Computer-Assisted Photo Identification Outperforms Visible Implant Elastomers in an Endangered Salamander, Eurycea tonkawae

Abstract

Despite recognition that nearly one-third of the 6300 amphibian species are threatened with extinction, our understanding of the general ecology and population status of many amphibians is relatively poor. A widely-used method for monitoring amphibians involves injecting captured individuals with unique combinations of colored visible implant elastomer (VIE). We compared VIE identification to a less-invasive method – computer-assisted photographic identification (photoID) – in endangered Jollyville Plateau salamanders (Eurycea tonkawae), a species with a known range limited to eight stream drainages in central Texas. We based photoID on the unique pigmentation patterns on the dorsal head region of 1215 individual salamanders using identification software Wild-ID. We compared the performance of photoID methods to VIEs using both ‘high-quality’ and ‘low-quality’ images, which were taken using two different camera types and technologies. For high-quality images, the photoID method had a false rejection rate of 0.76% compared to 1.90% for VIEs. Using a comparable dataset of lower-quality images, the false rejection rate was much higher (15.9%). Photo matching scores were negatively correlated with time between captures, suggesting that evolving natural marks could increase misidentification rates in longer term capture-recapture studies. Our study demonstrates the utility of large-scale capture-recapture using photo identification methods for Eurycea and other species with stable natural marks that can be reliably photographed.

Genetic fingerprinting proves cross‐correlated automatic photo‐identification of individuals as highly efficient in large capture–mark–recapture studies

“…), even from juvenile to adult stages, whereas photograph matching scores of an individual were negatively correlated with time in the approach of Bendik et al. (); and (4) unusual areas of a shape pattern that makes the individual special and are less frequently found in other individuals can be marked as a striking character for identification.…”

“…To our knowledge, only the study of Bendik et al. () has tested the performance of an automatic photo‐identification approach using a completely independent method, that is, colored visible implant elastomers, whereas other studies (e.g., Gamble et al. ; Bolger et al.…”

Treefrog lateral line as a mean of individual identification through visual and software assisted methodologies

“…Ever since the release of the program, it has been used for many species of animals, the majority of them with spots (Bolger et al 2012, Bendik et al 2013, Elgue et al 2014, Dala-Corte et al 2016). This study is uncommon in that it is testing the program on a linear pattern.…”

Individual identification of Eurasian perch Perca fluviatilis by means of their stripe patterns

“…Given the growing number of software tools for picture-based animal identification, one might ask: why did we not test and apply computer-based matching procedures as e.g. Wild-ID (Bendik et al, 2013)? There is no reason to assume that any computer-based technique would outperform the human eye in identifying perch based on their, rather simple, stripe patterns.…”

“…Computer-based methods can facilitate identification only when recognition is based on extremely complex pigmentation patterns (e.g. used to identify animals with complex web-like pigmentation patterns such as salamanders (Bendik et al, 2013)). However, such software requires a considerable amount of time to prepare the pictures and, in the most commonly applied software solutions, the final matching of picture-pairs is, again, left to the human eye.…”