What animals are cold-blooded? Reptiles, amphibians, most fish, and many invertebrates are commonly described as cold-blooded animals. Examples include crocodiles, snakes, turtles, frogs, salamanders, goldfish, butterflies, and crabs.
Scientists usually call these animals ectotherms. Instead of relying mainly on metabolic heat to maintain a relatively stable body temperature, ectotherms obtain much of their body heat from their surroundings.
But the term "cold-blooded" can be misleading. A lizard basking on a hot rock may have a higher body temperature than a human, while some fish and reptiles have special adaptations that help retain heat.
In this guide, you'll discover 35 examples of cold-blooded animals, how they regulate temperature, and the important exceptions to the usual rules.
What Is a Cold-Blooded Animal?
A cold-blooded animal is commonly understood as an animal whose body temperature depends strongly on environmental conditions rather than being maintained primarily through internally generated heat.
The more precise biological term is ectotherm.
Ectotherms may gain heat from sunlight, warm surfaces, water, or the surrounding air. They can also regulate body temperature through behavior, including:
Basking in sunlight to become warmer.
Moving into shade to prevent overheating.
Entering water or burrows to escape extreme heat.
Changing the time of day when they are active.
Reducing activity during unfavorable temperatures.
Therefore, ectotherms are not completely unable to regulate their body temperature. Many are highly effective behavioral thermoregulators.
Cold-Blooded vs Warm-Blooded Animals
| Feature | Cold-Blooded (Ectothermic) | Warm-Blooded (Endothermic) |
|---|---|---|
| Primary heat source | External environment | Internal metabolic heat |
| Body temperature | Often varies with environmental conditions | Often regulated within a relatively narrow range |
| Energy requirements | Generally lower for similar body sizes | Generally higher because maintaining body heat requires energy |
| Temperature management | Basking, shade-seeking, burrowing and other adaptations | Metabolic heat, insulation, sweating, panting and other mechanisms |
| Common examples | Lizards, frogs, most fish and insects | Most mammals and birds |
Note: Ectothermy and endothermy describe where an animal obtains its body heat. These terms are not exactly interchangeable with having a variable or constant body temperature. Some animals combine different thermal strategies.
35 Cold-Blooded Animals: Complete List
The following examples are organized into four groups: reptiles, amphibians, fish, and invertebrates.
12 Cold-Blooded Reptiles
1. Nile Crocodile
Scientific name: Crocodylus niloticus
Nile crocodiles are large aquatic reptiles found in freshwater habitats across much of sub-Saharan Africa.
They regulate temperature by moving between water, sunlight, and shaded areas. Basking can raise their body temperature, while entering water may help prevent overheating.
Crocodilians use their environment to manage body temperature.
2. American Alligator
Scientific name: Alligator mississippiensis
American alligators inhabit wetlands in the southeastern United States. Their body temperature changes with environmental conditions.
They often bask on banks when they need warmth and retreat into water during hot conditions. Cooler temperatures generally reduce their activity and feeding rates.
3. Green Iguana
Scientific name: Iguana iguana
Green iguanas are tropical lizards that frequently bask in sunlight before becoming active.
Because their body temperature influences digestion, movement, and other physiological processes, access to appropriate environmental temperatures is essential.
Green iguanas commonly warm themselves by basking in the sun.
4. Gila Monster
Scientific name: Heloderma suspectum
The Gila monster is a venomous lizard native to the southwestern United States and northwestern Mexico.
It spends much of its time sheltered in burrows or other protected places. Its activity patterns help it avoid extreme desert temperatures.
5. Komodo Dragon
Scientific name: Varanus komodoensis
The Komodo dragon is the world's largest living lizard. Native to several Indonesian islands, it uses sunlight and environmental warmth to support normal activity.
Despite its large size and powerful hunting abilities, it remains primarily ectothermic.
6. Central Bearded Dragon
Scientific name: Pogona vitticeps
Central bearded dragons are Australian lizards known for basking in sunny areas.
They move between warmer and cooler microhabitats to regulate body temperature. Their behavior is a classic example of ectothermic thermoregulation.
