Protected Seychelles atoll shelters nearly 183,000 giant tortoises

An estimated 183,000 adult and nearly adult giant tortoises inhabit Aldabra Atoll in the Seychelles, a new study has found. The results offer fresh evidence of a lasting recovery for animals once hunted to the brink of extinction.

Researchers from the Seychelles Islands Foundation and the University of Exeter analysed five years of monitoring data collected between 2018 and 2022. Their findings, published in Ecology and Evolution, indicate that the population remained relatively stable during that period.

The contrast with Aldabra’s past is striking. Heavy exploitation reduced its tortoises to fewer than 1,000 in the 19th century. Long-term protection helped reverse that decline, with the atoll becoming a strict nature reserve in 1981 and a UNESCO World Heritage Site the following year.

The new estimate is the highest recorded for the species, but it does not mean numbers have nearly doubled since the widely cited estimate of 100,000 from the late 1990s. Earlier surveys missed animals hidden in vegetation or shade. This study used statistical methods to account for unseen tortoises, producing a more reliable picture.

Threats remain: worsening droughts could reduce food and shade, rising seas threaten low-lying habitat, and introduced cats and rats prey on eggs and hatchlings. The improved estimate gives conservation teams a stronger starting point for tracking changes and responding early to emerging pressures.