Following the rut and entering late winter, all deer voluntarily reduce their daily activity, including basic moving around and even feeding, to slow the burn of those fat reserves until the first green plants emerge in spring. As crazy as it sounds, faced with extreme winter weather and having already lost weight, deer eat less. Even captive deer with unlimited food available reduce their daily consumption and continue to lose weight during winter.
Why? If you think about it, from a survival standpoint and proliferation of the species, relying on the best winters when temperatures are mild and food is abundant doesn’t make a lot of sense because those conditions are rare occurrences. So, deer have adapted to live through the worst winters possible. It’s probably one reason they’ve survived for so long.
However, there is a limit to this strategy and the supply of fat reserves that carry them through winter: time. Researchers have shown that a typical healthy doe begins winter with a 90-day fat supply. Deer can survive almost anything Mother Nature throws at them during those three months. The ticking clock begins winding down in March and is the reason why weather patterns in this month often play the biggest role in winter deer mortality.
If you’re concerned about deer survival, the best thing to do to help them get through the critical last days is break out the chainsaw and provide more of the food they are adapted to eat in winter.
Deer Behavior During Severe Weather
People avoid severe winter environments by simply changing locations to get away from the cold. Even though deer don’t have the ability to go inside or fly south for a few months, they in essence do the same. In general, deer will move to and congregate in areas that provide the best protection from the weather when conditions aren’t favorable, such as seeking shade when the mercury rises.
In winter, this behavior is commonly called “yarding.” In most cases, yarding areas are warmer, less windy and offer better mobility than anywhere else. In much of the country, deer might just bed on south-facing hardwood slopes within their home range to take advantage of the direct sunlight.
Or, in more northern climates, they can search for, travel to and find refuge in “deer yards” that may be well outside their typical home range. These traditional yards are often mature, select conifer stands with dense canopies, and they can be historically important with multiple generations of deer using the same spot.
Less common in white-tailed deer but more common for mule deer are true, long-distance migrations, which allow entire herds of either species to avoid harsh conditions at higher latitudes or elevations during winter and take advantage of high-quality forage during summer.
The Winter Diet Of Deer
Reliable winter nutrition for dee primarily comes from stored fat and water and is merely supplemented with items they consume at this time of year like buds, twigs, bark and dead leaves. Preferred winter forages include shoots of woody browse from small trees and shrubs, the same from a few select coniferous species, and any persistent fruits or leaves. There’s actually not a lot of difference in the nutritional quality of the things they eat in winter; quantity is more important. In fact, the true value is not in the calories but in the creation of internal heat via the digestion process.
Bodies Built for Winter
Perhaps what makes deer the most bullet-proof to severe winter conditions, however, are their physiological adaptations. First is their body size.
The further north a deer lives, the more likely that individual will be larger and have more compact appendages compared to its relatives from a more southern climate. This is called Bergmann’s rule and allows a species to save energy and conserve heat to inhabit inhospitable conditions found at the fringes of its range. The average mature Florida whitetail buck weighs about 150 pounds while in Canada the average is 300-plus pounds, a perfect example of Bergmann’s rule.
Second, deer shed and grow two coats per year, and the one they don in winter is key to their ability to deal with freezing temperatures and precipitation because it carries important thermoregulatory qualities. For example, a deer’s winter coat is five to six times thicker than it is in summer, and it is made up of long, hollow guard hairs and short underfur. This combination insulates deer so well that snow can ride on a deer’s back without melting from body heat.
Finally, deer have a musculoskeletal adaption that allows them to stand in deep snow for days or weeks on end without feeling cold toes. The bottom half of all four legs on deer are composed of a keratin hoof that makes contact with the ground, followed above that by a long carpal bone (basically to what most consider the “knee”) that is encased in tendons rather than true muscle. Tendon is a comparatively poorly vascularized tissue that requires very little blood flow. So, deer can walk through a foot of snow as if they are on stilts.
Though logical in theory, deer do not reduce their metabolism during winter as a winter survival strategy, which is a falsehood that’s been unfortunately perpetuated by writers and even some fellow biologists for decades. The truth is that a deer’s metabolism varies little across the seasons.
Can Deer Freeze to Death?
So, to answer the question: Can deer freeze to death?
No, deer don’t get hypothermia or freeze to death, and they have amazing abilities to withstand insanely cold winters.
That said, you clearly care about their well-being enough that you’ve read this far, and there are ways that you can help the next time we see things go north quickly.
More often, deer die naturally from starvation or predation in winter, and it’s frequently the youngest, oldest and weakest that succumb. Generally harsh winter conditions exacerbate these factors, and these other forms of mortality are seen more where there are short growing seasons, numerous predators, and large expanses of the landscape that lack appropriate yarding structure and/or forest disturbance and early successional cover that is important to deer.
In such places, you can work to improve fawn recruitment and overall herd productivity primarily by adjusting antlerless harvest intensity and improving habitat all year long. These are a deer manager’s quickest and most efficient tools to provide a buffer the next time we experience a bad winter.
About Matt Ross:
Matt Ross of Saratoga Springs, New York, is a certified wildlife biologist and licensed forester and NDA’s Director of Conservation. He received his bachelor’s in wildlife conservation from the University of Massachusetts-Amherst, and his master’s in wildlife management from the University of New Hampshire. Before joining the NDA staff, Matt worked for a natural resource consulting firm in southern New Hampshire, and he was an NDA volunteer and Branch officer. He and his wife Sadie have two daughters, Josephine and Sabrina.
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