Deer, foxes, rabbits, etc. are all warm blooded mammals that regularly experience sub-freezing temperatures that would kill humans in a matter of hours. How do they survive?
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“Warm blooded” means that they generate their own heat, typically in excess. They are their own little space heaters.
They also all have fur that’s very good at insulating them, a hide much thicker than our skin that’s also a good insulator, and natural oils that do a good job of making their fur rather waterproof. This helps keep the heat that they generate in their bodies.
These animals also have a seasonal coat. My dog is shedding like mad right now as she replaces her summer coat with her winter coat. In the winter they have thicker coats that are better at retaining heat.
Related to the seasonal coat is normal acclimatization. All animals are capable of acclimatizing to an extent, and northern mammals are pretty damn good at acclimatizing to cold winters. Their metabolism changes, their fur and hide changes, their circulatory system adapts.
It’s literally the same for us by the way. We acclimatize to hot and cold conditions, but a lot of our natural acclimatization is hindered by the fact that we spend most of our time in climate controlled dwellings, especially in the winter. When you’re warm all day in a heated office and warm all night in your heated home, it’s hard to acclimatize yourself. The more time you spend outdoors in the cold though, the more resilient you become to it. The exact same is true for working in hot conditions. You’re more likely to experience heat stress if you just jump right into hot work one day compared to someone who gradually spends more and more time working in the heat and builds a tolerance to it. Because we coddle ourselves indoors, we suffer outdoors. However if you spend more time outdoors, the winter won’t be as bad.
Most of these mammals also dig dens for shelter. Yes, even deer. This gets them out of the wind, so that when they settle down for the night they can stay mostly out of the wind and their thickest fur on their back can insulate their topside while their underside is tucked away and cozy. You’ve probably also noticed how neatly most animals can curl into a ball. Way better than us. This lets them fit into smaller dens and protect more of their bodies from the elements.
Lastly, diet and metabolism. Many of these animals tend to store fat as they acclimatize to colder weather. They were outside all autumn, which means they were able to adapt gradually. Some of these animals have a rather steady supply of food through the winter too. Many of these animals are just *always eating*. They need the constant supply of energy to stay warm. When they’re not eating, they’re resting for as much of the day as possible to conserve energy.
Winter food sources are a major, if not the biggest limitation to a species local population. When deer run out of food to eat, they freeze to death, and humans can have a devastating effect on this. If an area that used to be able to support 1000 deer gets ploughed for human development and can now only support 500, the deer don’t get the memo. It’s not like 500 deer move out in October so that the other 500 can eat through the winter. They all stay, and they all try to survive through January, February and March. They end up running low on food sources halfway through the season though and then they start scattering looking for more food. Many die. Because 1000 deer can’t go two months without food, the population can end up collapsing and far more than 500 die off. The survivors are ones who left for more food and were able to scrape by. The region ends up being left with less than 100 deer. This is actually why hunting can be important. If we keep track of deer populations through the year, then we can sell 500 deer tags. Hunters go out and get their 500 deer, and the remaining 500 actually have enough food to get through the year, and the region keeps 500 deer.
We wouldn’t have to hunt if we didn’t drive off their predators too. But we tend to not not be compatible with wolves hanging around developed areas, so they’re the first to get scared off.
When we wrap it all up, wild animals have developed the evolutionary traits that they need to survive the winter. So long as we don’t throw things out of balance for them (like their food sources or predator population), most of them will find enough to eat to keep their bodies warm.
Humans on the other hand gave up most of those evolutionary traits millennia ago in favor of big brains, opposable thumbs, and communication. This lets us form social networks or “tribes” that work together to achieve goals, create and build solutions to our problems (coats, huts, etc), and most importantly of all, create things that benefit more than one generation. That’s not only to say that building a house keeps the next generation warm. Our communication also allows one person to discover or invent a technology, and our entire society or civilization can benefit from it. We have dens and thick coats too, we just had to make them ourselves.
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