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Lecture 7

BIOL 1902 Lecture Notes - Lecture 7: Northern Water Snake, Ruffed Grouse, Supercooling

Course Code
BIOL 1902
Michael Runtz

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Ways animals keep warm in the winter
Subnivean Space: the crystalized zone of snow cover next to the ground & through
which small animals move around in winter
oRuffed grouse bed
Basking in the sun
Birds are endotherms
oOn cold nights Black-Capped Chickadees lower their body core temperature by
12 oC
oEntering a deep sleep called torpor
oShivering is an important means of thermogenesis
Snakes are ectotherms
Frost line: the level in the ground to which frost affects the ground
oSnakes survive by moving down below the frost line & becoming dormant
oBehaviour Freeze Avoidance
oNorthern Water Snake leaving its hibernaculum
All adult & most hatchling turtles escape subzero temperatures by going to
the bottom of ponds & lakes
So do many frogs
American Toads dig down beneath the frost line
As do many salamanders
Many insects survive winter above the frost line
oAdults die – before they die, they mate & lay eggs
oSome survive winter as eggs – Ootheca (egg case)
Either no water in the egg or antifreeze is used
Glycerol or sorbitol = Cryoprotectants
oWalking Sticks also overwinter as eggs
Ants collect eggs for the edible capitulum
oSome overwinter as larvae
Woolly Bear – antifreeze
When no ice forms inside the body = supercooling
oFemale mosquitos survive winter as adults
“hibernating” insects stop eating in the fall & void their gut of all contents
oAnglewing Butterflies overwinter as supercooled adults
First butterfly you see in spring
oSilk Moths overwinter as pupae in cocoons
Cocoons & pupal cases keep dormant insect from contacting water/ice
oSome insects overwinter in special sites
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