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Conservation Evidence Journal

Publishing evidence to improve practice


The Conservation Evidence Journal shares the global experience of those on the front line of conservation practice about the effectiveness of conservation actions. All papers include monitoring of the effects of the intervention and are written by, or in partnership with, those who did the conservation work. We encourage articles from anywhere around the world on all aspects of species and habitat management such as habitat creation, habitat restoration, translocations, reintroductions, invasive species control, changing attitudes and education. 

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Reptile management

This virual collection contains 18 papers on reptile conservation management.

Comparing post-release cover and burrow use by differentially head-started Mojave desert tortoises in southern California

McGovern P.A., Peaden J.M., Buhlmann K.A., Todd B.D. & Tuberville T.D. (2021), 18, 37-43


The effects of indoor rearing versus the conventional method of solely outdoor head-starting on post-release cover and burrow use of juvenile Mojave desert tortoises (Gopherus agassizii), a threatened endemic species, were investigated. We found that partially indoor-reared tortoises exhibited similar post-release behaviours when compared to both same-aged, but smaller, and similar-sized, but older outdoor-reared head-started tortoises, thus increasing the success and decreasing the costs of head-starting.


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

Nash D. J., Humphries N. & Griffiths R.A. (2020), 17, 7-11


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.


Improving capture rate for an invasive species in Mauritius: determining Asian musk shrew Suncus murinus bait preference

Field A.J., Copsey J.A., Tragett C.E.E. & Goder M. (2017), 14, 16-19


The Asian musk shrew Suncus murinus is an invasive insectivore that first colonised Mauritius in the eighteenth century. It is a significant predator and poses a threat to terrestrial endemic reptiles in Mauritius. On the islet nature reserve Ile Aux Aigrettes, Mauritius, shrews predate juvenile Telfair’s skink Leiolopisma telfairii, limiting the recruitment of this threatened species. It is therefore important to reduce numbers of Asian musk shrews, and live and fatal trapping are potential methods that can be used to control or eradicate invasive vertebrates. This study tested whether Asian musk shrews preferred the bait currently used for trapping shrews on Ile Aux Aigrettes compared to a novel bait, crushed cockroach. We also tested whether shrews preferred bait in the presence or absence of musk, a chemical attractant. Shrews were observed in a specially designed choice box where a behavioural tally recorded their activity. Their strongest preference was for compartments containing no bait, although they also displayed a significant preference for crushed cockroach in the presence of musk, and a lack of interest in the existing bait. These results suggest that the use of this novel bait plus musk could improve the success of trapping shrews on Ile aux Aigrettes and elsewhere.



Effects of culverts and roadside fencing on the rate of roadkill of small terrestrial vertebrates in northern Limpopo, South Africa

Collinson W. J., Davies-Mostert H. T. & Davies-Mostert W. (2017), 14, 39-43


We tested the effectiveness of low-level roadside fencing to direct wildlife towards existing culverts beneath the road (underpasses) in order to reduce road deaths of small terrestrial vertebrates. While our results showed a reduction in roadkill count (from eight to one) along the stretches of road where we installed barriers (from an average of 0.33 roadkill/day/km to 0.04 roadkill/day/km), this decrease was not significant, possibly due to the small number of dead animals detected across all sites. Our trial highlights the challenges in acquiring robust evidence for roadkill reduction interventions and, given the small sample size, we were unable to elicit firm conclusions for this study. We therefore propose further testing of the efficacy of roadside fencing to reduce roadkill.


Biologically significant residual persistence of brodifacoum in reptiles following invasive rodent eradication, Galapagos Islands, Ecuador

Rueda D., Campbell K.J., Fisher P., Cunninghame F. & Ponder J.B. (2016), 13, 38-38


Rat eradication resulted in prolonged presence of the anticoagulant rodenticide brodifacoum in exposed lizards, likely significantly contributing to the deaths of secondarily exposed raptors up to at least 773 days after bait application.


