Spatio-temporal patterns of foraging and feeding behavior of Elachistocleis bicolor (Anura: Microhylidae)

Abstract

We analyzed spatio-temporal patterns and behavior of the foraging activity of the myrmecophagous frog Elachistocleis bicolor. We delimit ten 1m 2 plots and recorded the number of frogs, distance between individuals and foraging behavior at half-hour intervals, during nine days. Using a generalized linear mixed model, we evaluated the maximum, minimum, and average daily temperature, microhabitat temperature, relative humidity, atmospheric pressure, the number of days since the last rain and last 48 hours accumulated rainfall as explanatory variables of frogs' activity. The variables that best explained frogs' activity were: mean atmospheric pressure, number of days since last rain and accumulated rainfall. Frogs showed an aggregated distribution pattern when foraging (Morisita standardized index= 0.501). The average distance between frogs was 47.53±25.28 mm. Frogs displayed a combined (active-passive) foraging strategy, actively searching ant trails, digging with their heads on trails running under the mulch, and them passively preying on ants as they pass through. Results showed that the E. bicolor foraging activity followed a circadian cycle that is regulated by several climatic variables, and that these frogs aggregated when foraging for ants.Key words. Mirmecophagy, phenology, feeding behavior, two-colored oval frog. RESUMENAnalizamos los patrones espacio-temporales y comportamiento de forrajeo de la rana mirmecófaga Elachistocleis bicolor. Delimitamos diez cuadrantes de 1 m 2 en los que registramos el número de ranas, distancia entre individuos y comportamiento a intervalos de media hora durante nueve días. Utilizando modelos lineales mixtos generalizados evaluamos el poder explicativo de las variables: temperaturas diarias máximas, mínimas y medias, temperatura de microhábitat, humedad relativa, presión atmosférica, días transcurridos desde la última lluvia y pluviosidad acumulada en las últimas 48 horas, sobre la actividad de las ranas. Las variables que mejor explicaron la actividad de las ranas fueron: presión atmosférica media, días desde la última lluvia y pluviosidad acumulada. Las ranas mostraron un patrón de distribución agregado durante el forrajeo (índice estandarizado de Morisita = 0,501). La distancia media entre ranas fue 47,53±25,28 mm. Las ranas exhibieron un comportamiento 346 Foraging activity of Elachistocleis bicolor