Deer are one of the most critical species in North America, and they have adapted well to survive winter.
Deer have thick, oily fur which repels snow and rain, and their footpads harden in winter. Caribou can change the temperature of their legs to low levels so that they retain body heat. Deer will seek shelter in blizzards and warm up on south-facing slopes on sunny days.
Please keep reading if you want to know how the deers deal with their wintery conditions.
1. Adapting Their Eyes
Caribou can alter the color and structure of their eyes according to the seasons they go through. They do this to adapt to the imminent cold.
The changes in the reflective membrane behind the retina are called the tapetum lucidum. The membrane allows the animals to adapt their eyes to see in the dark or the light.
The temperature, the atmospheric pressure, water and food, and the possibility of refuge are fundamental issues that influence the reindeer and their habitats. During the cold, they must be able to achieve all these aspects to survive.
Due to the positioning of their eyes, deer have a massive field of view of 310 degrees, compared to a human of 180 degrees. Deer can also see ultraviolet light, although they can only see two colors. Scientists believe the deer can see blue light and light between red and green.
Their enhanced field of vision comes from the eyes on the side of their head, enabling them a panoramic view.
Researchers confirm that UV vision can be helpful for deer in distinguishing food and predators in heavy snow. For example, lichens would be black in the eyes of deer in North America.
2. Nose To Regulate Temperature
The British Medical Journal magazine took the time to study deer and researched the reindeer’s nose. They concluded that the red nose is not just a story created for Rudolph.
Thanks to infrared light and a thermal camera, scientists could see the noses of the deer shine with a red or pink pigment. This information helped a considerable amount in determining how deer breathe during the winter.
Can Ince, a medicine professor, studied the microcirculation of deer and realized that the nose of this species is full of many tiny blood vessels. These blood vessels transport the red blood cells to discharge oxygen in the tissues that need it most.
Deer live in freezing temperatures, with some environments even reaching -40ºC. Even in a cold climate, deer must keep their vital organs at an ideal temperature. Researchers decided to see how the deer’s temperature changed when they were exhausted.
The highly vascularized nose of the deer was found to regulate the temperature of the animal’s brain. The nose acts as ventilation to the brain. The blood vessels are filled and emptied to a rhythmic flow that had never been observed before.
The deer’s noses have smaller vessels and a 25% greater density in those smaller vessels than those of humans. Vascularization helps keep the temperature of the organs in good condition and heat the air that enters the body.
This process makes it much easier for deers to emit the sounds they make as they warm the air that comes in, even during the winter. This is how their throats do not get damaged, and they can keep their voices for the mating season.
A deer’s red nose works like an air conditioner for the air they breathe. The nose also condenses the water in the mood to conserve moisture. The moisture in the mucous membranes is in the area of the face and connected to them.
3. Skin and Fur For Insulation
Skin is an excellent protection method and helps deer survive. The deer’s whole body is covered in fur, giving them the protection they need during winter.
The skin of the deer has an essential function for the animal. Skin gives protection against the cold temperatures that the winter brings. This is why the skin and fur of deer are so desired to make coats for big fashion houses.
The deer’s fur tends to be brown with some touches of black and can change throughout the seasons. The skin is thick with layers. Every day it grows more, and it is renewed like human hair. The skin can provide the animal with reliable protection during heavy snowfall.
Their fur is thick so that they can withstand winter snowfall. The skin works as a protective barrier against the cold, and the snowflakes melt on the skin. Some species have longer coats than others due to more extreme temperatures.
The primary function of the hair is to provide heat to the skin underneath. This keeps the organs from freezing in sub-arctic conditions.
The fur traps the air to keep the body insulated and acts as a flotation device when it enters the water. Deer are strong and fast swimmers. When they migrate, they travel through steep terrain and swim through large, icy rivers.
The deer’s winter coat absorbs more sunlight and traps more body heat than the fur they use in summer. Their winter coat allows them to enter winter in good shape.
4. Digging For Food
Deer use their antlers to dig for food in the winter months. Their antlers have a primary function: to help them reach winter food. They look for lichens that function as the deer’s energy source in late winter.
During winter, plants that deer usually eat fall on the ground and are buried. Covered by the snow, they may perish without being found and can also freeze on the floor. Deer must find the plants quickly and use their antlers to aid them.
Deer will tilt their heads and begin to dig into the snow to get food. Food is one of the essential ingredients for the species, and there is less food in winter.
Getting food from the ground is tricky when the antlers are not fully grown. However, deer will help each other to reach natural food sources when they are young. When they are adults, getting enough food is down to the individual. The longer the antlers are, help the deer to get food quickly. By doing this quickly, they are not expending energy.
5. Pads On The Feet
Deer have pads on their feet; during the winter, the pads adapt to different conditions. The pads harden, allowing them to use them like an ice pick. The deer use this to cut the surface of ice and snow, keeping them steady on their feet.
