Giant tortoises now outnumber people in the Seychelles. A landmark five-year survey has found that the Aldabra giant tortoise population on Aldabra Atoll stands at roughly 183,000 individuals, comfortably exceeding the nation's human population.

  • 183,000 adult and sub-adult tortoises estimated on Aldabra Atoll
  • 5 years of tortoise-count data analyzed, 2018 to 2022
  • Fewer than 1,000 tortoises survived the species' low point in the 19th century
  • 1981 — the year Aldabra became a strict nature reserve

The First Reliable Count in Decades

The survey, led by the Seychelles Islands Foundation (SIF) and the University of Exeter, is the first rigorous, atoll-wide population estimate since a widely cited 1990s figure of around 100,000 tortoises. Researchers analyzed five years of tortoise counts gathered by SIF field staff, then applied a statistical technique called Bayesian hierarchical distance sampling to correct for tortoises hidden in Aldabra's dense scrub and mangroves.

Aldabra is one of only two places on Earth where giant tortoises still roam wild — the other being the much smaller population on the Galápagos Islands. The findings were published in the journal Ecology and Evolution.

From Near-Collapse to Record Numbers

The scale of the recovery is hard to overstate. In the 19th century, heavy hunting for meat reduced Aldabra's tortoises to fewer than 1,000 animals. Protection since the atoll became a strict nature reserve in 1981, followed by UNESCO World Heritage status in 1982, allowed the population to rebuild into what researchers now call one of the greatest conservation success stories in the Indian Ocean.

The study found tortoises cluster most densely in Aldabra's open grasslands — nicknamed "tortoise turf" — and are harder to spot in dense scrub, where the new modelling helped correct for animals that earlier surveys likely missed entirely.

"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." — Dr. Frauke Fleischer-Dogley, CEO, Seychelles Islands Foundation

What Comes Next

Researchers are careful to note the new figure doesn't mean the population nearly doubled since the 1990s — rather, better statistical methods likely corrected for tortoises that older surveys simply couldn't see. Even so, the underlying trend is real: the population has genuinely grown and now looks healthy and stable.

Challenges remain. Longer droughts linked to a changing climate could reduce the shade and food tortoises depend on, and rising seas threaten low-lying parts of the atoll. Feral cats and black rats — the invasive predators that survived a successful 2012 goat eradication — still prey on eggs and hatchlings.

"These results are great news for the tortoises and testament to the fantastic work done in the field," said Dr. Dave Hudson of the University of Exeter, who helped build the statistical model behind the count. "But it's important to remember that the numbers provide a baseline — not an endpoint."

Conservation managers now have a solid benchmark to track the population for decades, and a clear next task: finishing off the remaining invasive predators so Aldabra's tortoises can keep climbing from there.