The Herpetological Journal

pp.1-7

Authors: Klaus Weddeling, Monika Hachtel, Ulrich Sander And David Tarkhnishvili

Abstract: Drift fences are frequently used to sample amphibians for population studies. Thus, some researchers do not mark animals, but use capture rates at the drift fence as an indicator of population size. Other workers use mark-recapture techniques to estimate population sizes. These approaches require different amounts of effort and lead to different results. Our study compares several estimates of population size for alpine newts (Triturus alpestris) and smooth newts (Triturus vulgaris) in five breeding ponds surrounded by pennanent drift fences and pitfall traps. The estimates based on mark-recapture techniques (Petersen method) do not vary substantially between the two modes of recapture applied (funnel traps, and drift fences with pitfall traps). These estimates give even better results than simple counts if a substantial part of the newt populations remain within the drift fences throughout the year. While unrecognized trespass by newts appears to be a rare event, some newts may leave a pond for a short time even during the breeding season. This is an important source of bias for population estimates in studies based on counts at drift fences when animals are not marked.

Keywords: capture methods, mark-recapture, Triturus alpestris, Triturus vulgaris