Naturespeak A naturalist's view of the world

January 21, 2011

Hot-blooded Squirrels on a Cold Day

Filed under: Uncategorized — wykes @ 8:59 pm

You might have noticed fox squirrels running about like mad mice lately. They are not rabid or reacting to global warming. No, Fox Squirrels-those large yellow-brown creatures of suburban yard and country woodlot -become hot-blooded during the cold season. They are in the mood for love. You’d think that mid-January would be the single worst month on the calendar to take up reproductive pursuits. This is, after all, the time when wild critters are hard put just to avoid the frigid edge of winter’s blade. Food is scarce, temperatures brutal, and existence is tenuous. None of this seems to bother the winter Fox Squirrel. For them this is spring, dog-gone it! Remember, these are the same rodents that prefer to re-cross the entire width of a road, rather than jump to the nearest curb, when a car approaches.

Fox squirrels actually have two peak breeding seasons. The second comes in June – a much more sensible month if you ask me. The early season involves individuals born in March of the previous year. In other words, winter conceived babies carry on the tradition of winter breeding as they mature, while July born squirrlets maintain the early summer breeding schedule.

January breeding behavior involves individuals running around like fools, lots of chattering, and a whole lot of tail talk. Territorial males will defend a “ripe” female from all other suitors until she is ready to mate. Since several interested males will hone in on a single gal, the dominant male will engage in vigorous chases and literally stand guard at the base of the limb where she resides.  It is not uncommon, then, to see groups of three or more. In these cases, the female will be up the tree and the males will be barking or chasing each other around the trunk. For her part, the female does not permit the dominant male to approach her until the time is right. He has to keep defending his right until she grants it. Eventually she will come into estrous and allow her defender to mate with her.

One of the most noticeable features of breeding time is that Fox Squirrels become very expressive.  Normally they are the quietest of the squirrel clan and will only bark or chortle on rare occasion (unlike the Red Squirrel which never shuts up). Come high time in January, however, they begin barking, grunting, squeaking, screaming, and chucking. Many of these sounds are directed at opposing suitors, but a few are uttered between potential mates. The female will squeal with disapproval, for instance, if her defender comes too close too soon.

The tail becomes a visual signal device to back up the verbal stuff. A passive female will sit on the branch with her tail coyly draped over her back (see here) while her defender waves his tail about at opposing squirrels. This appendage is whipped about like a flag in the wind to accompany, and accentuate, the verbal abuse.

I can only imagine the kind of trash talk a squirrel could come with. Surely it involves talk about oysters (and, no, I am not talking about the food item). Breeding squirrels are easily spotted because of their enlarged…well, oysters (o.k., testicles – there I’ve said it). When viewed from below these …er, … appendages…are conspicuous. They are black and about the size of a pair of pecans (what else could I use for a size comparison!). After the season is done they shrink down to the size of a peanut.

Fortunately, you don’t have to take any of this information without some visual proof. Earlier in the week I stumbled upon an argumentative male Fox Squirrel in my backyard silver maple. He was guarding a female and was in a very argumentative mood. Not only was he flashing his oysters, and flinging smack talk, at a rival male (unseen, but standing at the base of the tree), but he was barking at me as well. Take a look at these two short videos (here and here)– with the sound up – and examine the photos included with this essay and you’ll get a full dose of squirrel love. I did not stick around to see the mating, so don’t expect any shots of that. It was too darn cold and I was freezing my….er, fingers off.


  1. Interesting about the two breeding seasons. It would seem to imply a form of reproductive isolation between two subsets of a population (if they are sympatric). There are probably crossovers/overlaps though? Nice post.

    Comment by Hugh — January 22, 2011 @ 8:24 pm

  2. What is the period of gestation for fox squirrels? I can’t imagine it’s very long, so how come all squirrels don’t “celebrate” both mating seasons every year?

    Comment by Adam — January 23, 2011 @ 3:19 am

  3. So as Hugh says, the populations are pretty much sympatric, I’d imagine. You’d think that with a breeding pattern like that and a clime such as Michigan’s, the winter breeders would be selected for winter adaptations like lighter, longer fur and smaller bodies over time.

    But then again, I heard somewhere (probably VERY authoritative) that the fox squirrel is a breed which has only recently expanded to several of the territories it now occupies, so perhaps it is so with Michigan?

    Comment by Adam — January 23, 2011 @ 2:44 pm

RSS feed for comments on this post. TrackBack URL

Leave a comment

Powered by WordPress