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Shadows and Sex
The Real Meaning of Groundhog Day
You don’t need Punxsutawney Phil to know which way the wind blows. Groundhog Day isn’t about shadows or winter or spring. It is about sex. Birds and rodents now begin a season of foreplay.
No, spring is not around the corner, not anywhere on the continent, no matter what you hear from the ceremony in Pennsylvania. Even so, February 2 is indeed significant, falling about halfway between the Winter Solstice and the Spring Equinox, a period celebrated in various traditions from Paganism to Christianity. Early February is when we start to see 10 hours of daylight — a turning point for wildlife.
Songbirds cannot rely on the vagaries of weather to trigger their breeding cycles, which must coincide with an abundance of food for their offspring, mostly insects. That happens in May and June here in the north. A January thaw does not trick them into mating. A far more reliable calendar for animals is day length.
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 that when food is there in May songbirds will be ready … you know, physically.
As the days now grow longer, birds begin to prepare to make more birds. It’s why we’re starting to hear Black-capped Chickadees, Tufted Titmouses, Northern Cardinals, House Finches and other birds erupting into song on sunny mornings here in New England.
So why the groundhog as a mascot? 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. All winter long, groundhogs, or woodchucks as we call them, have been alone hibernating in underground burrows. By March they will awaken to begin mating on a schedule so that females bear young during food abundance in May.
But as it turns out, researchers working in south-central Pennsylvania more than a half century ago noticed males out of their burrows for a few hours in the dead of winter. The date: February 2. Female woodchucks were nowhere to be found. At least until a month or so later, when both males and females were out in equal numbers and beginning to breed in earnest.
During “arousal events,” the males seek out females at their burrows — simply for a visit, not much more.
With no food or females available in early February, what in the world would motivate a male woodchuck to wander around in the cold in Pennsylvania? As it turns out, those males are engaged in good old-fashioned courtship: dating.
During what another researcher calls “arousal events,” the males seek out females at their burrows — simply for a visit, not much more. He then heads back to his own burrow for more slumbers. Presumably these courtship visits pay dividends when it comes time to breed later. They might indicate to a female, for example, that he’s tougher than other males. Or perhaps they’re little more than like another February ritual: Valentine’s Day.
Red Squirrels aren’t nearly as tactful. Unlike their rodent cousins, Red Squirrels do not hibernate; they’ve been out all winter. But as the daylight now advances, females are in estrus, receptive to males for breeding, for only 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. This is not a civil situation.
The consequence of this skewed gender ratio and limited availability of females is that life during the breeding season can be, to say the least, challenging for the male, to say nothing of the burdens of reproduction that the female must endure. He’ll spend lots of time following a female 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 off other males for her affections — which actually amounts to a copulation that might last 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 light, song, courtship and, if you happen to be a Red Squirrel, unadulterated, chaos.
 Reproductive Cycle and Litter Size of the Woodchuck. Robert L. Snyder and John J. Christian. Ecology, Vol. 41, No. 4 (Oct., 1960), pp. 647-656.
 Male groundhogs hibernate less to visit the ladies. Penn State University. News Release. 24Jan2003.