Continued copulation in ovariectomized adrenal-suppressed stumptail macaques (Macaca arctoides)

Abstract Female stumptail macaques continue to copulate at moderate to high levels for years after gonadectomy. This study examined the extent to which sexual behavior of ovariectomized stumptail females was maintained by steroids of adrenal origin, and second, considered the possibility that ovarian fragments might have been left in situ following surgery. Daily injections of 0.1 mg of dexamethasone sodium phosphate suppressed serum cortisol, estradiol, and testosterone by at least 85% in three of four ovariectomized females, but dihydrotestosterone was suppressed by only 50 to 70%. The fourth female showed maximal suppression of cortisol but maintained much higher levels of the other steroids, in particular estradiol, and therefore it was strongly suspected that this animal had an ovarian fragment. Within the limits to which sex steroids were depressed with dexamethasone, no correlation was found between steroid levels and sexual performance. Ejaculatory frequencies and measures of attractivity, proceptivity, and receptivity collected during heterosexual pair tests remained unaffected in all four females during 4 weeks of dexamethasone treatment. Thus it was concluded that the maintenance of copulatory activity after ovariectomy in this species was largely due to nonsteroidal mechanisms.