Last Saturday 3 intrepid young families joined us for a morning with the Stokes Nature Center slipping and sliding along a canyon trail to discover animal and plant adaptations to survive the winter.
We marveled at the American dipper as it enjoyed plunging in icy water hoping to capture its prey. The dipper remains dry due to a super-sized uropygial gland used for waterproofing its feathers as it preens combined with a thick layer of super isolative fur like feathers. Its temperature actually drops in extreme cold reducing radiated heat loss.
Water reptiles and amphibians were in deep sleep in their mud cocoons. They manage winter through slowing metabolic processes which greatly reduces their need for oxygen, nutrition and waste elimination. What little oxygen needed can be absorbed through their skin without breathing.
Animals such as bears can go into an alternate, light hibernation state called a torpor. Torpor is like hibernation, but in this condition, the bear can be awakened easily. I was reminded of this fact from a friend tagging bear cubs in Book Cliffs of eastern Utah. She would enter the bear din very gingerly trying not to awaken a grumpy mom! Ground squirrels are also among animals who torpor, however they shift between hibernation, torpor, and being awake.
The common poorwill, an uncommon bird in Utah Mountains, is the only bird that goes into true hibernation. It hibernates during extreme temperatures — when it is either too hot or too cold — and at times of food scarcity. The common poorwill can even hibernate while they are incubating eggs, proving to be not only a true survivor, but also a riveting multitasking animal.
Snow is an excellent insulator where many of our more active animals spend most of their winters in subnivean (beneath the snow) environments. Mice, voles, and shrews retreat here for protection from cold temperatures, bitter winds, and hungry predators. Food is right at hand: grass, leaves, bark, seeds, and insects are free and unfrozen. These tiny mammals create long tunnel systems complete with air shafts to the surface above. Perhaps you’ve seen the pocket gopher tunnels revealed as the snow retreats- a snaking ridge of soil creating some interesting, artistic patterns.
It takes only six inches of snow for mice, voles, and shrews to have a sturdy roof over their heads and roomy living quarters below. Add another two inches and the subnivean zone remains within a degree or two of 32°F, regardless of the temperature and weather conditions in the outside world.
Living under the snow is not without risk. Owls can hear mice and voles running around underground from thirty yards away. With balled-up feet, they crash through the top crust and all the layers of snow to grab their prey. Foxes and coyotes detect by scent. With an acrobatic pounce, these predators will dive right in for their meal. Suffocation is a hazard for those left behind in a collapsed tunnel.
So what happens to these little critters in a low snow-no snow winter becoming more common in a changing climate? I’m guessing a much higher rate of mortality which may not bode well for those bigger critters- hawks, owls, fox, coyote, etc., who munch them.