Ecology and Calls of Four Species of Amazonian Forest Frogs

Abstract

First data on breeding biology and vocalization by the primary forest dwelling frog species Osteocephalus buckleyi, Chiasmocleis shudikarensis, Bufo dapsilis, and Leptodactylus rhodomystax, was obtained in the Central Amazon of Brazil in 1980, 1983, 1984, and 1985. Breeding habitat requirements of these species are quite specialized and emphasize the need for more ecological information on Amazonian forest frog species if efforts to preserve them in forest reserves are to be effective. Calling by Osteocephalus buckleyi and Chiasmocleis shudikarensis and Bufo dapsilis demonstrates certain vocal behaviors exhibited extensively by Amazonian forest frog species which may reflect predator avoidance strategies. A field survey of the frogs in the Insti- tuto Nacional de Pesquisas de Amazonica- World Wildlife Fund (U.S.) (I.N.P.A.- W.W.F.) primary forest reserves near Ma- naus in the Central Amazon of Brazil is part of I.N.P.A.-W.W.F.'s Minimum Crit- ical Size of Ecosystems (M.C.S.E.) project. The objectives and methods of the M.C.S.E. project are outlined in Lovejoy et al. (1984) and Lewin (1984) but basically, the project is an attempt to understand the ecology of primary Amazonian rainforest. Informa- tion on how plants and animals respond to restriction within forest fragments of different size will be used as the basis for conservation planning and design of na- ture reserves and national parks. The main goals of M.C.S.E.'s frog sub- project are to identify all species of primary forest frogs present in the I.N.P.A.-W.W.F. area, their habitat requirements for breed- ing, and their normal distributions and abundances within undisturbed primary forest. These data are needed to discern the effects of isolation within forest islands on breeding populations of frogs. An impor- tant tool used in the survey is knowledge of species vocalizations because most species of Amazonian forest frogs are dif- ficult to locate visually. An acoustic species list greatly extends the range of a survey and aids immeasurably in identification of habitat preferences and learning about the general ecology of the animal. Therefore all types of vocalization by a species are recorded and vocal patterns observed. First results of the anuran survey are presented in Zimmerman and Hodl (1983), Zimmer- man (1983), Zimmerman and Bogart (1984), and Zimmerman and Bierregaard (1986). The present study considers the identi- fication, ecology, and acoustics of four species of Amazonian forest frogs about which little or nothing was previously known: Osteocephalus buckleyi, Chiasmocleis shudikarensis, Bufo dapsilis, and Leptodactylus rhodomystax. Breeding biology and vocal behavior of these species illustrate certain characteristic features of the forest anuran community such as specificity of breeding habitat, infrequency of breeding, and in- frequent calling. The requirement of spe- cialized breeding habitat by many species and opportunistic breeding observed in some species has important implications for conservation. The widespread use of vocal patterns such as synchronized cho- rusing and low calling rates among forest frogs is interpreted as a predator avoidance strategy.