Cold-Blooded Creatures: Fact Sheet
(Link to Classroom Activities)

Why do we call some animals cold-blooded and others, warm-blooded? It has to do with how they manage their body temperatures. Look at these comparisons:

Cold-Blooded Animals
Warm-Blooded Animals

Their bodies take on the temperature of their surroundings. (They can't regulate internal temperatures.)

They maintain constant body temperatures despite the temperature of their surroundings.
Which Creatures? Insects, spiders, amphibians, reptiles, fish Mammals and birds
Energy Use

* Don't require food energy to maintain body temperature.
* Burn more energy in warm weather than cold. (Biological processes go faster in heat.)

* Costly! Humans spend about 75% of our food energy to maintain a constant body temperature.
* Burn more energy in cold temperatures as they generate heat. (In hot weather, rid excess heat by sweating or panting.)
Movement Body slows down in cold temperatures; more active in warmer weather. Can remain active in cold and warm temperatures.
More Advantages

Don't have to eat as often as warm-blooded animals do.

* Bodies function consistently regardless of weather.
* Can be active at night (nocturnal) and avoid predators.

More Disadvantages * Speed of body functions changes with outside temperatures.
* Rely on sun to warm up and protection to stay cool.
* Can freeze fairly easily.

* Must eat a lot to stay warm.
* Require insulation from extreme cold/heat.

* Small birds/mammals lose a lot of heat, so must be very active to stay warm (e.g., hummingbirds).

Some Adaptations for Surviving Cold Temperatures

* Burying themselves.
* Slowing down body processes almost to a stop.
* Clustering at night in large groups (e.g., monarchs).

* Migrating or hibernating.
Shivering (uses a lot of energy).
* Going into torpor: Body temperature drops to conserve energy. (Chemicals are released to prevent animal from freezing!)

Cold-Blooded Facts: More on Monarchs

  • Monarchs are paralyzed by cold temperatures. It must be at least 41 degrees F for them to crawl and 55 F to begin to fly.
  • Why do monarchs move so slowly in cold temperatures? Their muscle activity depends on chemical reactions that go slowly when its cold and quickly when its warm.
  • Like many warm-blooded animals, monarchs sometimes shiver (move wings rapidly) to warm up the muscles inside. Learn more about when and why monarchs shiver.

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