Cold Blooded Animals

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Created by: Team Biology at, Last Updated: April 25, 2024

Cold Blooded Animals

Cold-blooded animals, or poikilotherms, rely on environmental conditions to regulate their body temperature. Unlike warm-blooded species, these creatures do not generate their own heat. Instead, they must adapt to their surroundings to maintain their body temperature. This adaptation can include basking in the sun to raise their temperature or seeking shade and cool areas to lower it. This dependence on external heat sources makes them highly susceptible to temperature fluctuations, which can greatly influence their activity levels and survival. Cold-blooded animals include a diverse group such as reptiles, amphibians, fish, and insects, each uniquely adapted to their thermal environment.

Definition of Cold-Blooded Animals

Cold-blooded animals, or ectotherms, are species that regulate their body temperature according to the environment. This group includes reptiles, amphibians, fish, and invertebrates. They do not generate their own heat but instead rely on external sources like sunlight to warm up. Key characteristics include variable body temperatures, low food requirements due to minimal energy spent on heat production, and behaviors such as basking or seeking shade to manage their temperature.

Characteristics of Cold-Blooded Animals

Characteristics of Cold-Blooded Animals

Temperature Regulation

Cold-blooded animals do not regulate their internal body temperature through metabolic processes. Instead, their body temperature fluctuates with the ambient environment. This means they become warmer or cooler depending on the surrounding temperatures. For example, a lizard will sunbathe to increase its body temperature and seek shade or a burrow to cool down.

Energy Consumption

Because they do not need to maintain a constant body temperature, cold-blooded animals are more energy-efficient compared to warm-blooded animals. They require less food because they expend less energy on heating or cooling their bodies. This low energy requirement allows them to survive longer periods without food.

Behavioral Adaptations

To manage their body temperature, cold-blooded animals exhibit various behavioral adaptations. Common behaviors include basking in the sun to warm up and finding cool areas or submerging in water to lower their body temperature. These behaviors help them to thermoregulate effectively without the need for internal thermal regulation mechanisms.

Habitat and Activity

The dependency on external heat sources often influences the habitats cold-blooded animals choose and their patterns of activity. Many cold-blooded species are more active during the warmer parts of the day and may become dormant during colder periods. Seasonal changes can also impact their activity, leading to hibernation or aestivation during extreme temperatures.

Reproductive and Metabolic Rates

Temperature affects the metabolic and reproductive rates of cold-blooded animals. In warmer conditions, their metabolism speeds up, which can lead to faster growth and quicker reproduction. Conversely, cooler temperatures can slow down these processes.

Notable Examples


  • Snakes: All snakes are cold-blooded. They rely on the sun to warm up and often hide in cool places to lower their body temperature. Examples include the rattlesnake and the garter snake.
  • Lizards: Like snakes, lizards are ectothermic. They need to bask in the sun to increase their body temperature for daily activities. Common examples are the gecko and the iguana.
  • Turtles: Turtles, both sea and land-dwelling, regulate their temperature by moving between water and sunny basking spots. The sea turtle and box turtle are typical examples.


  • Frogs: Frogs are well-known cold-blooded animals that require external heat sources to manage their body temperature. Species like the American bullfrog and the tree frog fall into this category.
  • Toads: Similar to frogs, toads also depend on environmental heat to function. The common toad and the cane toad are examples of this group.
  • Salamanders: These amphibians are also ectothermic, using their surroundings to regulate their body heat. Notable examples include the axolotl and the spotted salamander.


  • Goldfish: Domestic and wild goldfish are ectothermic, maintaining their body temperature according to the water temperature.
  • Sharks: Most sharks are cold-blooded, relying on the temperature of the ocean waters to regulate their body heat. The great white shark and the hammerhead shark are examples.


  • Insects: Nearly all insects are cold-blooded. Bees, butterflies, and beetles, for example, must warm up in the sunlight to be active.
  • Crustaceans: Crabs, lobsters, and shrimp, all cold-blooded, adjust their activities based on the surrounding water temperature.

