Sleeping through winter
I was interested to learn last week about an initiative in place in Nova Scotia to look for sea turtles which may become stranded off our coast at this time of year.
Nova Scotia is home to several species of sea turtles which come up here to feed during the summer but migrate back to the Southern United States and the Gulf of Mexico to spend the winter and to lay their eggs. Last winter, a leatherback turtle was found frozen in the ice of the Bras d’Or Lakes. The turtle failed to leave the lakes in time and died when the temperature dropped.
Animals have evolved several behaviours which enable them to survive winter. My wife walks every day and is concerned that she may run into a bear, and she has crossed paths with several of them over the years. She looks forward to fall and the knowledge that bears will be denning up for the winter so she will have a few bear-free months when she won’t have to worry about running into one. While black bears undergo a type of hibernation, it differs from the real thing. True hibernators reduce their metabolic rate, body temperature and heart rate to enable them to survive very long periods of cold weather, surviving only on the food reserves they stored as fat in the fall. Bears, on the other hand, maintain a fairly high body temperature and may wake up during the winter during periods of mild weather. Groundhogs, along with bats, are the only true hibernators we have in Nova Scotia.
Hibernation is one type of behaviour animals use to deal with periods of low food availability. Many animals migrate to areas where food is more abundant. Birds, and sea turtles, are a perfect example. Others adapt to live in an environment of snow and ice. Snowshoe hares change colour and ruffed grouse grow pectinations — or little fleshy growths on their feet — in late fall, which serve as snowshoes to allow them to walk on the snow. Other animals, such as squirrels, remain active during the winter but store caches of food in the fall to help them make it through the tough months.
Hibernators are the masters of dealing with a harsh environment and groundhogs go through some pretty complicated physiological changes during this process. I think everyone is familiar with groundhogs, also known as woodchucks. They range throughout mainland Nova Scotia and can be found along the edges of fields where they feed on grass and shrubs. Late in the fall, groundhogs go on a major feeding spree which allows them to build up a thick layer of fat, then seal themselves into their burrow to wait out winter. Over a period of time, their body temperature will drop from a high of 37 degrees to a low of three degrees during the coldest days of winter. During hibernation, their heart rate will also drop from a high of 80 beats a minute when actively feeding in the summer to five beats per minute.
This low level of activity allows groundhogs to exist on their fat reserves until they emerge in the spring. Even with a healthy fat buildup going into the winter, groundhogs may lose up to a third of their body weight over the winter.
“Hibernators are the masters of dealing with a harsh environment and groundhogs go through some pretty complicated physiological changes during this process.”