Birds and mammals keep their body temperatures both high (95″ to 105’F) and constant. Walking dinosaur costume They do so by eating prodigious quantities of food and “burning” or metabolizing the energy it contains. Sophisticated, automatic thermoregulatory controls (sweating, panting, and shivering, among them) keep things on track. Hence, birds and mammals, called endothermic homeotherms, are much less dependent on the environment than reptiles. Realistic dinosaur costume In particular, they can get by without sun bathing (though some humans seem strangely unaware of this). some primitive mammals have intermediate metabolic systems. Monotremes (the platypus and the spiny anteater) and the tenrec (a relative of shrews), for instance, have a reptile-like metabolic rate when warm or resting, and body temperatures of about 85’F. T-rex costume But they keep their body temperature constant, and when cold or active they assume a high mammalian metabolic rate.
There is a possible difference in the way birds and mammals thermoregulate that may warrant attention. Mechanical dinosaur Both groups shiver to keep warm when they are really cold. when temperatures are cool, many mammals use what is called nonshivering thermogenesis to help keep body temperatures up. This heat is produced by special “brown” fat cells. For a long time it was believed that birds did not have brown fat or use nonshivering thermogenesis. Recent studies indicate that they do,a but perhaps not to the same extent as mammals.