Environmental influences on the population ecology of sixteen anuran amphibians in a seasonally flooded neotropical forest

Amphibians are declining globally from climate change, habitat destruction, pollution and disease. In tropical environments deciphering causes of decline is hampered by a lack of population data. In this study, climate, water quality and amphibian population was recorded at Caño Palma Biological Station in Costa Rica over 3 years. Population dynamics were recorded for 16 species of amphibian and the affects of flooding on them determined. Spearman Rank Correlation, Principal Component Analysis, Multiple Analysis of Variance and Linear Regression were used to investigate climate and flooding. Direct measurements of aqueous pH, conductivity, iron, nitrate, hardness, oxygen, carbon dioxide and salinity were made through periodic inundation. A mark-recapture program for 16 amphibian species collected population data from an area of Manicaria swamp forest and a breeding pond in lowland wet forest. Pollock Open Jolly-Seber and Petersen-Schnabel population models estimated amphibian abundance. Canonical Correspondence Analysis (CCA) was used to investigate relationships between climate, water quality and amphibian populations. Temperature and humidity remained stable. Rainfall data recorded up to 350mm in one 24 hour period. Flooding occurred annually and was governed by rainfall and spring river tides. Water quality of the environments changed little during flooding. CCA results suggested that amphibian abundance was not related to water quality. Salinity and conductivity levels increased but were not toxic. Amphibian populations fluctuated within and between years. Pollock Open Jolly-Seber estimates were completed for Chaunus marinus, Rana vaillanti and Oophaga pumilio. Petersen-Schnabel estimates were completed for Bufo coniferus, O. pumilio, Craugastor fitzingeri, Craugastor polyptychus and Leptodactylus melanonotus. All populations appeared unchanged across years. C. marinus, R. vaillanti, O. pumilio, B. coniferus, C. fitzingeri, C. polyptychus and L. melanonotus adapted to flooding by altering their preferred behaviour and microhabitat. Most amphibians suspended seasonal activity during flooding