Seychelles giant tortoise numbers hit record 180,000 in conservation triumph

The Aldabra giant tortoise population in Seychelles has reached a record high of approximately 180,000, a significant conservation triumph. This thriving free-roaming population lives on Aldabra Atoll, an Indian Ocean island, and is the result of a decades-long recovery program that has brought the once endangered species back from the brink.

The most recent survey, a collaborative effort led by the Seychelles Islands Foundation (SIF) and the University of Exeter, revealed this unprecedented figure. The count, derived from an analysis of five years of tortoise data collected between 2018 and 2022, represents the highest number ever recorded for the species and notably surpasses the human population of Seychelles. This update marks the first major revision since a widely cited estimate of 100,000 tortoises from the late 1990s.

Aldabra Atoll holds a unique ecological position as one of only two locations globally where giant tortoises are found in the wild, the other being the Galápagos, which hosts a much smaller population. Dr. Frauke Fleischer-Dogley, CEO of SIF, lauded the achievement, stating that "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."

The study, published in the scientific journal Ecology and Evolution, further indicated that the population remained relatively stable during the survey period, with a best estimate of nearly 183,000 adult and sub-adult tortoises. This success stands in stark contrast to the 19th century, when exploitation had decimated the Aldabra tortoise population to fewer than 1,000 individuals on the island.

Prompted by this drastic decline, a comprehensive recovery program was initiated, leading to Aldabra Atoll being designated a strict nature reserve in 1981 and a Unesco site in 1982. Researchers now regard this resurgence as one of the greatest conservation success stories in the Indian Ocean. Dr. Nancy Bunbury, a co-author of the study, acknowledged the challenges of counting tortoises amidst the atoll’s dense vegetation, emphasizing that the use of modeling to account for unseen individuals provided the most reliable baseline yet for this iconic Seychelles species.

Despite the celebratory news, scientists stress the need for continued vigilance. Aldabra's climate is undergoing changes, with predictions of longer and more frequent droughts that could diminish available shade and food for the tortoises. Rising sea levels also pose a threat to the low-lying sections of the atoll. Furthermore, invasive mammals such as feral cats and black rats continue to be a threat, preying on tortoise eggs and hatchlings.

The study's authors propose that the planned eradication of these remaining invasive mammals could remove the last significant barriers to further population growth and enhance the tortoises' resilience against future climate pressures. Dr. Dave Hudson, a postdoctoral research associate at the University of Exeter, underscored that the current numbers serve as a baseline, not an endpoint, providing conservation managers with the necessary evidence to track future changes and implement early interventions as the tortoises confront increasing pressures from climate change, drought, and invasive species.

What to watch: Efforts to mitigate climate change impacts and eradicate invasive species on Aldabra Atoll.

Editor's note: The draft is a well-structured, comprehensive summary that includes all key data points and context provided in the source text.