Adder Vipera berus hibernacula construction as part of a mitigation scheme, Norfolk, England

Whiting C. & Booth H. (2012), 9, 9-16


A significant adder, Vipera berus, population was identified within the Upper Thurne river catchment during baseline surveys in 2009. An adder bank (hibernacula) was constructed in the autumn 2009 in advance of flood defence works at Horsey in 2010 to mitigate any temporary loss of hibernation and natal den sites. Reptile fencing was erected around the adder banks and some adjacent grazing marshes in February 2010 to create reptile enclosures. During March to May 2010, 119 adders were moved to the adder banks from the flood banks that were then stripped of vegetation and topsoil to discourage animals from re-entering the working corridor. Sections of the adder fencing were removed in mid-May to allow animals to disperse to their summer foraging grounds. Surveys during summer 2010 indicated breeding success within the banks. Pre hibernation surveys in 2010 recorded a peak count of 22 animals, and a spring emergence survey of the adder bank in 2011 identified 17 individual adders. A further four were recorded using an adjacent store of rush, Juncus, bales. Monitoring through summer and autumn 2011 identified a further 16 individual animals on or close to the adder bank, including six gravid adders. Eighteen out of the 33 adders recorded using the adder banks in 2011 were recaptures. Fifteen ‘new’ adders (i.e. not relocated during the 2010 mitigation) were subsequently identified as using the adder banks to hibernate or give birth. The total cost of constructing the adder banks and erecting/dismantling the reptile fencing was £63,500.


Mitigating habitat loss by artificial egg laying sites for Reunion day gecko Phelsuma borbonica, Sainte Rose, Reunion Island

Sanchez M. (2012), 9, 17-22


During the construction of a water storage tank for a hydroelectric plant, areas of natural habitat of the Reunion day gecko were destroyed by embankments of deposited excavated material.  To offset this impact and encourage the gecko’s return, 40 artificial egg laying site (AELS) were established in the area between September 2009 and July 2010. An AELS provides the gecko with a site for oviposition, shelter and basking. Since their installation, the number of AELS used for reproduction increased from 11.8 % (4/34) in June 2010 to 20% (8/40) in September 2011. Also, the number of eggs has progressively increased: 10 in June 2010, 23 in September 2010, 36 in March 2011 and 41 in September 2011.


A trial wild-wild translocation of the critically endangered grand skink Oligosoma grande in Otago, New Zealand

Whitmore N., Judd L.M., Mules R.D., Webster T.A., Madill S.C. & Hutcheon A.D. (2012), 9, 28-35


The in situ management of the critically endangered grand skink Oligosoma grande currently hinges on the on-going health of a single large sub-population at Macraes Flat, Otago. Given its vulnerability, it was considered desirable to establish additional sub-populations to ensure the long-term survival of the species. A spatial meta-population simulation of grand skinks at Macraes Flat suggested that this could be facilitated by the translocation of grand skinks into areas of predator protected habitat. Areas identified by modelling as suitable translocation sites were ground-truthed by an experienced survey team in 2008. In October 2009 we began a translocation trial. We moved nineteen grand skinks from three locations to the translocation site. The founder population was made up of ten juveniles and nine sexually mature grand skinks. Seasonal estimation of persistence and abundance using a photographic re-sight methodology allowed the short- and medium-term performance of the translocation to be assessed.  High initial persistence rates suggested immediate homing was not a factor of concern. After one year, all translocated juveniles had persisted, but only four of the original nine adults remained at the release site. While the loss of adults was to some extent offset by the birth of the young-of-the-year (total skinks start: n = 19, finish: n = 20) there was a moderate loss of ~ 10% in terms of the population’s expected reproductive value. Overall, we viewed the outcome as favourable and on that basis undertook a follow up translocation.


Successful rapid response to an accidental introduction of non-native lizards Podarcis siculus in Buckinghamshire, UK

Hodgkins J., Davis C. & Foster J. (2012), 9, 63-66


Italian wall lizards Podarcis siculus campestris were accidentally introduced to a site in Buckinghamshire, UK with a consignment of stone originating in Italy. Many populations of this lizard and closely related species have been established outside their native range, sometimes from a small number of founders. Mindful of the potential for these lizards to establish in the UK, we decided on a “rapid response” intervention. We captured four lizards, including a gravid female, and removed them to a secure captive collection. The capture operation comprised two visits, with specialist advice assisting estate management and nature conservation staff. Vegetation around the stone was cut back to dissuade dispersal in an effort to contain any remaining lizards. The imported stone and surrounding area were placed under surveillance, and no further lizards were found over the course of two years. Good communications between landowners, a government agency and reptile specialists expedited this intervention. We conclude that this simple, low-effort example of rapid response has eliminated the risk of a non-native invasive species establishing.


