Table of Contents
- What are Cold-Blooded Animals?
- Cold-Blooded Characteristics
- Cold-Blooded Animals List
- Lesson Summary
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.
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.
In comparison, warm-blooded animals ingest food to serve two metabolic goals:
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.
|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
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.
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 included the following:
All birds and mammals are endotherms or warm-blooded.
Below you will learn more about the types of cold-blooded animals that you can keep as a pet or observe in the wild.
There are many types of cold-blooded creatures that make excellent pets. Some of the easiest cold-blooded pets are the following:
Each type of cold-blooded pet has its specific feeding and habitat needs. Some are better at escaping their pen, more so than others. Most live for a long time and require an ownership commitment longer than that for a dog or cat. And all cold-blooded pets need time to adjust to being handled and occasionally will need to see an exotic veterinarian to maintain their health and well-being. But even though they lack fur and feathers, they can still have a big personality making them a fun companion to observe and hold.
And don't forget fish! Betta fish are easy to care for because they do not require a filtration system for their water. Goldfish, guppies, mollies, and tetras are other great fish for home aquariums, to list a few. As with the terrestrial ectotherms, fish have specific habitat requirements, and not all types like to share a tank.
Most cold-blooded animals are meant to be viewed in the wild and sometimes from a safe distance. When hiking in the mountains of the United States, you may spot a rattlesnake and hear its warning rattle to ensure you stay away. A saltwater crocodile may slap your vessel with its tail when boating along a river in Australia's Northern Territory. When scuba diving in Hawaii, you may observe a hawksbill sea turtle swimming among the coral reefs. Or perhaps you may venture into your own backyard or explore a local wetland and hear frogs ribbitting like a banjo and katydids buzzing in accompaniment. Countless cold-blooded animals live across the world, welcoming your appreciation but not your touch. Other cold-blooded animals found in the wild are:
Cold-blooded animals, also known as ectotherms, are not named because they have cold-blood but because they must rely on an external source, the sun's radiant heat, to regulate their own body temperature. Reptiles, amphibians, fish, and arthropods (insects, arachnids, millipedes, centipedes, and crustaceans) are all types of cold-blooded creatures. Warm-blooded animals (mammals and birds) are endotherms because they can regulate their internal body temperature, no matter how hot or cold outside.
Cold-blooded animals come in a large variety of sizes because they only need food to grow and maintain a healthy body mass. Consequently, they can go days between a meal. Conversely, warm-blooded animals must consume larger quantities of food every day to maintain all metabolic functions that control their weight gain AND body temperature. Although cold-blooded animals have strategies to avoid intense heat and cold temperatures, they cannot stay active year-round as most warm-blooded animals do. And while some cold-blooded creatures make excellent pets, like bearded dragons, corn snakes, and aquarium fish, most are meant to wander the Earth appreciating only a view from a safe distance.
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Ectotherm is another term for cold-blooded animals because "ecto" means "external" or "outside" in Greek and "therm" means "heat" in Greek.
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.
The lack of feathers or fur to trap body heat and are unable to generate body heat on their own.
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.
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.
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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