Optimal Patch Use: Variation in Selective Pressure for Efficient Foraging

Abstract

Using both field and laboratory experiments, I examined the patch use of an aquatic insect, Notonecta hoffmanni. In both the laboratory and the field these foragers concentrated their efforts in more rewarding regions. However, based on the laboratory work, they did not maximize energy. More interestingly, their feeding rates were almost always higher than would be expected from patch use. In addition, a pattern emerged concerning the degree of inefficiency: Starved, older foragers came closer to maximizing energy than did well-fed older foragers or younger foragers with either feeding history. This pattern was consistent with variations in the selective pressure for efficient foraging. In particular, based on rearing experiments (Fox 1973), feeding rate appears to have a stronger effect on the fitness of starved, older foragers than on other foragers. Finally, I discussed some general predictions based on the view that variations in selective pressure might influence foraging efficiency.