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

Abstract

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 freeliving 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.

Physiological suppression eases in Damaraland mole-rat societies when ecological constraints on dispersal are relaxed

“…First, subordinate females commonly exhibit down-regulated reproductive physiologies when in the presence of the dominant female (e.g. Clarke et al 2001;Saltzman et al 2009). This may be due either to the subordinate exercising physiological restraint given a threat of interference by the dominant (Young et al 2008;Saltzman et al 2009) or to the dominant forcibly downregulating the subordinates' fertility by subjecting them to chronic stress (e.g.…”

Policing of reproduction by hidden threats in a cooperative mammal

“…However, the finding also suggests that reproductive coercion may extend well beyond the systems in which infanticide is common. Hidden threats of policing can deter subordinates from reproducing in the first place (44)(45)(46), or select for counterstrategies [such as synchronous birth (26,37), egg-laying (47), or egg-mimicry (48)] to render threats noncredible (i.e., unprofitable for a threatening individual to carry out, in the event that a transgression occurs). In both cases, threats of infanticide influence reproductive behavior even though no offspring are killed.…”

Experimental endocrine manipulation by contraceptive regimen in the male marmoset (Callithrix jacchus)

“…for reproductive toxicology and or fertility suppression). We wanted to investigate whether the endocrine regulation of testicular function in the marmoset ) and the strong social component regulating reproduction and natural fertility in this species (Abbott et al 1988, Saltzman et al 2009 allow studies that enable translation of findings to the human situation.…”

“…This is a unique feature among available NHP models (Saltzman et al 2009). In males, there are no data available on whether spermatogenesis is suppressed to some extent; however, it has been demonstrated that offspring are almost exclusively sired by the dominant male (Nievergelt et al 2000) and supported by the lack of sexual dimorphism in marmosets, a monogamous mating system was suggested (Abbott & Hearn 1978).…”