Winter Sleepers and Direct Register

       My semester one Maine Fish and Wildlife students could tell you that creatures in Maine have three options to survive our typically long, brutal winters. They can Hibernate, Migrate, or "Resist". It seems ecologists are locked in a never ending battle to define a true "Hibernator" and as the argument stands today, Maine has only a handful of true hibernators. Woodchucks (Marmota monax), little brown bats (Myotis licifugus), and the black bear (Ursus americanus) would fit into this elite group. Although, some people are still skeptical about awarding this title to the bear. In order to be considered a true hibernator, a creature must slow its metabolism and body temperature down to levels so low that it cannot easily wake up. Those backyard woodchucks notorious for munching on freshly planted gardens in June are truly amazing creatures. Their heart rate can dip as low as 4-5 beats per minute during their long winter slumber! Sorry folks, our beloved groundhog day is an elaborate hoax. There is simply no way a wild groundhog (a.k.a. woodchuck) could wake up from its hibernation as quickly as ol' Punxsutawny Phil.
       There are many mammals in Maine that are assumed to be hibernating because they seem to disappear during the winter only to show themselves again in the spring. The striped skunk (Mephitis mephitis) is one of them. Skunks remain in dens for the majority of the winter and are able to lower their body temperature a few degrees but nothing close to the woodchuck. Skunks remain mostly dormant living off their fat stores but during warm spells they can be observed out and about foraging for food.

This skunk seen above is taking advantage of a recent warm spell by getting out in search of food.

       A classic Maine winter resistor is the red fox. They are awake and active all season. Wild canids including the red fox walk in a manner that is often described as "Direct Register". This is when an animal's back foot lands exactly in the track made by its front foot on that side. This method is also referred to as "perfect walking". It often amazes me how strait a set of fox or coyote tracks can be compared to the sloppily laid impressions from your average house dog. Over millions of years, wild dogs have evolved to conserve energy in a variety of ways. It makes sense that direct register is a simple way to move more efficiently in deep snow. Foxes have large home ranges and must cover a lot of ground to find enough prey to survive our winters. Without this perfect gait, wasted energy would spell certain doom. While people walk on two feet making this method difficult, we obviously appreciate the value of direct register. Who hasn't utilized another person's previously laid tracks when wading in deep snow?

 

Watch closely as this red fox steps perfectly in the tracks laid by its front feet.