Category: Mammals

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The Shape of Wildlife in Winter

The Shape of Wildlife in Winter: Short-tailed weasels, also known in winter as ermine, have a long, slender body shape that allows them to invade subnivean tunnels to prey upon smaller mammals.
Short-tailed weasels, also known in winter as ermine, have a long, slender body shape that allows them to invade subnivean tunnels to prey upon smaller mammals.
Photographer: Steven Hint
Courtesy Wikimedia
Licensed under Cc-by-sa-3.0

Hi, this is Mark Larese-Casanova from the Utah Master Naturalist Program at Utah State University Extension.

Now that snow is finally accumulating in Utah’s mountains, weekend hiking trips have come to an end. But, that means it’s time to dust off the snowshoes and skis and get back outside. We humans are lucky in that we have countless types of gear to help us adapt to almost all winter conditions.

While a fur coat might help keep mammals warm or camouflaged in winter, there are many other adaptations that also aid in winter survival. Decreased mobility in deep snow can often prevent animals from finding food, possibly causing starvation in winter.

Some animals have feet that are particularly large for their body size, which helps them travel on top of deep snow. One of the best examples of this adaptation can be found in snowshoe hares. Snowshoe hare prints are easy to spot among the spruce and fir trees- the large teardrop-shaped hind feet leave prints that look like the hare was wearing miniature snowshoes, which is how it got its name.

While some animals are adapted to walk on top of deep snow, others do their best to simply walk though it. The long, slender legs of moose help keep the majority of their bodies above the snow, minimizing the energy required to travel in winter.

Instead of walking on top of or through the snow, small mammals such as mice and voles travel under the snow. As snow accumulates, mice and voles create vast networks of tunnels on top of the ground, but under the snow. This subnivean environment is typically warmer than air temperature above the snow, and still provides access to food, such as grasses, seeds, and bark.

Short-tailed weasels, also known in winter as ermine, have a long, slender body shape that allows them to invade subnivean tunnels to prey upon smaller mammals. As long as its head can fit into a tunnel, its narrower body can follow. This adaptation comes with a price, though. Slender bodies lose heat quickly, so weasels must consume around one-third of their body weight in food each day in order to produce enough heat to survive.

So while deep powder might seem like a winter wonderland to those of us who can adapt with the right gear, other mammals continually struggle to stay warm and find food. Some, however, choose to give up the fight and sleep the winter away.

For Wild About Utah, I’m Mark Larese-Casanova.

Credits:

Images: Pending rights approval
Text:     Mark Larese-Casanova, Utah Master Naturalist Program at Utah State University Extension.
Additional Reading:

Ellsworth, E. Surviving the winter: The importance of snowshoe hare foraging behavior. BEHAVE: Stories of Applied Animal Behavior. University of Idaho. Available at: https://www.cnr.uidaho.edu/range556/appl_behave/projects/hare_forage.html

Gellhorn, J. (2002). Song of the alpine: The Rocky Mountain tundra through the seasons. Johnson Books.

Lieberg, A. (2009). Charismatic minifauna. Northwest Connections. Available at: https://www.northwestconnections.org/documents/news/EOE_09feb26_Lieberg.pdf

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Cache and Retrieve

Click for a larger view of the Clark's Nutcracker, Nucifraga columbiana, Image licensed through the noted CCL. Stephen Pavlov, Photographer
Clark’s Nutcracker
Nucifraga columbiana
Courtesy Steven Pavlov
This file is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license 

Common Raven
Corvus corax
Courtesy US FWS
Gary M. Stolz, Photographer 

Hi I’m Holly Strand.

Every year, just before Christmas, I comb through the house looking for presents hidden earlier in the year. I check inside old shoes, unfold towels in the closet, and peer way back into the dark recesses of seldomly-used cabinets. With a child in the house, you have to be tricky! The problem with this complex gift stashing behavior is that sometimes I forget where I hid the present when it’s time to wrap it! And once in awhile I forget that I bought something at all! Out of sight—out of mind!

You wouldn’t make a very good magpie, I have been told. For magpies– along with jays, crows and ravens, are masters at hiding–or caching as it’s called– and then retrieving. Of course, what they cache is not Christmas presents but food.

One Utah bird that is much admired for its caching and retrieving skills is Clark’s nutcracker . This large jay lives in mountainous areas throughout the west. Experts say that Clark’s nutcracker can cache 10s of thousands of pinyon, whitebark or limber pine seeds in a single season. Starting in August, the bird will hide 1-15 seeds at a time, often distributing them several kilometers and at much different elevations from the original tree. Caches lie 1-3 centimeters deep in forest litter, bare soil, under bark, in holes, in logs or stumps.

