No Measured Effect of PIT-Tagging on Demographic Estimates from a Reintroduced Western Toad (Anaxyrus boreas) Population

Often organizations engaged in amphibian conservation are simultaneously trying to understand the mechanisms of species’ decline and evaluate conservation actions employed to mitigate or reverse these declines. Capture–recapture monitoring methods are commonly used to identify and evaluate factors influencing population dynamics and associated vital rates, but these methods require individual identification for a subset of the population. Two commonly used anuran identification methods include passive integrated transponder (PIT) tags and pattern recognition. We combined these approaches via a double-marking method to quantify tag retention over five years and estimated potential effects of PIT-tagging on demographic rates for Western Toads (Anaxyrus boreas) in a reintroduced population in Colorado, USA. We used sharp, sterile scissors to cut a small dorsal incision (<3 mm) and inserted a 12 mm PIT tag subcutaneously. We found no negative effect of PIT-tagging on apparent survival, temporary emigration (skipped breeding), or recapture probability and no tag loss five years post-tagging. Vital rates from this reintroduced population were comparable or higher than those estimated from healthy populations in the same region. Our findings of 100% PIT-tag retention and no negative effects on toad demographic rates, together with high annual apparent survival and a growing population, suggest switching to PIT tags as an identification method is prudent for continued monitoring, though we encourage using the double-marking method for several more years until these findings are confirmed.