A comparison of measures of abundance of reptiles in Kwongan vegetation of the SouthWest of Australia, determined through systematic searching and pitfall trapping

Abstract

Fauna surveys to determine the species richness, relative abundance and community structure of reptile assemblages are often important first steps in their conservation. Several sampling techniques are commonly used. Most involve trapping and assume a simple relationship between the absolute abundance of a species and the index of abundance obtained by sampling. However, comparing the effectiveness of different trapping techniques reveals biases among techniques. Therefore, without knowing absolute abundance, bias in a trapping technique can only be determined relative to other, biased techniques.To investigate this issue, measures of absolute abundance of reptiles were obtained by intensively searching measured quadrats (total removal plots), usually 5 m by 5 m, in two areas, with results compared with those obtained from pitfall trapping in one of these areas. Pitfall trapping was extremely biased towards large, surface-active lizards compared with the reptile assemblage determined by total removal, which was numerically dominated by small, fossorial species.Trapping data are influenced by the morphology and life history of a reptile species compared with results from total removal plots.Therefore, searching may provide a baseline for interpreting abundance data from trapping techniques, and for studies of population dynamics critical to assessing a population's robustness and its response to impacts.