Computer-assisted photo identification outperforms visible implant elastomers in an endangered salamander, Eurycea tonkawae

PLoS One. 2013;8(3):e59424. doi: 10.1371/journal.pone.0059424. Epub 2013 Mar 21.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Biocompatible Materials / chemistry
  • Biometric Identification / instrumentation
  • Biometric Identification / methods*
  • Conservation of Natural Resources
  • Ecosystem
  • Elastomers / chemistry
  • Endangered Species*
  • Image Processing, Computer-Assisted / statistics & numerical data*
  • Photography / methods
  • Photography / veterinary*
  • Pigmentation / physiology
  • Texas
  • Urodela / anatomy & histology
  • Urodela / physiology*

Substances

  • Biocompatible Materials
  • Elastomers

Grants and funding

Work was primarily funded by the City of Austin, through staff time and purchase of materials. This includes the City of Austin Balcones Canyonland Preserve and Watershed Protection Department. The Texas Parks and Wildlife Department also provided staff assistance with this project. The funding agencies had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript (with the exception of the authors and acknowledged individuals).