As winter blankets Michigan in snow and frigid temperatures, white-tailed deer employ a complex array of survival strategies to cope with the harsh conditions.
During the winter, food becomes scarce, and snow covers much of the vegetation that deer normally consume.
To cope, white-tailed deer change their diet from green plants to woody browse. They consume twigs, buds, and bark from trees and shrubs such as aspen, maple, birch, cedar, and hemlock, according to the Minnesota Department of Natural Resources.
During the abundant autumn months, deer actively build up fat reserves for the coming winter. This fat accumulation provides essential energy during times when food intake is limited.
Osborn and Jenks’ study, published in the Journal of Mammalogy, discovered that these fat stores are critical for winter survival.
To maximize their fat reserves, deer reduce their metabolic rate and overall activity.
“Their winter coats of hollow hair that conserve body heat, along with decreased movement and a slower winter metabolism that requires fewer food resources, help most deer navigate winter in relatively good condition,” the state’s Department of Natural Resources says.
According to the Minnesota DNR, winter affects deer differently depending on their age and sex. Fawns are typically the most vulnerable due to their lower fat reserves.
Adult males, or bucks, are also at greater risk because they may enter winter with depleted energy stores from the breeding season. Adult females, or does, typically have higher survival rates during harsh winters.
“Deep snows have a far greater effect on deer survival than cold temperatures because deer must use more of their energy reserve to move through deeper snow,” the state of Minnesota’s DNR says.
White-tailed deer seek out thermal cover, which consists of dense coniferous forests and provides shelter from the wind and lower snow depths. The Maine Department of Inland Fisheries and Wildlife notes that these areas, known as deer wintering grounds or “yards,” are critical for survival.
Deer congregate in these yards in groups, increasing their chances of survival. Grouping behavior improves predator detection and leaves packed trails in the snow, making movement more energy efficient.
Dense conifer stands, hardwood and conifer swamps, brushy areas, and thick grasses offer protection from wind, cold, and snow.
According to the Michigan United Conservation Clubs, mature conifers and hemlock trees are particularly important because of their dense canopies, which can slow strong winds.
The National Park Service describes how deer grow a thick winter coat made up of hollow guard hairs that trap air for insulation. This coat, combined with dense underfur, helps to retain body heat. Deer can also restrict blood flow to their extremities, which reduces heat loss.
Deer have devised methods to access food beneath the snow. According to Michigan State University Extension, they use their hooves to paw through snow and find buried vegetation. This method enables them to exploit food sources that would otherwise be unavailable.
According to the National Deer Association, when liquid water sources freeze or are covered in snow, deer may consume snow to stay hydrated. This practice, however, raises metabolic demands because the body must use energy to melt the snow internally.
“It is safe to say that deer require the most water in the spring and summer, when biological and seasonal conditions dictate it.
Fortunately, this time of need coincides perfectly with a period when preferred foods are abundant and water is plentiful,” according to the National Deer Association.
Deer face unique challenges in urban and suburban environments. Habitat fragmentation and increased human presence can cause deer to change their behavior.
According to Cornell University’s Cooperative Extension, urban deer may have less fear of humans and change their movement patterns due to fragmented habitats.
According to the Michigan State University Extension, these deer frequently eat ornamental plants and gardens.
Despite the harsh conditions, Michigan’s white-tailed deer use a combination of adaptations and behaviors to survive winter and emerge ready for spring.