Science & Tech · Science & Environment · 2 days ago
Survey estimates nearly 183,000 giant tortoises on Seychelles atoll
A survey estimates that nearly 183,000 Aldabra giant tortoises live on Aldabra Atoll in the Seychelles.
The study, led by the Seychelles Islands Foundation and the University of Exeter, used five years of monitoring data collected from 2018 to 2022.
Earlier estimates put the population at about 100,000, but tortoises can be hard to see in the atoll’s dense vegetation.
Researchers used statistical modelling to account for animals they may have missed.
In the 19th century, hunting and exploitation left fewer than 1,000 tortoises on the island.
Protection measures helped the population recover, and the new estimate gives conservation managers a baseline for tracking it in future.
Longer droughts, rising sea levels, and invasive cats and rats still threaten tortoises and their young.
Plans to remove the remaining invasive mammals are underway, while researchers say continued monitoring will help guide conservation efforts.
A survey led by the Seychelles Islands Foundation and the University of Exeter estimated that nearly 183,000 Aldabra giant tortoises live on Aldabra Atoll in Seychelles.
The estimate is the highest recorded for the species and is substantially above the widely cited figure of 100,000 from the late 1990s.
Researchers analysed tortoise counts collected over five years and used a statistical method to account for animals hidden by dense vegetation and other habitats.
The population was estimated to have fewer than 1,000 tortoises in the 19th century, before conservation measures helped it recover.
The study says drought, rising sea levels and invasive mammals that prey on eggs and hatchlings remain threats to the tortoises.
- Who
- Aldabra giant tortoises; researchers from the Seychelles Islands Foundation and the University of Exeter
- What
- A survey estimated nearly 183,000 tortoises, the highest recorded figure for the species
- When
- The survey analysed counts collected between 2018 and 2022; the study was published in October 2026
- Where
- Aldabra Atoll, Seychelles
- Why
- To establish a reliable population baseline for monitoring and conservation
This story does not have two clearly opposing sides.
Hunting and exploitation left fewer than 1,000 Aldabra tortoises on the atoll.
Aldabra was designated a strict nature reserve.
Aldabra became a UNESCO World Heritage site.
Feral goats were eradicated from the atoll, according to Interesting Engineering.
Researchers collected the tortoise counts used in the latest survey.
- Population estimate
- Almost 183,000 adult and sub-adult tortoises
- Location
- Aldabra Atoll, Seychelles
- Survey period
- 2018–2022
- Previous widely cited estimate
- 100,000 tortoises in the late 1990s
- Publication
- Ecology and Evolution
What people are saying
More than 180,000 giant tortoises roaming freely on our atoll is proof of what long-term commitment to conservation can achieve. This is wonderful news for Seychelles, for the world, and for everyone who has worked to protect Aldabra.
By modelling what we didn’t see, as well as what we did, we’ve produced the most reliable baseline yet for this iconic Seychelles species, establishing a benchmark we can use to track the population for decades to come.
But it’s important to remember that the numbers provide a baseline – not an endpoint.
Sources
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