EFFECTS OF CASTRATION ON GROOMING IN GOATS

In African antelope and North American cervids, breeding males during the rut engage in less oral self-grooming, and harbor a greater densit y of ticks, compared with conspecific females and non-breeding males. The purpose of this study was to experimentally test the proposition t hat down-regulation of self grooming in some male bovids occurs via th e direct or indirect action of testosterone. Domestic dairy goats (Cap ra hircus) were used as a model. In Experiment 1, comparative observat ions conducted on twelve gonadally intact male goats (bucks), nine mal es castrated at 3 weeks of age (wethers), and twelve intact females (d oes) supported the prediction that the grooming rate of intact males w ould be depressed relative to wethers and does. Bucks oral groomed at one-third and one-fourth the rate of wethers and does, respectively, a nd they scratch groomed half as much as does. There was no significant difference between wethers and does in oral or scratch grooming rates . Experiment 2 involved castration of eleven bucks from Experiment 1, followed by 2 months of observation. Similar to the pattern of other t estosterone-dependent behavioral changes after castration in adult mal es, there was a good deal of variation in the individual grooming resp onse of males to castration, with increases in grooming taking 2 to 8 weeks to be manifested in ten of eleven goats. Overall, castrated male s oral groomed about 3 x above their intact rates, supporting the pred iction that castration removes testosterone-mediated suppression of gr ooming. This is the first example of alteration of grooming behavior i n males by gonadal androgen, and the first demonstration of enhancemen t of any mammalian behavior by removal of gonadal androgen. (C) 1998 E lsevier Science Inc.