7. Leopard Gecko
Scientific name: Eublepharis macularius
Leopard geckos are primarily ground-dwelling lizards from parts of Asia.
They use warm surfaces, sheltered spaces, and changes in activity timing to maintain suitable body temperatures.
8. Ball Python
Scientific name: Python regius
The ball python, also called the royal python, is native to western and central Africa.
Like most snakes, it depends heavily on environmental temperatures for normal digestion and activity.
Some python species can also temporarily generate additional heat through muscular contractions during egg incubation, showing that reptile temperature biology is more complex than a strict hot-versus-cold classification.
9. Green Anaconda
Scientific name: Eunectes murinus
Green anacondas are large semiaquatic snakes associated with tropical wetlands in South America.
They depend on their aquatic and terrestrial surroundings for heat exchange, adjusting where they rest and move as conditions change.
10. Rattlesnakes
Scientific group: Crotalus and Sistrurus
Rattlesnakes include multiple species native to the Americas.
They may warm themselves in sunny locations during cooler conditions and retreat into shade or sheltered areas when temperatures become excessive.
11. Red-Eared Slider
Scientific name: Trachemys scripta elegans
Red-eared sliders are freshwater turtles well known for basking on logs and rocks.
Basking helps them raise body temperature, while returning to water can provide cooling.
12. Leatherback Sea Turtle
Scientific name: Dermochelys coriacea
Leatherback sea turtles provide an important exception to the simplistic idea that ectothermic animals always have the same temperature as their surroundings.
Because of their large body size, insulation, activity, and specialized heat-exchange mechanisms, leatherbacks can maintain body temperatures above the surrounding seawater.
They are generally described as ectothermic reptiles with remarkable heat-retention adaptations.
7 Cold-Blooded Amphibians
13. Common Toad
Scientific name: Bufo bufo
The common toad is widespread across much of Europe. It depends on surrounding temperatures and suitable moisture levels to remain active.
During unfavorable weather, it may shelter in protected areas rather than remain exposed.
Toads rely on environmental temperatures and moist habitats to regulate their activity.
14. American Bullfrog
Scientific name: Lithobates catesbeianus
American bullfrogs are large amphibians commonly found around ponds, lakes, and other freshwater habitats.
Their activity, feeding, and development are influenced by water temperature and seasonal conditions.
15. Red-Eyed Tree Frog
Scientific name: Agalychnis callidryas
Red-eyed tree frogs are tropical amphibians known for their bright eyes and green coloration.
They depend on humid environments and appropriate temperatures, often remaining sheltered during the day and becoming active at night.
16. Axolotl
Scientific name: Ambystoma mexicanum
The axolotl is a permanently aquatic salamander native to Mexico.
Its body temperature closely reflects water temperature. Excessively warm conditions can cause serious stress, making temperature an important aspect of its biology and care.
17. Fire Salamander
Scientific name: Salamandra salamandra
Fire salamanders are associated with cool, moist woodland environments in Europe.
They avoid excessive drying and high temperatures by using shaded or sheltered microhabitats.
18. Eastern Tiger Salamander
Scientific name: Ambystoma tigrinum
Eastern tiger salamanders spend much of their time underground, where temperature and moisture conditions are more stable than at the surface.
This behavior helps them cope with environmental variation.
19. Olm
Scientific name: Proteus anguinus
The olm is a cave-dwelling salamander adapted to cool underground waters in southeastern Europe.
Its low-energy lifestyle and slow metabolism are well suited to environments where food is often scarce.
For another example of the relationship between metabolism and energy requirements, read our guide to animals that can survive long periods without food.
7 Cold-Blooded Fish
Most fish are ectothermic, although some species possess unusual heat-producing or heat-retaining adaptations.
20. Goldfish
Scientific name: Carassius auratus
Goldfish are freshwater fish whose body temperature changes with the surrounding water.
Water temperature affects their metabolism, feeding, oxygen requirements, and activity.
21. Ocellaris Clownfish
Scientific name: Amphiprion ocellaris
Ocellaris clownfish inhabit tropical marine environments and live in association with sea anemones.