Together with their antlers, the hooves are one of the main ways deers survive the winter. Deer use their feet to excavate food that is buried under a foot of snow or more.
6. Keen Sense Of Smell
Deer have a keen sense of smell that is very useful for finding food during the winter season. Deer are herbivores and only eat plants. Favorite foods include ferns, sprouts, herbs, mosses, fungi, and leaves. An adult deer can eat four to eight kilos of vegetation per day.
Deer have an excellent sense of smell, which helps them to find food under the snow. They will first try to locate the food with their keen sense of smell.
When they have found the food by smell, they will then start digging. They will do this by using their hooves and their antlers. Their keen sense of smell can tell them how far down the food is in the deep snow.
Deer have such a fantastic sense of smell that they can find lichens below the snow. Lichens are full of energy and helpful in heating the blood of deer. Also known as deer moss, lichen can be buried up to 60 cm (2 ft) below the snow.
With their excellent sense of smell, deer can quickly and efficiently find the lichen, even buried so deep in the snow. Their keen sense of smell is one of the main ways deer survive winter.
7. Controlling Body Temperature
During winter, caribou have adapted to survive the cold by controlling their body temperature. When they feel extreme temperatures, it’s not uncommon for deer to adjust their internal temperature.
Lowering the temperature of their legs enables the body to redistribute the heat. The body prioritizes sending heat to the principal organs of the deer’s body. The heat is sent to the heart, lungs, face, and body.
Caribou are endothermic, so warm blood is circulated down to the feet to stop the legs from freezing.
8. Safety In Numbers
Deer are animals that travel in a herd. The deer herd is very close and always protects each other, with the strong protecting the weak. Deer are very social animals and do not like to be left alone. The unity in the pack helps them to survive the winter weather.
During winter, snowstorms make it challenging to see and locate other deer. To stay as a herd during these times, the deer must adapt.
The method they use is through sound waves. When they are walking, deer will make sounds with their knees. The sound of the knees tells other deer where the rest of the herd is.
These sounds work exceptionally well in blizzards, where the deer cannot see each other. By using their large ears, they can hear these sounds over the storm.
Deer have a more extensive range of hearing than humans. Although we can hear every bleat and grunt deer make, they hear higher frequencies than us and make many more sounds.
Deer can hear up to frequencies of at least 30,000 hertz. Humans can only hear up to about 20,000 hertz. This enables them to be able to hear higher-pitched sounds better than us.
9. Fat storage
Deer begin to prepare for winter in the months before. They make psychological and physical changes long before the temperatures fall.
They begin by storing fat around the internal organs and under their skin, providing energy reserves. This helps to protect them for the next few tough months. Deer will eat much more during summer and fall to enable the fat to build up for the winter.
The deer start to create internal fat that helps protect the main organs, including the heart, lungs, stomach, and liver. They will then generate further fat under the winter coat.
As winter arrives, fat works as a natural heat generator that helps the deer be comfortable even in freezing temperatures.
10. Activity Slows Down
Deer have an excellent talent for running, and they are a very active species. However, this changes drastically when they enter the cold winter season. They adapt their lifestyle to a slower pace, knowing the new shortage of food they will face.
During the winter, deers can not consume 8 kg of food per day, as they did during spring or summer. As the snow falls, this covers the few plants, and with little growth, they have to find new ways to adapt.
Deer do this by decreasing their activity. When winter approaches, deer will stop running and traveling long distances. This gives them the energy to survive throughout the winter with the minimum amount of food they eat.
The body of the animal fulfills the main vital functions only. These are the heartbeat, breathing, digestion, and controlling body temperature. Any other activity they want to perform can not be done since the body is at minimum power. Deer keep their functions intact to run or perform any activity that involves a significant expenditure of energy if needed.
When the winter is over, and with an abundant supply of new plant matter plentiful, the deer return to all the physical activities they did before; physical activity keeps their legs from atrophy, and they can burn off any excess fat they have left in the winter months.
Although deer have many ways to protect themselves from cold, they also need good to find a good place to shelter. This must be a comfortable place where they can take cover when the weather is very bad. Deer, during winter, tend to seek refuge in coniferous stands.
These areas are much sought after by deers because they are an ideal refuge from the conditions. These stands consist of firs, spruces, pines, and larches. They form a uniform stand with low shrubs beneath, making an excellent winter location for the deer.
The wind speed in the coniferous stands is reduced, and snow accumulates on the trees. This provides a much better cover than a field would. As more snow accumulates in these spaces, the deer maintain a higher temperature at night. This helps them stay warm and sleep better.
The shelters they choose are not far from where they usually live in other seasons. They typically spend the nights in their burrows, trying to warm up, using the herd’s warmth. They also take advantage of the ground with thermal cover from the blanket of snow. Once they wake, they go out to look for food.
12. Winter Diet
Depending on their location, some deer change their diet for winter survival. Deer can change their diet from green plants to nuts and woody plants. They look for ends of hairy branches or jagged scars on the trees where other deer have used their lower teeth to tear off limbs.
