Análisis de la población de Caiman crocodilus en el Refugio Nacional de Vida Silvestre Caño Negro, Costa Rica
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Fecha
2000
Autores
Junier Wade, Earl Fernando
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Universidad Nacional (Costa Rica)
Resumen
Se determinó la densidad, tendencia, estructura poblacional, proporción sexual, época de anidamiento y biometría de Caiman Crocodilius en el RNVSCN, Alajuela, Costa Rica entre 1992 y 1994. Se determinó la densidad de los caimanes sobre cada transecto dividiendo la cantidad de individuos observados por el número de kilómetros recorridos. Se estimó la fracción de animales visibles en cada transecto, dividiendo el promedio de animales vistos por el número máximo de animales observados en conteos en el transecto. La instantánea se estimó dividiendo el logaritmo de la densidad estimada de caimanes en un año por el logaritmo de la densidad de caimanes del año anterior. La estructura poblacional se determinó mediante estimaciones visuales y capturas de individuos. Los individuos fueron sexados utilizando los métodos descritos por Chabreck (1996) y Brazaitis (1968). La menor densidad promedio observada en el transecto Caño Negro-Betel, se atribuye a la cantidad de animales que se mantienen en las lagunas periféricas, y a la cercanía de poblaciones humanas lo que facilita la cacería ilegal. El promedio de la fracción visible de animales para el periodo de estudio fue alto 0.88+- 0.070, debido a la realización del estudio durante la época seca y la utilización de métodos estandarizados. La tasa de incremento de la población en el periodo 1993-1994 fue positiva debido posiblemente a movimientos de traslado de los animales y/o al aumento en el reclutamiento de neonatos. La mayor cantidad de caimanes tanto para el curso del Río Frío dentro del RNVSCN, como en las lagunetas y pozas se encuentran en tallas menores a 120 cm debido a la preferencia de los cazadores por las tallas superiores a 120 cm. La proporción sexual promedio para la población fue de 1 macho: 0.80 hembras. A partir de 180 cm solo se observaron machos. El tamaño de las hembras que se observaron cuidando nidos estuvo entre 140 cm y 150 cm. Los mese de junio y julio corresponden al periodo de anidación y de setiembre a octubre al periodo de eclosión. La mayor distancia promedio entre el nido y el cuerpo de agua se obtuvo para agosto de 1993 con un valor de 15.2+- 17.6 m, con un ámbito entre 1m y 50 m. La temperatura promedio de los nidos a nivel del segundo estrato fue de 31.6 +-0.2°C. El número promedio de huevos por nido fue de 21.6 +- 0.6. Los coeficientes de regresión fueron mayores a 0.97, lo que indica que existe una alta correlación entre las variables biométricas utilizadas para la predicción de la medida de la longitud total de animales en el campo.
The density, trend, population structure, sexual proportion, nesting time and biometry of Caiman Crocodilius were determined in the RNVSCN, Alajuela, Costa Rica between 1992 and 1994. The density of alligators on each transect was determined by dividing the number of individuals observed by the number of kilometers traveled. The fraction of visible animals in each transect was estimated by dividing the average number of animals seen by the maximum number of animals observed in counts in the transect. The snapshot was estimated by dividing the logarithm of the estimated density of alligators in one year by the logarithm of the density of alligators in the previous year. The population structure was determined through visual estimates and captures of individuals. The individuals were sexed using the methods described by Chabreck (1996) and Brazaitis (1968). The lower average density observed in the Caño Negro-Betel transect is attributed to the number of animals kept in the peripheral lagoons, and the proximity of human populations, which facilitates illegal hunting. The average of the visible fraction of animals for the study period was high 0.88 + - 0.070, due to the conduct of the study during the dry season and the use of standardized methods. The rate of increase of the population in the period 1993-1994 was positive, possibly due to movement of the animals and / or the increase in the recruitment of newborns. The largest number of alligators both for the course of the Río Frío within the RNVSCN, as well as in the lagoons and pools, are found in sizes smaller than 120 cm due to the preference of hunters for sizes greater than 120 cm. The average sex ratio for the population was 1 male: 0.80 females. From 180 cm only males were observed. The size of the females that were observed guarding nests was between 140 cm and 150 cm. The months of June and July correspond to the nesting period and from September to October to the hatching period. The greatest average distance between the nest and the body of water was obtained for August 1993 with a value of 15.2 + - 17.6 m, with a range between 1m and 50 m. The average temperature of the nests at the level of the second stratum was 31.6 + -0.2 ° C. The average number of eggs per nest was 21.6 + - 0.6. The regression coefficients were greater than 0.97, which indicates that there is a high correlation between the biometric variables used to predict the measurement of the total length of animals in the field.
The density, trend, population structure, sexual proportion, nesting time and biometry of Caiman Crocodilius were determined in the RNVSCN, Alajuela, Costa Rica between 1992 and 1994. The density of alligators on each transect was determined by dividing the number of individuals observed by the number of kilometers traveled. The fraction of visible animals in each transect was estimated by dividing the average number of animals seen by the maximum number of animals observed in counts in the transect. The snapshot was estimated by dividing the logarithm of the estimated density of alligators in one year by the logarithm of the density of alligators in the previous year. The population structure was determined through visual estimates and captures of individuals. The individuals were sexed using the methods described by Chabreck (1996) and Brazaitis (1968). The lower average density observed in the Caño Negro-Betel transect is attributed to the number of animals kept in the peripheral lagoons, and the proximity of human populations, which facilitates illegal hunting. The average of the visible fraction of animals for the study period was high 0.88 + - 0.070, due to the conduct of the study during the dry season and the use of standardized methods. The rate of increase of the population in the period 1993-1994 was positive, possibly due to movement of the animals and / or the increase in the recruitment of newborns. The largest number of alligators both for the course of the Río Frío within the RNVSCN, as well as in the lagoons and pools, are found in sizes smaller than 120 cm due to the preference of hunters for sizes greater than 120 cm. The average sex ratio for the population was 1 male: 0.80 females. From 180 cm only males were observed. The size of the females that were observed guarding nests was between 140 cm and 150 cm. The months of June and July correspond to the nesting period and from September to October to the hatching period. The greatest average distance between the nest and the body of water was obtained for August 1993 with a value of 15.2 + - 17.6 m, with a range between 1m and 50 m. The average temperature of the nests at the level of the second stratum was 31.6 + -0.2 ° C. The average number of eggs per nest was 21.6 + - 0.6. The regression coefficients were greater than 0.97, which indicates that there is a high correlation between the biometric variables used to predict the measurement of the total length of animals in the field.
Descripción
Junier Wade, E. (2000). Análisis de la población de Caiman crocodilus en el Refugio Nacional de Vida Silvestre Caño Negro, Costa Rica. [Tesis de Licenciatura]. Universidad Nacional, Costa Rica.
Palabras clave
CAIMAN, CAIMAN CROCODILUS, REFUGIO NACIONAL DE VIDA SILVESTRE CAÑO NEGRO (COSTA RICA)