A cost-benefit analysis of nocturnal feeding in the rat.

Rats are nocturnal feeders. The present results show that when either the cost of procuring a meal or the cost of consuming it increases differentially in the dark relative to the light, rats shift their feeding activity to the light phase of the light/dark cycle. These results suggest that some of the same factors that presumably provided the selection pressure for nocturnal feeding in the phylogeny of the rat are still capable of modifying its current patterns of feeding.