Watch Out in the Winter Woods

Several weeks ago on a gray, gray day with gently falling snow I took a long walk in the Big Woods. Several miles from the road I came across two young ladies taking advantage of the four inches of snow to cross-country ski through the forest. Due to the tracks I had seen along the way I thought of alerting them to a potential danger – but thought better of it after I realized that they probably would ignore the old codger.

Because most people don’t venture outdoors in the coldest weather and, at best, have only a rudimentary understanding of biology, they've never heard of two creatures that inhabit woodlands in the colder portions of the northeastern U.S. and eastern Canada. Two species (Palteris mendacious and P.  pseudofictivous) of what are commonly called snow snakes occur throughout those snowy regions. Snow snakes leave clearly defined tracks when there are only a few inches of snow on the ground, and those tracks are what I had seen –

 

Both species are closely related to, and apparently highly evolved from, the coral snakes of the southeast, which in turn are related to the cobras of Asia and Africa. It appears that during the Illinoian glaciation (240,000-140,000 years ago) some of the higher peaks of the Appalachian Mountains remained ice free, and that is where isolated populations of coral snakes rapidly evolved into the two species of snow snakes. Then, as the glaciers melted the snakes spread from their ancestral homes. They managed to survive the more recent Wisconsinan glaciation which ended about 10,000 years ago and now occupy areas where winter snow cover normally exceeds 45 days; here in northcentral Pennsylvania we’re close to the southern limit of their range.

As both species evolved they lost all pigment other than in the eyes and thus appear white, although some individuals have a slight pinkish cast due to the hemoglobin in their blood, great camouflage in snow. They also evolved to be partially warm-blooded which enables them to be active and catch prey in a cold environment. These snakes are so intolerant of high temperatures that they must estivate (the warm-weather equivalent of hibernation) from April to November. Being only partially warm-blooded, they must catch and subdue their prey quickly so their poison is even more toxic than that of coral snakes and they are extremely fast over short distances.

The two species inhabit extensive forests of mixed hardwoods and conifers where they hunt small mammals up to the size of gray squirrels, but have very different hunting techniques. P. mendacious, the larger species, is an ambush predator, climbing trees and shrubs to lie on horizontal limbs from which it drops onto its prey. P. pseudofictivous pursues its prey on the ground, typically following voles and mice through the rodents’ tunnels beneath the snow.

As much time as I’ve spent in the winter woods over the last 50 years I’ve never had the pleasure of seeing a live snow snake, but their tracks are readily apparent –

Since the snakes are partially warm-blooded I’ve hoped my camera traps would capture a photo during a snow-free period as one did of a weasel in its white winter coat several years ago, but no such luck. Snow snakes are nowhere common and are certain to become even less so as the climate warms – they will probably be extirpated from Pennsylvania by mid-century.

So, when you’re out in the winter woods watch out for snow snakes and watch out for those who would go through an elaborate spoof  like this one just to spin a tall tale and interject a bit of humor into an otherwise colorless winter day.