DO THE STEREOTYPIES OF PIGS, CHICKENS AND MINK REFLECT ADAPTIVE SPECIES-DIFFERENCES IN THE CONTROL OF FORAGING

The food-related stereotypies of some captive species (e.g. mink) are performed most often prior to feeding, while those of others (e.g. pig s and chickens) occur at low levels before feeding and increase after food consumption. It has been suggested that these differences reflect adaptive species differences in how feeding behaviour is controlled. However, this hypothesis rests on several underlying assumptions for w hich there is incomplete support. One assumption is that there are ind eed species differences in the design of motivational systems, and we suggest some specific predictions to test this idea. For example, the ingestion of small portions of food should lead to greater enhancement of local searching behaviour in species whose food supply is particul ate and patchy. The basic premise underlying this evolutionary explana tion for species differences in stereotypy is that such differences ar e genetically based, not an artefact of the way different animals are kept. However, we argue that variation in husbandry may also cause var iation in stereotypies. For example, the autoshaping literature reveal s factors likely to affect pre-feeding stereotypies: unreliable predic tors of food delivery, or predictors that occur some time before food is presented, give rise to general locomotory search phases of appetit ive behaviour rather than behaviour related to food handling. Farmed m ink may therefore show high levels of pre-feeding locomotor behaviour principally because sounds predicting the delivery of their dairy meal are quite unreliable and commence long before the food arrives. Lack of space may also inhibit locomotor forms of pre-feeding stereotypies in pigs and chickens. In addition, the high post-feeding appetitive be haviour of these two species may be caused by lack of satiation follow ing food. Overall, evolutionary hypotheses make predictions about ster eotypy based on feeding ecology, but there are also alternative causal hypotheses that make predictions based on aspects of husbandry. Toget her, these may help to explain the forms of existing stereotypies, and to anticipate the forms likely to arise in new husbandry systems or i n newly captive species. (C) 1997 Elsevier Science B.V.