Can animals die during hibernation?

When scientific media and literatures describe the concept of hibernation in mammals, its always as if every single attempt made by every single mammal is successful.

Here’s what the typical text reads like:

“Come winter, the animals transitions into a state of suspended animation and when summer approaches, the animals (must) awaken from their ‘slumber’ and immediately resume their normal activities.

One thing is always left behind. And thats the critical question of whether or not hibernating animals can perish while attempting to do so.

In this article, we aim to bridge this information gap and provide answers (rooted deeply from a comprehensive investigation) to this question, and also discuss lightly on other interesting but related matters.

Can animals die during hibernation?

There are many observed incidents of animals dying during hibernation. These deaths often occur as a result of the animals completely depleting their energy reserves before winter hibernation is over, or, when they are tracked down, dug up from their protective shelters and are eaten alive by their predators.

Animals can perish while hibernating

Hibernation is a state of physiological and physical inactivity that many animals go through during the winter period.

The primary purpose is to dodge the inhospitable climate of the winter season and the severe energy constraints that often accompany it.

True hibernating animals generally record a massive plunge in their metabolic rates, heart rates, breathing rates and internal body temperatures.

Some species like the arctic ground squirrels record a 90% plunge in their metabolic rate which cause their internal body temperature to plummet down to near freezing conditions (less than 40F).

Under these circumstance, animals spontaneously transition into a state of suspended animation and only rouse periodically to defecate, urinate, stretch and sometimes feed from their food cache.

For many animals, entering into a state of hibernation presents a safe and effective strategy for surviving through the harsh conditions of winter, for others however, it’s a risky maneuver that is fraught with uncertainties that can perhaps lead to their unanticipated demise.

A death sentence!

Although not very common, animals occasionally perish in their hibernation chambers as a result of two main occurrences.

First happens when they are tracked down, dug up “unconscious and oblivious” from their hibernation chambers and consumed alive by their predators, and second happens when they run out of energy reserves, either of food cache or subcutaneous fat, prerequisite for maintaining their hibernation activities.

For instance, hibernating animals need energy to maintain their markedly reduced physiological activities alongside their compulsory periodic arousal on a very frequent schedule. 

Prior to entry into hibernation, animals receive some set of external cues that enable their bodies recognize the onset of winter.

Falling temperatures, shortening of days and dwindling food resources among a few others, are some of the external cues that animals receive. In response to these stimulus, they begin preparation by excavating dens and building enough energy reserves that would last them throughout the entire period of hibernation.

Some animals rely on internal stimuli (and some on both internal and external stimuli) rather than strictly on external cues to predict and prepare for the onset of winter.

The denning homes that animals excavate are often built to be inconspicuous and well insulated from the winter surroundings. For denning homes that are too obvious to offer any sort of predatory-camouflage, occupants may end up being excavated (when they are totally oblivious to their surroundings), and eaten alive by hungry predators.

Badgers are known to excavate ground squirrels from their hibernating burrows and prey on them while they’re still unconscious. The great tit bird has also been observed to follow bats to their hibernating chambers (underground spaces such as caves and mines) and prey on them while they’re mid-way hibernating.

Next comes food storage. Animals, depending on how large or small they are, may choose to build energy reserves in the form food cache, fat stores or a combination of both.

Smaller animals usually build food cache, and they do so by collecting their favorite non-perishable food items and storing them up in their hibernation chambers. They rely on these stock pile as their main energy source when they become depleted during hibernation.

Larger animals on the other hand accumulate fat stores, and they do so by becoming extremely hyperphagic months before entry into hibernation, consuming large amounts of food and storing the energy as fat deposits in their bodies.

They rely mostly on these fat reserves to generate energy and be able to fuel their normal hibernation activities. Animals that do both food cache and fat reserve, use their fat deposits to kick start hibernation for the first few months, and then replenish their depleted energy from their stockpile of food reserve.

All hibernating animals require sufficient energy reserve in any of the forms mentioned above to be able to fuel their hibernation conditions throughout winter.

If animals are unable to build enough energy reserves that will last them over the course of winter, their chances of successfully completing hibernation is greatly reduced and are now extremely likely to perish mid-way hibernating.

The reason is simple, when they run short of energy reserve mid-way hibernating, they have no viable means to replenish the depleted energy (since going out to forage in the hunting cold and on an weak and drained out body isn’t really an option), and so are unable to support basic hibernation activities like maintaining low physiological functions and periodically rousing to restore body to normal conditions.

Animals that are more likely to run out of fat energy reserves are late-born juveniles that have trouble gaining sufficient energy reserves for both growth and deposition of pre-hibernation fat stores.



Hibernating animals use up most of their energy reserves during their scheduled periodic arousal. Why they do so isn’t clear yet, but it‘s likely to be a strategy to prevent them from becoming moribund.


Animals that store food cache usually feed to replenish depleted energy during this period. Richardson’s ground squirrel (Spermophilus richardsonii) have been observed to expend about 83% of all the energy that they use up during hibernation when they awoken periodically to regain euthermic conditions.


If individuals were to deposits less the minimum amount of fat stores required for them to fuel their hibernation activities, they would be effectively killing themselves after few periods of arousal. Animals bumble around, stretch and sometimes feed during this period.

Who lives longer hibernating animals or non-hibernating animals?

While death by hibernation is a true and real phenomenon, it seldom occurs with the majority of hibernators.

As a matter of fact, and in contrast to may things we mentioned above, hibernation helps saves millions of species in the wild each and every year. It’s a special and efficient survival tactic to evade the pressing constraints of winter and allows animals to be able to live and see the productive vegetation of spring. 

According to a research published in 2011, hibernating animals are more likely to have a longer life span compared to similarly sized non-hibernators, the increase in survival rate is estimated to be around 15 % or more. The only thing is that hibernating animals reproduced slower, matured at much older ages, and have much longer generation times that non-hibernatiors. [1].

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Cite this Article (APA Format)

Bunu. M. (2020, April 24). Can animals die during hibernation?. Retrieved from

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