by Geoffrey Carpentier
We are nearing the end of our discussion on how animals deal with winter’s cold and snow: having dealt with birds, amphibians, reptiles, a few insects and some aspects of mammalian survival over my last few columns. So, let’s finish up with some specialized strategies, mammals employ, to fight off the cold.
Finding food to sustain the animal begins well before the bad weather sets in. Many herbivores (plant eaters) will create food caches, to make sure they have resources, should it become difficult to find new sources of food when the weather turns nasty. Beavers store extra branches underwater, near the lodge, and chipmunks hide seeds underground, in their pantries. Muskrats need an additional strategy to ensure survival, since they don’t store food like beavers, and instead must forage daily. This can be problematic in a frozen aquatic environment, as they must breathe and avoid predators. To deal with this, they create ‘push-ups’, a pile of mud and plant material which keeps the water open around it and allows an escape route for the muskrat. This mound is large, is often a meter (three feet) in height and becomes their safe access point into and out of the water.
Avoiding becoming dinner is another issue. Mice and voles generally stay under the cover of snow, in what is known as the subnivean zone, in small nests made of plant fibres or human-made materials. Not being seen by predators certainly increases one’s chances of survival but it doesn’t guarantee it. Predators are excellent hunters and use visual, olfactory and audio signals to find prey. Some animals, such as ermine, Arctic fox and snowshoe hares actually change in fur colour to white and blend into the background! This disguises them as a predator but also hides them from those same predators.
While some animals, as noted above, have white camouflage which hides them, others sport coats are much darker. Although they might be more visible to predators, the advantage of the dark pelage for them is, it absorbs heat more readily from the sun which can transfer through the skin, to the inner core of the body, to help it keep warmer.
Many mammals are aquatic or semi-aquatic and this of course will pose challenges, as they enter frigid waters to feed and move between habitats. Two things must be protected: the core body temperature and the appendages. The fur of these mammals (i.e. muskrats and otters) is very dense and well cared for by the animals, as it is essential it function as expected. Constant care and realignment of the outer 'guard' hairs helps keep water away from the skin of the animal. This outer fur is extremely dense. One report I found states, there are over 400,000 individual hairs per square inch in the otter. Wow! The otter is one step further, as they have a unique adaptation in the outer and inner fur layers. In most animals, these are truly separate layers, one lying above the other. However, in the otter, the inner layer is much more densely packed than in most animals and the inner fur is linked, via interlocking scales, to ensure water can’t penetrate the two layers.
Muskrats also have these dense interlocking fur layers, and still utilize a specialized tactic to protect their extremities. Their bodies conserve energy by using regional heterothermia which controls the blood flow to the feet and tail. This adaptation allows the furless body parts to be cooler while keeping internal organs warm. This is akin to how ducks and herons have limited blood flow to their legs and feet.
Finally, other physical adaptations some animals experience include built-in snowshoes, for the varying hares and the Canada Lynx. These are comprised of long hairs on large feet, aiding them to stay on top of the snow. Other mammals, such as Caribou and Mountain Goats have sharp-edged hooves which help grip slippery surfaces as they forage for food.
So, there you have it, animals are an amazing lot, taking advantage of many techniques and adaptations to survive our extreme winter weather conditions.
Geoff Carpentier is a published author, expedition guide and environmental consultant. Visit Geoff on-line on LinkedIn, Facebook and Instagram.
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