Sexual coercion in a territorial salamander: females punish socially polygynous male partners

Sexual intimidation (sensu Smuts & Smuts 1993, Advances in the Study of Behavior, 22, 1-63) occurs when members of one sex aggressively 'punish' members of the other sex that refuse to mate with them or that merely associate with other individuals of the opposite sex. We examined Clutton-Brock & Parker's (1995, Animal Behaviour, 49, 1345-1365) concept that while males of many species use punishment (intimidation) to coerce females into social or even mating monogamy, such behaviour by females towards males should be rare. However, females in some species are territorial, and aggressive, and thus they may play an active role in sexual intimidation. We tested this proposition in laboratory experiments with territorial red-backed salamanders, Plethodon cinereus, that had been found as single (nonpaired) individuals and in male-female pairs (we term members of a pair 'partners') in the forest. We manipulated paired males such that they either had associated with another female before returning to their female partners (socially polygynous) or had not (socially monogamous). In addition, we manipulated single males such that they either had associated with another female before encountering a focal female for the first time (socially polygynous) or had not (socially naive). During the autumn courtship season, females were significantly more aggressive (threat displays and biting) towards socially polygynous partners relative to those that were socially monogamous. In addition, females spent significantly less time touching socially polygynous partners relative to socially monogamous partners. However, females that met a male for the first time did not differ significantly in their behaviour towards socially polygynous and naive males. During the late spring, females displayed no behavioural differences towards either male partners or strangers. Thus, female aggression was context dependent, with increased aggression directed only towards polygynous partners and only during the autumn. We infer that females attempt to control social polygyny by partners through aggression during the courtship season but that this coercion ceases in the spring when the females are preoccupied with searching for nest sites for brooding their eggs. (C) 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All tights reserved.