Precipitation Dependent Reproductive Patterns of Brazilian Pantanal Anuran Species

1. Precipitation Dependent Reproductive Patterns of Brazilian Pantanal Anuran Species Janet Buckner1, Dr. Vanda Ferreira2 Department of Biological Science, SUNY Oswego, Oswego, New York1, Universidade Federal de Mato Grosso do Sul, Campo Grande, Brazil2 Introduction Methods Phenologists study patterns in the lives of organisms which are initiated by or correlated with climate patterns. This knowledge is important to understand the requirements of various species for vital life functions. In recent times, phenology can help us to understand the consequences of major changes on Earth for species including global warming. In relation to phenology, many animal species employ reproductive strategies which are weather dependent. In this study we test the validity of this observation in species of anurans in the Brazilian Pantanal by comparing precipitation data from the period 2005-2006 with anuran survey data from those years. We believe there exists a correlation between precipitation and anuran reproduction and age of individuals in this area. Data collection – the study was conducted in the Brazilian Pantanal in the state of Mato Grosso do Sul at various locations within Fazenda Nhumirim. Anurans were surveyed during the years 2005 to 2006 using pitfall traps (see Figure 1). These traps were opened and checked daily over nine approximately week long intervals. Specimens were collected from the traps and the following measurement s taken daily: species, sex, age, length and weight (Figure 2). Determinations – sex was determined by the presence of sexually dimorphic traits when applicable. This was usually not possible for juveniles who were not yet sexually mature. Age was determined by CRA (the length of the animal from snout to cloaca) parameters published in Prado and Haddad 2005. For the species Leptodactylus chaquensis, reliable data on the size of adult individuals was not available so the average of the sizes of known adults from our own data were used to verify ages of all individuals of this species. For Physalaemus albonotatus, the smallest recorded size for adult males within our data was used to determine the age for those animals with undetermined ages. Animals between eighteen and 23.5 centimeters were excluded if sex could not be determined. Figure 1. The set-up for a pitfall trap used to collect specimen. Objectives To describe the phenology of amphibians. To organize anuran population data into the categories adult, sub-adult and juvenile. Determine possible temporal population patterns among these age ranges . To determine if a correlation between rainfall and reproduction exists in various anuran species. Determine if those correlations hold only for certain reproductive strategies. Figure 2. Students taking measurements of captured specimen. Results Based on the data presented here it seems plausible that the reproductive patterns of the following species are dependent upon or closely correlated with precipitation. Acknowledgements Conclusion References It seems that there is a delayed response in the abundance of juveniles in relation to precipitation. However, this is expected if we consider that the adults are triggered to lay eggs at the time of the rain, it will take some time for those eggs to metamorphose into juvenile frogs. Since we used the juvenile populations to make the graphs, we should expect a time lapse between rainfall and peaks in juvenile frog population. To confirm a positive correlation between precipitation and reproduction, though, statistical analyses will be necessary as well as additional years of data. A software is being developed to identify the best associations between rainfall and abundance of juveniles considering the biological attributes of each species and finally to infer the rainy season which led to the spawning of the species. Thome, M.T.C, Brasileiro, C.A. 2007. Dimorfismo sexual, uuso do ambiente e abundancia sazonal de Elachistocleis cf. ovalis (Anura: Microhylidae) em um remanescente de Cerrado no estado de Sao Paulo, sudeste do Brasil. Biota Neotropica 7: 27-33. Prado, C.P.A, Haddad, C.F.B. 2005. Size-fecundity relationships and reproductive investment in female frogs in the pantanal, south-western Brazil. Herpetological Journal 15: 181-189. Prado, C. P.A, Uetanabaro,M., Haddad, C.F.B. 2005. Breeding activity patterns, reproductive modes, and habitat use by anurans (Amphibia) in a seasonal environment in the Pantanal, Brazil. Amphibia-Reptilia 26: 211-221. Prado, C.P.A., Uetanabaro, M., Lopes, F.S. 2000. Reproductive Strategies of Leptodactylus chaquensis and L.podicipinus in the Pantanal, Brazil. Journal of Herpetology 34: 135-139.