Diet, Reproduction, and Density of the Leptodactylid Litter Frog Zachaenus parvulus in an Atlantic Rain Forest of Southeastern Brazil

Abstract

Amphibians and reptiles are important constituents of leaf litter communities in tropical forests (Fauth et al., 1989; Allmon, 1991; Vitt and Caldwell, 1994). Forest floor leaf-litter frogs forage for arthropods (Toft, 1980a,b), and three general guilds can be recognized depending on the proportions of different kinds of prey: ant specialists, non-ant specialists, and generalists (Toft, 1980a). In general, leptodactylid frogs are considered non-ant specialists eating predominantly soft-bodied, mobile arthropods, mainly orthopterans and spiders (Toft, 1980a,b, 1995). Zachaenus parvulus is a small leptodactylid frog, which occurs among the floor litter of the Atlantic rain forest of eastern Brazil (Duellman and Trueb, 1986; Rocha et al., 1998). Information on the species is restricted to data on reproduction (Lutz, 1944) and defense tactics (Sazima, 1978; Rocha et al., 1998), with almost nothing known about other aspects of its biology. In the Atlantic rain-forest leaf-litter anuran community that we studied, Z. parvulus is the second most abundant species (after the brachycephalid Psyllophryne didactyla). Herein, we report an investigation of some aspects of the ecology of Zachaenus parvulus providing information on its diet, reproduction, and density at Ilha Grande, Brazil. The study site was in the Atlantic rain forest at Ilha Grande (23?10'558S; 44?12'499'W), an island in southern Estado do Rio de Janeiro, southeastern Brazil (Fig. 1), at an elevation of approximately 240 m. Rainfall is seasonal, with mean annual rainfall of 2240 mm and monthly averages ranging from 87 mm (July) to 293 mm (January; Bittencourt, 1998). Mean air temperature is 22.5?C, with February being the hottest month (25.7?C) and July the coldest (19.6?C; Bittencourt, 1998). Ilha Grande is covered by Atlantic rain forest with different levels of succession resulting from disturbances caused by human activities through the last centuries (Araujo and Oliveira, 1988). The study area consists of a remnant of undisturbed Atlantic rain forest with trees reaching 30 m, covered by bromeliads and vines, and with a relatively deep leaf-litter layer (80-150 mm). From August 1996 to November 1997 frogs were