An education programme and establishment of a citizen scientist network to reduce killing of non-venomous snakes in Malappuram district, Kerala, India

Balakrishnan P. (2010), 7, 9-15


A public education and citizen science programme was developed to improve data collection on incidences of deliberate killing of snakes and to reduce unfounded killing of snakes in human dominated landscapes of Kerala, southwest India. During 2003-2009, citizen scientists recorded 278 direct human kills and more than 200 kills of snakes by vehicular collision, agricultural practices and attack by pets. Participants managed to prevent killing of 276 non-venomous snakes (of 14 taxa). The non-venomous Travancore wolf snake Lycodon travancoricus (a batesian mimic of the deadly venomous Indian krait Bungarus caeruleus) was the species that benefited most of the programme. In addition, the conservation education programme (highlighting ecosystem services of reptiles) resulted in positive attitudinal changes among local people towards the conservation of snakes and general biodiversity of the region.


Artificial incubation of yellow-headed sideneck turtle Podocnemis unifilis eggs to reduce losses to flooding and predation, Cojedes and Manapire Rivers, southern Venezuela

Herández O., Espinosa-Blanco A.S., May Lugo C., Jimenez-Oraa M. & Seijas A.E. (2010), 7, 100-105


Although widespread in South America, the yellow-headed sideneck turtle Podocnemis unifilis is considered 'Vulnerable' in Venezuela. A large portion of eggs of this riverine species may be lost due to predation (including collection by humans) and flooding. As a technique to enhance reproductive success, transfer of wild-laid clutches of eggs to protected zones for incubation has been successfully carried out. This study undertaken in 2009, evaluated the hatch success of clutches transferred to artificial nest chambers at protected locations compared with natural clutches left in situ along stretches of the Cojedes and Manapire rivers (Venezuela). Along the Cojedes River, 78 turtle nests were located, 27 of which were excavated and eggs transferred for incubation. In the Manapire River, 87 nests were located, eggs from 13 of which were transferred for incubation. In the Cojedes River, 28.2% of study clutches (n=22) were lost due to predation and flooding; in the Manapire River, 85% of nests (n=74) were lost due to predation (humans and other animals). At Cojedes River, hatching success of eggs in artificial nests was 88.2% and 63.2% in natural nests. At Manapire River, hatching success of eggs in artificial nests was 42% and 0% in natural nests.


Artificial incubation of wild-collected eggs of American and Orinoco crocodiles (Crocodylus acutus and C. intermedius), Gua-rico and Zulia, Venezuela

Barros T., Jiménez-Oraá M., Heredia H.J. & Seijas A.E. (2010), 7, 111-115


During 2009, wild eggs of two Venezuelan crocodilians (Orinoco crocodile Crocodylus intermedius and American crocodile C. acutus) were collected and artificially incubated using low-technology methods under basic conditions. Hatch success was 53.7% for C. intermedius eggs, and 65.6% for C. acutus eggs. Overall, 316 hatchlings were obtained from a total of 521 eggs (60.7% hatch success). These results compare favourably with similar artificial incubation trials, but incubation time for C. acutus eggs (87 to 102 days) was rather longer than the typical incubation period for the species (around 82 to 83 days). This may be indicative of a low incubation temperature; if so, most of the hatchlings may have been females. Only as these young mature will their sex be determinable. Hatchlings were taken to captive-rearing facilities where they will be maintained until they reach a suitable size for release into the wild. Participation of local people in this project was considered a very important factor in its success, and had additional conservation benefits including raising public awareness of the plight of crocodile populations and problems of over-exploitation in the study areas.


