Caimans, those reptiles related to alligators, can stay for long minutes without moving a single one of their scales. Immobile on the beach of the tropical rainforest, even their breathing can’t be detected. They’re very much alive, nonetheless.
Why do they go so long without moving?
The answer is simple: these are cold-blooded animals. But it’s not completely fair to say that an animal is cold-blooded or warm-blooded. All animal species have developed mechanisms or behaviors that allow them to control their internal temperature. This is called thermoregulation. There are two animal types: homoiothermal, more commonly called “warm-blooded,” and ectothermic, or “cold-blooded.”
An internal furnace : homeothermy
Birds and mammals are warm-blooded animals, meaning they can keep their body temperature relatively constant no matter what the temperature around them is. This type of thermoregulation, however, requires a great amount of energy, and the animal must therefore feed regularly to get it. On the other hand, it makes it possible to move freely and provides greater endurance. The two-toed sloth is in fact a mammal, but it’s an exception. It can tolerate a range in its body temperature from 24 to 33°C depending on ambient air temperature.
A variable temperature : ectothermy
Like the caiman, reptiles, fish, amphibians and insects are cold-blooded animals. Unable to produce their own heat, they have to find other means of regulating their body temperature. In certain reptiles, that temperature can vary by about 20°C without putting their lives in danger. It’s often by adapting their behavior that they succeed in maintaining a constant temperature. For instance, reptiles must expose themselves to the sun before becoming active. Fish adjust the depth at which they live according to the temperature of the water. Desert insects or reptiles hide in the coolest sand. Some insects rub their wings together to stay warm at night. Bees ventilate the hive with their wings to keep it cool in hot weather. Ectothermy demands little energy, and the animal generally doesn’t need to feed as often. However, its movements are sometimes limited when the temperature is low, and it’s highly dependent on external conditions. At the Biodôme, the caimans warm up not only thanks to the sun, but also with the help of a heating plate concealed under the sand. When they get too hot, they open their mouths to rid the body of excess heat, or else quite simply go for a refreshing dip. On your next visit to the Biodôme, you’ll know that, despite their perfect immobility, the caimans are still very much alive.