<P> Animals also engage in kleptothermy in which they share or even steal each other's body warmth . In endotherms such as bats and birds (such as the mousebird and emperor penguin) it allows the sharing of body heat (particularly amongst juveniles). This allows the individuals to increase their thermal inertia (as with gigantothermy) and so reduce heat loss . Some ectotherms share burrows of ectotherms . Other animals exploit termite mounds . </P> <P> Some animals living in cold environments maintain their body temperature by preventing heat loss . Their fur grows more densely to increase the amount of insulation . Some animals are regionally heterothermic and are able to allow their less insulated extremities to cool to temperatures much lower than their core temperature--nearly to 0 ° C (32 ° F). This minimizes heat loss through less insulated body parts, like the legs, feet (or hooves), and nose . </P> <P> To cope with limited food resources and low temperatures, some mammals hibernate during cold periods . To remain in "stasis" for long periods, these animals build up brown fat reserves and slow all body functions . True hibernators (e.g., groundhogs) keep their body temperatures low throughout hibernation whereas the core temperature of false hibernators (e.g., bears) varies; occasionally the animal may emerge from its den for brief periods . Some bats are true hibernators and rely upon a rapid, non-shivering thermogenesis of their brown fat deposit to bring them out of hibernation . </P> <P> Estivation is similar to hibernation, however, it usually occurs in hot periods to allow animals to avoid high temperatures and desiccation . Both terrestrial and aquatic invertebrate and vertebrates enter into estivation . Examples include lady beetles (Coccinellidae), North American desert tortoises, crocodiles, salamanders, cane toads, and the water - holding frog . </P>

How do endotherms balance heat loss and gain