Prey size and prey density affect meal patterns of rats in depleting and nondepleting patches

We examined meal-ending decisions by rats feeding in depleting patches (where the rate of return decreased during a meal) and nondepleting patches (where the rate of return was constant) in a closed-economy, laboratory setting that allowed the precise measurement of feeding rates and meal patterns. The rats were free living in an environment where costs were imposed with bar-press requirements for (1) travelling to a patch to begin a meal and (2) earning prey during the ensuing meal in that patch. The prey in each patch were large or small, and dense or sparse. In both depleting and nondepleting patches, meals were larger as travel price increased. In nondepleting patches, meal size (in grams) was unaffected by the rate of return within the patch, but in depleting patches, meals were larger where the rate of return was higher. In depleting patches, the rats ate the same number of small and large prey per meal, suggesting that meals end when the rate of return reaches some level relative to a comparison value; however, the end-of-meal rate was lower than the average rate (calculated over foraging and feeding time), and thus meals were too large to maximize rate or minimize cost. No obvious rule of thumb explained meal size in both depleting and nondepleting patches. Copyright 1999 The Association for the Study of Animal Behaviour.