A groundhog is a widely distributed marmot of North American variety with a reddish brown fur and a rough bushy tail. Also called woodchuck, though it is no way related with chucking of wood.

Being a rodent type groundhog is basically a burrowing mammal and lives in a hole in the ground (this is why the name!). It goes into a deep long slumber during the winter and comes out of the hole when the spring is on the verge. For a groundhog the moths before and after winter are very important. This is when the marmot remains extremely busy, searching for food, looking for a nice mate, helping the family grow, making good storage, furnishing new home (or hole) and getting thoroughly prepared for the next winter. The more active the groundhog remains during the summer the happier he spends the winter.

Now the legend: According to the traditional belief it comes out of the hole after checking out its own shadow. This is where it applies its wit, or that is what the legend says:
If a shadow of its own is seen under the sun, it slips back into the hole. For, it knows the winter is yet to be over by another six weeks.
If no shadow, it comes out finally. For, it predicts, the spring is close by.

Though there is no statistical evidence favoring this belief, it is fact that the woodchuck is a very nervous creature. It gets terribly scared with the slightest provocation and sprints back in to its hole.

It is also a very shy animal and stays away from all possible human presence. There is, however, no evidence that a woodchuck has the power of predicting the change of season by studying the shadow.

Well, many of us just laugh away the capability of groundhog. They say, if a groundhog really goes back to its hole on seeing its own shadow that is due to its nervous and scary nature. After such long time of underground sleep detached from the outer world, it simply gets startled by its own shadow and runs back to its cozy, secured home to be pent up for a few more weeks.

Yes, it is only a possible explanation. But who knows if this met-marmot(?) has got some magical power to foretell the arrival of spring!

Power or not, this North American native has become very popular for being used as the predictor of spring.