How to be a predator

Abstract

This paper discusses what would appear to be the optimal strategy of a predator given two alternative objectives: (1) maximum yield commensurate with the long-term maintenance of the prey species, and (2) extinction of the prey species. The problem is examined in terms of past research on Daphnia and Hydra, and takes into account estimates of ecological efficiency, population efficiency, and growth efficiency based on many laboratory experiments. It is shown that there may be distinct differences in the effects of removing different kinds of individuals from a prey population. The optimal system for a predator wishing to insure the continued availability of its prey is to take animals which are about to die anyway, i.e., to alter the natural pattern of mortality as little as possible. It is concluded, with some reservations, that predators in nature generally act in this manner. Conversely, if one's intent is to exterminate a prey species (e.g., an objectionable pest), the animals removed should be those which natural predators do not select. © 1968 by the American Society of Zoologists.