Crocodile Predators
Crocodile Speed
Croc/Human Interaction
Crocodile Size
Crocodile Hunting
Crocodile Defense
Alligators vs. Crocodiles
Crocodile Mothering
Crocodile Infections
Crocodile Bites
Crocs in Water
Croc Body Heat
The Crocodile Heart
Q: On Croc Body Heat
Hi! I have a question: How do reptiles control their body temperature and why?
Thanks!
Michiel
Mammals and birds are called "endotherms" because they produce their own body heat internally (hence "endo" for inside, and "therm" for heat). Reptiles, amphibians, fish and other vertebrates are called "ectotherms" because they gather heat from their environment (hence "ecto" for outside). This can be from the sunlight, from warm water, warm rocks — any medium from which they can absorb heat.
Each strategy has its advantages and disadvantages. To produce heat, endotherms like mammals need to eat regularly. At its most extreme, small mammals like shrews have to eat at least once an hour when they're awake! They spend the vast majority of their lives either sleeping or eating. Sound like fun? Not if you can't find any food — in that case you die from starvation.
Ectotherms like reptiles, on the other hand, gather their heat free of charge from the sun and their surroundings. They don't need to eat regularly to warm their bodies, and so they save an enormous amount of energy that can be put to other use or stored for a later date. This is one reason why larger crocodiles can go at least 18 months without a bite to eat, and why they can afford to be patient when hunting. In truth, a crocodile could never be an endotherm like a mammal — it would never work!
So to answer your question, reptiles control their body temperature by moving between warmer and cooler areas in their environment. They have a preferred body temperature, which in crocodiles is normally around 86 to 89 degrees F. When they're too cool, they move into warmer areas, such as a sunlit bank or warm water. This heats their bodies and raises their core body temperature. When they're too hot, they move into cooler areas such as shade or cooler water. In the tropics, where most crocodilians live, ambient temperature is normally fairly similar to preferred body temperature, so they spend little time adjusting it.
In extreme temperatures, crocodilians have more of a challenge — if they fail to prevent overheating or freezing they will of course die. In cool climates, such as the United States or China, alligators shelter in burrows or deep water where there is still warmth. Alligators can survive in pools of water where the surface freezes — they stick their nostrils above the water, which then freezes around their jaws! The alligator survives because its body is floating in slightly warmer water below the ice. Larger individuals can become partially encased in ice for several hours, and suffer little more than frostbite to parts of their skin. And people ask me why I find crocodilians awesome!
In very hot conditions, crocodilians also find water to protect them from dehydration, or failing that, they dig burrows and hide from the heat. They can survive for several months without food or water in these burrows — another big advantage of being ectothermic. Frankly, it's cool to be a reptile.