Do trails affect relative abundance estimates of rainforest frogs and lizards?
Austral Ecology
2009
Journal Article
34
613-620
Los Amigos;impacts;habitat preferences;amphibians;reptiles;field techniques
The selection of a sampling protocol is critical to study amphibian and reptile communities and in many instances researchers have combined the use of visual encounter sur veys (VES) conducted on trails and off trails. The effect of human-made trails on relative abundance estimates of amphibians and reptiles has been assessed in a few temperate locations, but data are lacking for tropical sites. Our study was designed to address this issue by comparing abundance estimates of frogs and lizards on and off trails in a lowland rainforest in south-eastern Perú. We used nocturnal VES to sample frogs and lizards along transects established on trails and off trails in two different forest types. We found that the obser ved relative abundance estimates of frogs and lizards were affected by the location of transects (on trail vs. off trail) and the type of forest (floodplain forest vs. terra ï¬rme forest). We also found an interaction between the two main effects, indicating that the effect of transect location with respect to trails varies as a function of habitat. Observed frog abundances were higher on trails than off trails, indicating that studies that include VES on trails will bias relative abundance estimates in contrast to studies that include only VES off trails. We suggest that transects should be established only off trails, especially for monitoring studies because trail use by humans can have a strong influence on obser ved animal abundance.