The Round Island boa once occurred on mainland Mauritius and several other offshore islands, until the introduction of invasive species restricted this snake to just a single island. The global population is estimated at less than 75 individuals on one island and invasive herbivores have turned Round Island into a 'moonscape' with severe consequences for the boas.
As the tiny and restricted wild population is under serious threat of extinction, a captive population of Round Island boas is established at Jersey Zoo to safeguard the future of the species. A total of four snakes are collected despite the mission hampered by threats of cyclones, and Durrell experts are able to breed the snakes for the first time just four years later.
The removal of invasive species is part of a wider programme to restore the habitat on Round Island. Introduced goats and rabbits heavily impact the natural plant communities and ecosystem function of Round Island which is home to six endemic Mauritian reptiles, including the Round Island boa which is now restricted to its namesake island.
As part of continuing habitat restoration, the removal of rabbits further promotes the regeneration of the island's vegetation which is essential to the recovery of the unique reptile communities. With the permission of the Government of Mauritius, Durrell engages New Zealand experts and assists them in the eradication.
The plan recognises the threat of invasive species to native fauna and recommends populations of threatened reptiles are established on rat-free islands. It also calls for regular monitoring of the recovery of the boa and an initial study conducted by Durrell's Simon Tonge reports a slight increase in the number of individuals detected since the eradication.
The eradication of rats and hares from Gunner's Quoin is the first step in restoring the unique reptile community that once existed on this island. Now Durrell, MWF and NPCS are able to plan the reintroduction of Telfair's skinks, a species once native to the island and the main prey item for the Round Island boa.
Although significant efforts have been made over the past 20 years to restore the habitat on Round Island, monitoring suggests that no more than 250 snakes exist in the wild. Intense restoration work is required on other offshore islands before populations of boas can be supported and translocations are considered.
Research by Durrell's Nik Cole into improving the status of threatened endemic Mauritian reptiles by restoring offshore island reptile communities leads to the formation of a collaborative programme. Partners include Durrell, MWF and NPCS and funding is secured for three years from the Darwin Initiative to initiate restoration activities.
Following the eradication of rats from Gunner's Quoin, and the confirmation of the recovery of smaller reptiles that had survived on the island, 250 Telfair's skinks were successfully reintroduced. As a main source of food for the Round Island boa it is important that a stable population of skinks is established on Gunner's Quoin before translocations can be considered.
The reptile team visit Round Island to obtain data on the population of boas and to conduct health screening and disease sampling of individuals in preparation for the translocations to Gunner's Quoin. Surveys show a dramatic recovery in the wild population to 1400 snakes as a result of the habitat restoration work and minimal disease and parasite risk is identified.
After rigorous disease screening to ensure there is no risk to resident reptile fauna or to the boas, 30 male and 30 female snakes are carefully transported from Round Island and are successfully released onto Gunner's Quoin. This is a key step in the conservation of the boas as by increasing the number of populations and the range of the species, the risk of extinction is substantially reduced.
Juvenile Round Island boas are found during a survey on Gunner's Quoin proving the boas that were released as part of the restoration programme are successfully breeding. This is a milestone in the conservation of this endemic species as the restoration of an offshore island ecosystem was needed before this stage of the programme could be achieved.