From the brink of extinction...183 thousand giant tortoises “rule” Aldabra Island in the Seychelles

A new survey conducted on one of the remote islands of the African state of Seychelles indicates that the numbers of giant tortoises, which were on the verge of extinction, now exceed the number of humans in their habitat. The survey, led by the Seychelles Islands Foundation (SIF) and the University of Exeter in the United Kingdom, estimated the presence of about 180,000 Aldabra giant tortoises on Aldabra Atoll, a group of islands located in the Indian Ocean off the eastern coast of Africa.

This is the highest recorded number ever for this type of turtle, and it far exceeds the population of the small country, which amounts to about 122,000 people. Aldabra Atoll is one of only two places in the world where giant tortoises are found in their natural habitat, with a much smaller population found in the Galapagos Islands of Ecuador.

The island also represents one of the most intact island ecosystems in the world, and is home to many unique organisms that thrive in this remote haven. The numbers of these turtles have recovered after a sharp decline, after excessive exploitation during the 19th century led to a decrease in their numbers on the island to less than a thousand turtles, which pushed this species to the brink of extinction.

A recovery program led to the atoll being designated a “Strict Nature Reserve” in 1981, and a UNESCO World Heritage Site a year later, allowing turtle numbers to flourish. “The presence of more than 180,000 giant tortoises roaming freely on our atoll is proof of what a long-term commitment to environmental conservation can achieve,” Frauke Fleischer-Dogli, CEO of the Seychelles Islands Foundation, said in a statement.

“This is great news for the Seychelles, for the world and for everyone who has worked to protect Aldabra,” she added. The process of arriving at this new estimate was not limited to just a census of numbers, as the numbers were based on an analysis of turtle counts that lasted five years (between 2018 and 2022).

This is the first data update since the estimate that there were 100,000 turtles in the 1990s. “The giant tortoise monitoring program at Aldabra Atoll is one of the oldest ongoing programs in the region, but the dense vegetation on the island makes counting tortoises very difficult in some areas,” said study co-author Nancy Banbury.

Banbury added that the study team of scientists has determined the most reliable baseline for this species, so that it can be used as a standard to track the numbers of these turtles over the coming decades. Despite the encouraging estimates of turtle numbers, the study's authors stressed the need to continue to be cautious, as the climate crisis is leading to longer and more frequent droughts, which may reduce the sources of shade and food available to turtles.

Rising sea levels due to global warming also threaten the low-elevation habitats of the atoll. It is noteworthy that the oldest known turtle in the world, a 194-year-old turtle named “Jonathan,” originally came from the Aldabra atoll or most likely from the granite islands of the Seychelles.

Guinness World Records lists Jonathan's tortoise as the oldest living land animal and the oldest tortoise ever.