They depend on suitable water temperatures for normal physiological function.
22. Atlantic Cod
Scientific name: Gadus morhua
Atlantic cod are marine fish found in cooler waters of the North Atlantic.
Their metabolism, growth, distribution, and activity are influenced by water temperature.
23. Common Carp
Scientific name: Cyprinus carpio
Common carp are freshwater fish able to live across a relatively broad range of environmental temperatures.
Their feeding and activity typically change with seasonal water temperatures.
24. Ocean Sunfish
Scientific name: Mola mola
Ocean sunfish are unusually shaped marine fish. They move between different water depths and may spend time near the warmer ocean surface.
Changes in depth allow these fish to experience different thermal conditions while foraging.
Ocean sunfish move between ocean depths with different water temperatures.
25. Great White Shark
Scientific name: Carcharodon carcharias
Great white sharks are not ordinary thermal conformers.
They possess specialized blood-vessel arrangements that retain heat in certain body regions, allowing some tissues to remain warmer than the surrounding water.
This adaptation is called regional endothermy.
Great white sharks can maintain elevated temperatures in certain body regions.
26. Atlantic Bluefin Tuna
Scientific name: Thunnus thynnus
Atlantic bluefin tuna also possess regional heat-retention adaptations.
Specialized countercurrent heat exchangers help retain warmth generated by swimming muscles, supporting activity in cooler water.
Because of these adaptations, describing all tuna simply as ordinary cold-blooded fish can be misleading.
9 Cold-Blooded Invertebrates
27. Monarch Butterfly
Scientific name: Danaus plexippus
Monarch butterflies depend heavily on appropriate environmental temperatures for flight.
They may bask in sunlight and orient their wings to absorb warmth before taking flight in cooler conditions.
28. Desert Locust
Scientific name: Schistocerca gregaria
Desert locusts are insects whose activity is strongly influenced by temperature.
They can warm themselves by basking before becoming fully active.
Locust activity and movement are strongly affected by environmental temperature.
29. House Cricket
Scientific name: Acheta domesticus
House crickets are insects whose development, feeding, and activity depend strongly on temperature.
Like many insects, they usually become less active in cooler conditions.
30. Dragonflies
Scientific group: Anisoptera
Dragonflies are predatory insects whose flight performance depends on body temperature.
Some dragonflies can temporarily warm their flight muscles through muscular activity, illustrating how certain insects combine external heating with internally generated heat.
31. Red Wood Ant
Scientific name: Formica rufa
Red wood ants form colonies that can influence nest temperatures through nest structure, location, and colony activity.
This does not mean each ant maintains a mammal-like constant body temperature, but social insects can show sophisticated temperature-management behavior.
32. Common Garden Snail
Scientific name: Cornu aspersum
Common garden snails are terrestrial mollusks whose activity depends on suitable moisture and temperature conditions.
During hot or dry weather, they may withdraw into their shells and become less active to conserve water.
33. Common Octopus
Scientific name: Octopus vulgaris
The common octopus is a marine mollusk whose body temperature depends strongly on the surrounding water.
Water temperature affects its physiology, development, and behavior, as it does in many marine ectotherms.
34. European Shore Crab
Scientific name: Carcinus maenas
The European shore crab is a marine and estuarine crustacean that experiences changing water temperatures and other environmental conditions.
Its metabolism and activity are influenced by those conditions.
35. Antarctic Krill
Scientific name: Euphausia superba
Antarctic krill are small crustaceans that live in cold Southern Ocean waters.
They are adapted to cold marine environments and form an essential part of the Antarctic food web, supporting animals such as penguins, seals, and baleen whales.
Are All Reptiles and Fish Cold-Blooded?
Most living reptiles are primarily ectothermic, and most fish depend strongly on environmental heat. However, neither group can be described accurately using an overly rigid temperature classification.
Exception 1: Tuna and Some Sharks
Some tuna and sharks retain metabolic heat in specific parts of their bodies through countercurrent heat exchange.
This is regional endothermy, which allows those tissues to remain warmer than the surrounding water.
