Reindeer Adapt to Summer Heat by Changing Their Cud

Reindeer are amazing animals that have adapted to live in the harsh conditions of the Arctic. They have many remarkable features, such as hollow hair that insulates them from the cold, eyes that change color with the seasons, and antlers that grow and shed every year.

But did you know that reindeer also have a unique way of sleeping? Reindeer sleep while chewing their cud, a strategy that may help them in the summer.

What is Cud and Why Do Reindeer Chew It?

(Photo : OLIVIER MORIN/AFP via Getty Images)

Cud is a ball of partially digested food that ruminant animals, such as reindeer, cows, and sheep, regurgitate from their stomachs and chew again.

This process helps them break down the tough plant fibers in their diet and extract more nutrients. Reindeer mainly eat lichens, mosses, grasses, and leaves, which are low in energy and high in cellulose.

By chewing their cud, reindeer can increase their digestion efficiency and survive on less food.

Reindeer usually chew their cud when they are resting, but not sleeping. They can spend up to eight hours a day ruminating, which is more than any other ruminant.

However, a recent study found that reindeer also chew their cud when they are sleeping.

The researchers observed the behavior of reindeers in a semi-natural enclosure in Norway and recorded their sleep patterns using EEG electrodes attached to their heads.

They found that reindeer slept for about four hours a day, mostly during the daytime, and that they chewed their cud during 77% of their sleep time.

Also Read: Reindeer Have Unique Eyes That Help Them Find Food in the Winter, New Study

How Does Chewing Cud Help Reindeer Sleep?

The researchers speculated that chewing cud while sleeping may have several benefits for reindeer, especially in the summer.

One possible benefit is that it may help them regulate their body temperature. Chewing cud generates heat, which may be useful for reindeer in the winter, but not in the summer, when the temperature can rise above 30°C.

By chewing cud while sleeping, reindeer may be able to dissipate some of the excess heat through their mouths and noses, and avoid overheating.

Another possible benefit is that it may help them cope with the long periods of daylight and darkness in the Arctic.

Reindeer live in a region where the sun does not set for several weeks in the summer and does not rise for several weeks in the winter.

This can disrupt their circadian rhythms, or internal body clocks, which normally regulate their sleep and wake cycles.

Reindeer have a unique ability to switch off their body clocks and adjust their sleep patterns to the environmental conditions.

By chewing cud while sleeping, reindeer may be able to synchronize their sleep with their feeding, and avoid wasting time and energy.

A third possible benefit is that it may help them avoid predators and parasites. Reindeer face many threats in the wild, such as wolves, bears, and eagles.

They also have to deal with swarms of mosquitoes and flies that can transmit diseases and cause stress.

By chewing cud while sleeping, reindeer may be able to mask their sleep and appear more alert and active. This may deter potential attackers and reduce the risk of being bitten by insects.

Reindeer are fascinating creatures that have evolved to survive and thrive in one of the most extreme environments on Earth.

Their sleep habits are just one of the many examples of their amazing adaptations. By studying reindeer, we can learn more about their biology, ecology, and behavior, and appreciate their role in the Arctic ecosystem.

Related article: Reindeer Shrinking in Size, Starving Due to Climate Change