Reproductive Phenology and Age Structure of Dendrobates pumilio in Northeastern Costa Rica

Abstract

Dendrobates pumilio occurs year-round at the La Selva Biological Reserve in northeastern Costa Rica. To determine seasonality in reproduction and age structure, a sample of 468 individuals was dissected and the conditions of gonads, reproductive tracts, and vocal slits were examined. There were no obvious seasonal trends in patterns of overall abundance, although seasonal reproduction was indicated by pulses in the appearance of small juveniles and changes in female reproductive condition. lo , ol. 23, No. 4, pp. 362-367, 1989 ciet for the Study of Amphibians and Reptiles lo and Age Structure of ili i ortheastern Costa Rica The strawberry poison-dart frog, Dendrobates pumilio is an abundant frog at the La Selva Biological Reserve in northeastern Costa Rica. D. pumilio is characterized by complex courtship (Limerick, 1980), terrestrial oviposition (Limerick, 1980), and parental transport of larvae to water (McDiarmid, 1978; Wells, 1981). Previous studies of D. pumilio at this lowland tropical forest site have focused on territorial behavior (Kitasako, 1967; Bunnell, 1973; McVey et al., 1981; Donnelly, 1987), reproductive behavior (Limerick, 1980) and feeding patterns (Lieberman, 1986). Adult dendrobatids do not migrate to breeding ponds and many species are restricted to forest leaf-litter habitats, making them ideal subjects for studies of population dynamics. Based on the year-round occurrence of this anuran at La Selva, it might be expected that 1 Present Address: Department of Herpetology and Ichthyology, American Museum of Natural History, New York, New York 10024-5192, USA. a berry poison-dart frog, Dendrobates ili is an abundant frog a the La Selva Bil eserve in northeastern Costa Rica. D. ili is characterized by complex courtship ic , 1980), te restrial ovipos tion (Lim, 980), and parental transport of larvae to ( cDiarmid, 1978; Wells, 1981). Previous i s of D. pumilio at this lowland tropical th species breeds continuously but data on population structure for this frog are not available. Patterns of reproduction have been examined in a few South American dendrobatid species (Crump, 1974; Toft and Duellman, 1979). Crump (1974) concluded that four dendrobatids were continuous breeders at Santa Cecilia, Ecuador, based on the year-round occurrence of gravid females and juveniles. While fecundity levels a e highly variable among anurans, a positive relationship between body size and size of the ovarian complement (number of ovarian eggs) occurs both interspecifically (Duellman and Trueb, 1986), and intraspecifically (Henderson, 1961; Oplinger, 1966; Pettus and Angleton, 1967). Eleven of the 41 Santa Cecilia anuran species studied by Crump (1974), including one dendrobatid (Epipedobates [=Dendrobates Myers (1987)] pictus), exhibited a significant positive correlation between body size and egg number. E. parvulus did not exhibit significant monthly variation in body size or fecundity at Santa Cespecies breeds conti uously but data on ulation structure for this frog are not avail362 This content downloaded from 157.55.39.72 on Thu, 15 Sep 2016 06:19:00 UTC All use subject to http://about.jstor.org/terms DENDROBATES REPRODUCTIVE PATTERNS cilia (Crump, 1974). Toft and Duellman (1979) described reproductive conditions for five dendrobatid species from the lower Rio Llullapichis, Peru but did not measure the ovarian complements. The largest number of gravid females were collected during the rainy season. However, a few gravid females (E. trivittatus, E. pictus, and E. petersi) were collected in the dry season. Dendrobates pumilio is a member of the monophyletic Dendrobates histrionicus species group; the group includes at least eight species (arboreus, granuliferus, histrionicus, lehmanni, occultator, pumilio, speciosus, and at least one undescribed taxon) that share call type, social, and parental behaviors (Myers and Daly, 1976, 1979; Myers et al., 1984). D. pumilio ranges from Nicaragua to Panama (Savage, 1968; Silverstone, 1975) and throughout the range, populations vary in color, color pattern, density, body size, and calls (Myers and Daly, 1976). Female D. pumilio act as nurse frogs (Weygoldt, 1980,1987), and transport larvae to water-filled axils of bromeliads. They return to these axils regularly to deposit nutritive eggs upon which the larvae feed. This paper reports sizes at sexual maturity and describes phenological patterns of reproduction, recruitment, and abundance for D. pumilio at the La Selva Biological Reserve.