Bitter tastes can influence birds’ dietary expansion strategies

Abstract

Deciding whether or not to expand one’s diet is problematic: if novel foods are accepted, they could be harmful or less profitable than familiar foods, but if they are rejected, then opportunities to gain valuable nutrients could be lost. One way to reduce the costs associated with dietary expansion is to initially incorporate small amounts of each novel food into the diet, allowing time to assess the quality of food while minimizing the risk of ingesting large amounts of harmful substances. In predatory animals, one way to reduce the amount of novel food eaten is to select smaller prey individuals when faced with a population of variably sized novel prey, particularly when novel prey are presented alongside cues that indicate that there may be toxic prey in the environment. Using naive domestic chicks Gallus gallus domesticus as predators and colored pastry caterpillars for prey, I found that ingesting quinine, a bitter-tasting toxin, caused birds to shift their preference away from large palatable prey and toward small palatable prey, but only when the prey were visually novel. This behavior could be adaptive in situations when size is positively correlated with toxicity and could potentially influence the population dynamics of prey.