warmer and shorter winters. Over the 3-year period of that study, researchers found that 70% of moose calves died during the winter months, primarily as a result of emaciation and blood loss from extreme tick infestations (an average of 47,371 ticks per moose). Adult moose were better able to cope with the ticks, but they were in noticeably worse body condition as well.
To counter that sobering bit news, I’ll close with a more uplifting story. Those who read last week’s post should recall the close encounter I had with a female moose when I was nine. This encounter seems all the more incredible given how aggressive moose can be. But in the past three years, I’ve had a few encounters that mirror that early experience.
The first of these happened in Alaska three years ago when I was exploring the Kenai Peninsula. I was hiking a relatively remote trail when I came across a mother moose and her large twins taking a late-afternoon siesta about 150 feet off the trail. I watched them nap for a few minutes, and then continued hiking along the trail. On my return trip, the moose had relocated to the trail, cutting off access to the road and my vehicle. I stopped and watched, thinking that after a few minutes they would make their way off the trail, and I would be able to pass by without disturbing them. Normally I would have been content to sit and watch them for hours, but sunset was an hour away, my car was a 30 minute hike, and I still needed to find a camping spot for the night. After 15 minutes had elapsed and the moose showed no signs of moving on, I thought I might provide a little encouragement. I began walking slowly towards them while keeping a sharp eye on mom to see how she would respond. She turned towards me, ears twitching, head slightly down, and took a few steps in my direction. Ok—message received. I stopped and looked around to see what I could use as a barrier in case things escalated. A downed tree behind me and off to the left would provide an ideal, and safe, vantage point. A wall of dead branches created a barrier in front, and the ground dropped off behind the horizontal trunk, allowing me to duck under the tree if necessary. As I made my way onto the trunk, I talked quietly to the moose thinking it might help calm her down. To my surprise, it did. Her ears stopped twitching, and she raised her head back up. Not only did her demeanor change, but she began moving in my direction with her two calves trailing behind her. I watched her closely to see if there were still signs of agitation or aggression, but she seemed to have decided that I was not a threat. The three moose eventually made their way to within 20 feet of me, and contentedly munched on aspen leaves and other greenery. Soon the two calves wandered down the hill, and after a few minutes I could hear them splashing around in the water of a nearby pond. Mom stayed with me and continued eating. Even though mom seemed comfortable with me, I had no desire to push the boundaries, so I stayed put on my tree trunk, a very happy, but thoroughly stuck prisoner.
Finally, after maybe 45 minutes, mom began moving off the trail. She gave a bugle-grunt vocalization, and from down the hill I could hear the twins racing through the water and then begin heading up the hill. It was time for all of us to move along, and so I skirted around mom, and made for the car in the failing light.
Lest you think this was an isolated incident, a similar scene played out just last week about ½ mile from our place here in Colorado. I had left the house for an early-morning walk when I came across a mom moose and her twins. After an initial period of uncertainty on mom’s part (twitchy ears, head slightly bowed, a few steps in my direction), I had a quiet chat with her, which again seemed to do the trick. Mom relaxed and then slowly brought her twins to within 15 feet of me. In fact, when she went to investigate something in the woods (I think a bull moose was in there), she left the two calves with me for about 10 minutes before beckoning them with her bugle-grunt call.
The calves, however, were enjoying their bit of freedom (and I suspect they liked their new babysitter). The mooselings were busy nosing about, and when one found a bit of coyote scat in the road, it got down on its knees to give it a thorough inspection. The calf sniffed the scat a few times, got to its feet, and then gave the scat a few agitated kicks. After another call from mom, the twins took off and vanished into the grove of aspens, leaving me with another wild moose tale to tell.
Next week: Bears of the West
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When I was nine, I had an encounter with a moose that bordered on the fantastical. The setting for this story is Baxter State Park, located in the heart of the Maine woods, and my dad had taken me there for my first real camping trip. It was a warm, mid-August day, and we were hiking up Mt. Katahdin, which at that point was the terminus of the Appalachian Trail. We had been on the trail for maybe four hours when we rounded a corner, and there she stood; an enormous adult female moose. She turned her massive head with her elongated snout and radio-antenna ears, and gave us an appraising look. She was perhaps 30-40 feet away, but she occupied my entire field of view. I could hear people approaching from behind us on the trail, so I darted back to alert them to the moose’s presence. I then returned to my spot and watched as the moose began slowly moving towards us. I then did something that was fairly foolhardy and which could have gotten me into heap of trouble; I began slowly walking towards her. I’m not entirely sure what motivated me to approach the quarter-ton wild animal, but at the time it seemed like the logical thing to do. I was convinced that once I got to within 20 feet of her, she would amble off the path like the other moose we’d seen in the preceding days, and disappear into the understory. But that’s not how events unfolded. As the distance between us shrank, I began to realize that she wasn’t exhibiting any signs of fear or agitation, and she also wasn’t showing any signs of altering her path. When we were no more than eight feet apart, I stopped and let her close the final gap. She plodded up to me, stopped, and peered down.
