Homeotherms and Poikilotherms Use Different Strategies to Regulate Body Temperature
Fish, reptiles, and amphibians are called “cold-blooded animals,” or poikilotherms, because their body temperature varies with the temperature of the environment. However, this does not mean that these animals have no control over their body temperature.
They use behavioral methods to prevent major changes in their temperature. For example, the lizard basks on a sun-baked rock to increase its temperature early in the morning and hides beneath the rock later in the day to prevent overheating. Veterinarians are sometimes asked to advise on the management of captive poikilotherms; it is important to remind owners to provide supplemental heat if they want their animals to be active at the cooler times of the year.Mammals and birds are Iiomeotherms; they maintain a constant body temperature in the presence of considerable changes in environmental temperature. Although the maintenance of a constant temperature allows mammals to live in a wide variety of environments and to remain active during the cold times of the year, it is not without cost. Homeotherms must maintain a high metabolic rate just to provide the heat necessary to maintain body temperature. This requires a high energy intake and therefore almost constant foraging for food. Poikilotherms require much less energy and are better able to survive times of food shortage. Because most veterinarians are primarily concerned with mammals and birds, this chapter focuses on the maintenance of a normal body temperature by homeo- therms.