Do Squirrels Hibernate?


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Throughout the autumn months, squirrels are hard at work, hiding acorns and other nuts away for the coming winter. Once the hard freezes set in, you may notice fewer squirrels tramping through your yard. So where do these bushy-tailed critters go during the winter? Do squirrels hibernate?

Some squirrels hibernate over the winter, and some squirrels don’t. Ground squirrels must hibernate in order to survive the cold. But tree squirrels only enter a period of relative dormancy and can remain active throughout the winter.

What is hibernation?

Before we find out whether or not squirrels hibernate, it’s important to define the term first. Hibernation is an umbrella word used to describe winter dormancy. While there are some variations in hibernation patterns between species, the basic principle remains the same. Hibernation is the downregulation of the metabolism during the winter to conserve energy.

Food is hard to come by in the winter. The summer fruits are gone and the autumn nuts have all been foraged. There’s not much left over. Plus, it’s cold, so it takes more energy to keep warm. If animals were to continue searching for food, they would be using more calories than they would be able to replace. As a result, many animals would die. 

When you get down to it, hibernation is simply more efficient for some animals than staying awake to endure the cold months. During hibernation, core body temperature falls and the heart rate slows. This prevents them from expending too much energy, enabling them to survive an otherwise unsurvivable winter.

Are there different types of hibernation?

Just because an animal goes to sleep over the winter doesn’t necessarily mean they’re hibernating. When reptiles sleep through the winter, the process is called brumation. It’s classified as a type of hibernation, but it’s not the same as hibernation because cold-blooded brumating animals have different metabolic processes than warm-blooded hibernating animals. For instance, cold-blooded creatures don’t require as much oxygen during their sleep as warm-blooded creatures do.

Some animals may go dormant over the summer months in response to extreme heat and dry conditions. This kind of hibernation is called aestivation. It helps prevent these creatures from becoming overheated and getting dehydrated. 

Brumation and aestivation are both different forms of hibernation. But true winter hibernation is something else altogether. In order to truly hibernate, animals must enter deep sleep. If they’re just dozing, waking up every so often to leave their nests, then they’re not hibernating. They’re going through winter dormancy or winter rest. 

True hibernation can be further divided into two categories: facultative and obligate. Facultative hibernation is a hibernation of opportunity. If the winter season is too cold and if food is too hard to find, animals who utilize facultative hibernation can just downgrade their metabolisms. Obligate hibernation is when an animal must hibernate every winter. Even if the winter is mild and food is still available, these animals sleep through it. 

Now that we know what hibernation is and how it compares to winter dormancy, let’s see how squirrels factor into the equation.

Which squirrels hibernate? 

Ground squirrels are the only species of squirrel that truly hibernate, and they can do so for up to eight months. Starting in September, ground squirrels begin their long winter nap. They are obligate hibernators, so every winter, without fail, they hole themselves up in their burrows and sleep until warmer weather arrives. 

Ground squirrels are well-suited to hibernation because they have the ability to regulate blood concentration. Just as their metabolisms slow down, so, too, do their bodily functions. Their respiratory rate decreases and their caloric output is reduced. Their digestive and urinary tracts also adapt, meaning ground squirrels don’t even need to wake up to urinate and defecate. 

Because they don’t need to wake up to eat, drink, or *ahem* answer nature’s call, they can continue sleeping undisturbed all winter long. Hibernation is a great way for them to manage their metabolisms. Even though their body temperatures still fluctuate throughout the day, they’re able to get all of the fuel they need from their fat stores. 

Tree squirrels, however, simply don’t need to sleep through the winter. These squirrels include red squirrels, fox squirrels, gray squirrels, and flying squirrels. Tree squirrels are much furrier and fatter than ground squirrels, so they’re able to handle cold temperatures better. Because they’re able to stay warm enough, there’s no need for them to hibernate.

How do squirrels prepare for hibernation?

How tree squirrels and ground squirrels spend the winter months may differ, but how they prepare for the winter months is pretty much the same. Beginning in autumn, both types of squirrels start loading up on food.

Squirrels enjoy a wide variety of foods. Plants, nuts, eggs, fruits, insects, and small vertebrates create the bulk of their diet. But as we get closer to winter, barometric pressure falls. And that drop tells the squirrels to turn their attention away from low-calorie greens and put all their focus on gathering nutrient-dense foods instead. Nuts and seeds are packed with proteins and fats that keep squirrels fuller longer. They’re just what these little guys need to gain enough weight to see them through the cold. 

Ground squirrels will eat whatever food they can find in the weeks before hibernation. However, tree squirrels prefer to stash nuts and seeds away so they can come back to them later. Tree squirrels may not even remember where they hide all of their nuts and seeds. And it’s believed their negligence is responsible for planting millions of new trees every year.

Another way that squirrels prepare for winter is by growing thicker coats. As the days get shorter leading up to the winter solstice, there’s less and less sunlight for us to enjoy. This decrease in sunlight directly corresponds to an increase in melatonin production. 

Elevated melatonin doesn’t just help squirrels sleep during the winter. It also leads to an increase in hair growth — something that isn’t just true for squirrels. It’s the same with any mammal that grows a winter coat. Interestingly, melatonin also stimulates the accumulation of brown adipose tissue, which helps mammals stay warmer than regular adipose tissue. After the winter solstice, daylight increases, bringing melatonin back to normal levels by spring when squirrels lose their winter coats and shed the extra weight.

