Researchers Count 180,000 Giant Tortoises on Seychelles Atoll

A survey led by the Seychelles Islands Foundation (SIF) and the University of Exeter has counted approximately 180,000 Aldabra giant tortoises living free on Aldabra Atoll in Seychelles, according to a report from The Guardian. The figure is the highest ever recorded for the species and exceeds the human population of Seychelles, the Guardian reported.

How did researchers arrive at the 180,000 figure?

The team analyzed five years of tortoise counts conducted between 2018 and 2022, according to the Guardian. The findings, published in the journal Ecology and Evolution, produced a best estimate of nearly 183,000 adult and sub-adult tortoises, with the population described as relatively stable over that period.

How does this compare with earlier tortoise counts?

The new survey is the first update to tortoise population estimates since a widely cited figure of 100,000 tortoises from the late 1990s, the Guardian reported. Aldabra Atoll is one of only two places in the world where giant tortoises live in the wild; a much smaller population survives in the Galápagos, according to the report.

By the numbers

• 180,000: approximate total Aldabra giant tortoises counted in the new survey, per SIF and University of Exeter researchers.
• 100,000: the prior population estimate, dating to the late 1990s, that the new figure replaces, according to the Guardian.

Why did the tortoise population nearly collapse in the 19th century?

Exploitation of the animals during the 19th century reduced the Aldabra tortoise population to fewer than 1,000 individuals, the Guardian reported. A recovery effort followed, and the atoll became a strict nature reserve in 1981 and a UNESCO World Heritage site in 1982, according to the report.

What are officials saying about the recovery?

Dr. Frauke Fleischer-Dogley, chief executive of the Seychelles Islands Foundation, said the count reflects decades of sustained conservation work.

"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."

Researchers describe Aldabra's recovery as one of the strongest conservation outcomes in the Indian Ocean, a conclusion the Guardian said the new study confirms.

What made counting the tortoises difficult?

Aldabra's monitoring program is one of the longest-running in the region, but the atoll's dense vegetation complicates direct counts, according to the Guardian's report, which did not specify the exact survey methods beyond the five-year count window used by SIF and Exeter researchers.

What to watch next

• Whether SIF and University of Exeter researchers schedule a follow-up count beyond the 2018–2022 window used in this study.
• Any peer review response to the Ecology and Evolution paper from other tortoise or island-ecology researchers.
• Seychelles government or UNESCO statements on funding for continued Aldabra monitoring, given the atoll's protected status since 1982.
• Comparative population data from the Galápagos tortoise population, the only other wild giant tortoise habitat.