Study

The end of 16 years of tortoise and terrapin conservation on Silhouette Island, Seychelles

  • Published source details Gerlach J. (2011) The end of 16 years of tortoise and terrapin conservation on Silhouette Island, Seychelles. Testudo, 7.

Actions

This study is summarised as evidence for the following.

Action Category

Release captive-bred reptiles into the wild: Tortoises, terrapins, side-necked & softshell turtles

Action Link
Reptile Conservation

Release captive-bred reptiles into the wild: Tortoises, terrapins, side-necked & softshell turtles

Action Link
Reptile Conservation

Breed reptiles in captivity: Tortoises, terrapins, side-necked & softshell turtles

Action Link
Reptile Conservation

Breed reptiles in captivity: Tortoises, terrapins, side-necked & softshell turtles

Action Link
Reptile Conservation
  1. Release captive-bred reptiles into the wild: Tortoises, terrapins, side-necked & softshell turtles

    A study in 1997–2011 on tropical islands in the Seychelles (Gerlach 2011) found that captive-bred Arnold’s giant tortoises Dipsochelys dussumieri arnoldi released into the wild survived for at least five years. After being released from captivity on Silhouette Island, five of five Arnold’s giant tortoises survived in the wild for at least five years and nests were found one and five years after release. After the remaining giant tortoises from a captive-breeding programme were released in 2011, the author reported that the tortoises settled in their release environments. In 1997–2011, a giant tortoise captive breeding programme was carried out on Silhouette Island. In 2006, five adult Arnold’s giant tortoises (three male and two female) were released at Grande Barbe, Silhouette Island (2010 ha). After the programme closed in 2011, 38 juvenile Arnold’s giant tortoises were moved and released on North Island (210 ha) in February–March 2011 and 92 were released on Fregate Island (207 ha).

    (Summarised by: Katie Sainsbury)

  2. Release captive-bred reptiles into the wild: Tortoises, terrapins, side-necked & softshell turtles

    A study in 1997–2011 in Silhouette Island, Seychelles (Gerlach 2011) found that captive-bred adult black mud turtles Pelusios subniger parietalis released into the wild survived at least six months to two years and yellow-bellied mud turtles Pelusios castanoides intergularis survived at least several months. In 2002, five of five adult black mud turtles survived at least six months. One of the adult black mud turtles was recaptured two years after release. The author reported that released captive-bred and captive-maintained yellow-bellied mud turtles were seen regularly after release in 2010. In 2002, five captive-bred adult black mud turtles were released at Grande Barbe, Silhouette Island. In 2003, eighteen captive-bred juvenile turtles were released and in 2009 the remaining adult black mud turtles from the captive breeding programme were also released (total number of adults not provided). Three captive-bred juvenile and several captive-maintained adult yellow-bellied turtles were released into a lake in 2010 (total number of adults not provided). Adult black mud turtles were monitored by occasional trapping and tracking using radio tags for six months.

    (Summarised by: Katie Sainsbury)

  3. Breed reptiles in captivity: Tortoises, terrapins, side-necked & softshell turtles

    A study in 1997–2009 in a captive facility in the Seychelles (Gerlach 2011, same experimental set-up as Gerlach 2003) reported that black mud turtles Pelusios subniger parietalis hatched in captivity, but that very few yellow-bellied mud turtles Pelusios castanoides intergularis hatched successfully in captivity. In 1997–2009, eighteen black mud turtles and three yellow-bellied mud turtles hatched successfully. The author reported that yellow-bellied mud turtles had a 70% mortality rate during hatching. Captive adult black mud turtles (1–3 males and 3–4 females) and yellow-bellied mud turtles (two males, three females) were held in captivity in 1997–2009 on Silhouette Island. Different pairing approaches were trialled for yellow-bellied mud turtles, including: keeping pairs together, keeping one female with two males, one male with two females, and rotating females between ponds with just males and just females. 

    (Summarised by: Katie Sainsbury)

  4. Breed reptiles in captivity: Tortoises, terrapins, side-necked & softshell turtles

    A study in 1997–2011 in a captive facility in the Seychelles (Gerlach 2011, same experimental set-up as Gerlach 2003) reported that Arnold’s giant tortoises Dipsochelys dussumieri arnoldi and Seychelles giant tortoises Dipsochelys dussumieri hololissa bred successfully in captivity. In 2002–2006, forty Seychelles giant tortoises were reared from one female and one male and 140 Arnold’s giant tortoises were reared from two females and one male. In 1997–1998, six Seychelles giant tortoises (four males, two females) and six Arnold’s giant tortoises (three males, three females) were placed in captivity on Silhouette Island. In 2002, captive groups were reorganised, and all giant tortoises were put together in the same enclosure.

    (Summarised by: Katie Sainsbury)

Output references
What Works 2021 cover

What Works in Conservation

What Works in Conservation provides expert assessments of the effectiveness of actions, based on summarised evidence, in synopses. Subjects covered so far include amphibians, birds, mammals, forests, peatland and control of freshwater invasive species. More are in progress.

More about What Works in Conservation

Download free PDF or purchase
The Conservation Evidence Journal

The Conservation Evidence Journal

An online, free to publish in, open-access journal publishing results from research and projects that test the effectiveness of conservation actions.

Read the latest volume: Volume 19

Go to the CE Journal

Discover more on our blog

Our blog contains the latest news and updates from the Conservation Evidence team, the Conservation Evidence Journal, and our global partners in evidence-based conservation.


Who uses Conservation Evidence?

Meet some of the evidence champions

Endangered Landscape Programme Red List Champion - Arc Kent Wildlife Trust The Rufford Foundation Save the Frogs - Ghana Bern wood Supporting Conservation Leaders National Biodiversity Network Sustainability Dashboard Frog Life The international journey of Conservation - Oryx British trust for ornithology Cool Farm Alliance UNEP AWFA Butterfly Conservation People trust for endangered species Vincet Wildlife Trust