INFLUENCE OF A CONSPECIFIC AGEMATE ON DISTRESS BLEATING BY LAMBS

Lambs typically display behavioral and physiological indicants of dist ress when they are removed from their mother. In the present experimen t, we assessed the effects of the presence of agemate conspecifics on the rate of distress bleating by 3-week-old lambs immediately followin g maternal separation. When removed from,their mother and tested in is olation, lambs emitted more distress bleats than they did when paired with a social partner-either their twin (P <0.01) or an unfamiliar lam b (P < 0.05). Moreover, rates of distress bleating by paired unfamilia r lambs were greater than for familiar twins tested together (P < 0.02 ). The presence of an agemate lamb therefore appears to alleviate, at least to some extent, the stress associated with maternal separation. Lower rates of bleating by twin pairs in contrast with paired unfamili ar lambs suggest that twins recognize one another. Prior to testing, t wins interacted closely and thereby had the opportunity to become mutu ally acquainted.