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What Animals are Cold-Blooded?

Lesson Transcript
Instructor: Christopher Muscato

Chris has a master's degree in history and teaches at the University of Northern Colorado.

Insects, reptiles, and amphibians are some examples of cold-blooded animals. Learn about the characteristics of cold-blooded animals, and discover their advantages over warm-blooded animals. Updated: 01/04/2022

Cold Blood

If you've ever had a pet lizard or a pet dog, you may have noticed that both of them spend a lot of time laying in the sun. While lizards and dogs share this behavior, the reasons for it are very different. Dogs basically just enjoy being in the sunshine, while for lizards it's a matter of survival.

Lizards are an example of animals that cannot control their own body temperature. Biologists describe these animals as being ectothermic, which is a fancy way of describing animals that get their body heat from external sources. We often call these animals cold-blooded. Basically, if the environment is warm, a cold-blooded animal will be warm. If the environment is cold, the animal is cold. While these animals can't naturally regulate their own body temperatures, they do have some other interesting adaptations, so maybe calling somebody cold-blooded shouldn't be such an insult.

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  • 0:04 Cold Blood
  • 0:57 Cold-Blooded Animals
  • 1:25 Cold-Blooded Characteristics
  • 3:30 Cold-Blooded Advantages
  • 4:42 Lesson Summary
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Cold-Blooded Animals

Which animals actually live without control over their body temperatures? Basically, cold-blooded animals include the insects, arachnids, reptiles, fish, and amphibians. These are the oldest groupings of animals on Earth, evolving much earlier than birds and mammals, which tells us that being cold-blooded is an ancient biologic system. Warm-bloodedness, or being able to naturally regulate body temperature, is a more recent adaptation.

Snakes are examples of cold-blooded animals

Cold-Blooded Characteristics

Cold-blooded animals must rely on external sources like sun or shade to control their body temperatures. This means that there are many behavioral traits found commonly amongst cold-blooded critters. For one, they behave very differently in different environments. Many cold-blooded animals, from trout to turtles to salamanders, will be active in the sun, but become very sluggish in colder environments.

Another behavioral trait we often see is absorbing heat. To absorb heat, cold-blooded animals will often spend hours basking in the sun. Lizards are especially known for this. A lizard may spend hours basking, re-positioning itself so that the maximum amount of its body surface is directly facing the sun. This maximizes the amount of heat it can gather. Then, when the lizard becomes too hot, it jumps into the shade or a cool puddle. Changing its body temperature requires a change in the environment.

As they move between hot and cold environments, their body temperatures can change drastically. We know that people have a nearly constant body temperature of 98.6 degrees Fahrenheit. If your temperature goes up or down by a degree, that's a big deal. For cold-blooded animals like snakes, body temperature can go up or down much more dramatically throughout the year.

Sun-bathing is common for cold-blooded animals

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