FORAGING COSTS AS A DEFINING FACTOR FOR GROWTH AND ASYMPTOTIC MASS

Modeling the growth of animals as parts of ecosystems often presumes t he existence of an asymptotic weight which, when reached by the indivi dual, stops its further growth. We show that the asymptotic weight is influenced by environmental conditions, and that growth is limited bec ause of a trade-off of foraging costs and gain of feeding. We show tha t the so-called asymptotic mass is a comprehensive value, which also c ontains an environmental parameter. We develop our model for organisms of neutral buoyancy in an aquatic environment; for terrestrial and ae rial animals it has limited validity only. We discuss examples and der ive a critical value for resource availability in a habitat, which inf orms us whether foraging in that habitat is worthwhile or not.