As winter wears on, the nutcracker will retrieve its caches with the help of visual landmarks such as rocks, trees or logs. Using these visual cues, the nutcracker will retrieve the seeds through summer of the following year. Forgotten or abandoned seed caches often germinate, growing into trees that produce more food.

Just as I worry about prying eyes when I hide Christmas presents, birds who cache must be careful to notice who is watching. The common raven is notorious for its spying and thieving behavior. One raven will covertly observe while another caches scraps of meat, eggs, bones or seeds. The observer will then shamelessly raid the cache usually within a couple of days. But having probably raided someone else at some point, the caching raven is on the lookout too. If the caching raven senses the presence of a would-be looter, it might wait for the other bird to become preoccupied. Or it may move the food to a different site altogether. Caching ravens will also hide behind some structure to avoid being seen.

Interestingly, these sly birds will even engage in fake caching. Ravens will cache inedible or low value food items in plain view of other ravens but then stash the good stuff in secret. Fake caching seems designed to throw looters off track, . But perhaps it’s also a character test for fellow ravens? Or maybe—for the intelligent raven—it’s all just an amusing shell game?

For sources and pictures for this and past stories, go to www.wildaboututah.org

For Wild About Utah, I’m Holly Strand.

Credits:

Theme: Courtesy & Copyright Don Anderson as performed by Leaping Lulu
Images: Courtesy Wikimedia/ Steven Pavlov, Photographer
and Courtesy US FWS, Gary M. Stolz, Photographer
Text & Voice: Holly Strand

Sources & Additional Reading:

Balda, R.P. & Kamil, A.C. 1989. A comparative study of cache recovery by three corvid species. Animal Behaviour 37: 486-495. https://doi.org/10.1016/S0003-3472(89)80041-7

Boarman, W. I. and B. Heinrich (2020). Common Raven (Corvus corax), version 1.0. In Birds of the World (S. M. Billerman, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.comrav.01 or https://birdsoftheworld.org/bow/species/comrav/cur/introduction

Bugnyarf, Thomas and Kurt Kotrschal. 2001. Observational learning and the raiding of food caches in ravens,Corvus corax: is it ‘tactical’ deception? Animal Behavior, Volume 64, Issue 2, August 2002, Pages 185–195. https://doi.org/10.1006/anbe.2002.3056

Heinrich, Bernd and John W. Pepper. 1998. Influence of competitors on caching behaviour in the common raven, Corvus corax . Animal Behaviour. Vol. 56, 1083–1090, https://doi.org/10.1006/anbe.1998.0906

Marzluff, John and Tony Angell. 2005. In the Company of Crows and Ravens. Yale University Press. https://yalepress.yale.edu/yupbooks/book.asp?isbn=0300100760

Schaming, T. D., D. F. Tomback, and T. J. Lorenz (2024). Clark’s Nutcracker (Nucifraga columbiana), version 2.0. In Birds of the World (N. D. Sly, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.clanut.02 or https://birdsoftheworld.org/bow/species/clanut/cur/introduction

[Page Updated February 12, 2026]

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Feed the Birds

Pine Siskins and a Goldfinch feed on thistle from a sock feeder. Photo Courtesy and Copyright 2008 Jim Cane
Pine Siskins and an
American Goldfinch feed
feed on thistle from a sock feeder
Copyright © 2008 Jim Cane

Hopper Feeder
Copyright © 2008 Jim Cane

Hopper Feeder with Squirrel
Copyright © 2008 Jim Cane

Suet Feeder
Copyright © 2008 Jim Cane

Many of our songbirds have flown south to spend the winter. I confess that on frigid days I envy them. Like you and I, though, many birds remain behind. They fluff their feathers to trap body heat and spend these short days in a perpetual hunt for food to keep them warm. You can help their hungry quest by feeding our diverse songbirds using a convenient birdfeeder.

For loose seed, I use a hopper feeder. The hopper resembles a tiny roofed house which is filled with seed that is dispensed from a trough at its base. Another common style of seed feeder is a broad tray. It will need a roof and drain holes to keep the seed dry and free of mold.

(https://wildstore.wildsanctuary.com/collections/special-collections)

Our feeder is above a stone walkway for birds like juncos that prefer seed spilled on the ground. A ring of upturned tomato cages around this area excludes cats, and the season’s discarded Christmas tree will provide cover for the birds.

(https://wildstore.wildsanctuary.com/collections/special-collections)

Chickadees and finches prefer black oil sunflower seed, rich in fats and proteins, with a thin shell. If you buy seed mixes, juncos and sparrows will take white millet, but milo or so-called red millet is a filler. Doves and jays like cracked corn.

(https://wildstore.wildsanctuary.com/collections/special-collections)

Goldfinches and pine siskins flock to Niger thistle seed dispensed from a fine mesh sock that you can buy where you purchase the seed. Woodpeckers and nuthatches appreciate a suet feeder, which is a wire mesh cage containing a block of seed-filled suet. Expect magpies to hammer chunks off the suet block occasionally.

