World’s largest free-roaming giant tortoise population hits record 180,000 in Seychelles
A landmark survey of the world’s largest free-roaming giant tortoise population has revealed the once-endangered species is now thriving.
The latest count on the Seychelles atoll of Aldabra revealed that approximately 180,000 tortoises are living on the islands. This is the highest figure ever recorded for the species and far exceeds the human population of the Seychelles.
The team, led by the Seychelles Islands Foundation (SIF) and the University of Exeter, analyzed five years of tortoise counts collected between 2018 and 2022. It is the first update since the widely cited figure of 100,000 tortoises from the late 1990s.
Aldabra Atoll, a ring of coral islands in the Indian Ocean east of Africa, is one of only two places in the world where giant tortoises can be found in the wild, with a much smaller population living in the Galapagos.
“More than 180,000 giant tortoises roaming freely on our atoll is proof of what long-term commitment to conservation can achieve,” said Dr. Frauke Fleischer-Dogley, CEO of SIF. “This is wonderful news for Seychelles, for the world, and for everyone who has worked to protect Aldabra.”The study, published in the scientific journal Ecology and Evolution, found the population was relatively stable during this period, with a best estimate of almost 183,000 adult and sub-adult tortoises.
In the 19th century, exploitation meant there were fewer than 1,000 Aldabra tortoises on the island. But a recovery program led to the island becoming a strict nature reserve in 1981 and a UNESCO World Heritage Site in 1982.
Researchers are now calling it one of the greatest conservation success stories of the Indian Ocean.”Aldabra’s giant tortoise monitoring program is one of the longest running in the region, but the atoll’s dense vegetation makes counting tortoises genuinely difficult in places,” said Dr. Nancy Bunbury, one of the study’s co-authors. “By modeling what we didn’t see, as well as what we did, we’ve produced the most reliable baseline yet.”
Conservationists warn that threats remain. Aldabra’s climate is changing, with longer and more frequent droughts predicted to reduce shade and food. Invasive mammals including feral cats and black rats that prey on eggs and hatchlings also remain a key threat.
The planned eradication of these remaining invasive mammals could lift the last barriers to further growth and help the population withstand future climate pressures, the authors said.
