Our Environment by Katherine Fletcher
When temperatures plunged to -33ºC last week,
most of us threw another log on the stove, raised the
thermostat, and survived. However, wildlife survives
outside. How do they manage?
Avoidance
Our Environment by Katherine Fletcher
When temperatures plunged to -33ºC last week,
most of us threw another log on the stove, raised the
thermostat, and survived. However, wildlife survives
outside. How do they manage?
Avoidance
Just like human “snowbirds,” some animals migrate. Birds such as warblers and herons and even some insects such as monarch butterflies evade winter by flying south.
Dormancy is another type of avoidance. Black bears fatten up in autumn, then enter a period of dormancy characterized by reduced heartbeat and breathing, where they don’t defecate or urinate, and don’t eat. Although we once thought bears slept throughout winter, now scientists say they’re not true hibernators because they move about.
Adaptation
However, many critters remain here and cope with the extremes. Lynx, raccoons, mink, deer, coyotes, foxes and others stay, as do birds such as chickadees, blue jays, great horned owls, goldfinches and more. What
are their survival strategies?
Ectothermic adaptation
“Ecto” (outside) + “thermic” (heat). Ectothermic
animals don’t generate their own heat but absorb it from their immediate external environment. Invertebrates like mollusks and worms avoid freezing by overwintering underground or underwater, where they alter their internal chemistry to create substances resembling “antifreeze.” Hinterland Who’s Who explains, “Water that isn’t pure, or that is mixed with sugars and proteins, freezes at a temperature lower than 0°C, so some species add these molecules to their fluids in the fall.” (hww.ca)
Fish, reptiles and amphibians are ectothermic
vertebrates: fishes’ body fluids can survive temperatures below 0ºC. Amphibians’ adaptations depend upon whether they are terrestrial (land-based) or aquatic. Leopard frogs survive underneath the ice of ponds; terrestrial American toads bury into soil.
Endothermic adaptations
Mammals and birds are endotherms (“endo” =
“within”). They maintain an active metabolism (create and sustain their own body heat) and regular body
functions.
How do they stay warm? Ruffed grouse dive beneath a blanket of snow. (Downside? Freezing rain may entomb them.) Some birds roost together at
nighttime, conserving heat by huddling. (Added
benefit? Grouping means better detection of
predators.) As well, feathers trap body heat: watch blue jays fluff themselves up in extreme cold to stay warm.
Mammals protect themselves in various ways. Small mammals – mice, voles – live in the subnivean zone [“sub” (below) + “nive” (snow)] digging tunnels beneath its protection to travel from underground
burrows to food sources. Even though the subnivean world appears safe, nature never offers complete
security: tube-shaped weasels reign as supreme
subnivean predators.
Other winter adaptations? Mammals grow denser fur which traps air, keeping them warm. Muzzles and nostrils grow additional protective hairs which warm cold air before it is inhaled. Lynx and snowshoe hares grow fur between their toes not only for heat capture but also to create “snowshoes”, enabling them to
run on the surface of snow.
So, when temperatures plunge and we snuggle indoors with fortunate pets, marvel at wildlife’s astonishing adaptations.
More information?
Winter: An Ecological Handbook, ISBN 1555660363; Life in the Cold; ISBN 1611684285
Katharine Fletcher is a freelance writer.
Contact her at fletcher.katharine@gmail.com
