Sexual behavior in older monkeys,Macaca radiata

This report presents preliminary observational data on the sociosexual behavior of two newly formed groups of older (11.5 to 18.5 years of age, mean age of 15.3 years) bonnet monkeys observed over a period of 18 weeks. Qualitatively, their sexual behavior was similar to that of the younger mature bonnets. The males and females engaged in species-typical proceptive and receptive behavior patterns. The mean duration of copulations was somewhat shorter than that reported for younger mature bonnets. Decreased sexual function was recorded in males that were chronically ill. One male that copulated infrequently died of renal failure in the sixth week of study. Another male that was never observed copulating suffered from fatal diabetes mellitus. One male died apparently during coitus; autopsy findings were compatible with sudden cardiac death. The findings indicate that sexual dysfunction in aged primates can be a sign of serious illness. Sexual and agonistic behaviors for males correlated significantly, a finding reported in studies of rhesus macaques, which are typically a more aggressive macaque subspecies. Low sexual behavior during the first six-week period in Group A was correlated with a high amount of grooming. Possibly, increased grooming by females serves as a reactive behavior under conditions which do not allow sexual outlet.