Comparing the predatory impact of captive–bred and free–living yellow spotted mountain newt (Neurergus microspilotus) on the larval green toad (Bufotes variabilis)

Abstract

Captive breeding of endangered species is an important conservation tool, but it is not clear how long–term captive breeding can influence fitness attributes such as predatory ability. We experimentally investigated the predatory impact of adult captive–bred newts (CBN) and adult free–living newts (FLN) on the survival and growth of larval green toad (B. variabilis) in four predator density treatments containing none, one, two, or three newts. FLNs performed a rapid density–dependent predation, yielding average survival rates of tadpoles in no, low, medium, and high densities to 81 %, 74 %, 60 % and 17 %, respectively. CBNs had an average lower predation rate on B. variabilis tadpoles with a decrease in survival rate of tadpoles to 83 %, 81 %, 82 % and 77 % for 0, 1, 2 and 3 predator treatments, respectively. However, contrary to FLNs, they exhibited a significant increase in predation rate with time from 0.37 to 0.60 tadpoles per day. In addition, the growth rate of tadpoles reared with predators for the FLN group was significantly higher than the growth rate of tadpoles reared in control containers without the predator. In conclusion, our findings suggest that exposing captive–born adult yellow spotted mountain newts to their potential prey enriches the environment, and may be a useful approach in the development of more efficient captive breeding and reintroduction programs for this highly endangered amphibian.