Julia L. Michalak
Department of Biology, Carleton College, Northfield, MN, USA, 55057
Abstract In this study, the Cantarana swamp in La Selva Biological Reserve in Costa Rica was surveyed nightly for eight days. The presence or absence of the species Hyla ebbricata, Agalychnis sp., and Scinax sp. was recorded and the number of individuals in each species was counted by listening for calls. Additionally, the rate of bout calls in the species Hyla ebbricata was quantified. These data were then compared to average daily rainfall and temperature. The number of H. ebbricata and rate of bouts were significantly correlated, showing that an increase in frogs number causes an increase in the rate of bout calls. Male frogs may be responding to the calls of their neighbors and may also be calling more frequently in large choruses due to a reduced risk of predation. No significant correlations were found between frog chorus attendance and the abiotic factors. This indicates that frog chorus attendance may not be influenced by slight daily variations in temperature and rainfall during the breeding season. Larger fluctuations in these abiotic factors may be necessary to effect a change in chorus attendance.