Developmental and hair-coat determinants of grooming behaviour in goats and sheep

Self-grooming is a common behaviour among many species of ungulates, as it is among several other mammalian taxonomic groups. In goats, as in rodents and small felids, self-grooming appears to reflect an underlying endogenous timing mechanism, resulting in what has been referred to as programmed grooming. We tested the prediction from the programmed grooming model that newborn and young goats, Capra hircus, would groom more frequently than similarly maintained conspecific adults. This prediction was upheld in that goat kids, from 2 weeks of age, orally groomed and scratch-groomed significantly more frequently than adult females. When the body surface-to-mass ratio of young goats, which was initially about 230% that of adults, declined to about 150%, the difference in grooming rate of the young was no longer significantly elevated over that of adults recorded at the same time of year. We also tested the predictions that oral grooming in wool sheep, Ovis aries, is inherently programmed and will occur in adults after shearing and in lambs with undeveloped fleece at levels similar to those of ancestral hair sheep and lambs. When fully fleeced adult wool sheep were shorn, they engaged in grooming in a pattern and frequency not different from that of hair sheep with a pelage representative of ancestral sheep. Wool lambs also groomed at a rate similar to that of hair lambs. Therefore, the elevated rate of programmed grooming of newborn and young ungulates appears to reflect their developmental precociousness and consequent exposure, in nature, to ectoparasites.