How Do Cold-Blooded Animals Survive Winter?

Cold-blooded animals, or ectotherms, rely on external sources of heat to regulate their body temperature. During winter, when temperatures drop significantly, these animals employ various strategies to survive the harsh conditions. Here’s how different groups of cold-blooded animals cope with winter:


  • Hibernation: Many reptiles, like certain species of snakes and lizards, hibernate during winter. This state of dormancy allows them to conserve energy by significantly lowering their metabolic rate. They often hibernate in groups in burrows that stay at a stable temperature, safe from freezing conditions.
  • Brumation: Similar to hibernation, brumation is a term specifically used for the winter dormancy of reptiles. During brumation, reptiles do not sleep throughout the season; instead, they wake up intermittently to drink water and then return to their dormant state. Turtles, for instance, burrow into the mud at the bottom of ponds, where the water doesn’t freeze, allowing them to survive the cold.


  • Frogs and Toads: Some frogs and toads can survive freezing temperatures by allowing their bodies to partially freeze. They produce a kind of “antifreeze” in their bodily fluids, which protects their vital organs from freezing damage. For example, the wood frog has the remarkable ability to freeze solid and then thaw come spring without injury.
  • Salamanders: Similar to frogs, some salamanders also use the freeze tolerance strategy. Others burrow deep into the soil below the frost line or find refuge in logs or burrows.


Cold Water Habitats: Fish adapt to lower temperatures by moving to deeper waters where temperatures are more stable and do not reach freezing points. Some fish, like carp and goldfish, slow their metabolism so much that they require very little oxygen and can survive in water that is nearly freezing.


  • Insects: Many insects enter a state called diapause, a form of dormancy that is not completely understood but helps them to survive unfavorable environmental conditions. Insects might also seek out insulated crevices or burrow into the soil to escape the cold.
  • Arachnids: Spiders and other arachnids often seek shelter in frost-free areas, hiding under rocks, bark, and leaves or even entering human dwellings to escape the cold.

Benefits of Ectothermy

Ectothermy, or cold-bloodedness, offers several distinct advantages to animals. These creatures do not need to maintain a constant body temperature, which allows for a greater variety of body sizes—from minuscule insects to vast crocodiles—since the ratio of body weight to surface area is less critical. The variable body temperature of ectotherms also makes them less attractive hosts for parasites, thereby reducing the risk of diseases. Furthermore, because they do not use food to generate heat, cold-blooded animals can survive long periods without eating, with some species, like certain snakes, only needing to feed once a month. During times of food scarcity, they can significantly reduce their activity levels, conserving energy effectively. Most of the food they consume is used for growth rather than heat production, making them highly efficient in converting food into body mass.

Disadvantages of Ectothermy

However, ectothermy also comes with notable disadvantages. These animals are generally confined to warmer climates, as their activity levels and metabolic rates are directly influenced by environmental temperatures. In cooler temperatures, an ectotherm’s metabolism slows dramatically, which can diminish their ability to find food, escape predators, and perform other necessary functions. If temperatures fall below a critical threshold and remain low for extended periods, it can become lethal for these creatures. This dependency on external heat sources restricts their geographic distribution and can impact their survival during unexpected cold spells.


Do Cold-Blooded Animals Freeze?

Cold-blooded animals can become lethargic in cold conditions but have adaptations to avoid freezing, such as burrowing or entering a dormant state.

Are Humans Cold-Blooded Mammals?

Humans are warm-blooded mammals, meaning they regulate their body temperature internally, unlike cold-blooded creatures.

Do Cold-Blooded Animals Feel?

Cold-blooded animals have sensory responses and can feel stimuli in their environment, similar to warm-blooded animals.

Do Cold-Blooded Animals Feel Pain?

Cold-blooded animals experience pain. They have nervous systems capable of responding to painful stimuli, indicating distress or discomfort.

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