These trees help them accumulate fat as they consume approximately five to nine pounds of food daily. Deer use this fat reserve during the winter to supplement their food intake. They can lose up to 20 percent of their body weight before spring.
Deer understand there will not be as much food during this time of year. The lack of food is why they will eat as much as possible in the fall.
By storing enough energy, deer are ready going into winter. Although their food supplies are lower in the winter, deer will not need to eat as much as they have this energy reserve.
Among the food that deer can eat is white cedar, which, although not the most nutritional tree for the deer, is easy to digest. Deer know which foods are easier to digest and which foods to avoid, and they will do this until starvation becomes a realistic possibility.
Deer choose foods that are easy to digest in the winter. Due to their metabolism decreasing, digestible food is preferred. By choosing easier-to-digest plants and trees, the deer do not have to expend the same energy to digest heavy meals.
Deer are herd animals and do not function well when alone. When groups of deer assemble, they protect each other, and it is common to see a group of deer looking in different directions, watching for predators.
If a predator is discovered, a tail swish serves as a warning signal to the rest of the herd. This way, all deer in the area can be alert and protect themselves from predators.
Deer will fight to protect themselves and will do what they can to protect themselves and the herd. They may kick and bite to escape predators.
14. Using The Sun
Deer use the sun in winter to help them survive. Deer look for slopes oriented to the south, predominating those towards the southeast. These areas are where you will see the highest numbers of deer. West-facing slopes may also receive some deer migration activity.
South-facing slopes receive the most sunlight throughout the day, making the area more attractive. Gaining more daylight produces more vegetation, so deer have more opportunities to eat during the winter.
15. Exerting Minimum Energy
One of the deer’s main tricks is not doing much physical activity in winter. Deer can sit for long periods during a severe storm without moving for days. At this time, they do not even eat. They make this possible by depending on the reserves of fat that they have created during the fall.
They hunker down in thick forests and woodlands where they can remain hidden from predators and find shelter from the cold and windy weather.
The lack of physical activity leads them to use the minimum energy. This is why, even if they do not eat well enough in winter, their body will always have the power to assist with vital functions. They are known to consume large amounts of food before the winter season so that they have enough stored energy reserves to last them until springtime.
During this time, they also reduce their activity levels and lower their metabolism, which helps them conserve energy while they wait out the colder months.
Deer have oil-producing glands in the skin that help the hair repel water, which is especially valuable in the snow. These oil droplets are similar to the cells in human hair that prevent snowflakes from melting in your hair. If the cold rain and snow reached the skin under the fur, this would likely freeze the animal.
If these glands did not exist, all the snow that falls on them would land without a problem until their skin causes them to cool down and lose the body heat they are trying hard to preserve. The oil-producing glands are distributed throughout the skin, with some studies revealing that they can be found in hair follicles.
17. Lowering The Heart Rate
Due to their large bodies, energy can be used up very quickly. One adaptation the deer has is the direct correlation between the heart rate and the deer’s body temperature.
When things get tough during the winter, the deer lower their heart rate and body temperature, reducing energy expenditure. The resting heart rate of a deer is 40 to 50 beats per minute. Humans have resting heart rates of between 60 and 100 beats per minute.
It does not matter if the deer eat too much or too little to store energy; the heart rate slows down during the winter. The heart rate, which is generally 65 beats per minute in spring, lowers to as much as 40 beats per minute in winter.
The winter coat keeps these animals warm even in temperatures of -30º Fahrenheit. The highest quality sleeping bags only protect people in cold temperatures of zero degrees. This makes a deer’s winter coat much more protective than today’s most advanced sleeping bags.
Every hair in a deer’s winter coat is hollow, so the air is trapped inside, allowing them to retain heat. This heating method has been used in cold-weather clothing, bedspreads, and window panes.
All deer need water to survive, but they can meet their water needs in a few ways. Deer can get their intake from bodies of water in their habitat or from consuming the foods they eat. Through digestion, water is released from the food that they eat.
During the winter, deer do not feel as much need to drink water in summer or spring. This is convenient since freshwater freezes in winter conditions.
Although they do not need to drink as much in winter, deer will consume water at every opportunity. During winter, deer can recycle their urine and dry their feces internally to conserve water.
Deer can face hypothermia if they fall into icy water or get too cold. Like any other living animal, they will eventually succumb to hypothermia.
Deer can handle much colder temperatures before hypothermia is a concern. They can swim for a few minutes until they get out of the water.
The reason why the cold water does not affect them is due to their skin. The skin acts as a flotation device when they begin to swim, either voluntarily or accidentally.
Hypothermia can occur if they last more than five minutes in the water. After five minutes, they will lose all body heat no matter how thick their fur and skin are.
Bryan Harding is a member of the American Society of Mammalogists and a member of the American Birding Association. Bryan is especially fond of mammals and has studied and worked with them around the world. Bryan serves as owner, writer, and publisher of North American Nature.