Kenyon, Nicole, Phillott, Andrea D., and Alford, Ross A. (2009) Evaluation of the photographic identification method (PIM) as a tool to identify adult Litoria Genimaculata (anura: hylidae). Herpetological Conservation and Biology, 4 (3). pp. 403-410.

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Abstract

Marking anurans by invasive methods has been strongly debated on the grounds of ethics, public opinion, the potential for infection, and potential impacts on behavior and survival of marked animals. One possible alternative is the use of photographs to enable identification of individuals by their patterns. This requires that individuals have distinguishable markings that remain constant through time. We compared the accuracy of the photographic identification method (PIM) to marked frogs in the field to evaluate whether PIM can be used to identify adult Greeneyed Tree Frogs, Litoria genimaculata. We captured 59 animals on second and subsequent nights of trips. Thirteen were correctly identified as recaptures; 61.5% of them by using the PIM. This was a substantial (39.5%) improvement over chance (expected rate if frogs assigned as recaptures at random was 22%), but was less accurate than the toe-tipping method, with which only one recapture was misidentified (92.3% correct). The majority of frogs, including all of the individuals that were not correctly identified, lacked a distinct dorsal "hourglass" pattern. This may have contributed to the relatively high error rate. We found that the PIM was slower than toe-tipping animals in both time taken for application and identifying individuals. We conclude that the PIM needs to be carefully validated before it is applied to a new species. For L. genimaculata it may be of use in short-term studies when the goal is to reduce the chance of doublesampling individuals. Even then, it will probably only be worth using when a relatively high proportion of the population is being sampled on each occasion, so that a 60 to 70% reduction in double-sampling rates over random is worth achieving.

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