Population characteristics of rats and mice in evergreen forest and grassland at Khao Yai National Park
1996
Somkiat Soontornpitakkool
Capture-recapture was conducted from 1-12 February 1995 in evergreen forest and grassland at Khao Yai National Park to examine the population characteristics of rats and mice. A total of 27 animals was captured in 2,400 trap nights. Species captured were lesser bandicoot (Bandicota savilei) and roof rat (Rattus rattus). Bandicota savilei was found only in the evergreen forest while only one specimen of Rattus rattus was found in the grassland. There are no quantitative data for this species because the number of capture was too small. Two methods of estimating population size from capture-recapture technique are the Lincoln-Petersen estimator and program CAPTURE. The model selection procedure of the program CAPTURE indentified individual heterogeneity as the prevailing source of variation in capture probabilities and suggested the appropriate estimator would be the Jackknife. The Jackknife estimator is more accurate and precise than the Lincoln-Petersen estimator in this study. Population size of Bandicota savilei in evergreen forest gird (0.81 ha) is 25-31 animals and estimated density is 13-18 animals/ha. Home range size as determined by exclusive boundary strip, observed range length and adjusted range length for Bandicota savilei were considered. The home range size in evergreen forest of females are larger than those of males. The mean home range size is 0.025 ha. Sex ratio in the evergreen forest is not significantly different from 1:1. The age ratio is significantly more adults than juveniles in both male and female. The population size and density of rats and mice in the grassland is lesser than in the evergreen forest because of the higher vegetational homogeneity and lower diversity. The diversity index of rats and mice in each habitat type is equal to one because only one species had been captured in each grid location.
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