Abundancia y estructura poblacional de Caiman yacare en lagunas de la llanura inundable de los ríos Ichilo y Chapare (Bolivia)

Abstract

SIZE STRUCTURE AND ABUNDANCE OF Caiman yacare IN FLOODPLAIN LAKES OF THE ICHILO AND CHAPARE RIVERS (BOLIVIA) El estudio se llevo a cabo en poblaciones de Caiman yacare, en 17 lagunas pertenecientes a la llanura inundable de los rios Ichilo y Chapare, ubicadas entre los 16o 57' y 16o l' S y los 64o36' Y 64o53' con el fin de conocer la estructura y abundancia de las mismas. Para ello se realizaron censos nocturnos en cuatro epocas hidrologicas y el calculo de abundancia se realizo en Base al numero de individuos encontrados por km de recorrido.Caiman yacare presenta una abundancia poblacional promedio de 5 ind/km, mostrando variaciones si- milares en todas las lagunas entre las epocas hidrologicas, observadose los mayores valores de abundancia en la epoca de aislamiento (9 Ind/km) y valores muy bajos durante la inundacion (0.5 Ind/km). Respecto a la estructura en tamano, si bien existen diferencias entre lagunas y entre epo- cas, se encontro una mayor proporcion de individuos juveniles, especialmente, durante la epoca de aislamiento hidrologico. Finalmente, al relacionar la abundancia de las poblaciones con el grado de intervencion humana en las lagunas, se encontro clara tendencia al aumento de abundancia a,medida que disminuye el grado de intervencion. Palabras clave: Caiman yacare, lagartos, Crocodylia, llanura inundable, lagunas tropicales, Amazonia, Bolivia ABSTRACT The purpose of this study was to determine size structure and abundance of the Caiman yacare populations in 17 shallow lakes of the floodplains of Ichilo and Chapare rivers at 16°57' -16°1' S and 64°36' -64°53' W The study was based on night surveys during tour different hydrological periods. Abundance was estimated on the basis of number of animals observed per km. The average population density of C. yacare was 5 Ind. km-1 with small variations in all shallow lakes and hydrological periods. The highest values (9 Ind. km-1) were observed during dry periods, while very low values (0.5 Ind/km-1) were detected during periods of flooding. With respect to the size structure, differences were found between shallow lakes and hydrological periods and a higher proportion of juvenile indivi- duals was detected during the dry season. Finally the study also related population abundance with the degree of human intervention in these shallow lakes. It was clearly established that population density of C. yacare increased as human intervention decreased. Key words: Caiman yacare, lagartos, Crocodylia, floodplains, tropical shallow lakes, Amazonia, Bolivia.