A landmark survey of the world's largest free-roaming giant tortoise population found approximately 180,000 Aldabra giant tortoises living on Aldabra Atoll in the Seychelles — the highest figure ever recorded for the species, and one that far exceeds the human population of Seychelles. The survey was led by the Seychelles Islands Foundation (SIF) together with the University of Exeter, analyzing five years of tortoise counts collected between 2018 and 2022. It is the first major population update since the widely cited figure of about 100,000 tortoises from the late 1990s. Aldabra Atoll is one of only two places on Earth where giant tortoises live freely in the wild, alongside a much smaller population in the Galápagos.

The study, published in the scientific journal Ecology and Evolution, estimated a best figure of nearly 183,000 adult and sub-adult tortoises and found the population was relatively stable across the survey period. The scale of the recovery is striking: in the 19th century, exploitation of the animals had reduced the population to fewer than 1,000 on the island. According to Interesting Engineering, the successful eradication of invasive feral goats in 2012 also paved the way for the historic recovery. Researchers now call Aldabra one of the greatest conservation success stories of the Indian Ocean, and the new study confirms it.

Determining the count was genuinely difficult. Aldabra's landscape of sharp coral and dense, tangled vegetation means tortoises routinely hide in shade under bushes or vanish into mangroves. Nancy Bunbury, a study co-author, said the atoll's monitoring program is one of the longest running in the region but that dense vegetation makes counting 'genuinely difficult in places.' According to Interesting Engineering, previous surveys relied on raw headcounts and likely missed tens of thousands of hidden animals, so the team used Bayesian hierarchical distance sampling — a statistical method that models what researchers did not see — to produce the most reliable baseline yet for the species.

Frauke Fleischer-Dogley, CEO of the Seychelles Islands Foundation, called the result proof of long-term conservation commitment: '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.' Dave Hudson, a postdoctoral research associate at the University of Exeter, Cornwall, said the results are 'great news for the tortoises and testament to the fantastic work done in the field,' while stressing that the numbers provide a baseline, not an endpoint. OrissaPOST reports the monitoring data behind the study was collected by SIF staff living and working on the atoll year after year.

Despite the good news, the study's authors warn that vigilance is essential. Aldabra's climate is changing, with longer and more frequent droughts predicted to reduce the shade and food available to tortoises, while rising sea levels threaten low-lying parts of the atoll. Invasive mammals remain a key threat too: feral cats and black rats prey on tortoise eggs and hatchlings. According to Interesting Engineering, plans to eradicate these remaining invasive mammals are already underway, and the authors say that could lift the last barriers to further population growth and help the tortoises withstand future climate pressures.

The new estimate establishes a benchmark that conservation managers can use to track the population for decades, with Bunbury describing it as a baseline for future monitoring. Hudson said the hope is that the evidence lets managers track future change and act early as the tortoises face increasing pressures from climate change, drought and invasive species. The eradication of the remaining invasive mammals — feral cats and black rats — is planned as the next major intervention. For now, Aldabra Atoll offers a rare story of hope: an island where nature rebounded from near collapse and giant tortoises reclaimed their habitat.