One of the secrets to really understanding squirrel behavior is knowing when they have babies in your local forests.
Squirrel mating behaviors are a frequently misunderstood topic in the life of squirrels because their breeding habits have such incredible diversity that all depends on each individual squirrel.
As a general rule most Gray and Fox squirrels have their babies during September or October, while most Red and Douglas squirrels have their babies in July, August or September.
However, many squirrels also have a secondary breeding season in winter, which means some squirrels are born February through May.
On a good year, up to 30% of female squirrels can have babies during both breeding seasons!
This is a huge window of possibility… made even more complex by the fact that individual female squirrels each have their own estrus period lasting for just a single day during these two breeding periods.
If this all sounds quite complicated, don’t worry!
Today we’re going to sort through all the variables to help you know exactly when squirrels are having babies in YOUR backyard.
Let’s start by understanding why squirrels have so much variety in their birth dates.
4 Factors That Influence When Squirrels Have Babies:
If you want to know when squirrels are having babies, it’s important to understand why individual squirrels have such dramatic differences in their breeding times.
Within the average breeding season, exact dates of individual squirrel births will depend on the following four factors:
1. What Type of Squirrel Do You Have?
Do you have red squirrels, gray squirrels, fox squirrels or douglas squirrels?
It’s important to know that different types of squirrels mate & give birth during different months.
So to make this easy, here’s a reference chart showing an overview of all squirrel behaviors related to breeding and having babies, listed by month:
We’ll come back to this chart in a little bit… For now I just want you to see why it’s so important to know which type of squirrel you have.
- Notice that gray and fox squirrels start having babies as much as 2 months earlier than red and douglas squirrels.
- Nest defence is not a useful indicator of breeding in red and douglas squirrels because they’re almost always territorial regardless of the context.
- There are significant differences in gestation times and how long it takes for young squirrels to become independent, depending on their species.
(We’ll explore specific mating behaviors much more closely in the next section because these behaviors are really the secret to knowing when squirrels are actually being born locally)
4 Common Types of Squirrels To Know
This article focuses on the mating habits of the 4 most common types of squirrels you’re likely to encounter:
- Red squirrels are small, reddish colored squirrels who especially enjoy storing up the cones of fir & spruce trees, and have highly territorial behavior.
- Gray squirrels are quite a bit larger than red squirrels. Their tail is especially bushy & large. Gray squirrels come in many colors besides gray. They can also be black, red, blonde or brown.
- Douglas squirrels: On the west coast of North America, red squirrels are replaced by douglas squirrels who look and sound a bit different, but they are behaviorally almost identical.
- Fox squirrels are even larger than gray squirrels, but these two are so similar in terms of behavior & mating habits, they even interbreed in places where their range overlaps.
If you don’t yet know what type of squirrel you have, this article will still be helpful, but there may be some differences in the exact calendar.
2. What Is Your Location? (latitude, climate, local ecology)
In general – squirrels that live further south will tend to breed earlier and are more likely to have 2 breeding cycles per year. Squirrels in the north typically only have one breeding season per year.
This is primarily due to the energy expenditure required for survival in harsh climates. It’s a balance of how much food squirrels are able to store compared with how mild or harsh the winter is.
In the year following a mild winter, you may see a dramatic increase of squirrels having multiple breeding seasons.
Likewise, following particularly harsh winters, squirrels are most likely to only have a single breeding season (likely during the summer as you get further north and west).
3. The Mast (stored seeds & nuts) Conditions Of The Previous Year
A key thing to remember about squirrels is their success depends on storing huge caches of food for winter from trees that produce massive harvests of high calorie seeds & nuts.
These seed and nut trees are what’s known as mast species and includes oak, hazelnut, spruce, fir, hickory & beech among others.
Stored seeds and nuts are a squirrel’s primary food source during winter. The challenge is that mast harvests are notoriously variable.
Some years there are tons of nuts & seeds, while other years they’re much more scarce with less food to go around.
This means squirrels go through periodic gluts & lacks in their food stores, which can significantly affect their reproductive success in the following year.
In years with significant mast harvests, squirrels are able to store a lot more food to reduce the stress of winter. This enables them to mate earlier and in some cases to even mate twice in the same year.
4. Biology & Health of Individual Female Squirrels
The fourth mystery of squirrel breeding is simply that female squirrels have a lot of biological randomness around when they’re fertile and receptive to male advances.
During the entire 2-3 month breeding season, female squirrels will only allow mating for one single day, but there’s really no way to predict which day it will be until it happens.
To make this more complicated, each female has her own individual estrus cycle that doesn’t necessarily line up with the other females in her area.
This means one squirrel might be ready to mate in December, while her neighbor might wait until February.
The birth of young squirrels is then set by the mating date for individual females:
- Gray and fox squirrels give birth 45 days after mating
- Red and Douglas squirrels give birth 35 days after mating
Being able to identify the day of mating is really the secret to knowing exactly when squirrels are being born in your backyard.
This means looking for behavioral indicators during the average breeding season that tell you when individual females are mating.
To do this, we need to observe some basic squirrel behavior…
Squirrel Mating Behaviors Explained
There are 3 common behaviors that can tell you when squirrels are having babies.
- Mating (Aggressive Male Behavior)
- Nest Defence (Aggressive Female Behavior)
- Young Dispersal (Aggression Towards Juvenile Squirrels)
The squirrel breeding calendar tells you which months you might observe each of these behaviors, however you still need to use your own observation skills because each behavior may only occur for several days during that period.
