Deactivation of dietary wariness through experience of novel food

Abstract

When a forager encounters an unfamiliar type of food, it must decide whether to eat it and risk being poisoned or avoid eating it and risk forfeiting a potentially valuable resource. Birds typically respond to such situations with "dietary wariness"; they show a transient aversion to approaching new food (neophobia), and many individuals also show a much longer lasting reluctance to consume the new food (dietary conservatism), even once neophobia has waned. Very little is known about how these processes, together termed "wariness," are controlled. We therefore present a series of experiments investigating how wariness of novel foods in domestic chicks, Gallus gallus domesticus, can be deactivated and reactivated by different experiences of colored foods, varying in their degree of novelty and palatability. We found that prior experience of a single novel color of palatable chick crumbs was sufficient to deactivate both neophobia and dietary conservatism of any other novel color of crumbs tested. Relatively little prior experience of a novel training food was needed to deactivate neophobia, after which the birds would peck at any other novel food. In contrast, much more extensive experience of eating a novel training food was needed before the birds would incorporate other novel foods into their diet. Chicks needed direct physical contact with the training food before they overcame their wariness to eat another novel food. However, observational learning was sufficient to encourage them to peck at the food (overcoming their neophobia). Reinstating wariness was much more easily achieved than its deactivation. We discuss these surprising results in relation to the foraging behavior of wild and domestic birds. Copyright 2007, Oxford University Press.