Aldabra Giant Tortoises Outnumber Seychelles’ Human Population

A scientific survey published in Ecology and Evolution in October 2026 estimated that 180,000 to 183,000 Aldabra giant tortoises live on Aldabra Atoll in the Seychelles. The estimate exceeds the country’s human population, which was about 123,000 at the end of 2025 and estimated at 134,959 in mid-2026.

Population estimate and survey

The survey was led collaboratively by the Seychelles Islands Foundation and the University of Exeter in the United Kingdom. Researchers collected data over five years, from 2018 to 2022. It was the first rigorous estimate covering the whole atoll since the late 1990s.

An earlier estimate put the population at about 100,000. The later estimate used advanced statistical modelling to account for tortoises concealed by dense vegetation. The study’s range of 180,000 to 183,000 is an estimated population, rather than a direct count of every animal.

Species and conservation

The Aldabra giant tortoise, Aldabrachelys gigantea, is a tortoise native to Aldabra Atoll, a coral atoll in the western Indian Ocean. Its population had fallen to fewer than 1,000 individuals in the 19th century following exploitation.

Aldabra Atoll became a strict nature reserve in 1981 and a UNESCO World Heritage Site in 1982. These conservation measures form part of the context for the population’s recovery. The atoll is managed by the Seychelles Islands Foundation.

Habitat and continuing threats

Aldabra’s tortoises depend on the atoll’s terrestrial habitat. Climate change can contribute to drought and sea-level rise, while invasive species such as feral cats and black rats pose risks to the habitat and tortoise survival.

Population estimates can vary with survey coverage and methods, particularly where animals are hidden by vegetation. Long-term monitoring of the atoll’s tortoise population and habitat continues to be relevant to conservation management.

Important Facts for Exams

• Aldabra Atoll is part of the Seychelles in the western Indian Ocean.
• The Seychelles Islands Foundation and the University of Exeter led the tortoise survey.
• Aldabra Atoll was declared a strict nature reserve in 1981.
• Aldabra Atoll was inscribed as a UNESCO World Heritage Site in 1982.

The survey used data collected between 2018 and 2022 and estimated 180,000 to 183,000 Aldabra giant tortoises. The species’ atoll habitat faces risks from drought, sea-level rise and invasive species.