Don’t forget water, a scarce commodity for birds in winter. Plug in models remain ice free with scant power use.

Nothing quite cheers a wintry day for me like colorful songbirds noisily bustling at our feeders. If you do put up feeders, consider joining in Project Feeder Watch. You can find details on our Wild About Utah website.

Credits:

Photo: Courtesy & Copyright 2008 Jim Cane, Bridgerland Audubon Society, www.bridgerlandaudubon.org
Text: Jim Cane & Linda Kervin, Bridgerland Audubon Society

Bird Recordings Courtesy and Copyright Dr. Kevin Colver, WildSanctuary, Soundscapes, https://wildstore.wildsanctuary.com/collections/special-collections

Additional Reading:

Project Feederwatch, Cornell Lab of Ornithology, https://feederwatch.org/

How to Attract Birds to your Yard, All About Birds, Cornell Lab of Ornithology, https://www.allaboutbirds.org/Page.aspx?pid=1138

The Great Backyard Bird Count, Birdsource.org, https://www.birdcount.org/

Creating landscapes for Wildlife — A Guide for Backyards in Utah, A production of the Utah Division of Wildlife Resources, Utah State University Cooperative Extension Service & Department of Landscape Architecture and Environmental Planning, https://wildlife.utah.gov/pdf/landscapingforwildlife.pdf

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A New Winter Coat

Snowshoe Hare Summer Coat
Lepus americanus
Photo Courtesy US NPS


Snowshoe Hare Winter Coat
Photo Courtesy USDA Forest Service

Hi, this is Mark Larese-Casanova from the Utah Master Naturalist Program at Utah State University Extension.

November is the time of year in Utah when the weather takes a quick turn from autumn to winter. As the line of snow from occasional October storms creeps further down the mountains, I’m inspired to bring wool sweaters and down jackets out of storage. It’s easy for us to simply wear extra layers, but what about the animals that live high in the mountains, where winter set in weeks ago?

While some mammals are cued by their internal clocks to begin sleeping the winter away, many brave creatures prepare to spend the winter searching for food. Being active in the cold requires a warmer coat, just like it does for us. The reduced amount of daylight in autumn triggers hormones that cue many mammals to grow a thicker and warmer fur coat.

Some mammals, such as weasels and hares, counter the onset of winter by ‘changing’ the color of their fur from brown to white. For instance, snowshoe hares grow long, white guard hairs that cover their brown fur in winter. The snowshoe hare benefits from this thicker, white fur not only by retaining heat, but also by using camouflage to hide from its many predators.

Surprisingly, white fur also helps insulate. It might make more sense for brown fur to be warmer since it is darker in color. But, white hairs, which lack the pigment melanin, have more air spaces that result in greater insulation.

While weasels are predators, there are other animals, including birds of prey, that feed upon them. The winter coat of the ermine, also referred to as the short-tailed weasel, is entirely white, except for the black tip of its tail. When an ermine runs, the tip of its tail swings wildly, drawing the attention of a predator away from its body to its expendable tail.

The timing of change from brown to white fur in autumn is critical to survival. An early snow can create a white backdrop for a snowshoe hare that is still brown, likely increasing the chance of predation. Conversely, a lack of snow late in autumn can make a snowshoe hare that has already turned white stand out like a sore thumb.

The number of days with snow on the ground has been decreasing in mountainous areas, and predation of snowshoe hares has been highest in spring and autumn. In some areas of the country, such as the Cascades and Olympic Mountains, snowshoe hares are mottled white and brown year round, or never turn white in winter. Comparing these populations to others across the West will help us better understand how animals, such as the snowshoe hare, are able to adapt to our changing climate.

For Wild About Utah, I’m Mark Larese-Casanova.

Credits:

Images: Courtesy US NPS & USDA Forest Service
Text:     Mark Larese-Casanova, Utah Master Naturalist Program at Utah State University Extension.
Additional Reading:

University of Montana (2009, February 24). Climate Change Hurting Hares: White Snowshoe Hares Can’t Hide On Brown Earth. ScienceDaily. Retrieved November 22, 2011, from https://www.sciencedaily.com/releases/2009/02/090224220347.htm

Rust, C.C., R. M. Shackelford, and R.K. Meyer (1965). Control of Pelage Cycles in the Mink. Journal of Mammalogy, Vol. 46, No. 4 (Nov., 1965), pp. 549-565, https://www.ncbi.nlm.nih.gov/pubmed/5838224

Fraley, J. (2006). Snowshoe Hare: Lepus americanus. Montana Outdoors Portrait. Montana Fish, Wildlife, and Parks, https://fwp.mt.gov/mtoutdoors/HTML/articles/portraits/snowshoe.htm