DIETARY HABITS AND SOCIAL INTERACTIONS AFFECT CHOICE OF FEEDING LOCATION BY SHEEP

Individuals often occur in subgroups that differ in their choice of fo rage and habitat, even within the same environment. Different foods oc cur in disparate locations and thus differences in dietary habits coul d provide one explanation for the formation of subgroups and their use of the environment. In addition, subgroups may form as a result of so cial interactions, We conducted experiments to study the effects of fo od preference and social interactions on choice of feeding location by lambs. In 1992, 12 lambs that had been reared together were separated into two groups of six lambs. Groups were conditioned to prefer one o f two grains, either mile (Sorghum bicolor) or wheat (Triticum aestivu m) by feeding mile or wheat for 14 days. Lambs were conditioned to avo id the other grain by following its ingestion with a mild dose of the toxin lithium chloride (LiCl) on 3 consecutive days. During testing, m ile and wheat were placed at opposite ends of a 0.25 ha pasture. Lambs were first allowed to feed as groups consisting of three lambs that p referred mile and three lambs that preferred wheat, and then allowed t o feed as groups in which one lamb preferred mile with three lambs tha t preferred wheat, and vice versa. Under both conditions, lambs always foraged on their preferred food, even when the locations of the foods were switched. In 1993, we repeated the study from 1992 in a larger p asture ( 1 ha) and without the use of LiCl. Lambs were reared in three different groups and fed either mile (Group 1), wheat (Group 2), or h alf of the lambs were fed mile and the other half were fed wheat (Grou p 3) for 4 months to condition a preference for either mile or wheat. When we combined lambs that preferred mile from Group 1 with lambs tha t preferred wheat from Group 2 to form subgroups of strangers, lambs f ed in different locations. Conversely, social interactions and food pr eferences both affected choice of foraging location when lambs were re ared together (companions). For instance, some lambs that preferred wh eat grazed in the vicinity while peers ate mile, whereas lambs that pr eferred mile grazed in the vicinity while peers ate wheat. In other ca ses, one or two lambs separated from the rest of the group and ate the ir preferred grain. We conclude that food preference had a primary inf luence on choice of foraging location when lambs were reared separatel y (strangers) and preferred different foods. Food preferences and soci al interactions both influenced