Ex situ population of Aldabrachelys gigantea (Reptilia: Testudines) in the European Association of Zoos and Aquaria and its perspectives: Hidden extinction and how to prevent it
Publication Type: |
Journal Article |
Authors: |
Ivan Rehák, Petr Velenský, Veronika Zahradníčková, Iva Martincová |
Keywords: |
Aldabra, conservation, demography, European Ex situ Programme, giant tortoises, population assesment, studbook, zoo biology |
Abstract:
For the needs of adequate management, we carried out an assessment of the Aldabrachelys gigantea
(Schweigger, 1812) population in the institutions of the European Association of Zoos and Aquaria. This population
was established a hundred years ago and is continuously growing. Today it is the largest ex situ population of all
regional zoo associations. Currently it has 402 individuals, including animals aged over 100 years (up to 162 years).
However, our study shows that this increase is depending on the import of individuals from outside sources. The
longevity of this species and the relatively low mortality rate in the population makes this process very slow, so
that it goes unnoticed. Our predictions show that without imports, this population would become extinct in the long
term unless existing natality increases. If there is no change in the reproductive rate (and there is no import), within
20 year the population will drop from current 402 to approx. 280 individuals. To maintain current population size
8–9 hatches/year are needed. However, the successful reproduction of A. gigantea in EAZA remains an exceptional
event. Our analysis of the demographic and genetic status shows that it has enormous potential. If it was used, the
population would have a very long-term perspective secured. Achieving this goal will mean significant improvements
in husbandry practices, the issues of which we outline.