At present, some 11,440 extant reptile species have been described on Earth and several hundred new species have been described each year since 2008 (Uetz & Hosek 2018). As grazers, seed dispersers, predators, prey and commensal species, reptiles perform crucial functions in ecosystems (Böhm et al. 2013).
Reptiles are a hugely diverse group of animals (Pincheira-Donoso et al. 2013) and are adapted to live in a wide range of tropical, temperate and desert terrestrial habitats, as well as freshwater and marine environments (Böhm et al. 2013). That said, reptile species usually have narrower geographic distributions than other vertebrate taxonomic groups (e.g. birds or mammals), and this coupled with particular life history traits makes some reptile species particularly vulnerable to anthropogenic threats (Böhm et al. 2013, Fitzgerald et al. 2018). For example, some turtle species are
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typically very long lived, take years to reach full maturity, produce small clutches and have variable reproductive success, which means that they are vulnerable to loss of adults and take many years to recover from declines (Congdon et al. 1994).
Multiple threats to reptile populations have been identified and are implicated in species declines (Gibbons et al. 2000, Todd et al. 2010). These threats include habitat modification, loss and fragmentation (Neilly et al. 2018, Todd et al. 2017), environmental contamination (Sparling et al. 2010), potentially unsustainable harvesting and/or collection (van Cao et al. 2014), invasive species (Fordham et al. 2006), climate change (Bickford et al. 2010, Sinervo et al. 2010) and disease and parasitism (Seigel et al. 2003). Also, due to their physical characteristics, reputation (warranted or otherwise) and in some cases venomous bites, some reptile species are viewed with distaste, which leads to apathy around their conservation (Gibbons et al. 1988). According to the IUCN Red List, of 10,148 reptile species that have been assessed, some 21% are considered to be threatened (IUCN 2021). Extinction risks are particularly high in tropical regions, on oceanic islands and in freshwater environments (Böhm et al. 2013), with some 59% of turtle species assessed at risk of extinction (van Dijk et al. 2014). Reptiles with specialist habitat requirements and limited ranges that are in areas accessible to humans are likely to face greater extinction risks (Böhm et al. 2016). Many island reptile species are endemic and are therefore even more vulnerable to extinction as a result of human disturbance (Fitzgerald et al. 2018). For a comprehensive summary of threats to different families of reptiles see Fitzgerald et al. (2018).
Evidence-based knowledge is key for planning successful conservation strategies and for the cost-effective allocation of scarce conservation resources. To date, reptile conservation efforts have involved a broad range of actions, including protection of eggs, nests and nesting sites; protection from predation; translocations; captive breeding, rearing and releasing; habitat protection, restoration and management; and addressing the threats of accidental and intentional harvesting. However, most of the evidence for the effectiveness of these interventions has not yet been synthesised within a formal review and those that have could benefit from periodic updates in light of new research.
Targeted reviews are labour-intensive and expensive. Furthermore, they are ill-suited for subject areas where the data are scarce and patchy. Here, we use a subject-wide evidence synthesis approach (Sutherland et al. 2019) to simultaneously summarize the evidence for the wide range of interventions dedicated to the conservation of all reptiles. By simultaneously targeting all interventions, we are able to review the evidence for each intervention cost-effectively, and the resulting synopsis can be updated periodically and efficiently. The synopsis is freely available at www.conservationevidence.com and, alongside the Conservation Evidence online
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database, is a valuable asset to the toolkit of practitioners and policy makers seeking sound information to support reptile conservation. We aim to periodically update the synopsis to incorporate new research. The methods used to produce the Reptile Conservation Synopsis are outlined below.
This synthesis focuses on global evidence for the effectiveness of interventions for the conservation of reptiles. This subject has not yet been covered using subject-wide evidence synthesis. This is defined as a systematic method of reviewing and synthesising evidence that covers broad subjects (in this case conservation of multiple taxa) at once, including all closed review topics within that subject at a fine scale, and analysing results through study summary and expert assessment, or through meta-analysis. The term can also refer to any product arising from this process (Sutherland et al. 2019). This global synthesis collates evidence for the effects of conservation interventions on terrestrial, aquatic and semi-aquatic reptiles, including all reptile orders, i.e. Crocodilia (alligators, crocodiles and gharials), Testudines (turtles and tortoises), Squamata (snakes, lizards and amphisbaenians) and Rhynchocephalia (tuatara). This synthesis covers evidence for the effects of conservation interventions for wild reptiles (i.e. not in captivity). We have not included evidence from the substantial literature on husbandry of marine and freshwater reptiles kept in zoos or aquariums. However, where these interventions are relevant to the conservation of wild declining or threatened species, they have been included, e.g. captive breeding for the purpose of increasing population sizes (potentially for reintroductions) or gene banking (for future release).