Aldabra has far more giant tortoises than thought
A new study estimates the population at around 180,000 animals, partly thanks to long-term protection of the atoll.
An estimated 180,000 Aldabra giant tortoises live on Aldabra Atoll in the Seychelles. This is according to a study by researchers from the University of Exeter and the Seychelles Islands Foundation, published in Ecology and Evolution.
The new estimate is the largest ever published for this species. Researchers analysed monitoring data from 2018 to 2022 and used a statistical model to account for animals that were not seen during fieldwork.
The result is good news for a species that was under pressure for a long time. Aldabra is a protected atoll with one of the largest populations of giant tortoises in the world. The Seychelles regard the species as an important part of the country’s natural heritage.
The researchers do warn, however, that the new estimate does not necessarily mean that tens of thousands of animals have been added in a short period. Part of the difference from older estimates is probably because previous counts could not properly include animals in dense vegetation.
That is precisely why the study is also methodologically important. Populations on remote islands are difficult to count in full. Models can include hidden animals, but they still produce an estimate with margins of uncertainty. The precise size of the population is therefore not fixed as one exact figure.
The results do show that long-term protection and monitoring can support a population on a large scale. The Seychelles Islands Foundation has been monitoring the animals for years and uses the data to manage the atoll, which is protected as a World Heritage site.
The situation is therefore hopeful, but not without risks. Climate change, changes in vegetation and disturbance on the island could affect food, reproduction and habitat. The new count is above all a strong basis for tracking the population’s development more closely.
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The new population estimate and research method have been confirmed by two independent public sources. The text correctly distinguishes between a better estimate and actual population growth.
- confirmed The population of Aldabra giant tortoises is estimated at around 180,000. — Reported by Seychelles News Agency and EurekAlert! source
- confirmed The study used data from 2018–2022 and statistical modelling. — Description of the research design. source
- confirmed The species is no longer classified as threatened in the Seychelles. — Mentioned by the Seychelles Ministry of Environment. source
- confirmed The new estimate does not prove that the population has grown by 180,000 animals. — Methodological inference from the difference between earlier counts and modelling. source
Editor's note
The population estimate of around 180,000 animals has been confirmed by the study and two public sources. The growth was not measured directly; part of the difference probably results from improved counting methods.Sources
- New study estimates Aldabra’s giant tortoise population at around 180,000 — Seychelles News Agency
- New study reports largest-ever population estimate for Seychelles’ giant tortoises — EurekAlert!
- Endangered Species — Ministry of Environment Seychelles