So let’s talk about what specifically you should look for…
1. Aggressive Male Groups Looking To Mate
Before female squirrels mate, there’s a short period of 3-5 days when her body produces a scent that is extremely attractive to male squirrels.
When a female squirrel is close to breeding, groups of males (as many as 10) will all converge on her location and engage in long intense fights and chases through the forest.
These aggressive male groups really stand out because of all the activity & sound they generate, making this event very easy to observe.
Whenever you see aggressive male groups chasing & following each other around the forest, see if you can locate the female at the front of the pack.
These aggressive battles will continue for up to 5 days until she’s finally ready to mate.
You may or may not get to witness the actual mating event, but you will notice that after a few days the group disbands and leaves the area.
When the male squirrels leave the area, it means mating is finished. As mentioned above, this is the key moment because it sets the clock on when the babies will be born:
- Gray and fox squirrels give birth 45 days after mating
- Red and Douglas squirrels give birth 35 days after mating
At this point, your attention can turn towards finding the nest, while the males go off in search of other females coming into estrus.
2. Nest Defence In Gray & Fox Squirrels (but not red or douglas)
Another way to identify when squirrels are being born is to locate the active nest tree of a pregnant female.
Female squirrels will aggressively defend their nest tree from other squirrels, so if you see a squirrel being defensive around a particular tree, this is a good indicator of female pregnancy (especially if you recently observed mating).
Note that this is only true for Gray & Fox Squirrels because they are communal squirrels who are typically not aggressive towards other members of their local community.
Red Squirrels and Douglas Squirrels are naturally very aggressive under almost all circumstances, which means you really can’t rely on nest defence as an indicator of pregnancy.
If possible, try to watch the female every day and look for a sudden change in her behavior. Pay attention to where she goes and what she does.
When she gives birth, the female squirrel will suddenly disappear for several days. Squirrel umbilical cords stay attached for several days after birth, so she will not leave the nest during this time.
3. Dispersal of Young
The third way to know when squirrels are having babies is to look for signs that the juveniles are dispersing away from the home nest.
When young squirrels reach their age of independence, some of the new squirrels will be forced to leave their home territory and try to find a new home.
As they move through unfamiliar territories, the squirrels living there will frequently act aggressive towards them, chattering away and alternating with loud trilling calls to assert their dominance.
This happens several weeks or months after their birth, but it can help you reflect back on recent squirrel behaviors to more accurately interpret your observations.
- Gray squirrels take a total of 3-4 months before baby squirrels are ready to move out on their own.
- For red squirrels, it’s 7-8 weeks.
This is once again most challenging with red and douglas squirrels because these squirrels are almost always territorial regardless of the situation.
How To Understand & Interpret Aggressive Squirrel Behavior
As you can see from each of these examples, the key to knowing when squirrels are giving birth is being able to interpret aggressive squirrel behavior.
We need to discern whether aggressive behavior is related to breeding activity, nest defence or dispersal of the young squirrels.
- In the case of breeding, look for trains of male squirrels all following a single leader. The fighting will primarily happen between the males as they jockey for position in line.
- When a female is protecting her nest, you will only see two squirrels involved and she will always protect the same tree. In this case, the aggression is associated with a single location, rather than moving around the landscape.
- When young are dispersing, you will encounter wide-spread aggressive behavior that isn’t associated with a string of males, and may change positions many times throughout the day.
The hardest thing about all of this squirrel action is it really depends on the individual squirrel.
If you want to really get a deep understanding of this, here are some next steps to follow:
- Download a copy of the squirrel breeding calendar.
- Start visiting a sit spot where you can watch squirrels regularly in the forest.
- In the calendar months with check marks, watch for the three aggressive behaviors and keep notes.
Get that squirrel journal going and let me know what you observe out there!
Frequently Asked Questions About Squirrel Babies:
How Many Babies Do Squirrels Have?
Gray squirrels have 3-5 young in each litter, and can have as much as two litters per year. Red Squirrels have 2-8 young and less commonly have two litters per year.
Where Do Squirrels Build Nests?
Gray squirrels build big leafy nests in the tops of deciduous trees that are typically used during summer. Winter nests are more commonly made in tree cavities.
Red squirrels and douglas squirrels typically make nests in tree cavities, or underground in the root systems of coniferous trees. They can also build leaf nests near the trunk of trees in warm weather, but it’s less common.
When Do Squirrels Leave The Nest?
Gray squirrels will begin exploring outside the nest after 4-5 weeks, but it takes 3-4 months before they’re fully independent and heading out on their own.
Red squirrels take about 30 days to emerge from the nest, and are independent at the time of weaning (7-8 weeks).
When Do Squirrels Start Their Own Families?
Female Gray squirrels are capable of mating as early as 5.5 months old, but they typically wait until they’re at least a year old. Males typically wait until they’re at least 2 years old before starting to mate.
How To Tell If a Squirrel Has Babies?
If you watch the nest for long enough, eventually you’ll get to see baby squirrels emerging from the nest to explore. Occasionally you might hear little sounds coming from inside the nest as the squirrels become active.
I once watched a mamma squirrel move her babies from her nest in a bird box to a tree cavity out in a forested maple tree.
Click play if you want to hear the story of a mamma squirrel moving her babies to a new nest.
How Did You Learn So Much About Squirrels?
It comes from spending many hours following squirrels around in the woods, plus some excellent books on animal behavior.
The research materials for this article are “Peterson’s Guide To Behavior of North American Mammals” by Mark Elbroch and Kurt Rinehart, as well as “Stokes Guide to Animal Behavior” by Donald & Lillian Stokes.
If you want to learn more about animal behavior & the life of squirrels, I highly recommend getting both of those books!
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