Cold Blooded Animals: Examples | What Does Cold Blooded Mean? - Video & Lesson Transcript |

Cold-Blooded Animals

Kathryn Reis, Christopher Muscato
  • Author
    Kathryn Reis

    Kathryn B. Reis is a wildlife biologist with 5 years of research experience addressing wildlife ecology and conservation governance. She also has 8 years of professional experience in policy advocacy and governmental affairs and over 4 years of experience as an environmental educator and nature trail interpreter. She earned her B.S. in Wildlife Biology with a minor in Zoology from Colorado State University and a M.S. in Wildlife Ecology from Michigan State University. She is certified as an Associate Wildlife Biologist through The Wildlife Society and as an Educator and Facilitator of the Leopold Education Project.

  • Instructor
    Christopher Muscato

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

What are cold blooded animals and what does cold blooded mean? Learn the cold blooded definition and learn about the variety of cold blooded creatures. Updated: 08/17/2021

Table of Contents


What are Cold-Blooded Animals?

Do the terms "cold-blooded" versus "warm-blooded" refer to an animal's blood temperature? No. Cold-blooded animals are creatures that must rely on their physical environment to regulate their body temperature. It is more appropriate to call such animals ectotherms because "ecto" is Greek for "external" or "outside" and "therm" is Greek for "heat". In other words, ectotherms must capture heat from the sun, either directly or indirectly, to raise and maintain their body temperature.

In contrast, warm-blooded animals are endotherms. The word "endo" is Greek for "internal" or "inside". Endotherms have multiple mechanisms within their body to maintain their optimal internal temperature range, regardless of how hot or cold their environment is.

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Cold-Blooded Characteristics

What does it mean to be a cold-blooded animal? It means that the animal must alternate between warm and cool environments to maintain its body temperate between 80 and 90 degrees Fahrenheit. These creatures regularly lose body heat to their environment because they have no layers of fur, feathers, or blubber to trap heat underneath their skin. Consequently, this environmental dependency lets the ectotherms focus on eating for only one purpose: to build or maintain their body mass.

Turtle balancing on log while sun-bathing

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In comparison, warm-blooded animals ingest food to serve two metabolic goals:

  1. grow and maintain healthy body weight; and
  2. generate heat to maintain an internal body temperature between 97 and 104 degrees Fahrenheit for mammals and between 106 and 109 degrees Fahrenheit for birds.

Advantages and Disadvantages to Being Cold-Blooded

Since cold-blooded animals absorb heat from their environment to aid metabolism, they can spend several days digesting their food and wait up to a week before seeking their next meal. Moreover, the sizes of ectotherms vary significantly because no caloric energy is needed to generate internal body heat. Hence they can be as small as a pin or tall as a refrigerator, whereas warm-blooded animals can rarely get much smaller than a tennis ball. Indeed, for any endotherm to be extremely tiny, the animal would have to eat a tremendous amount of food constantly, every day, to avoid losing its body heat to the environment.

There are disadvantages to being an ectotherm. Regardless of the season, all cold-blooded animals are sensitive to extreme temperature fluctuations. Therefore, it is imperative that they immediately escape excessive heat and cold by finding proper hiding spaces to cool or warm their bodies. Without such retreats, ectotherms would die from overheating and freezing.

Advantages Disadvantages
Needing food for only body growth and weight maintenance means ectotherms can assume a wide variety of sizes Overheating or freezing can be fatal if there are no shelters within ectotherm's required temperature range
Slow food digestion yields more time for rest than search for food

Sources: *Texas Parks and Wildlife, **Zoo Atlanta

Behavior of Cold-Blooded Animals

Since the ambient temperature dictates the internal body temperature of a cold-blooded animal, it must have ready access to a warmer environment to avoid freezing to death. It is for this reason ectotherms are typically concentrated in warmer climates.

All cold-blooded creatures living on land will bask in the sun while sitting on a log or laying on a heated rock to limber their muscles and maintain their metabolic functions. Aquatic ectotherms will seek warmer water to heat their body. And because all cold-blooded animals must rely on their environment to change their body temperature, they will seek a cooler environment to avoid overheating, such as under a rock, in the shade of a tree, or colder water.

Even though cold-blooded animals love to sunbathe, they must have a way to escape the intense heat. Many do so through a process known as aestivation. Then, for just one day, the animal will burrow someplace cool, such as in the muddy bottom of a pond, and enter a state of torpor. Torpor is a state of deep sleep, from which it is difficult to rouse. Additionally, ectotherms can release heat-shock proteins throughout their body to protect the molecular structure of all proteins found in their organs (brain, heart, lungs, muscles, etc.). Without such adaptations, the cold-blooded animals would die from heat stress.

Alligator cooling off under a plant

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To escape colder temperatures, terrestrial ectotherms burrow underground to seek warmth and enter a state of torpor for many weeks, if not months. Consequently, the metabolic processes of cold-blooded creatures slow down, so they can go without food for even longer periods of time. Some cold-blooded animals die before the onset of winter but maintain viable populations by laying their eggs or spinning their cocoons in the shelter of a tree or under the eaves of a home. Once warmer temperatures arrive in the spring, the eggs and cocoons hatch, creating a whole new generation of the animal population. Some aquatic ectotherms have the special ability to alter their body chemistry to prevent or limit the growth of ice crystals in their cells and tissues. In sum, cold-blooded creatures have multiple adaptations to avoid freezing to death.

Cold-Blooded Animals List

Cold-blooded animals included the following:

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Frequently Asked Questions

What are cold blooded animals called?

Ectotherm is another term for cold-blooded animals because "ecto" means "external" or "outside" in Greek and "therm" means "heat" in Greek.

What is difference between cold blooded and warm blooded animals?

Cold-blooded animals must rely on the temperature of their physical environment to regulate their internal body temperature. That is, to warm their body they must seek heat (e.g., sun-bathing) and to cool their body they must seek someplace colder (e.g., a cave). Warm-blooded animals rely on the metabolism of food to regulate their internal body temperature and have fur (and in some cases blubber) or feather to help trap heat in their body.

What makes animals cold blooded?

The lack of feathers or fur to trap body heat and are unable to generate body heat on their own.

Do cold blooded animals die in the cold?

Cold-blooded animals may die in the cold if they cannot find warm shelter, such as underground or under a bale of hay in a barn, and/or lack abilities to alter their body chemistry to prevent or limit the growth of ice crystals in their tissues.

What is a cold blooded animal?

Any type of reptile, amphibian, fish or arthropod. These animals lack fur, feathers and blubber to trap heat in their body and, therefore, lose body heat to their surrounding environment.

How does being cold-blooded work?

The animal must warm its internal body temperature directly from sun rays or from heat radiating from its environmental surroundings (such as a rock) to insure it can limber its body for movement and metabolize its food. To avoid over-heating, the animal must seek a cool shelter. To avoid freezing, the animal must seek a warm shelter.

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