Factors Affecting the Retention of Visible Implant Elastomer (VIE) Tags in Smooth Newts (Lissotriton vulgaris) During the Breeding Period

Abstract

Population parameters can be estimated on the basis of capture-mark-recapture (CMR) studies, which require accurate and continuous identification of studied individuals. Amphibians that cannot be identified by unique color patterns represent a problem for these types of studies due to variable interspecies suitability of different marking methods. One alternative to the traditional but questionable toe-clipping method is visible implant elastomer (VIE) tagging. VIE has been used successfully, mainly for tagging different species of terrestrial salamanders, but it has not been evaluated systematically for biphasic newts. In this study, the efficiency of VIE tagging was tested on smooth newts (Lissotriton vulgaris), with controls for body length, sex, position of tag, color of tag, and personal experience with tagging. Two tags, originally injected into each individual, were visible only in 39.5% of the newts after 49 days. Most of the tags that failed (72.4%) were lost completely. Retention rates for the VIE tags were lowest for younger tags but improved over time. Tags were lost more from the front than from the hind legs (42.1% vs. 34.2%), the person more experienced in marking had fewer tag losses (22.8% vs. 51.2%), and males lost more tags from their hind legs than females (52.8% vs. 17.5%). This study shows that VIE marking is not a conclusively reliable method for CMR studies of small salamanders during the breeding (water) period. The future of individual recognition, for the purpose of CMR studies, lies probably in non-invasive, computer-assisted photo identification methods.