Détails de cette espèce dans Sangalaki Is.
Statut d'envahissement: Envahissant
Source: Meier, 2003
Notes sur l'espèce pour cette localité:
Soon after Sangalaki Island's declaration as a marine turtle sanctuary it became clear that the island had a significant
population of ship rats (Rattus rattus), probably subspecies diardii (the Malayan House-rat),
which are not native to Indonesia although widely distributed. Although these animals were known to be
present (probably unintentionally introduced years earlier, perhaps in times as egg collectors brought
over construction materials for the building of a former permanent settlement on the island) their real
pest-status to the island and especially its marine turtle’s nests and hatchlings has only recently been
recognized as before the majority of these nests were collected by poachers. The severe impact of the
exotic rat population on the turtles and their hatchlings was clearly witnessed by everybody on the island.
Notes sur la gestion de l'espèce dans cette localité:
After other options (for example to introduce cats!) had been rejected, InGrip-Consulting recommended a rat-eradication
attempt and the islands' further protection as the solution of the problem. The decision to try a complete eradication was
made because of the island’s small size, the absence of any endemic, native or threatened rodent species and even any
terrestrial mammals at all, the specific extent of the problem the rats pose to this conservation site, the approximate
population size the invasive rats had established, the significance of Sangalaki as a unique marine turtle nesting site in
the region, the availability of funds, time and motivated personnel to undertake such an operation, including the necessary
follow up work, the potential to use such a project as a demonstration project for other places with the same problem in the
area, and the support and willingness to act by all potential partners and stakeholders involved. All operational cost were
carried by the Turtle Foundation. The project was planned in great detail and began in 2003.
It was decided to use a commercially available rodenticide, from the group of so called ‘second generation anticoagulants’ –
poisons which interrupt the animals Vitamin K production thus hindering the process of natural blood clotting. It is produced
in poisoned grains that are mantled by a wax layer for better weather protection and pressed into cube form. The toxin is
‘brodifacoum’ in a concentration of 0.005 mg, which allows a rat to ingest a lethal dose within a single feeding. The trade
name of the poison chosen was “Klerat” and is worldwide available from the production company, Syngenta.
The last living rats were observed on the 14th of July and all bait and bait station were withdrawn on the 26th of July
2003). The total amount of bait used reached around 55 kg, (equivalent to 4,15 kg/ha). Live trapping with Tomahawk
collapsible live-traps (Type TLT no. 202 - squirrel size), was undertaken for several days to detect any potentially
surviving rat. Highly attractive bait (fish, shrimps, chicken, fruits, peanut butter, toasted bread and cookies) was used
and traps set on carefully chosen localities, spread over the whole island, but in totally 444 trapping hours
between the 19th of July and 26th of July 2003 no rat was caught. The same live-trapping procedure was undertaken on the 2nd
and 3 rd July 2003 and resulted in the catch of 8 animals (including one female with juvenile) in only 7 trapping hours.
Until proven different Sangalaki Island was therefore declared temporarily rat free at Guntram Meier’s departure on the 28th
of July 2003. A full report is available (InGrip-Report).
A visit by Guntram G. Meier in January 2004 confirmed that no rats survived the eradication. As no further losses of turtle eggs or hatchlings due to rat predation were recorded, the eradication of this invasive alien species on the island can be considered a complete success and contributed to the ongoing marine turtle protection work on the island. Plans for related work on neighboring islets are currently under discussion (Marine Turtle Newsletter No. 106, 2004). While the rat eradication project was designed for the well-being of marine turtles, it also seems to have benefited megapodes such as Megapodius cumingii on the island (Megapode Newsletter 2004).
Notes sur la localité:
Sangalaki's environmental importance arises from the island being a general refuge for various threatened
species. However, its main weight for conservation lays in the islands function of being a nesting site for
populations of Green Turtles (Chelonia mydas) which for centuries now have been coming every night to
the beach to dig their nests. Although numbers have decreased from a few hundred animals in the past to
only a few dozen at the moment (2003), it is still the most important nesting site in the whole Derawan Island
group. In addition Sangalaki is famous as a diving spot with a rich variety of marine fauna and flora.
A combination of all these factors has led to the Sangalaki’s official declaration as a strict conservation
site by the local governmental environment authority KSDA. The new sanctuary included the whole island
as well as a 3 km marine zone around and granted all marine turtles in this area a basic protection status.
Through further conservation lobby work of different NGO’s like German based “Turtle Foundation”,
Indonesian’s “KEHATI“ and “WWF-Indonesia” and with support of the German Embassy in Jakarta, a
100 % protection status to all species in the sanctuary was granted in January 2002 and a monitoring
station was constructed on the island. To enforce this protection status the Indonesian National Police
and the country’s military send support personnel to the island for control work of different extents.
Other local NGO’s are meanwhile flanking this conservation initiative through their engagement in
community organising and awareness creation within the regions' peoples and settlements.
Inconnu: Up to five grey imperial-pigeons (see Ducula pickeringii in IUCN Red List of Threatened Species) have been sighted on Sangalaki, which is around 100 km east of East-Kalimantan in the Derawan-Island group, by the invasive species eradication team. The grey imperial-pigeon is classified as vulnerable and specialises in inhabiting small islands with fig trees. Neighbouring islands with suitable habitat probably hold populations of grey imperial-pigeons, although they are likely to be threatened by hunting and deforestation. The few birds on
Sangalaki, however, are safe now because the island is strictly protected as an important nesting ground for green turtles Chelonia mydas, and the rat eradication was successful (Meier, Guntram., 2004.).
Prédation: Ship rats have eaten the eggs of green turtles (see Chelonia mydas in the IUCN Red List of Threatened Species) as well as hatchlings on their way to the sea. Often whole nests (containing
around 80 eggs/hatchlings) were terminated completely in a matter of minutes. Also juvenile turtles were
hunted by the rats and killed instantly or wounded deadly by pulling out their intestines. The
soft shell of the turtles didn’t offer any protection. Survival rate of the attacked nests or
hatchlings were at best 10 % but mostly tended to be zero, allowing no hatchling to reach the comparable
safety of the sea (Images available in InGrip-Report).
Dernière mise à jour: 7/07/2005 8:56:10 a.m.