Over the last three decades, research in behavioural ecology has focussed on the choices that individuals make over food (Stephens/Krebs 1986), mating opportunities (Andersson 1995), parental care (Clutton-Brock 1991) and cooperation with other group members (Brown 1987; Clutton-Brock/Parker 1995b). Yet, in social species, most individuals rarely have the opportunity to choose freely because their options are constrained by the behaviour of dominant animals (Clutton-Brock/Parker 1995b). Coercion is common in many contexts where conflicts of interest occur, but is particularly important in interactions between the sexes, where it often has substantial costs to females. In a recent paper (1993), Smuts and Smuts argue that sexual coercion should be regarded as a third form of sexual selection, separate from intrasexual competition and intersexual mate choice. Whether or not this is accepted, it is clear that sexual coercion has not received the attention that it deserves.