The effects of olfactory deprivation and hormones on territorial marking in the male mongolian gerbil ( Meriones unguiculatus)

Abstract

Mongolian gerbils ( Meriones unguiculatus) mark objects in their environment with a midventral sebaceous scent gland. In the male the response is androgen dependent. The first study shows that olfactory bulb aspiration almost completely eliminates marking behavior. The reduction is apparently independent of any hormone dysfunction, as indicated by weights of seminal vesicles, testes, and adrenals. Marking, however, can be at least partially reinstated with massive doses of testosterone propionate (640–1280 μg every 5 days), indicating a hormone compensation for a neurological defect and demonstrating that smell is not absolutely necessary for marking. The second study shows that 80 μg of estradiol benzoate but not 800 μg progesterone administered to males twice a week for 6 weeks significantly depresses marking frequency, causes atrophy of the testes and seminal vesicles, and stops spermatogenesis. It would appear that estrogen acts by antagonizing the secretion of gonadotropins. Animals were also assessed for preference or aversion of premarked pegs during this study, but no differential marking could be demonstrated. It is concluded that territorial marking is normally controlled by androgen and that the disruption of the response can occur either because of a lack of sensory input or an antagonism of the gonadotropic system.