Population dynamics of the rat Microryzomys minutus (Rodentia: Muridae) in the Venezuelan Andes

ABSTRACT

The population dynamics of the small forest rice rat Microryzomys minutus, a murid rodent that occurs in the high altitudes of the northern and central Andes, was studied in disturbed and primary environments in a cloud forest of the Venezuelan Andes (Juan Pablo Peñaloza National Park, 8 degrees 11'N, 71 degrees 49'W). We collected 121 animals (66 female female and 55 male male) between 1995 and 1998, using pitfall traps with formalin. Adult males were heavier than adult females. Relative abundance was much greater in the disturbed environments (over 10 individuals in some periods) than in the primary cloud forest 4-8 individuals. In the disturbed environments, the rats were extremely abundant in the first sampling period, and less frequent afterwards. In the cropland, abundance showed some fluctuations during the study and displayed two small abundance peaks in March-June 1997 and 1998. In the mined area, the rats had irregular fluctuations until March-June 1997 and were not recorded in July-October 1997. The occurrence of this rat in both disturbed and natural habitats confirms the wide ecological tolerance of this species.

RESUMEN

Se analizó la dinámica poblacional de las pequeñas ratas silvestres del arroz Microryzomys minutus en ambientes alterados y primarios, en un bosque nublado de los Andes venezolanos. El estudio fue basado en 121 animales(66 [hembra hembra] y 55 [macho macho] ) recolectados entre 1995 y 1998, usando trampas que contenían formalina. Esta especie está presente en ambos hábitats lo que confirma su ampliatolerancia ecológica. La abundancia poblacional fue mayor en ambientes alterados que en los no alterados. M. minutus presenta dimorfismo sexual en el peso los machos son más pesados que las hembras.