Estado de las poblaciones de cocodrilos (Crocodylus acutus) (Reptilia: Crocodilidas) en tres ríos del Pacífico Central de Costa Rica
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Fecha
2000
Autores
Piedra Castro, Lilliana
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Universidad Nacional (Costa Rica)
Resumen
Se evaluó la densidad y la estructura de tallas de las poblaciones de cocodrilos (Crocodylus acutus) en los ríos Tusubres, Grande de Tárcoles y Jesús María, en el Pacífico Central de Costa Rica. Se empleó la metodología propuesta por Chabreck (1966) y Messel y Vorlicek (1989) y que ha sido empleada con otros estudios alrededor del mundo (King et al 1990; Levy 1990;Cerrato 1991). Se determinó que existen diferencias entre las densidades estimadas de cocodrilos de las tres poblaciones, siendo la mayor que se ubica en el río Grande de Tárcoles. Así mismo, se observó que existe una tendencia de los individuos a agruparse en la zona media del río Tusubres y en la zona baja del río Grande de Tárcoles, como una respuesta a la alteración del hábitat y a la frecuente presencia humana en estas zonas. Los resultados obtenidos para la población del río Grande de Tárcoles se compararon con las estimaciones de las densidades de cocodrilos, con estudios anteriores, determinándose que la población hasta 1997 presentaba una tendencia hacia el crecimiento, pero a partir de ese año se empieza a observar un decrecimiento de la población, probablemente ocasionada por la matanza indiscriminada de los individuos adultos y que ha sido fomentado, posiblemente, por la alimentación de los cocodrilos silvestre por parte de las empresas que realizan viajes "ecoturísticos" en este río. Se observó que la estructura de la población en los tres sitios tiende a comportarse de acuerdo con la curva de sobrevivencia tipo III. Los individuos más grandes observados en el río Grande de Tárcoles y Jesús María alcanza la talla VIII, en tanto que en Tusubres son de talla VII.
The density and size structure of the crocodile (Crocodylus acutus) populations in the Tusubres, Grande de Tárcoles and Jesús María rivers, in the Central Pacific of Costa Rica, were evaluated. The methodology proposed by Chabreck (1966) and Messel and Vorlicek (1989) was used and has been used with other studies around the world (King et al 1990; Levy 1990; Cerrato 1991). It was determined that there are differences between the estimated densities of crocodiles of the three populations, the highest being located in the Rio Grande de Tárcoles. Likewise, it was observed that there is a tendency for individuals to group in the middle zone of the Tusubres river and in the lower zone of the Grande de Tárcoles river, as a response to the alteration of the habitat and the frequent human presence in these zones. The results obtained for the population of the Rio Grande de Tárcoles were compared with the estimates of crocodile densities, with previous studies, determining that the population until 1997 showed a trend towards growth, but from that year onwards, a population decline, probably caused by the indiscriminate killing of adult individuals and which has been encouraged, possibly, by the feeding of wild crocodiles by companies that make "ecotourism" trips on this river. It was observed that the population structure in the three sites tends to behave according to the type III survival curve. The largest individuals observed in the Rio Grande de Tárcoles and Jesús María reach size VIII, while in Tusubres they are size VII.
The density and size structure of the crocodile (Crocodylus acutus) populations in the Tusubres, Grande de Tárcoles and Jesús María rivers, in the Central Pacific of Costa Rica, were evaluated. The methodology proposed by Chabreck (1966) and Messel and Vorlicek (1989) was used and has been used with other studies around the world (King et al 1990; Levy 1990; Cerrato 1991). It was determined that there are differences between the estimated densities of crocodiles of the three populations, the highest being located in the Rio Grande de Tárcoles. Likewise, it was observed that there is a tendency for individuals to group in the middle zone of the Tusubres river and in the lower zone of the Grande de Tárcoles river, as a response to the alteration of the habitat and the frequent human presence in these zones. The results obtained for the population of the Rio Grande de Tárcoles were compared with the estimates of crocodile densities, with previous studies, determining that the population until 1997 showed a trend towards growth, but from that year onwards, a population decline, probably caused by the indiscriminate killing of adult individuals and which has been encouraged, possibly, by the feeding of wild crocodiles by companies that make "ecotourism" trips on this river. It was observed that the population structure in the three sites tends to behave according to the type III survival curve. The largest individuals observed in the Rio Grande de Tárcoles and Jesús María reach size VIII, while in Tusubres they are size VII.
Descripción
Piedra Castro, L. (2000). Estado de las poblaciones de cocodrilos (Crocodylus acutus) (Reptilia: Crocodilidas) en tres ríos del Pacífico Central de Costa Rica. [Tesis de Licenciatura]. Universidad Nacional, Costa Rica.
Palabras clave
COCODRILO, CROCODILE, CROCODYLUS ACUTUS, ANIMAL POPULATION, POBLACION ANIMAL, RIO GRANDE DE TARCOLES (COSTA RICA), RIO TUSUBRES (COSTA RICA), RIO JESUS MARIA (COSTA RICA)