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Lecture 7

BIOL 1902 Lecture Notes - Lecture 7: Northern Water Snake, Arctiinae (Moth), Ruffed Grouse


Department
Biology
Course Code
BIOL 1902
Professor
Michael Runtz
Lecture
7

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BIOL 1902 – Week 7
Snow as insulation:
- Tree animals, but in winter, spend time under snow
- Mice burrows into snow
- Layer that animals walk through beneath snow: subnivean space (warm spot; nivea =
snow)
- If snow is really deep & ice layer forms on top, animals can suffocate
- Snowmobiles compress snow, causes subnivean space to decrease
- E.g. Ruffed Grouse snow bed – dive into snow & use for warmth
How to keep warm:
- Bask in sun
- On cold nights, Black-capped Chickadees lower their body core temperature by 12°C
oWhy? – burn less fuel, reduces gradient temperature from inside to outside
oHummingbirds can do as well
oEnter deep sleep called torpor
- Shivering = important means of thermogenesis
- Snakes = ectotherms (e.g. Northern Water Snake)
oCannot be out in sub-zero temperatures
Hibernate; go down into burrow to avoid cold
- Herps = collective term for reptiles & amphibians
Frost line:
- Level in ground to which frost affects ground
- Snakes survive by moving down below frost line to prevent bodies from freezing &
becoming dormant (behavioural freeze avoidance)
oNorthern Water Snake leaving its hibernaculum (pl.: hibernacula)
- E.g. Snapping Turtle – All adult & most hatching turtles escape subzero temperatures by
going to bottom of ponds & lakes
oSo do many frogs, but not all – e.g. Bull Frog will go down to bottom
American Toads dig down beneath frost line
oAs do many salamanders - e.g. Spotted Salamander
Many insects survive winter above frost line:
- How? – praying mantis dies in fall, but before they die, they mate, they lay eggs
- Some survive winter as eggs
- Ootheca: egg case that protects eggs all winter
oEither no water in egg or antifreeze used – glycerol or sorbitol
Cryoprotectants (anything used to keep animal alive by using chemical
process)
- Walking Sticks overwinter as eggs
oEggs have ant-snack food on them; ants bring them underground & guard them
oAnts collect eggs for edible capitulum
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