Long-term Retention, Readability, and Health Effects of Visible Implant Elastomer (VIE) and Visible Implant Alpha (VI Alpha) Tags in Larval Eastern Hellbenders (Cryptobranchus alleganiensis alleganiensis)

Abstract

The ability to identify individuals is essential for determining population demographics of a species, but traditional marking techniques, such as passive integrated transponder tags, are often limited to individuals that meet minimum size thresholds. Visible implant elastomer (VIE) and visible implant alpha (VI Alpha) tags are promising methods for marking small-bodied individuals. However, the efficacy and health effects of VIE and VI Alpha tags are not established for many, increasingly imperiled, herpetofauna. Over a 12-mo period, we examined tag retention, tag readability, VIE tag color readability, and effects on growth and body condition of VIE and VI Alpha tags in larval Eastern Hellbenders (Cryptobranchus alleganiensis alleganiensis), a species of conservation concern. We observed 100% retention of VIE tags and 80% retention of VI Alpha tags over 1 yr. Readability degraded over time for both tag types but was consistently higher for VIE relative to VI Alpha tags. Degradation in readability over time increased our reliance on a 450-nm-wavelength VI light to read VIE tags but had more severe implications for VI Alpha codes, which were illegible after 4 mo. Pink- and green-colored VIE tags performed similarly well and we found that neither VIE nor VI Alpha tags negatively affected growth or body condition of larval hellbenders. Our findings collectively suggest that VI Alpha tags are an unviable tagging method, but VIE tags were safe and effective for identifying unique larval hellbenders up to 1 yr.