Mating Patterns of Red-Eyed Treefrogs, Agalychnis callidryas and A. moreletii

Male frogs may mate several times throughout a breeding season; however, energy and time constraints of producing mature eggs severely limit breeding opportunities for a female (Berven 1981; Andersson 1994). Male competition for females is expected because the operational sex ratio is malebiased (Emlen 1976; Kvarnemo & Ahnesjö 1996). Yet anisogamy dictates that females are usually the choosier sex (Maynard Smith 1982) with significant associated fitness costs (Parker 1982; Reynolds & Gross 1990). This differential parental investment is thought to directly affect mating patterns (Trivers 1972; Andersson 1994). Among anurans, considerable variation exists in mating patterns and some of this variation can be explained by the length of breeding season (Wells 1977; reviewed by Sullivan et al. 1995), in addition to the operational sex ratio (Emlen & Oring 1977). In explosively breeding species that congregate en masse for short periods, the opportunity for intense male–male competition is greater and there is typically little occasion for females to exercise choice. Mating instead may involve a scramble competition among males for females (Emlen & Oring 1977). In this case, deviations from random mating may be expressed as a large-male mating advantage. However, in species with protracted breeding periods the opportunity for females to exercise choice is greater Correspondence Venetia S. Briggs, Boston University, Department of Biology, 5 Cummington St., Boston, MA 02215, USA. E-mail: [email protected], [email protected]