Do squirrels migrate?

Squirrels do not migrate. Most squirrels live in the same region their whole lives. They may move around a bit within a limited area in order to forage for food. And they also tend to retreat to wooded areas when the temperature starts to drop. But they tend to stay close to where they were born.

Occasionally squirrels may decide to seek greener pastures. Whether due to competition or a lack of resources, some squirrels will spontaneously pack up and leave. But, since they don’t come back, this isn’t technically migration. It’s just moving. 

Where do squirrels go in the winter?

Tree squirrels can stay warm enough without hibernating. However, they do enter a period of dormancy throughout the winter to help save energy. So they spend most of their winter curled up in their nests napping. They only wake up to forage for food in the morning and evening hours.

Just because tree squirrels can survive the cold doesn’t mean that they like it. In fact, they can make themselves quite a nuisance to homeowners during this season. Tree squirrels will actively seek shelter from the elements. If they find out you’ve got an attic, they’ll want to live there rent-free. 

Squirrels can worm their way through small holes in your siding. They’ll even create new holes, or work to make existing holes (likely created by woodpeckers searching for bees) big enough for them to crawl through. It’s important to inspect the exterior of your home regularly and to patch up any potential squirrel doors. If you suspect you already have squirrels in your attic, call a professional to check. They can capture and safely relocate them.

Squirrels may also build their winter nests in barns, sheds, and garages. They’ll even crawl up into the engine compartment of your car, especially after you’ve been for a drive and the motor’s still warm. So wherever you go and whatever you do this winter, keep an eye out for squirrels. You never know where those crafty little guys will turn up. 

How can you help squirrels make it through the winter?

The first and most important thing you can do to help your local squirrels make it through the winter is to provide them with a source of water. The ponds, lakes, and streams squirrels drink from during the rest of the year are usually frozen over during the winter. So leave a shallow dish filled with warm water out for them.

Squirrels love nectar, too. So making some homemade hummingbird food for them can provide them with an additional source of calories. An added benefit of this is that sugar water has a lower freezing temperature than regular water, so it won’t freeze as easily.

The second most important thing you can do is feed your squirrels. Not by hand, of course. Instead, try a peanut feeder. Squirrels love peanuts, shelled or otherwise, and they’re an excellent source of proteins and fats. Even just throwing a few handfuls of peanuts in your yard every day can help them meet their nutritional demands.

You can also try feeding them corn. Specialized corn feeders are available commercially to give your squirrels a place to congregate. Tossing handfuls of corn right alongside those peanuts you threw out earlier works just as well. Plus, it’ll help keep them busier longer. Squirrels are happy to eat from feeders, but you’ll attract more of them when you spread the food out. This way, they won’t have to compete with each other so much.

Suet is another excellent source of nutrition that will attract squirrels during the winter. Suet is lard mixed with nuts, seeds, dried fruits, and insects. Most squirrels are happy to chow down on storebought suet designed for birds. Place a couple of suet feeders where the squirrels can reach them, but be careful not to leave the blocks out in the open. The squirrels may run off with them!

How can you help squirrels stay warm?

Squirrels reinforce their nests in late fall to help them stay warmer over the winter. They use things like dead leaves, straw, and pine needles. They’ve been known to destroy outdoor pillows during this time, too, to steal the filling inside (a lesson we learned the hard way).  

So another way that you can help your squirrels make it through winter is by providing them with materials to line their nests. Save up some dried lawn clippings in the summer, then set them out in a pile for squirrels to dig through before winter arrives. Biodegradable bedding designed for hamsters and guinea pigs can also be used to build nests. 

The next time you give your dogs and cats a good brushing, take the loose fur and set it where the squirrels can see it. Throw your own locks out there, too, when you give your hair a trim. Hair acts as insulation, providing another layer between your friendly backyard squirrel and the bitter cold of winter. Feathers work just as well, so if you’ve got an old down comforter you don’t want anymore, your squirrels could probably make some use of it!

If you’re really dedicated to helping your squirrels, consider nesting boxes. They’re easy to build and they can make a world of difference to them. Set up one or two nesting boxes in your backyard to provide a safe haven for your squirrels. And, when spring finally arrives, they may decide to use them to raise their young. Who doesn’t want to have a bunch of baby squirrels in their backyard?

When do squirrels wake up from hibernation?

Hibernating ground squirrels usually start waking up in March. They may wake up even later if they think it’s still too cold out. But, in general, you’ll start seeing more squirrels scurrying around pretty early in the spring.

This is also when tree squirrels become more active. Remember, increasing sunlight reduces melatonin production. With less melatonin going through their systems, they quickly perk back up. This is good because springtime is when most squirrels give birth. They need their energy back to forage for food to support themselves and their young. 

Even though most squirrels don’t hibernate, they still slow down in the winter. By making your backyard a refuge with water, food, and shelter, you can help the squirrels in your neighborhood survive during the coldest time of the year. 

About The Author
Michelle Sanders is an outdoor enthusiast who is passionate about teaching others how to observe and support their local wildlife. She enjoys gardening, birdwatching, and trying (in vain) to get butterflies to land on her.

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