EFFICACY OF VISIBLE IMPLANT ELASTOMER TAGS WITH PHOTOGRAPHIC ASSIST FOR IDENTIFYING INDIVIDUALS IN CAPTURE- MARK-RECAPTURE STUDIES USING LARVAL FROGS

Population demography studies often rely on marking individuals to estimate survivorship, population sum, and dispersal. Ideally, marking methods allow researchers to identify individuals reliably over a given time frame (e.g., specific life stages); however, finding effective marking methods for larval amphibians can be particularly challenging. We evaluated efficacy of using a combination of visible implant elastomer tags and photo identification to identify individual larval anurans in the field. Initially, our pilot study in the laboratory using American Bullfrog (Lithobates catesbeiansts) tadpoles showed that the probability of tag retention was higher for tags placed on the tail than tags placed on the body. We then used a combination of VIE tags placed on the tail and photo identification of tail spot patterns to identify tadpoles of Northern and California Red-legged Frogs (Rana aurora and R. draytonit) in the field at several sites across Oregon and California. We placed four VIE tags in the tail using unique sequences of colors for each individual. The retention rate of individual tags varied between sites from 82% to 98% with a mean of 92%. The proportion of individuals retaining all four tags varied significantly among sites, from 53% to 94% with a mean of 76.3%. Using photo identification of tail-spot patterns for tadpoles with missing tags, we successfully identified 98% of recaptured animals. Our work demonstrates that using VIE tags with photo assist can be highly effective for identifying individual tadpoles across a variety of conditions. The combined method is more reliable than using only VIE tags and requires less overall effort than using photo identification of markings exclusively.