Nature scrapbook: Groundhogs


Long after the hoopla in early February, true groundhog day usually doesn’t come until well into March in southern Ontario and April farther north. Once they’re up and about, though, the solitary waddling rodents have a busy spring agenda re-establishing turf and pecking order, finding mates, and starting new families.

Fat-fuelled wake up

To rouse from torpor, groundhogs (a.k.a. woodchucks), like all hibernating mammals, metab­olize blood-rich deposits of brown fat, stored between the shoulders. The fat heats up and accelerates the heart, jolting their sluggish circulations into rushing torrents. Males usually surface first, when snow’s still on the ground, though they often snooze until the weather warms.

Spring fever

Male groundhogs wake up with a mission to procreate. Venturing above ground for one to five hours at midday, they establish their territories and reputations, while seeking the boudoirs of the opposite sex, by rubbing scent from their muzzles on burrow entrances, tree trunks, and other objects, and fighting or chasing away rivals. A successful warrior woodchuck carves out a piece of real estate containing the dens of several females.

Slim pickings

Although the tubby marmots lose between one-quarter and one-half of their pre-hibernation weight by the time they emerge, they must subsist on a starvation diet of bark, buds, and twigs for weeks, until fresh grass and leaves sprout.

Love ’em and leave ’em

A female is receptive for 16 to 20 days after hibernation and usually mates within a week of waking. A local Lothario may be permitted to shack up with her for up to several days, until the deed is done. Then he’s on his way again to knock on other doors. A month later, she delivers a litter of typically three to five thumb-sized pups and raises them alone. At about 42 days old, the young are weaned, and their mother usually moves to another burrow in her territory.

Summer digs

While groundhogs often have winter burrows that are sheltered within woods or in steep, south-facing hillsides,
in warmer weather they like to be near flat, open ground where grass and leafy plants are more abundant. A single animal normally maintains at least two summer homes, often refresh­ing burrows from past generations. Males and females dig separate burrows up to 10 metres long, which are furnished with a central grass- and leaf-lined bedchamber, separate bathroom nooks, one or more back doors, and well-hidden “plunge holes” that drop steeply into the tunnel for quick escapes from above.