Red Squirrels

We have had an active red squirrel in our yard recently. I keep a tray full of sunflower seeds on our deck for the birds, and a squirrel has been taking full advantage it. I frequently see it sitting inside the tray, eating like a king.

Red squirrels don’t hibernate. They typically have several nests scattered across their territory in hollow logs, crotches of trees, and the like. During extreme cold, they’ll stay in the safety and warmth of their nests, but when it’s mild they’re quite active.

Red squirrels are known to be territorial. They occupy a home range of perhaps upwards to an acre. They’ll mate in late winter, with the young being born roughly a month later.

Watching the red squirrels can be good entertainment, but there’s an aspect of red squirrels biology that I’ve recently found quite intriguing. Occasionally the acorn crop is extremely heavy. That’s a food bonanza for squirrels. However the frequency of this “seed masting” is intermittent and unpredictable. We humans haven’t been able to figure it out, but the red squirrels may have.

Litter size in a species is somewhat variable. You would think that the variation in litter size for red squirrels would largely be a function of the food supply before and during the rearing of a litter. A few years ago, however, a study published in the journal Science reported that red squirrels have larger litters the spring before a summer masting event. They somehow seem to know a heavy seed crop is going to occur, and increase their litter size to take advantage of the abundant food supply. In other words, red squirrels are responding to an upcoming heavy acorn crop by having more offspring long before the acorn crop is actually produced (and well before we humans know what’s going on).

It’s not known what cue (or cues) the squirrels or plants use in determining litter size and seed crop. It may be that they both are using the same cue(s). Assuming this study holds up to scientific scrutiny, it’s a rare instance of an animal cued in to its future food supply. So the next time you see a red squirrel scurrying around near your home, just remember that the little bugger probably knows more about next summer than Zola the Amazing Fortune Teller.

Chuck Lura

Natural North Dakota is supported by NDSU Central Grasslands Research Extension Center and Minot State University-Bottineau, and by the members of Prairie Public. Thanks to Sunny 101.9 in Bottineau for their recording services.