Reproductive behaviour, testis size and faecal androgen metabolite concentrations in the African lesser bushbaby

Abstract

Periods of reproduction are linked to changes in male behaviour, physiology and physical parameters. Although high androgen concentrations hold numerous advantages, especially during reproductive periods, chronically elevated androgen concentrations over long periods may be costly and thus need to be regulated. As such seasonal breeders will display temporary elevated androgen concentrations, increased testis levels and mating behaviour only during important reproductive periods. We studied a captive as well as a free-ranging population of the polygamous strepsirrhine primate, the African lesser bushbaby Galago moholi, to clarify the link between androgen concentration, reproductive behaviour and testis size and the importance of the two mating periods observed in the species. To monitor androgen patterns, we used faecal sampling and quantification of faecal androgen metabolites (fAM). We additionally collected testicular measurements and behavioural data. G. moholi displayed a strong degree of reproductive seasonality, with maximum fAM concentration, testicular volume (TV) and behavioural activity focused on the mating periods. In contrast to other studies, TV increased prior to fAM, with reproductive activity being initiated only when fAM concentrations reached high levels. Changes in TV and fAM concentrations were not significantly different between both mating periods. Based on the absence of a significant difference between mating seasons, it is likely that male G. moholi attempt to maximize their reproductive success by utilizing both mating periods equally. This study is the first to describe the reproductive endocrine pattern linked to physical changes and mating behaviour in any galago species, increasing our understanding of the reproductive biology of nocturnal, polygamous primates.