Lecture six

Heat Exchange in Animals

  • Heat Loss: Animals can lose heat to cold air, making it essential for them to adapt.

  • Role of Blood Vessels: Blood vessels act as heat exchangers in cold environments.

Roosting Behavior in Birds

  • Definition of Roosting: Roosting refers to the practice of birds resting or sleeping at night.

  • Behavioral Adaptation: Birds choose specific places, called roost sites, to sleep, which provide shelter from cold weather.

Animal Shelters and Structures

  • Shelters: Some animals find existing shelters, while others build them.

  • Muskrat Lodges: Muskrats construct lodges and dams creating ponds, which serve as habitats.

  • Beaver Dams: Beavers build large dams with sticks, creating ecosystem changes beneficial for various species.

Thermal Protection in Cold Weather

  • Natural Structures: Cavities in trees or animal-built structures offer thermal protection against winter cold.

  • Snow as Insulation: Snow acts as insulation, trapping heat near the ground, protecting small mammals.

Hibernation Adaptations

  • Lowering Body Temperature: Some small mammals can lower their body temperature by up to 12°C during winter.

  • Torpor State: Animals enter a state of torpor, significantly reducing their heart rate and metabolic activity for extended periods, sometimes four months or more.

  • Periodic Waking: True hibernators wake briefly during hibernation, possibly as a safety mechanism.

Ectothermic Animals

  • Ectotherm Definition: Ectotherms, like snakes, do not produce their own body heat and rely on environmental temperatures.

  • Survival Strategies: Snakes survive through winter by burrowing below the frost line, avoiding lethal temperatures.

Insects and Winter Survival

  • Insect Lifespan: Insects generally have shorter lifespans compared to larger animals, sometimes only lasting one season.

  • Overwintering Strategies: Different species adapt in various ways:

    • Praying Mantis: Adults die off, while eggs overwinter, surviving in a dormant state.

    • Surviving Adults: Some species, like female mosquitoes and social wasps, survive the cold as adults in hidden locations.

Cryoprotective Mechanisms

  • Freeze Tolerance: Certain animals can survive freezing by having ice form between their cells, not inside them.

  • Cryoprotectants: Animals produce chemicals that prevent intracellular freezing, allowing survival in extreme cold.

Freeze-Tolerance in Frogs

  • Specific Frogs: Some frogs, such as the wood frog and great tree frog, can freeze during winter.

  • Behavior: These frogs remain in the soil and can tolerate freezing processes without significant harm.