Oestrous females avoid mating in front of adult male bystanders in wild chacma baboons

In social species, female mating strategies can be constrained by both male and female groupmates through sexual conflict and reproductive competition, respectively. This study tests if females adjust their sexual behaviour according to the presence of male and female bystanders in wild chacma baboons ( Papio ursinus ) and assesses their relative importance. Our results show that oestrous females initiate fewer copulations in the presence of adult male bystanders, irrespective of whether they are mate-guarded or not. This inhibitory effect probably reflects a response to indirect sexual coercion by males, whose close proximity may dissuade females to initiate copulations with rival males to avoid punishment and/or aggressive mating interference. By contrast, females initiate more matings with their mate-guard in the presence of higher-ranking female bystanders, which may reflect an attempt to secure bodyguard services from their mate when they feel threatened. These results emphasize the importance of intra- and intersexual conflicts in shaping female sexual behaviour in this promiscuous society.

Asymmetrical reproductive interference between two sibling species of tea looper: Ectropis grisescens and Ectropis obliqua

Ectropis grisescensWarren andEctropis obliqua(Prout) are two morphologically similar sibling species with overlapping ranges. In this study, manipulative laboratory experiments were conducted to examine the possibility of reproductive interference in sympatric populations ofE. grisescensandE. obliquaand the potential consequences of the mating interaction. Our results showed that the presence of males or females of different species could incur mating interference and significant reduction ofF1offspring. The reduction was not significant relevant to the initial relative abundance ofE. grisescensandE. obliqua. Detailed observations of mating opportunity showed that female mating frequencies of both species were not significantly affected by the absolute species density, but the mating success ofE. obliquafemales with conspecific males depended on species ratio. In addition, adding males to the other species resulted in lower number of offspring suggesting that the males’ behaviour might be linked with mating interference. Males of bothE. grisescensandE. obliquacould interfere the intraspecific mating of the other species, but the impact of the mating interference differed. These combined data indicated that asymmetric reproductive interference existed inE. grisescensandE. obliquaunder laboratory conditions, and the offspring of the mixed species were significantly reduced. The long term outcome of this effect is yet to be determined since additional reproductive factors such as oviposition rate and progeny survival to adulthood may reduce the probability of demographic displacement of one species by the other in overlapping niches.

Reproductive skew in female common marmosets: what can proximate mechanisms tell us about ultimate causes?

Common marmosets are cooperatively breeding monkeys that exhibit high reproductive skew: most subordinate females fail to reproduce, while others attempt to breed but produce very few surviving infants. An extensive dataset on the mechanisms limiting reproduction in laboratory-housed and free-living subordinate females provides unique insights into the causes of reproductive skew. Non-breeding adult females undergo suppression of ovulation and inhibition of sexual behaviour; however, they receive little or no aggression or mating interference by dominants and do not exhibit behavioural or physiological signs of stress. Breeding subordinate females receive comparable amounts of aggression to non-breeding females but are able to conceive, gestate and lactate normally. In groups containing two breeding females, however, both dominant and subordinate breeders kill one another's infants. These findings suggest that preconception reproductive suppression is not imposed on subordinate females by dominants, at a proximate level, but is instead self-imposed by most subordinates, consistent with restraint models of reproductive skew. In contrast to restraint models, however, this self-suppression probably evolved not in response to the threat of eviction by dominant females but in response to the threat of infanticide. Thus, reproductive skew in this species appears to be generated predominantly by subordinate self-restraint, in a proximate sense, but ultimately by dominant control over subordinates' reproductive attempts.