Squirrels are among the most common wildlife that we see in urban environments and they generate a lot of curiosity with their behavior and antics.  People are especially fascinated with baby squirrels because, let’s be honest, they are absolutely adorable!  If you are excited about the thought of seeing some of these delightful itty bitty fur balls then you are probably wondering, “When do squirrels have babies?”

Squirrels have a litter of 2-4 babies, called kits or kittens, in February and March.  Older female squirrels will produce a second litter in August.  The timing of the births will vary based upon latitude and availability of food.  The babies will leave the nest at three months of age and reach full size nine months after being born.

The Months That Squirrels Have Babies

We are going to be specifically looking at the Eastern Grey squirrel for this article as it is one of the most common squirrel seen and asked about in urban environments.  Other species of squirrels (Fox, Red, Flying) follow similar patterns of reproductive behavior but with different breeding dates and gestation periods.

Eastern grey squirrels breed in late December through February in warm climates.  In colder climates the breeding season is delayed and occurs in January through March.  Grey squirrels have a second breeding season in May through June which extends into July in colder climates.

Grey squirrels will carry their babies for 44 days which results in the earliest baby squirrels being born in late January and the latest being born in April.  In the fall breeding season the babies will be born in June and July.

Breeding Month	Gestation	Birth Month
December	44 days	January
January	44 days	February
February	44 days	March
March	44 days	April
May	44 days	June
June	44 days	July
July	44 days	August

By taking the differences in climate into account you can see that squirrels in Florida will have babies in late January and June while squirrels in Michigan will have babies in April and August.

The numbers and dates presented above are general ranges but they can vary dramatically based on environmental conditions.  An article published in the Journal of Ecology by John Gurnell in 1996 showed a strong statistical correlation between both food availability and winter severity with the breeding patterns of grey squirrels.  To quote from the article’s abstract:

“In good seed years, breeding starts in December, in poor seed years the start of breeding is deferred until the spring. There was no or very little spring breeding in 5 years when food supplies were poor.” 

Here is a more detailed article describing what squirrels eat that shows the importance of different food sources.

How Many Babies Are in a Litter?

Grey squirrels average three babies per litter with a maximum liter size of eight. These babies, called kits or kittens, are born blind, deaf, and furless, like most other species of rodents. Their ears are also folded against their skull and they are completely helpless.  The kits weigh about 15 grams which is about the same weight as two tablespoons of flour.

The mother remains in the nest with the babies, where she cares for them by herself. They are fed every few hours and require constant care by their mother for several weeks.

When Do Baby Squirrels Leave the Nest?

The timeline for the development of young squirrels can be described as follows

• 1-2 weeks old: Pink skin, eyes and ears closed. Kits are nursing.
• 2-3 weeks old: Dark skin, eyes and ears closed. Kits are nursing.
• 3-4 weeks old: Fuzz type fur, eyes and ears closed. Kits are nursing.
• 4-5 weeks old: Fur development, eyes and ears open.  Kits are nursing.
• 6-7 weeks old: Bushy tail and looks like a miniature adult. Kits are nursing.
• 7 weeks old: Weaning begins and solid food is introduced.
• 10 weeks old: Weaning is complete.
• 11 weeks old: Young squirrels leave the nest and are independent.

Baby squirrels become fully independent and are able to leave the nest roughly three months after being born.  This means that the squirrels that are born in late January will start running around your yard towards the end of April while ones born from the summer breeding season will emerge in the September/October timeframe.  

Depending on the number of squirrels in the immediate area and available nesting sites, the young squirrels may try to build their nest close to their mother. Grey squirrels are not territorial and most stay within two miles of their home nest. If the area is crowded with other squirrels, the young squirrels may be forced to travel further away to establish their nest.

Squirrels born from the summer mating season have little time to prepare for winter by fattening up and caching nuts than squirrels born in the spring. As a result, the long term survival rate for summer babies is typically lower than spring babies. The other major factor that influences how long squirrels live is the abundance of predators.

How Old Are Squirrels When They Mate?

Young squirrels reach their full adult size and mass around 9 months of age but sexual maturity takes longer to obtain.

Females grey squirrels typically reach sexual maturity when they are about 15 months old while male squirrels are sexually mature closer to 12 months old but will be delayed if in the presence of dominate males.  This means that a female squirrel born in November would be ready to mate in the following summer season.

The reproductive cycle of male grey squirrels is interesting and is defined through testicular development.  Sexually active male squirrels have very pronounced testicles that go through two seasons of testicular regression where the size of their testicles shrink by up to 90%.  These times of regression correspond to seasons where females are not breeding and are thought to be a way to conserve energy.

