What Make Animals Cold Blooded and Warm-Blooded: Meaning and Reason

We all learned in science class of elementary school that all mammals and birds (with few exceptions) are warm-blooded and all reptiles, insects, amphibians, and fishes are cold blooded. But ever wondered what does it mean to be warm blooded and cold blooded and how can body temperature is related to blood temperature? Let’s ease your curiosity on What Make Animals Cold Blooded and Warm-Blooded Meaning and Reason in detail.

What Make Animals Cold Blooded and Warm-Blooded Meaning and Reason

Cold-Blooded Animals Meaning

Cold blooded animal or scientifically called as ectotherm, are the ones that do not have a mechanism for regulating body temperature, if you’ve observed a lizard, you might know that they spend a lot of time laying in the sun – it’s a matter of survival for them! The reason is, they get their body heat from external sources. The body temperature is very versatile, if there’s cold outside their body temperature will be cold, if hot then their temperature it’s hot as well. Basically, they don’t have any control over their body temperature.

Cold-Blooded Animals

What Make Animals Cold Blooded and Warm-Blooded Meaning and Reason
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Reptiles, fish and amphibians are some common examples of cold-blooded animals, They often bask themselves under the sun to absorb heat. The biologic system of these animals does not let them regulate their own body temperature, hence they always have to rely on external sources.

What Makes Them Cold-Blooded?

The body temperature of cold-blooded animals changes with the ambient temperature. In aquatic animals, like fishes, the osmotic concentration of the body fluid change with that of the ambient water osmotic concentration. These animals are called as conformers.

We might think that why these conformers had not evolved and change the temperature of the body with surrounding?

Thermoregulation is energetically very expensive for some organism and small cold blooded animals lack enough energy. Heat loss and heat gain is a function of surface area, cold blooded animals have the larger surface area in terms of volume and tend to lose body heat very fast when it is cold outside. The muscle activity of cold blooded animal depends on the chemical reaction which runs quickly when it is hot and slowly when cold. Which is why cold blooded animals are very active during warm environment and not found in cold regions. While laying in the sun, cold blooded animals, face the direction of the sun, thus allowing the maximum amount of sunlight to directly fall on their skin and absorb as much as they can. To increase the surface area (in terms of volume) they expand their rib cage and darken their skin to absorb more heat.

I know, a question of how do they keep themselves warm during cold pops up your mind, take a deep breath, we have the answer.

  • When it’s too hot, some organism moves away temporarily from the stressful habitat and return when the stressful period is over. This is called as migration.
  • If some animals are unable to migrate, they choose other methods like hibernation (bear go to hibernation during winters) and go into aestivation to avoid summer related problems like heat and desiccation.
  • Fishes have the special protein in their body which acts like an antifreeze and protect them from cold.

Advantages Of Cold Blooded Animals

  • They require less energy and less food to survive.
  • It’s easy for them to survive almost anywhere.

Warm-Blooded Animals Meaning

To understand better, look at an example, we often miss school when our body temperature increase ( few degrees higher than the normal), it is because we humans are warm blooded animals. Our bodies maintain a constant temperature, regardless of the environment outside. Warm blooded animal is also called as endothermic as we generate heat from within our body, and that’s very cool thing!

Warm Blooded Animals 

What Make Animals Cold Blooded and Warm-Blooded Meaning and Reason
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Only a small number of species out of all comes in warm-blooded animals list, it all evolved from the time when dinosaurs died, which led to the beginning of ice age – being warm blooded is actually a benefit! Without relying solely on external sources like sun, we can keep ourselves warm.

What Makes An Animal Warm-Blooded?

To generate heat, warm-blooded animals convert food into energy. To maintain a normal body temperature warm blooded animals have to eat a lot, only a small amount goes to body mass, rest is used in the conversion process. To stay cool, they sweat or pant to lose heat by water evaporation. Some organism can maintain homeostasis (stable state of organism or equilibrium of stable state) ensures constant body temperature and constant osmotic concentration. All birds, humans and warm-blooded animals are capable of such regulations.

Many biologists believe that longer lifeline of the mammal is largely due to their ability to maintain a constant body temperature. 

The mechanism used by warm-blooded animals to regulate their body temperature is similar to what humans use, we maintain a common body temperature (that is 37 degree). In summers, when outside temperature is more than our body temperature, we sweat a lot. The resulting sweating brings down the body temperature. In winters, when the temperature is less than 37 degree, we start to shiver, which produces heat and raises body temperature.


  • Remain active in cold environment, when cold-blooded animals are freezing outside.
  • They can seek food and defend themselves.


  • They tend to lose their energies very quickly.
  • Warm places tend to increase the number of virus, bacteria, and fungi, which is why warm-blooded animals get infected a lot.

In a world full of animals, not all animals function in the same way. Our understanding of animals and temperature is ever evolving. Read along to know What Makes an Animal Cold or Warm-Blooded and what makes them unique and different from each other.