Effectiveness of head-starting to bolster Philippine crocodile Crocodylus mindorensis populations in San Mariano municipality, Luzon, Philippines

van de Ven W.A.C. , Guerrero J.P., Rodriguez D.G., Telan S.P., Balbas M.G., Tarun B.A., van Weerd M., van der Ploeg J., Wijtten Z., Lindeyer F.E. & de Iongh H.H. (2009), 6, 111-116


The freshwater Philippine crocodile Crocodylus mindorensis (endemic to the Philippine archipelago) is the most threatened crocodilian in the world with an estimated wild population of less than 100 mature individuals. Due to low survival of wild hatchlings, a head-starting program was initiated in 2005. Hatchlings are collected from the wild just after hatching and released back into their natural habitat after being raised in captivity for 14-18 months. Several ponds were created to provide suitable release habitat. Between 2005 and 2008, 88 hatchlings were collected. Hatchling survival after one year in captivity was 63 out of 88 (72%), compared to 47% for 36 hatchlings monitored in the wild (as low as 13% in some areas). Thirty two head-started crocodiles were released back into the wild (31 still held in captivity in 2009). Of the 32 released crocodiles, minimum survival after one year in the wild was 50%. Post release observations and recaptures showed that the released juvenile crocodiles adapted well to natural conditions and were increasing in size. The ultimate goal of the program will only be achieved if the head-started crocodiles survive to maturity and reproduce.



Control of the black rat Rattus rattus for the conservation of the Antiguan racer Alsophis antiguae on Great Bird Island, Antigua

Daltry J.C. (2006), 3, 28-29


The critically endangered Antiguan racer Alsophis antiguae, used to be abundant throughout the Lesser Antillean islands of Antigua (and its satellite islands) and Barbuda. Non-native black rats Rattus rattus were identified as a serious predator of the snake on Great Bird Island, therefore the decision was made to eradicate the rats. A poison-baiting programme proved successful, with the racer population more than doubling in only 18 months in response. Other fauna, including several species of seabirds and hawksbill turtle Eretmochelys imbricata, also benefited greatly from rat removal.


The effect of black rat Rattus rattus control on the population of the Antiguan racer snake Alsophis antiguae on Great Bird Island, Antigua

Daltry J.C. (2006), 3, 30-32


Following black rat Rattus rattus eradication, the Antiguan racer Alsophis antiguae population on Great Bird Island increased by over 300% over the next nine years.


Reintroduction of the critically endangered Antiguan Racer Alsophis antiguae to Rabbit Island, Antigua

Daltry J.C. (2006), 3, 33-35


Ten Antiguan racers Alsophis antiguae were introduced to Rabbit Island in 1999. Breeding was first recorded in 2002 and by 2006 the population was estimated at 40-50 individuals.


Reintroduction of the critically endangered Antiguan racer Alsophis antiguae to Green Island, Antigua

Daltry J.C. (2006), 3, 36-38


Between 2002 and 2005, a total of 46 Antiguan racers Alsophis antiguae were introduced to Green Island. A radio-telemetry study undertaken in 2003 of four of the founding females, confirmed the racers were adjusting well to their new environment. Young snakes were first observed in 2005.


Eradication of introduced mammals and reintroduction the tuatara Sphenodon punctatus to Motuhora (Whale Island), New Zealand

Towns D. (2005), 2, 92-93


Following removal of Norway rats Rattus norvegicus and rabbits Oryctolagus cuniculus from Motuhora (Whale Island), 32 adult tuatara Sphenodon punctatus were introduced in 1996. They produced at least two clutches of offspring, and about 50 individuals were present when surveyed in 2005.


Creating hibernacula for common lizards Lacerta vivipara, The Ham, Lowestoft, Suffolk, England

Showler D.A., Aldus N. & Parmenter J. (2005), 2, 96-98


Three hibernacula were created for common lizards Lacerta vivipara in an area set aside for a suburban nature conservation area in the town of Lowestoft, eastern England. Six months later in the spring following construction, lizards were present in small numbers around each hibernaculum. The lizards apparently preferred to use natural gaps for entry rather than the entrance pipes provided.


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