Literaturdatenbank
Literaturdatenbank |
|
 |
|
Velosoa, J., Randriamahita, Kuchling, G., García, G., Lewis, R. E., & Ratsimbazafy, J. H. , Restoring a depleted population of madagascar sideneck turtles, erymnochelys madagascariensis, in ankarafantsika national park. Unpublished paper presented at 6th World Congress of Herpetology.
Added by: Admin (21 Nov 2009 12:00:09 UTC) |
| Resource type: Conference Paper BibTeX citation key: Velosoa2008 View all bibliographic details  |
Categories: General Keywords: Erymnochelys, Erymnochelys madagascariensis, Habitat = habitat, Madagaskar = Madagascar, Podocnemididae, Schildkröten = turtles + tortoises Creators: García, Kuchling, Lewis, Randriamahita, Ratsimbazafy, Velosoa Collection: 6th World Congress of Herpetology |
Views: 4/811
Views index: 15% Popularity index: 3.75% |
| Abstract |
|
In order to save an important population of the critically endangered Malagasy endemic turtle Erymnochelys madagascariensis, a captive breeding program started in 1999 in Ampijoroa, Ankarafantsika National Park, Madagascar. Hatchlings were also collected from wild nests for headstarting. In March 2004, 158 head-started juveniles, aged 3 to 5 years, were released in lake Ankomakoma, the same watershed as the hatchlings were born in. The species had been virtually extirpated from the lake during the 1990s due to over-fishing, but management changes since then ended the exploitative use of the shore area (e.g. Raffia collection) and the fishing pressure. Monitoring of the released turtles is conducted in November and February in the lake, and April in the out-flowing Andranohobaka river to coincide with the wet season. The methods used are mark-recapture by trapping in the lake and by using nets in the river. Captured individuals are weighed and measured before release. Monitoring was halted during November 2006 and February 2007 due to the threat from crocodiles. 58 released juveniles have been captured during the 10 trapping sessions in the lake and river. The probability of re-capture is about 0.60, similar to wild re-capture rates. Analysis of survival probability predicts that 90% of the 58 captured individuals are alive in 2008 and remain in the lake and river. Therefore at least 52 individuals (90% of 58), representing 32% of the released population, probably survive, four years after release. These results demonstrate that a good proportion of the head-started turtles successfully established home ranges in the release habitat. The mean growth rate of released turtles during the first two years was positive, with some individuals losing and some gaining body mass. From the third year onwards, all captured individuals showed body mass increases, even those that had lost weight before. The comparative analysis of Body Condition Index (BCI), before and after release, shows no significant differences. This suggests that the lake is a good habitat for the species and that the initial weight losses were simply due to adapting to wild conditions. Population reinforcement through headstarting appears a good method to speed up the recovery of depleted natural populations of E, madagascariensis once the causes of their decline have been removed.
Added by: Admin |