Moving towards greater success in translocations: recent advances from the herpetofauna

Abstract

Conservation translocations are occurring at ever-increasing rates (Seddon, Armstrong & Maloney, 2007). These include reintroduction, reinforcement and more recently, ecological replacement and assisted colonization (Seddon et al., 2014). Additionally, over the past two decades, there has also been an increase in the movements of animals as minimization or mitigation for human development (Miller, Bell & Germano, 2014; Germano et al., 2014; Sullivan, Nowak & Kwiatkowski, 2014). Alongside the overall increase in the number of conservation translocations occurring worldwide, there has also been a shift in how these releases are carried out. While many early translocations occurred as isolated management projects, there has been a move to better monitoring and research that tests a priori questions and theories. This helps add to our knowledge base and ability to carry out more effective releases (Ewen et al., 2012). It is critical that the literature reflects advances made in conservation translocations so that solutions are shared across the growing application of this conservation management tool and its use as a valid technique for mitigation or minimization during development. Despite the need by conservation practitioners for knowledge that can be applied to a broad range of circumstances, past studies have shown a marked taxonomic bias both within conservation translocation projects being carried out (Seddon, Soorae & Launay, 2005) and within those translocations that make it to the published literature (Bajomi et al., 2010). In both of these cases, the bias has been towards vertebrates with a further overrepresentation of mammals and birds within the vertebrate groups (Seddon et al., 2005; Bajomi et al., 2010). This special issue has two aims: first, to present a collection of articles covering recent advances in conservation translocation, and, second, to do so by highlighting translocations from one under-represented taxonomic group, herpetofauna. We hope that this will provide a valuable resource to the translocation community and help guide amphibian and reptile translocations in the future. One of the common concerns discussed in this collection of papers and in the literature is the need for well defined criteria for success as part of any translocation initiative (Seddon, 1999; Miller et al., 2014). Ideally, these criteria should be compatible with the biology of the target species and the socio-economic context in which the translocation is developed. Ewen et al. (2014) present an analysis of the range of both biological and non-biological objectives set by translocation practitioners to assess the success of herpetofauna translocations and what aspects are being judged as affecting the outcomes of these translocations. Their study calls for a more rigorous development of translocation objectives and a clearer distinction between required technical improvements as means of moving towards more fundamental project goals such as population establishment. Once criteria for success are clearly stated, the next important step is to find ways to improve the chances of success by careful planning. Much of this planning depends upon knowledge of the biological, ecological and behavioural needs of the target species. McCoy et al. (2014) experimentally explore the complex interactions of environmental conditions and their relationship to translocation success of the threatened Florida sand skink (Plestiodon reynoldsi). Their study highlights the importance of habitat heterogeneity, available micro-habitats at recipient sites and the behavioural choices of the species for initial survival and reproduction. Aiello et al.'s (2014) study reinforces the need to consider behaviour more prominently in translocation efforts with a particular focus on the interactions of behaviour and disease risks. They offer a caution about use of translocations to either top-up remnant populations, follow-up on previous translocations or otherwise release animals at sites where there are conspecifics. Their study presents a model of disease dynamics with altered transmission rates through changes in contact networks following translocation of host animals. Preliminary modelling of a case study, the Mojave desert tortoise (Gopherus agassizii) and the pathogen Mycoplasma spp., reveals that translocation of tortoises results in dispersal-driven changes in contact frequency and network structure and that this can increase a disease outbreak risk. Technique improvement is a dominant theme across this special issue, covering both captive husbandry and release techniques through to evaluating appropriate monitoring methods that provide the data against which population establishment and persistence can be assessed. For example, Sacerdote-Velat et al. (2014) critically evaluate the role of headstarting in captive breeding of smooth green snake (Opheodrys vernalis) in reducing juvenile pre-release mortality and improving released animal body size. Their study found no benefit of headstarting and some evidence for increased breeding potential in snakes that had been through natural brumation. Similarly, Knox and Monks (2014) evaluated the role of penning at the release site as a tool to restrict dispersal of translocated animals, by allowing them to habituate to the release area prior to full release. Their study on jewelled geckos (Naultinus gemmeus) showed that a period of penning substantially reduced dispersal and allowed a greater chance for released animals to interact, breed and contribute effectively to population establishment. Burton and Rivera-Milán (2014) provide a technical evaluation of monitoring a species, which is difficult to mark and where a proportion of the population is unavailable for detection. Their comparison of distance and repeat counts with complete census data of Grand Cayman blue iguana (Cyclura lewisi) shows that less intensive and invasive survey methods can provide both accurate and precise counts of animals in this population. Literature reviews have shown that habitat quality or lack of specific habitat characteristics are one of the greatest reasons for translocation failure (Griffith et al., 1989; Wolf et al., 1996; Germano & Bishop, 2009). The task of selecting a release site with suitable habitat is even more difficult when considering the impacts of climate change and the impacts this will have on habitat suitability. Dade et al. (2014) demonstrate how a spatially explicit, multiple criteria analysis can be used to identify suitable release sites for assisted colonization of the endangered western swamp tortoise (Pseudemydura umbrina). Furthermore, as some reptiles have temperature-dependent sex determination, for many species, assessment of habitat quality must include an evaluation of the thermal suitability of possible release sites. Jarvie et al. (2014) address this through the development of a strategic framework, which they have used for tuatara reintroduced to the South Island of New Zealand. While the idea of moving an animal may seem simple at first glance, the reality is that translocations are inherently complex. In order to improve our rates of success, this complexity must be considered. As shown in the articles found in this special issue of Animal Conservation, the tools and techniques to help deal with that are continually being tested and improved. The publication and presentation of these advances, across all taxa involved, will help to ensure that translocations are used responsibly for both the wildlife and ecosystems involved.