Earth Science

Shadows and Sex

red-squirrel-1144x400
Red Squirrel / © Bryan Pfeiffer

By Bryan Pfeiffer –

YOU DON’T NEED PUNXSUTAWNEY PHIL to know which way the wind blows. Groundhog Day ain’t about shadows. It’s about sex. Birds and rodents now begin a season of foreplay.

No, spring is not around the corner – at least not here in Vermont. Songbirds don’t rely on the vagaries of weather to calculate their breeding cycles. Instead, they schedule mating and nesting to take advantage of a reliable abundance of food for their offspring, mostly insects, which happens in May and June here at our latitude. As the days grow longer, birds do get ready to, well, um, make more birds. It’s why we’re starting to hear Black-capped Chickadees, Northern Cardinals, House Finches and other birds erupting into song on sunny mornings.

Black-capped Chickadee / © Bryan Pfeiffer
Black-capped Chickadee / © Bryan Pfeiffer

Day length is a far more reliable calendar than weather. It is not entirely clear how birds measure day length, but we do know that photo-receptors in bird brains sense increasing light. It triggers the production of hormones that act like birdie Viagra. Their sexual organs revive from a state of dormancy. So when the food is there in May, songbirds will be ready … you know, physically.

February 2 is indeed significant. It falls about halfway between the Winter Solstice and the Spring Equinox, a period celebrated in various ways in human traditions from Paganism to Christianity. And early February is when we start to get 10 hours of daylight – February 6 this year. It seems to be a turning point for wildlife.

But why the groundhog? Couldn’t we have picked a loftier critter to represent the coming of the light? As it turns out, this rodent is indeed a worthy messenger of spring. In February, woodchucks begin to emerge from hibernation on the prowl. They need to breed soon so that females produce litters during greater food abundance in April and May. Males emerge from their burrows to find and visit with females. But many of these early encounters are merely courtship visits, which pay dividends, research suggests, when it comes time to breed a bit later. It’s sort of like another February ritual – Valentine’s Day.

Squirrels aren’t so tactful. Female red squirrels are in estrus, receptive to males for breeding, for about eight hours on only a single day during this season. And male squirrels outnumber females in the wild by as much as five to one. The consequence of this skewed gender ratio and hard-to-get females is that life during the breeding season can be, to say the least, challenging for the male. He’ll spend lots of time following her in the days before she is in estrus. Should the male be too forthcoming, too eager before she is ready, she will rebuff his advances with a swat to the face or a painful bite. (I hate it when that happens.)

And when those precious eight hours finally arrive, a male is hardly alone in this drama. He often must compete with or fight other males for her affections – actually for a copulation that might last only about 20 seconds. Out there in the trees, it’s a free-for-all. “To the casual observer, what ensues is probably best described as pure and unadulterated chaos,” write biologists Michael A. Steele and John L. Koprowski in their fantastic book, North American Tree Squirrels.

So let’s recognize the real significance of Groundhog Day. This isn’t a holiday about six more weeks of winter. It’s a celebration of romance, even if it turns out to be unadulterated, chaotic rodent romance.

Bryan Pfeiffer teaches writing in the Field Naturalist and Ecological Planning programs.

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