Humans categorize animals in many ways. We have entire phylogenetic trees dedicated to dividing families, genera, and species. We even differentiate them based on the foods that animals eat, dividing animals into carnivores, herbivores, and omnivores. Another valuable way to differentiate animals is by whether they are warm-blooded or cold-blooded. Today, we’re going to evaluate the two different types of creatures and tell you the difference between warm-blooded animals vs cold-blooded animals.

By the time we’ve finished, you’ll know what makes these animals unique as well as several examples of each type of creature!

The Key Differences Between Warm-Blooded and Cold-Blooded Animals

Warm-Blooded Cold-Blooded
Regulation of Body Temperature – Can maintain a constant or nearly constant body temperature regardless of the ambient temperature – Unable to maintain a constant body temperature
– Body temperature depends on the environment’s temperature
Types of Animals – Mammals and birds – Insects, reptiles, fish, amphibians, and more
Methods of Body Temperature Regulation – Generally, two types of processes allow warm-blooded creatures to live: endothermy, and homeothermy
– Many use endothermy, the ability to produce their own body heat through metabolic processes
– Others use homeothermy to maintain a stable body temperature
– Rely on a combination of three mechanisms for temperature regulation: ectothermy, poikilothermy, or heterothermy
– Usually involves moving from warm to cool areas to maintain body temperature, ectothermy, along with other strategies
– Some cold-blooded animals live in places with constant temperatures, making them homeothermic ectothermsOther Names– Homeothermic or endothermic- Ectothermic or poikilothermicExamples– Humans, wolves, eagles, whales, bears- Crocodiles, bees, frogs, turtles

The difference between warm-blooded animals and cold-blooded animals is that warm-blooded animals can keep a steady body temperature regardless of their environment’s temperature, but cold-blooded animals cannot regulate their body temperature against their environment’s temperature.

Warm-blooded animals use internal mechanisms to maintain the same body temperature as they move from one area to another. Warm-blooded animals need to maintain a certain temperature to stay alive. For example, warm-blooded mammals often maintain an internal body temperature between 97 °F to 103 °F, and birds have a slightly higher average body temperature closer to 105 °F.

Cold-blooded animals do not have the means to keep a constant body temperature, so their body temperature is essentially controlled by their environment. If a cold-blooded animal stays in an area where it’s 60 degrees, its body will assume that temperature over time. If the temperature then drops to 50 degrees, so will the animal’s body.

What Types of Animals Are Warm-Blooded or Cold-Blooded?

Generally speaking, only birds and mammals are warm-blooded animals. Meanwhile, cold-blooded animals include amphibians, fish, reptiles, and insects.  Take a look at some examples of animals that are warm-blooded and cold-blooded.

Warm-Blooded Cold-Blooded
Eagles Snakes
Humans Crocodiles
Wolves Bees
Bears Frogs
Crows Salmon
Whales Turtles
Seagulls Grasshoppers

As you can see, there is a wide variety of different animals that are endothermic and ectothermic. Whether or not an animal can regulate its body temperature greatly impacts various aspects of its life such as where it can live and even its size.

Modern Terminology for Warm-Blooded and Cold-Blooded Animals

Another difference between warm-blooded and cold-blooded animals is the modern terminology used to refer to each type of organism.

You’ll rarely hear the terms warm-blooded or cold-blooded in scientific circles. Instead, warm-blooded creatures may be called homeothermic or endothermic, and cold-blooded animals are called poikilothermic or ectothermic.

Typically, scientists will discuss specific animals based on their methods of temperature regulation since they can vary even within the broad confines of warm-bloodedness or cold-bloodedness. We’ll explain these factors in greater detail below.  

How Warm-Blooded Animals Regulate Their bodies

Alaskan Brown Bear
Generally speaking, only birds and mammals are warm-blooded animals.

Tory Kallman/Shutterstock.com

Warm-blooded animals, also called endothermic or homeothermic animals can use several mechanisms to maintain a steady body temperature, also called thermal homeostasis, in adverse environments. These mechanisms are endothermy, homeothermy, and tachymetabolism.

For example, they may use endothermy to control their body temperature by burning food energy or shivering to warm the body, or they can utilize homeothermy to maintain a constant internal temperature.

As a result, mammals and birds can survive in a lot of places with wild temperature variations. Also, these endotherms tend to have structures in their bodies that aid them in their thermoregulation. They use their feathers or fur to keep them warm in cold places or utilize sweat glands to cool them off in hot areas.

Still, that doesn’t make endothermic organisms immune to adverse conditions. That’s why we often see creatures like bears hibernate during the winter. They can’t maintain the metabolic processes needed to be active when food isn’t available and the weather is very cold, so they enter a state of torpor and reduce their activity.

How Cold-Blooded Animals Survive

animals that estivate: crocodile
Cold-blooded animals include amphibians, fish, reptiles, and insects.

iStock.com/Vladimir Bolokh

Cold-blooded organisms are at the mercy of their environments, and a sudden change can negatively impact these animals. They use ectothermy, heterothermy, and poikilothermy to regulate their temperatures. Like warm-blooded animals, cold-blooded animals rarely rely on one form of thermoregulation, so it’s common to see each of these in use by animals.

Ectothermy is a common thermoregulation technique where an animal will use an external element to control their temperature. For example, an alligator may bask in the sun to increase its temperature, or a person keeping a snake as a pet might use a heat lamp to give it somewhere to warm up.

Some animals are poikilotherms, and that means their internal core temperature will stay the same despite the overall internal temperature of the animal undergoing significant variations based on changes in the environment.

Lastly, some animals are a mix between homeothermy and poikilothermy, called heterotherms. These animals may have the environment affect their body temperature or they can self-regulate it. Examples of animals that exhibit heterothermy are bats and some ground squirrels like the 13-lined ground squirrel.

Warm-Blooded vs Cold-Blooded Wrap-Up

The simple explanation of warm-blooded and cold-blooded animals is enough for most people. The mechanisms to sustain endotherms and ectotherms are complex, nuanced, and overlap in places. Worse yet, you’ll find that some types of animals don’t fit neatly into their proposed categories.

Only by studying thermoregulation in great detail can you completely understand the minutiae of these processes and underlying mechanisms.

Still, with this basic rendering of how animals control their temperatures in mind, though, you can at least tell the basic differences between these two kinds of thermoregulation in animals.  

hummingbird in flight with blurred background
Although most endotherms appear “warm-blooded” and most ectotherms appear “cold-blooded,” some animals display characteristics of both groups. They are called heterotherms. A hummingbird is an example.

Keneva Photography/Shutterstock.com

Up Next:

Leave a comment