Season, Rather than Soft- or Hard-Release, Has Most Effect on Translocation Outcomes for a Critically Endangered Reptile

Abstract

Globally, many reptile populations are declining. Translocations, the intentional release of individuals at a location to establish or re-establish populations, offer a key pathway to mitigate these declines. Translocations typically involve one of two release strategies: soft-release (with acclimation) and hard-release (without acclimation), although the efficacy of the two strategies is rarely tested. Here we evaluate the effects of soft- versus hard-release on the body weight, movement, and survival of captive-bred Canberra grassland earless dragons (Tympanocryptis lineata), a critically endangered and cryptic reptile. We radio-tracked 56 individuals across three release seasons (summer, autumn, spring) for up to 42 days per season. We observed trends of decreased weight over time for hard-released individuals while autumn-released individuals increased in weight regardless of release strategy, compared with other release seasons. Soft- and autumn-released individuals had the lowest daily movement as well as significantly lower risk of mortality. Our results suggest that release season, regardless of release strategy, may help maintain body weight and reduce movement and thereby improving short-term survival and therefore overall reintroduction success for those lizards.

Keywords: Threatened species, Conservation, Translocation, Release strategy, Survival