My mind raced—“What do I do?” I wondered to myself.
“Feed her!” my brain answered. I reached down, grabbed a fistful of grass and wildflowers, and held them up to her. She leaned down to sniff the offering and I waited without breathing. In my mind, she was going to reach out, delicately grasp the bouquet from my hand, savor the wonderful selection of hand-picked greens, and we would be forever friends; a boy and his moose. She would live in our yard and I could ride her to school. It seemed inevitable. But as with so many nine-year-old’s dreams, it was not to be. After giving my would-be gift a few good sniffs, she turned away, wandered a few steps off the trail and grabbed a mouthful of pine needles.
“Pine needles!?!” I thought, feeling rejected. Even at that age I knew pine needles were considerably less nutritious than what I had in my hand (although I didn’t know that moose can happily subsist on evergreen needles). I tossed my unwanted offering onto the ground and after a few final moments watching my moose-friend, we continued with our hike.
For most people the experience would likely have been noteworthy, maybe even inspiring. But for me, it was transcendent. We lived in Boston at the time, right in the transition zone between the urban and suburban environments. Up to that point, my experiences with large wildlife had consisted of visits to zoos and aquaria, and watching nature shows on PBS. Of all the North American fauna, the one I developed the greatest fascination for was the moose. For some reason, moose became the embodiment of wilderness to me. And the fact that I could possibly see one in parts of New England made it all the more thrilling. When my dad announced that he and I would go on a camping trip to Baxter State Park (a well-known moose mecca), I was beside myself with excitement. For me, this was akin to traveling to the middle of the South American rainforest or the plains of Africa.
What bears mentioning at this point is that I was a bit obsessed with animals. As a youngster, I eschewed traditional television shows like Sesame Street, or Mr. Roger’s Neighborhood in favor of animal-themed programming like Wild America and Nature. Most of the time I got my wildlife fix by flipping over rocks in our yard and grabbing whatever poor beetles or red-backed salamanders were residing underneath. But a trip to Baxter meant access to a whole new world, and I went with one goal: to see moose.
The trip was, by every possible measure, a huge success. We saw almost a dozen moose, and in addition to the moose encounter on the Mt. Katahdin trail, I witnessed an interaction between a pair of moose calves and a white-tailed deer that also sounds made up.
On our final day in the park, we did a short hike, and then decided to visit Sandy Stream Pond in the hopes of seeing a few more moose. The pond did not disappoint. A solitary moose was foraging on aquatic grass at one end of the pond, and towards the other end a mother moose grazed in the shallows while her twin calves played along the shoreline a little ways away. A huge white-tailed deer buck was also present, foraging at the pond’s edge. I was perched on a large hunk of granite that afforded me a clear view of the entire pond. The twins were the most active participants at the pond, and while the adults were all focused on the important business of eating, the young calves were focused on carousing. They chased each other in circles, kicking up their legs as though they were bucking broncos, and splashing through the shallow water with wild abandon. I don’t remember how long they danced like this, but at some point, their attention was drawn away from each other and towards the giant white-tailed deer that was still foraging about 100 feet away. The twins must have had the same thought, because they began running side-by-side towards the deer. To my surprise (and probably that of the moose calves), the deer looked up and started running towards the twins. Even though the twins were a few months old and were as large as a normal white-tail, this buck dwarfed them. He ran with his head up, holding his massive spread of antlers high.
I sat glued to my rock, watching as this high-stakes game of deer-moose chicken unfolded across from me. The two parties closed on each other and at the last instant, the buck leapt over the two calves, and vanished into the woods. Yes, you read that right. He jumped clear over the moose calves. The twins meanwhile crashed into one another and collapsed in the water in a tangled mass of limbs and ears. Momma moose must have been watching, because at that point she swam over to her babies to collect them, and presumably to scold them for fraternizing with dirty* deer. They soon departed from the pond, and so did we.
(*See next week’s post for information about the parasites deer carry that can be deadly for moose.)
Looking back on these experiences, I can see that they were instrumental in laying the foundation for my lifelong fascination with wildlife. All of my subsequent adventures and wildlife encounters are tied to these early memories; they are the bar against which my experiences are measured. A handful of experiences have met that bar since then, but what is striking to me is that in the past few years I’ve had a few experiences that were strongly evocative of those early encounters.
Stay tuned for Part II next Tuesday to read about those encounters, and for more information about moose natural history, and the challenges moose face today.
About the author:
Loren grew up in the wilds of Boston, Massachusetts, and honed his natural history skills in the urban backyard. He attended Cornell University for his undergraduate degree in Natural Resources, and received his PhD in Ecology from the University of California, Santa Barbara. He has traveled extensively, and in the past few years has developed an affliction for wildlife photography.