Copulatory plug displacement and prolonged copulation in the Iberian rock lizard (Lacerta monticola)

Abstract

Male Iberian rock lizards (Lacerta monticola) produce copulatory plugs that adhere firmly inside the female cloaca and occlude both oviducts. These plugs do not prevent rival male insemination, as they neither re- duce female attractiveness or receptivity to rival males nor do they function as "chastity belts". Prior to copula- tion, males bite various regions of the female body, in- cluding the cloacal region. A previous plug in the female cloaca is expelled only after rival male intromission. We hypothesized that: (1) such male pre-copulatory be- haviours function to loosen plug adherence to the female cloaca, thereby facilitating intromission, and that (2) the hemipenis plays a role in displacing a previous plug prior to the delivery of a new plug. Neither of these hypotheses was supported. Instead, our results indicate that rival males can intromit the hemipenis past a previous plug in the female cloaca and deliver their own plug underneath it. Consequently, previous plugs are pushed away from the oviductal openings and even dislodged from the fe- male cloaca. Copulation duration was determined both by the time used by males to deliver a plug and by the fact that males prolonged copulation beyond plug delivery. There seemed to be sexual conflict over prolonged cop- ulation, which was resolved by the male/female head- length ratio. The adaptive value of Iberian rock lizard copulatory plugs and prolonged copulation in Iberian rock lizards is discussed in the context of sperm competition.