A landmark scientific study has estimated that approximately 183,000 adult and sub-adult Aldabra giant tortoises inhabit Seychelles’ Aldabra Atoll, confirming the largest recorded population estimate for the species. Published in Ecology and Evolution in October 2026, the research was led by the Seychelles Islands Foundation (SIF) and the University of Exeter, offering fresh evidence of the value of sustained wildlife protection.
The findings draw on years of monitoring data collected by SIF research staff between 2018 and 2022. Using modern statistical modelling, researchers accounted for tortoises that conventional surveys might have missed, particularly animals concealed by dense vegetation and shade. The resulting estimate provides a more reliable baseline for tracking the population and guiding future conservation decisions.
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Importantly, the figure does not mean the population has nearly doubled since the last widely cited estimate of 100,000 in the late 1990s. Earlier surveys used different methods and were less able to account for animals that remained undetected. The new study found that the population was relatively stable during the main monitoring period, highlighting the importance of distinguishing improved measurement from actual population growth.
The achievement is particularly significant given the species’ history. Heavy exploitation by sailors during the 19th century reduced Aldabra’s tortoise population to fewer than 1,000 individuals. Protection measures subsequently helped secure its recovery, with Aldabra designated a strict nature reserve in 1981 and a UNESCO World Heritage Site in 1982. The eradication of feral goats in 2012 further reduced pressure on the atoll’s vegetation.
Beyond their numbers, the tortoises play a crucial ecological role. As large herbivores, they shape vegetation through grazing, disperse seeds and help maintain the distinctive grasslands known as “tortoise turf”. The study found that their distribution varies across habitats, with the highest densities recorded in these grasslands. Their continued presence therefore supports the wider ecological balance of the atoll.
However, conservationists warn that the recovery is not guaranteed to continue without intervention. Climate change is expected to bring longer and more frequent droughts, potentially reducing the food and shade available to the tortoises. Feral cats and black rats also remain threats to eggs and hatchlings. Researchers have identified the removal of these invasive mammals as a potential next step in strengthening the species’ long-term prospects.
The findings demonstrate how long-term monitoring, habitat protection and targeted management can support wildlife recovery. They also provide conservation managers with a stronger scientific baseline for identifying future changes and responding to emerging threats.
For Africa, Aldabra offers a valuable lesson: conservation requires more than declaring protected areas. It demands sustained investment, reliable evidence, effective management and the willingness to respond to changing environmental pressures. The estimated 183,000 tortoises on Aldabra represent not simply a remarkable population figure, but a powerful example of what long-term commitment to protecting nature can achieve.
