The line transect method for estimating densities of large mammals in a tropical deciduous forest: An evaluation of models and field experiments |
| |
Authors: | K Surendra Varman R Sukumar |
| |
Institution: | (1) Centre for Ecological Sciences, Indian Institute of Science, 560 012 Bangalore, India |
| |
Abstract: | We have evaluated techniques of estimating animal density through direct counts using line transects during 1988–92 in the
tropical deciduous forests of Mudumalui Sanctuary in southern India for four species of large herbivorous mammals, namely,
chital (Axis axis). sambar (Cervus unicolor). Asian elephant (Elephas maximus) and gaur (Bos gaurus)
Density estimates derived from the Fourier Series and the Half-Normal models consistently had the lowest coefficient of variation.
These two models also generated similar mean density estimates. For the Fourier Series estimator, appropriate cut-off widths
for analyzing line transect data for the four species are suggested. Grouping data into various distance classes did not produce
any appreciable differences in estimates of mean density or their variances, although model fit is generally better when data
arc placed in fewer groups. The sampling effort needed to achieve a desired precision (coefficient of variation) in the density
estimate is derived. A sampling effort of 800 km of transects returned a 10% coefficient of variation on estimate for ehital;
for the other species a higher effort was needed to achieve this level of precision. There was no statistically significant
relationship between detectability of a group and the size of the group for any species. Density estimates along roads were
generally significantly different from those in the interior of the forest, indicating that road-side counts many not be appropriate
for most species. |
| |
Keywords: | Line transect method large mammals wildlife census tropical forest |
本文献已被 SpringerLink 等数据库收录! |