Spatial integration in infant sable antelope, Hippotragus niger.

I studied the relationship between the timing of birth relative to other births in the social group, and the rate of spatial integration into the herd in six cohorts of semi-free-ranging infant sable antelope at the National Zoological Park's Conservation and Research Center near Front Royal, Virginia. All calves spent the initial few days of life resting in seclusion ('hiding'), and interacted with mothers and other conspecifics only during activity bouts. With time, calves became increasingly likely to rest apart from the herd with other calves in crèches, and by 6 weeks of age, calves remained with the herd throughout all resting and activity bouts. The rate of spatial integration for individual calves depended upon the calf's birth date and the availability of peers of similar age (birth clustering). Only the first few calves born in each cohort were observed in crèches, and crèche groups synchronized their entry into the herd. First-born calves remained in crèches longer and began resting with the herd later in life than calves born later in the cohort. Last-born calves typically did not form crèches, but instead rested with the herd from an early age. Other infants may serve as social cover during the time that infants form crèches and when they first begin to accompany the herd. The observed individual differences in the rate of spatial integration may represent individual adjustments in response to the varying degrees of protection offered by the spatial environment. Copyright 1998 The Association for the Study of Animal Behaviour.