Winter Adaptations

As I deal with a pair of winter storms over the course of writing this blog, I am sitting cozy and warm inside my house. How do animals, who don’t live in houses with central heating or furnaces make it through the winter? Some migrate to warmer areas, but those that stay behind have special adaptations that help them cope with the cold and snowy weather.

Many animals go into mega energy conservation mode during the winter because not only do they lack heating systems for their homes, they also lack supermarkets that carry a reliable food source. For herbivores, their plant-based food supply is either dormant (and not producing the nutritious shoots they crave), or buried under snow and ice. Whether warm-blooded or cold-blooded, both need to keep warm to survive. Cold-blooded critters rely on the sun’s radiant heat to stay warm, and this is a challenge when it’s cold outside and the sun isn’t reliable. Warm-blooded critters metabolize food to stay warm- they eat much more than cold-blooded ones. One option to keep up metabolism is to spend energy to search for scarce food. But there are other ways to get by.

Hibernation is probably the first coping mechanism you think of, and it’s quite common in the mammal world. Bears do it, bats do it. What is it, compared to normal sleep? When you go to sleep your body slows down. Breathing and heart rate go down and metabolism slows, and your body temperature cools a bit. Hibernation is an extreme version of this. But to be asleep for weeks or months on end requires quite a bit of sustaining energy, even if bodily functions slow to the point of nearly stopping. That’s why bears go on a feed frenzy each fall, gorging themselves on spawning salmon or high-energy moths if they live in the right place.

NPS graphic of a hibernating bear

For those that don’t hibernate, finding food is a priority. Arctic foxes and snowshoe hares both grow a white coat for snow camouflage. The fox uses its camo to hunt; the hare uses its to avoid being eaten. The bison uses its large head as a snowplow to uncover buried vegetation. Ever wonder what that large hump at its shoulder is? Extra muscles to support all that head.

Snowshoe hare (Montana Fish, Wildlife, and Parks)

Bison plowing for food (NPS)

Preserving body heat is a great way to maximize caloric efficiency. The thick fur coat of a muskox traps body heat. Blubber insulates whales, seals, and walruses. Polar bears have black skin that absorbs heat, and their fur traps heat, including body heat that they radiate.

Walruses (US Fish and Wildlife Service)

Ease of mobility is also an efficiency adaptation. Lynxes and caribou both have large feet that act as snowshoes, making it easier to get around so they burn fewer calories doing so.

Check out the foot on that lynx! (Natural Resources Research Institute)

These are just a few of the many adaptations that make survival possible for warm-blooded mammals. There are others, and there are also adaptations for cold-blooded animals (like a frog with antifreeze in its blood) and plants too! Enjoy your heater for the rest of the winter! 

Still Hungry, Bearly Full

Time for a look at one of America’s most charismatic critters, the bear. We have three bear species (not Papa, Mama, and Baby). They are the black bear, which is the most wide-ranging, the grizzly, and the polar bear.

Grizzly bear (UNAGB)

Polar bear (Scientific American)

Black bear (ABC News)

Bears are omnivores, meaning the eat plant and animal products. Always the opportunists, they won’t hesitate to raid a dumpster or campsite. One of the reasons wildlife managers discourage you from feeding the bears is because they will learn to equate people with food. Once bears start looking for people, problems arise.

Processed bear food

Bears are very large, so it takes quite a bit of food to keep them going. Grizzlies and black bears sleep through most of the winter (called torpor- not all of them hibernate all the way through) and that helps them by not eating when food sources are most scarce. The rest of the year, they are eating to make up for their long winter’s nap. Sometimes bears will strip the bark from a tree and power up with sugary sap when they first emerge from torpor.

Tree sap breakfast nook

From then on, they are pretty much fattening up for the winter. In the Northwest (including Alaska and Pacific Canada), bears get a big boost of tasty fat in the form of salmon, which return to spawn just before bear bedtime. In the Rockies, an infusion of migratory moths makes an easy treat for the bears that know where to look. The salmon and moths giving the bears a goodnight kiss is another example of nature’s perfect timing.

Photo credits: 

Grizzly: United Nations Association of Great Boston https://unagb.wordpress.com/tag/grizzly-bears/

Polar bear: Scientific American https://www.scientificamerican.com/article/polar-bears-diverged-from-brown-bears-fairly-recently/

Black Bear: ABC News http://abcnews.go.com/US/florida-black-bear-takes-break-rests-hammock/story?id=23940797

Some days you're the windshield, some days you're the bug

I was driving home from work last week and noticed what appeared to be a moth, judging by the face, stuck on my windshield wiper. The wings were flapping wildly in the breeze. When I got to a red light, they didn’t look like moth wings and I could see the legs were moving. This bug was still alive and trying to escape. I pulled over at the next chance I could so I could free this mystery critter. I wasn’t sure what I was looking at (or how it was still alive; half its body was smashed) until I happed upon it in a book I was flipping through. It was a caddisfly.

What is a caddisfly? They are an order of insect (Trichoptera) that is similar to moths and butterflies (order Lepidoptera) with hairy heads and larval cocoons. However, the caddisfly larva lives underwater and makes its case from material in the stream, such as small pebbles, held together by silk that it secretes from glands. And unlike moths, the wings of a caddisfly are not covered in fine scales (the “powder” that gets on your fingers if touch a moth or butterfly’s wings).₁

Caddisfly larva, with and without case
South Dakota Game, Fish, and Parks

Adult caddisfly
Pennsylvania Fish and Game Commission

Caddisfly larvae are a favorite meal for aquatic critters like salmon. An entire cohort of caddisflies emerges from their cases at once and moves toward the surface to begin a brief (two weeks) adulthood. It becomes a veritable smorgasbord for fish. Caddisflies are also an important indicator species. An indicator species is one that’s absence or presence is an indicator of the general health of an ecosystem. Caddisflies are sensitive to water pollution, so an abundant population of caddisflies is a sign of a healthy stream.2

Caddisfly larvae, Mashel River

1 From Insects_, Their Natural History and Diversity by Stephen A Marshall

2 From The Northwest Coastal Explorer by Robert Steelquist