Chatowsky hibernation

Cartoon by David Chatowsky of Middletown.

When the cold weather of winter arrives, Rhode Islanders have the same three choices that wildlife have – they can migrate south to avoid the cold, continue their lives as usual and do their best to ignore the cold, or stay inside and hibernate for the winter.

In the animal world, the nectar- and insect-eating birds choose the first option, migrating sometimes great distances to wherever their preferred flowers or insect prey remain active and available. Like skiers and snowboarders, option two is the choice of coyotes, foxes, weasels and other hardy mammals, who tough it out through the cold months and may even benefit from the challenging conditions.

While most Rhode Islanders probably choose to avoid as much outdoor activity as possible during the winter, preferring instead to hibernate in their well-heated homes, few animals in our area make that choice. Woodchucks and some types of bats may be the only species to undergo the physiologically challenging process of hibernation.

According to wildlife biologist Peter August, a professor at the University of Rhode Island, hibernation is a state of inactivity that, unlike sleeping, involves a dramatic reduction in body temperature, a slowing of the metabolism, a reduced heart rate and slowed breathing.

“When a true hibernator goes down, they shut their body down for the season,” August said. “It isn’t remotely connected to being asleep.”

Successful hibernation requires lengthy preparation. Animals begin by putting on excess fat to provide them with enough energy to sustain them through the winter months.

I typically achieve this by hoarding sweets and leftovers following Thanksgiving and Christmas dinner. But most hibernating animals pack on the calories throughout the fall before entering their winter dens. Some smaller animals like chipmunks, which enter a reduced hibernation state called torpor that they awaken from periodically during the winter, cache large quantities of food in their burrows during autumn so they can nibble on it when they awaken.

While taking a three or four month nap may sound appealing, hibernation is not without its risks. If an animal hasn’t put on enough fat to last the winter, they may wake up too soon, which raises their metabolism and body temperature and speeds up the depletion of their fat reserves before additional food becomes available. It usually has tragic results.

That’s similar to what has caused millions of bats to die around the eastern U.S. in the last decade. An invasive fungus in the caves where they hibernate causes white nose syndrome, a disease that arouses the bats from their hibernation too soon. With no insects to prey upon in the middle of winter, the bats quickly use up their energy reserves and die of starvation.

Although true hibernation occurs only in mammals, other local creatures exhibit somewhat similar behaviors to survive the winter cold. Wood frogs, for instance, hide in the leaf litter and nearly freeze solid without any negative physiological effects. Painted turtles burrow into the mud at the bottom of a pond, surviving for long periods without oxygen. And garter snakes gather in massive aggregations – sometimes numbering in the thousands – in underground burrows, where they remain alert but quite sluggish.

Whatever your chosen strategy for outlasting the winter, be happy that at least you get to spend most of it indoors. With the exception of a few mice in my house, Rhode Island’s wildlife doesn’t have that option.

Naturalist Todd McLeish has been writing about wildlife and the environment for more than 25 years. His latest book is “Narwhals: Arctic Whales in a Melting World.”

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