Effectiveness of translocation in mitigating reptile-development conflict in the UK

The translocation of reptiles from development sites is a frequent but controversial intervention to resolve reptile-development conflicts. A general lack of post-translocation monitoring means that the fate of translocated reptiles is largely unknown. Here we report on the outcome of six reptile translocations carried out to mitigate the impacts of development. Through detailed post-translocation monitoring, we sought to determine whether translocated reptiles established populations within the receptor sites. To determine the effect of translocation, we investigated six sites within the UK that had received populations of translocated slow-worm Anguis fragilis, viviparous lizard Zootoca vivipara, adder Vipera berus and / or grass snake Natrix helvetica. Identification photographs were taken of all reptiles during the translocation. Following release, between one and three years of post-translocation monitoring was undertaken; during the monitoring, identification photographs were again collected to establish whether captured individuals were part of the translocated populations. Very few translocated individuals were encountered during the post-translocation monitoring. The mean number of translocated reptiles was 98 (SE 19.61). Of these, an average of 1.5 (SE 0.72) individuals or 1.6% of the population were captured during the monitoring. No recaptures of translocated reptiles were made at three (50%) of the study sites. The low recapture rates of translocated reptiles could be due to mortality, imperfect detection (including inaccurate identification of individuals) or post-translocation dispersal. There is some limited evidence to support each of the possible options, but post-translocation dispersal is considered to be the most likely explanation. The study found no confirmatory evidence that mitigation-driven translocations are compensating for the losses of populations to development.