![]() ![]() ![]() Some birds and mammals will huddle together to conserve heat. Mammals curl up, draw their legs in under them and cover their nose with their tail to conserve heat. An energy-rich tissue called brown fat is used by hibernants for internal heat production (nonshivering thermogenesis) during frequent periods of arousal.Īpart from growing more hair (underfur) or feathers (down) during winter, birds and mammals rely on behavioural strategies for staying warm. Hibernators such as jumping mice, nonmigratory bats and ground squirrels (including woodchucks and marmots) accumulate body fat for insulation and energy to survive long dormant periods. Woodchucks may breathe 10 times per hour, their hearts slow to 4-5 beats per minute and internal temperatures drop to a few degrees above freezing. Respiration and heart rates drop to low levels and become irregular. Hibernation, during which metabolism may be only 1-5% of normal, is marked by body temperatures 20° C or more below normal (hypothermia). Bears, raccoons, skunks and chipmunks awaken on mild, midwinter days to seek food or change dens. They may lose up to 40% of their pre-dormancy weight over winter. black bears, which accumulate fat to supply energy during winter, are deep sleepers because their temperatures remain nearly normal although respiration and heart rates decrease sharply. Some winter-active mammals (shrews and deer mice), and birds ( chickadees), undergo nightly torpor by dropping their body temperatures a few degrees to reduce heat loss. In winter birds and mammals often grow more fur and feathers, and these can be fluffed up (piloerection) to increase insulation. The Arctic fox has such a well-insulated coat that it is thermoneutral down to -80º C. Heat lost due to conduction and convection can be minimized through efficient insulation such as a fat layer and/or body coverings (fur or feathers). Heat is lost through conduction (direct transfer), convection (heat carried away by the movement of air), radiation (losing radiant heat) and evaporation (heat loss due to water evaporating). Some ectotherms are able to produce some heat thermogenically or by using the energy from the sun to heat up (for example, basking), so their body temperatures do not necessarily vary with the external temperature.īehavioural and complex biochemical responses to deepening cold and other environmental factors allow ectothermic animals to survive winter in the temperate zones of Canada.īirds and mammals tend to either escape winter by migrating south (for example many birds and barren-ground caribou, which leave the tundra and enter the Boreal Forest) or endure winter by either being active, entering periods of torpor or hibernating. ![]() However, for the animals above the snow and travelling through it, it adversely affects their movement.Īnimals may be endotherms (warm-blooded) maintaining a constant internal temperature or ectotherms (cold-blooded) with their body temperature tending to vary with the external temperature. ![]() Snow may also protect these animals from predators. Snow insulates so life at the soil surface beneath the snow in the so-called subnivean space can be favourable. Snow, however, is a blessing to many small animals including various invertebrates and small mammals. Lakes freeze over and rain turns to snow. When the temperature dips below 0º C fresh water turns from a liquid to a solid and since all life is based on water this becomes a problem for many organisms. Land takes time to cool down in fall and early winter so the depth of winter does not set in until January and as Canadians know, winter is by no means over on March 21. The sun is closest to Earth in January but it is the sun's radiation striking the land at an oblique angle that makes this season generally cold and the further north the more oblique this angle becomes and the colder it gets. In Canada cold and snow is associated with this season. Winter is the season that begins December 21 (winter solstice) and ends on March 21 (spring Equinox). ![]()
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