Exception 2: Opah (Moonfish)
The opah is a particularly remarkable fish because it circulates warmed blood throughout its body.
NOAA identifies the opah as the first fish discovered with whole-body endothermy.
Therefore, saying "all fish are cold-blooded" is scientifically incorrect.
Exception 3: Leatherback Sea Turtle
The leatherback sea turtle is a reptile with impressive heat-retention adaptations.
Its body size, insulation, and countercurrent heat exchange help it remain active in water colder than the temperatures tolerated by many other sea turtles.
Exception 4: Heat-Producing Insects
Some insects can temporarily warm their flight muscles through activity.
Examples include certain bees, moths, and dragonflies. This does not automatically make them equivalent to continuously endothermic mammals or birds.
Why Do Cold-Blooded Animals Need Less Food?
Many ectotherms require less energy than similarly sized endotherms because they do not continuously spend large amounts of metabolic energy maintaining a high body temperature.
This can allow them to survive on relatively limited food supplies, although their actual needs still depend on species, temperature, activity, and life stage.
A crocodile or snake may eat large meals relatively infrequently, while a warm-blooded animal of similar size may require more frequent energy intake.
However, this does not mean all cold-blooded animals can survive starvation equally well.
Read our 10 Animals That Can Survive the Longest Without Food guide for examples of prolonged fasting, dormancy, and energy conservation.
Are Cold-Blooded Animals More Sensitive to Cold Weather?
Many ectotherms become less active as temperatures fall because temperature affects enzyme activity, muscle function, digestion, and other physiological processes.
However, sensitivity varies considerably. Some cold-water fish are adapted to extremely low temperatures, while many tropical reptiles become stressed or inactive when conditions become too cold.
Cold tolerance depends on evolutionary history and environmental adaptation, not simply whether an animal is described as cold-blooded.
Explore our related article on animals that are especially sensitive to cold temperatures.
Frequently Asked Questions
What are 10 examples of cold-blooded animals?
Ten examples include the Nile crocodile, American alligator, green iguana, Komodo dragon, bearded dragon, ball python, common toad, axolotl, goldfish, and common garden snail.
Are snakes cold-blooded?
Yes. Snakes are primarily ectothermic reptiles. They depend heavily on their surroundings for body heat, although some python species can temporarily generate heat through muscular activity.
Are frogs cold-blooded?
Yes. Frogs and toads are ectothermic amphibians whose body temperatures are strongly affected by environmental conditions.
Are turtles cold-blooded?
Yes, turtles are primarily ectothermic reptiles. Some large species, especially leatherback sea turtles, have adaptations that help retain heat and maintain body temperatures above surrounding water.
Are sharks cold-blooded?
Many sharks are ectothermic, but some, including great white sharks and makos, retain heat in certain body regions. Therefore, sharks do not all use identical temperature-control strategies.
Are fish cold-blooded?
Most fish are ectothermic, but there are exceptions. The opah maintains elevated temperatures throughout its body, while tuna and some sharks can warm specific body regions.
Are butterflies cold-blooded?
Yes. Butterflies are generally ectothermic insects. Their activity and ability to fly depend strongly on suitable body temperatures.
Are humans cold-blooded?
No. Humans are endothermic mammals that generate metabolic heat and regulate body temperature through physiological and behavioral mechanisms.
Can cold-blooded animals regulate their body temperature?
Yes. Many regulate body temperature behaviorally by basking, seeking shade, changing location, or adjusting activity. What distinguishes ectotherms is their primary dependence on external heat sources.
Key Takeaways
Cold-blooded animals are generally called ectotherms.
Most reptiles, amphibians, fish, and many invertebrates rely heavily on environmental heat.
Cold-blooded does not mean the animal's blood is always cold.
Many ectotherms actively regulate temperature through behavior.
Some fish, reptiles, and insects have specialized heat-production or heat-retention adaptations.
There is no simple temperature rule that accurately describes every species.
Understanding ectothermy helps explain why animals behave differently across environments, from sun-basking lizards to cold-water fish and desert insects.
Scientific References
Reviewed October 27, 2026. Scientific classification and understanding of animal thermoregulation continue to develop.
