Animal Behavior

Behavior Basics

How does an animal’s energy level affect its behavior?

Every animal has a finite amount of energy available for use in a unit of time. This energy usage is its metabolic rate (measured in calories or kilocalories) plus the energy required for life activities. The energy budget places limitations on an animal’s behavior. For example, an ectothermic (cold-blooded) lizard uses less energy because it does not maintain a constant body temperature; thus, ectotherms such as amphibians and reptiles control body temperature by behavior. Endothermic (warm-blooded) animals like birds and mammals have a higher energy budget, most of which is used to maintain internal body temperature. This all means that endotherms require more energy than ectotherms of a similar size, so they may spend a greater portion of their day searching for food. Other factors that influence energy requirements are age, sex, size, type of diet, activity level, hormonal balance, and time of day. For example, in general, the energy expenditures (in kilocalories/kilogram weight per day) vary depending on the animal—a deer mouse (small mammal) expends 438, a penguin (larger bird) expends 233, a human (large mammal) expends 36.5, and a python (reptile) expends 5.5.


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