Sleep­ing through win­ter

The News (New Glasgow) - - PICTOU COUNTY - Don MacLean Don MacLean is an out­door writer and bi­ol­o­gist who lives in Pic­tou County.

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.”

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