Behav Ecol Sociobiol (1996) 39 : 259–266 © Springer-Verlag 1996 Michael S. Mooring · Andrew A. McKenzie · Benjamin L. Hart Role of sex and breeding status in grooming and total tick load of impala Received : 8 September 1995 / Accepted after revision : 7 July 1996 Abstract The role of sex and breeding status constraints on grooming behavior and tick load in impala was examined among females, bachelor males (B males), and territorial males (T males) during the breeding sea- son in Zimbabwe. T males orally groomed themselves much less than females or B males, whereas B males orally groomed themselves at a higher rate than, but not significantly different from, females. T males never engaged in allogrooming and B males allogroomed at a low rate that was not significantly different from that of T males; all males allogroomed much less than females. There was no difference in any of the groom- ing measures between T males with a breeding herd in residence, and solitary T males without a breeding herd on the territory. In conjunction with a management exercise, culled impala were examined for total tick burden using the digestion method, by which all ticks (larvae, nymphs, adults) are removed and counted. For all developmental stages, females harbored the fewest number of ticks and T males supported the most; tick loads of B males were intermediate to those of females and T males. When body surface area was taken into account, T males harbored a higher density of ticks than females and B males. All sex-breeding status groups supported a higher density of ticks on the head/neck region (inaccessible to self oral grooming) compared with accessible areas of the body. The results support the programmed grooming hypothesis, which predicts that those individuals that groom most will harbor fewest ticks, in contrast to the stimulus-driven model which predicts that those that groom most will harbor the most ticks. The lower grooming rates of males versus females can be attributed to competing behavioral demands on males for vigilance and rutting behavior during the breeding season, and /or to higher testosterone levels exerting a physiological suppression of oral grooming. The higher number and density of ticks harbored by T males indicates that lowered grooming rate is a significant cost to reproductively active impala males during the breeding season. Key words Impala · Grooming · Ticks · Breeding · Rut Introduction Among antelope and a number of other ungulate species, the behavior of females, territorial males and bachelor males differs markedly during the breeding season. Most research of behavioral ecologists on this topic has been focused on reproductive behavior and competition among males. Relatively little attention has focused on sex- and breeding status-related differences in maintenance behaviors such as grooming. Self grooming is common among African antelope. For example, small and medium-sized antelope may deliver an estimated 1000–2000 oral grooming episodes to their bodies per 12 h of daylight and engage almost as fre- quently in scratch grooming (Hart et al. 1992). Although reproductive behavior and competition among breeding males has an obvious influence on individual and inclusive fitness, it is becoming more apparent that the ever-present parasites of an animal’s environment also impact fitness (Hart 1990; Nelson et al. 1977; Price 1980). Among antelope and other ungulates, ticks represent a threat to fitness because of the amount of blood that they can extract, reducing M.S. Mooring (*) · B.L. Hart Department of Anatomy, Physiology and Cell Biology, School of Veterinary Medicine, University of California, Davis, California 95616, USA A.A. McKenzie 1 Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa Present address : 1 Wildlife Decision Support Services, P.O. Box 73528, Lynnwood Ridge 0040, South Africa