A few days ago I was having fun watching a few squirrels chase each other around the squirrel feeder I have in the backyard. The chase is sometimes part of the mating process, either through the establishment of the dominant male or by the pursuit of the available female. It got me wondering about the whole mating process (I think about things like that after three cups of coffee) and I decided to find out if squirrels mate for life. Here is what I learned.
Squirrels do not mate for life. Female squirrels are in estrus for only a few hours each year and will mate with any males in her territory. There is vigorous competition for the female and she will often mate with multiple males producing litters of mixed parentage. Once the mating is complete the male plays little role in the raising of the squirrel pups.
What the Experts Say
Noted biologist and squirrel expert Dr Albrecht Schulte-Hostedde was cited in an article from The Cottage referencing female squirrels at quite promiscuous who often produce litters with multiple fathers.
The occurrence of litters with multiple fathers is an interesting event. After the mating process is complete the male squirrel injects a “plug” into the female that prevents other males sperm from fertilizing the female’s eggs. However, the female squirrel will often quickly remove the plug so that she can successfully mate with other males.
After a gestation period of roughly 45 days a litter will be born that, depending upon a variety of factors, will have between one and four pups. Most squirrels will typically have babies twice a year in the Spring and Late Summer.
While male and female squirrels will often share a nest during mating season once the pups are born the male is kicked out and has to go find a new place to live. Squirrel pups born in tree cavities have a much greater chance for survival than pups in open air dreys simply due to ease of access to predators. This is a great reason to put up a squirrel nesting box if you live in an area where natural tree cavities are lacking.
Squirrel Family Relations
The term “mating” has multiple meanings. On one level mating refers to reproduction while on another it refers to relationships.
It turns out that while squirrels are not monogamous they do appear to be able to identify their family members and share protective bonds of various degrees.
On the male side of this equation the family bonds are best described as “not gruesome”. Male squirrels are known to raid nests of squirrel pups and kill them. However a recent study by Jessica Haines from the University of Alberta, and reported upon in National Geographic, showed through DNA testing that males were killing the offspring of other males and not their own.
The reasons behind the males behavior is complicated and open for further study but does indicate that they can identify their own offspring and choose not to harm them.
On the female side of the equation things are more nurturing when it comes to family relations. An article published the Great Good Magazine by Berkeley describes the adoptive behavior of female squirrels. Female squirrels will often adopt orphaned squirrel babies but ONLY if the squirrels are related.
What is fascinating is that female squirrels get more selective on the closeness of the genetic relationship depending upon the size of her litter. If a female squirrel only has one or two pups then she might adopt an orphaned “niece” or “nephew. However if her litter size is three or four then she will only adopt an orphaned “grandchild”. She knows that resources are scare and she can only provided for so many so she allocates to the closest relatives first!
It blows my mind that not only can a male squirrel identify his offspring but that a female squirrel can identify an entire family tree!
I guess if any animal would be good at identify trees then it would have to be a squirrel 🙂
Update: The one exception I have found are the Japanese Giant Flying Squirrels which are reported to form monogamous mating pairs.