Don’t tell the groundhog, who saw his shadow on Tuesday and retreated underground, but spring begins in February.

It seems crazy to suggest that spring begins in February, especially if we’re in a deep freeze or buried in snow. After all, this month’s full moon – coming on February 28 – is traditionally called the snow moon for good reason.

But once you notice what’s going on in the natural world, you’ll realize that nature is beginning to stir in Westborough.

First of all, there’s the light. Suddenly, days are noticeably longer. By the first week of February, the sun rises at 7 a.m. and is still shining (just barely) at 5 p.m., giving us 10 hours of daylight. Many creatures’ yearly biological rhythms are tuned to the light, with minor adjustments for local weather conditions.

The breeding season for great horned owls got underway in late January. You might hear them hooting in the woods.

One day soon you might be awakened by the first coos of a mourning dove.

Around Valentine’s Day, you’re likely to get a whiff of skunk, or unfortunately, see a skunk as road kill. Why? Around this time our local skunks leave their burrows for a while to meet up and mate.

Notice the first tentative cardinal songs this month. Listen for the first “hey-sweetie” songs of black-capped chickadees, our state bird. Hear the European starlings whistle.

In our local vernal pools, tiny fairy shrimp appear like magic. They hatch from dormant eggs, sometimes even under the ice.

Maple sap begins to flow toward the end of the month when we get a few warm days with cold nights.

In our swamps, skunk cabbage starts poking up, generating enough heat to melt snow as it does so.

In some years, a warm spell in February brings out the pussy willows.

In the snow near tree trunks, soot-like black specs turn out to be “snow fleas,” or springtails.

Late this month, you might spot a mourning cloak butterfly fluttering in the woods or feeding at tree sap, a mud puddle, or even old animal dung.

How could we get through February without watching nature?

But getting back to the groundhog who supposedly predicts the coming of spring, why do we say “he” and refer to “him”? Is this sexism? Or reality?

As it happens, there’s some truth to the picture we create of a male groundhog venturing early out of his burrow. The male groundhog, or woodchuck as we say in New England (using a name based on the sound of the Native American name for the animal), awakens first from hibernation and goes above ground. The motive, of course, is the breeding season.

Our native woodchucks (Marmota monax) aren’t alone in this get-there-first habit. In many migrating birds, the males fly north before the females, who follow a few weeks later. Why the rush? Male birds arrive early to establish good territories that will help to attract females. You might notice the showy male red-wing blackbirds, which in some years arrive in our cattail marshes by March first.

Likewise, male woodchucks come out first (although probably not as early as February 2) to stake out good territories and defend them from other males. A good territory is likely to include a burrow where a female woodchuck is still hibernating. When she emerges in late March or April, they’ll mate. The male and female may share a burrow for a short while, but the male leaves before their young are born, about a month later. Woodchucks are basically loners.

We tend to think of hibernation as a way of escaping the cold of winter, but more importantly, this long sleep is a way of surviving winter’s lack of food.

Take woodchucks, for example. They’re vegetarians, as the gardeners among us know all too well. Woodchucks graze on green things, such as clover and grasses, and lettuce, peas, and beans. This green food is scarce by the time they start hibernating in October, and woodchucks continue to live off the remaining fat on their bodies when they emerge in the spring, before the new growing season really gets going.

Other animals that hibernate for long periods to avoid starving in winter include bears, chipmunks, and some bats.

In preparation for hibernation, woodchucks get fat. (Their relatives, the squirrels, store nuts, but the woodchucks’ green food doesn’t keep well.) In late summer, their appetite increases, and they rapidly gain weight. Researchers have even used woodchucks in studies of obesity.

Substances in the woodchuck’s blood bring on hibernation. When researchers inject a summer woodchuck with its own blood taken and preserved when it was hibernating, that woodchuck goes into hibernation within days and may remain so for up to 3 months.

During hibernation, a woodchuck’s body processes and body chemistry slow down. The woodchuck keeps its body temperature a few degrees above the temperature of the burrow, which is generally deep enough in the ground to remain above freezing. Its heart may beat only 10 times per minute – compare that to normal at 130 beats per minute (or to our own resting heart rate of 60-70 beats per minute).

Do woodchucks sleep throughout their long winter nap? Not exactly. They’ll sleep soundly for 4-10 days, and then awaken for 1-5 days. As spring approaches, their wakeful times get longer. If it’s cold out, they stay underground even when they’re awake.

Woodchucks hibernate in burrows they’ve dug into sloping ground in the woods. During spring and summer, a woodchuck uses a different burrow, near a field or open area where it finds its food.

While digging a burrow, a woodchuck can move 700 pounds of earth (and stones – by pushing them with its head). It digs a tunnel or system of tunnels 2-5 feet deep and up to 40 feet long, with several entrances. You might notice a pile of dirt at the main entrance, but not at the other entrances, which it digs from the inside. It disappears into one of these holes when escaping a predator.

Woodchuck burrows become homes for many other animals. A cottontail rabbit, skunk, raccoon, or opossum might move in with a hibernating woodchuck. Mice, voles, chipmunks, and even cats may use abandoned woodchuck burrows. Foxes often enlarge an old woodchuck burrow as a den for raising their young.

If you spot a woodchuck on the move, you’ll probably see it waddling. But woodchucks also climb trees and swim.

Our woodchucks are native, but Groundhog Day is not. The tradition comes to us from Europe, where it involved different animals, such as badgers, hedgehogs, or bears. It has roots in early Christian celebrations of Candlemas Day on February 2, and possibly also in the Celtic festival of Imbolc, marking the birth of lambs at the half-way point through winter.

In any case, let’s enjoy the stirring of nature in February!