A RULE OF THUMB IN MAMMALIAN HERBIVORES

In two. experiments on appetitive learning we conditioned lambs, Ovis aries, to particular concentrations of a flavour by mixing the flavour with an energy-rich food that complemented their energy-poor diet. Th e lambs were subsequently offered energy-rich food with five different concentrations of the flavour (the concentration to which they were c onditioned, two higher concentrations, and two lower concentrations). At these tests, the lambs consistently preferred the weaker flavours. This finding stands in contrast to earlier results on generalization g radients. In a third experiment, similarly designed to the other two, we tested for effects of a strong flavour on the behaviour of lambs wh en they were offered a novel nutritious food. Half of the lambs were o ffered unadulterated wheat, and the others strongly flavoured wheat. W e found that the flavour in itself was initially aversive. We propose that the lambs' avoidance of foods with strong flavours may be an expr ession of a rule of thumb of the type 'given a choice, avoid food with strong flavours'. Such a rule could be part of a risk-averse foraging strategy displayed by mammalian herbivores, and which could be of par ticular importance when they encounter unfamiliar foods. (C) 1998 The Association for the Study of Animal Behaviour.