Time resources and laziness in animals.

Investigations of time budgets reveal that for many animals a surprising proportion of their active time is spent in inactivity. The question of why these beasts are often idle is investigated by examining their foraging behavior in a model which does not utilize optimization criteria. If an organism's goal is to stay alive, one satisfactory strategy is a thermostat feeding process whereby the animal initiates foraging when it perceives hunger and ceases when it becomes satiated. The simple model is formulated as a Markov chain and analyzed for three cases. Results from each case predict that for many combinations of activity levels and resource spectra, the time spent looking for food is smaller than the time spent not foraging, and laziness may result. Simple decision rules as well as optimization schemes are therefore useful for studying some types of foraging behavior.