Scientists discover 180k giant tortoises on one Seychelles island

Researchers led by the Seychelles Islands Foundation and the University of Exeter used five years of field counts (2018-2022) and modeling to estimate that about 180,000-183,000 adult and sub-adult Aldabra giant tortoises now roam Aldabra Atoll, the largest free‑living population of giant tortoises and a figure well above previous estimates from the 1990s. The result updates a long-running monitoring program and confirms a dramatic recovery from fewer than 1,000 individuals in the 19th century after intensive exploitation; protection as a strict nature reserve in 1981 and UNESCO inscription in 1982 underpinned the rebound. Researchers describe the finding as one of the Indian Ocean’s greatest conservation successes and present the new number as the most reliable baseline yet for tracking future change.

The team modeled detection gaps caused by dense vegetation to produce the population estimate and found stability across the study period, but they emphasize continued threats: climate change is expected to increase drought frequency and sea‑level rise that will reduce shade and forage, while invasive mammals such as feral cats and black rats prey on eggs and hatchlings. Planned eradication of those invasives is expected to remove remaining barriers to growth, and managers are urged to use this baseline to detect change early and guide ongoing conservation action.