The thought that testicular regression is an energy conservation mechanism is supported by a study that showed males which were extremely well fed in an enclosed environment did not undergo regression.  Further supporting this idea is another study which showed regression was prolonged when food was scarce.

Squirrels do not mate for life and are quite promiscuous.  Males will mate with multiple females and females will mate with multiple males.  It is not uncommon for a female squirrel to have a litter where the kits are sired by multiple fathers.  The mating process involves elaborate chases where males pursue the females and scare away other males.

I love feeding the squirrels and watching my dogs chase them in circles. Most of the time the critters are just scampering around like normal and chattering away at my dogs.  Sometimes though, you will see a squirrel that is acting incredibly aggressive towards humans or that is stumbling around when it walks.  Both of these behaviors are similar to what is seen in rabid wild animals. It made me ask the question, “Do squirrels carry rabies?”

Squirrels do not carry rabies but do carry other diseases.  If you see a squirrel behaving erratically then there are multiple reasons to explain the odd behavior other than rabies.

The Center for Disease Control states that squirrels are extremely unlikely to carry the rabies virus.  While rabies is certainly a dangerous disease for humans it is actually quite rare in the US population.  On average there are only 2-3 reports of rabies being transmitted to humans in this country each year.

Here is a link to the rather short list of all US rabies cases since 1951.  In almost all cases of infection the disease was transmitted to a human through contact with bats.

Squirrels May Carry Other Diseases

Just because you don’t have to worry about rabies doesn’t mean that it is safe to handle squirrels as they can spread tularemia and leptospirosis through their bites.

Tularemia is a bacterial disease that attacks the skin and lymph nodes. The lymph nodes may swell while ulcers may develop at the site of the bite. The symptoms may develop within several days up to two weeks.

Leptospirosis is also a bacterial disease. Those infected with this disease may experience headaches, fever, vomiting, rashes, and jaundice. Leptospirosis may also lead to kidney damage.

In rare cases, squirrels may also spread ringworm. Ringworm is not a worm. It is a fungal infection that primarily affects the skin. A red rash with a ring-like appearance may develop and become irritated. This infection may spread through contact with a squirrel and is less likely to spread as a result of a bite.

While squirrels rarely pass diseases to humans and pets, it is still important to visit a doctor if you are unfortunate enough to getting bitten to take preventative action against infections.

Why Is a Squirrel Acting Erratic?

One symptom people associate with rabid animals is the animal acting erratically.  Normally if you see a wild animal that has a staggering gait or is approaching you in an aggressive manner then you should be concerned about the animal being rabid.  However, there are many reasons to explain this behavior is squirrels other than rabies.

Aggressively Seeking Food

Squirrels are smart animals.  If one of their standard food sources comes from people sitting on park benches and feeding them peanuts then they are going to assume that anyone sitting on those benches has some food for them.

It is not uncommon for squirrels that are used to being hand fed by humans to run towards people and even start climbing on them and going through their pockets.  These squirrels can become quite aggressive at times and have been known to accidentally scratch people with their sharp claws as they climb around them.

Intoxicated

Squirrels have an extremely diverse diet that often includes fruits and vegetables.  If a squirrel eats fruit has fermented then the little guy can get drunk and will be wobbling around as it walks.

You can head over to YouTube and do a search for “Drunk Squirrels” and see how common this is.  There are videos of squirrels getting intoxicated from fermented pears, crabapples, cherries, apples and pumpkins.

Poisoned/Injured

Another reason for erratic behavior in a squirrel is if it is in distress from being poisoned or attacked by a predator.

There are a lot of people who dislike squirrels, especially ground squirrels, and resort to the use of poisons to eliminate them.  A poisoned squirrel is going to be suffering and walking/acting in a manner that is not normal.  Unfortunately there is nothing you can do to help a squirrel that has been poisoned.

Squirrels have many predators and are under frequent attack.  If you see a squirrel that is walking or acting strangely then there is a good chance that it has escaped a predatory attack but was injured in the process.  If you see an injured squirrel you can put some food and water into a sheltered location for it but do not try to catch it with your bare hands.

 

The dietary habits of squirrels can be frustrating, hilarious and complex.  On the frustrating part there is a multi-million dollar business dedicated to keeping voracious squirrels out of bird feeders. On the hilarious part are the videos you can find on YouTube of squirrels munching on a slice of pizza or eating away from inside a Halloween pumpkin.  On the complex part is how these animals feed in the wild and how the diets and behaviors change between species.

Have you ever wondered, “What do squirrels eat?”

Squirrels are opportunistic omnivores that primarily eat nuts (acorns, hickory, pecan), tree buds, grains, grasses and fungi.  Squirrels will also eat protein sources such as bird eggs, insects and small reptiles.  The exact diet of a squirrel is dependent upon both the species in question along with geographical location.

