It’s nearing the end of October, the leaves are falling, and temperatures are dropping. That means many of the animals we would normally see in the Arb are spending a final few days in the sun and getting ready for hibernation.
Snakes are no exception. Because snakes are cold-blooded (ectotherms), their body temperatures change according to environmental conditions. When temperatures drop below freezing, snakes can’t help but freeze as well.
So what do native Minnesota snakes do to survive the frigid winter weather? Most, including the common gartersnake (the species most frequently sighted in the Arboretum), enter a period of brumation.
Brumation is a fancy term for reptile hibernation, but it differs significantly from the traditional mammalian hibernation.
Snakes don’t actually sleep during brumation – they remain alert, but are generally inactive. Their cold-bloodedness translates to a low resting metabolism, meaning that they don’t require much food to sustain bodily functions. Consequently, they have no need to fatten up in the fall.
Although different species vary in their ability to survive extreme temperatures, most reptiles cannot survive in environments where temperatures dip below 4 C.
The key to winter survival for snakes is to burrow below the frost line, the depth to which groundwater freezes. Since cracks and crannies in the soil that extend this deep are difficult to come by, masses of snakes tend to hibernate together in suitable locations.
So if you happen to be out in the Arb on a warm day, keep a look-out for snakes heading down into the ground.