Let’s take a closer look at how the diet of a squirrel varies between different species.

Note: While there are over 250 types of squirrel in the world, this article will only focus on the most common species found in the United States.

Tree Squirrels

In general there are four different types of squirrels that live in trees.

• Grey
• Fox
• Pine
• Flying

The diets of the grey and fox squirrel are similar which makes sense given there overlapping territories and similar behaviors.  The diets of the pine squirrels and flying squirrels have distinct differences.

Grey/Fox

Grey and fox squirrels primarily consume tree nuts such as acorns, pecans, walnuts and hickory nuts.  They will also consume the flowers and buds from multiple species of trees along with any fruit or flowers that are produced.  These squirrels will supplement their diet with fungus, insects, moths and beetles.  Grey and fox squirrels will readily eat bird eggs and nestlings if the opportunity presents itself.

Both species are scatter hoarders that store large amounts of food, mainly nuts, in various locations for consumption in the lean winter months.

• Reference 1
• Reference 2
• Reference 3

Pine

The term “Pine Squirrel” refers to multiple species including the American Red, Douglas and Mearns’s squirrels.  While pine squirrels are omnivores their primary food source, as indicated by their name, are pine nuts.  In addition to pine nuts these squirrels rely heavily upon fungus in the summer and will actively dry fungus out for consumption during winter months. Pine squirrels are also meat eaters and will occasionally hunt chipmunks.

The hoarding behavior of pine squirrels is drastically different across the country.

In the western US pine squirrels will create a massive central store of pine cones called a midden.  It is estimated that a single squirrel will store up to 15,000 cones in its midden annually and that a single midden will have enough food for multiple winters.

In the eastern US the creation of middens is less common with pine squirrels relying upon the mast of oak, walnut and hickory tress.  These squirrels are scatter hoarders.

• Reference 4
• Reference 5

Flying (Northern/Southern)

The last of our notable tree squirrels are the Northern and Southern flying squirrels.  These nocturnal creatures all omnivores but their diet is unique in that fungus and lichens are primary food sources instead of a supplements.  The flying squirrel’s love of fungus will often lead it to steal the dried fungus that pine squirrels have carefully dried during the summer.

The National Wildlife Federation states, “Southern flying squirrels are considered one of the most carnivorous squirrels because they supplement their diet with eggs, birds, and carrion.”

Flying squirrels are scatter hoarders that maintain multiple stashes of nuts for winter consumption.

• Reference 6
• Reference 7
• Reference 8
• Reference 9

Ground Squirrels

There are many different types of ground squirrel and they are much less reliant upon nuts than their tree dwelling counterparts.  In general ground squirrels dine on grasses, shrubs and seeds.

The California ground squirrel provides an excellent example on the complexity of describing a squirrel’s diet.  The California ground squirrel has distinct seasonal food preferences and will almost exclusively eat green grasses and other plants in the February-May timeframe and then will abruptly switch to eating seeds for the remainder of the year.

Ground squirrels also enjoy protein sources such as insects and the eggs from ground nesting birds such as quail and towhees.  A food source that is surprising for ground squirrels is snakes.  It turns out that while snakes like to eat ground squirrels the squirrels will frequently fight back and win!

Ground squirrels are hoarders that store large amounts of seeds for their winter food supplies in complex burrow systems.

• Reference 10
• Reference 11

Bones and Antlers

One last food item that needs to be addressed is the squirrel’s need for animal bones or antlers.

All squirrels species, both tree and ground based, are rodents.  The defining characteristic of a rodent is the presence of front incisor teeth that never stop growing.  Rodents need hard substrates to gnaw upon.  The gnawing keeps the incisors sharp and prevents them from becoming overgrown.

An ideal substrate for squirrels to gnaw upon are the bones and antlers of other animals.  In addition to keeping heir teeth in shape, the bones and antlers provide a rich source of calcium for the animals.

I am always blown away by how many types of squirrels there are in the world.  When I started this project I thought I was just going to be talking about those grey and fox squirrels that were running around in the trees in my backyard.

It turns out that the term squirrel covers critters as small as chipmunks, as large as groundhogs and even has a bunch of giants! There are a dozen different species that are formally named as giant squirrels.  Four of the giants belong to the Ratufinae Subfamily and eight of the giants are flying squirrels from the Sciurinae Subfamily.

All of these animals exist outside of the United States so you are going to have to do some serious traveling if you want to see any of them in the wild.  Nevertheless, it is always fun to read about interesting animals so I wanted to give a complete breakdown of all twelve giant squirrels in the world.

Let’s get started!

[Read more…]