February 08, 2021
Researchers with the Giant Tortoise Restoration Initiative (GTRI) on an expedition to Alcedo Volcano in the northern part of Isabela Island, Galapagos, recently conducted a complete census of the tortoise population there (‘Chelonoidis vandenburghi’), resulting in population estimates far surpassing what was expected for this species. A total of 4,723 individual tortoises were located and marked, and scientists on the expedition noted the remarkable recovery of the region’s habitat overall following the eradication of destructive feral goats in 2006.
The area of the volcano covered during the expedition was concentrated to the summit and eastern and southern slopes of Alcedo Volcano, between 1,300-3,700 feet above sea level, as well as the interior of the caldera — where approximately 90% of the tortoise population is located due to the availability of food in these areas. Washington Tapia, Director of the GTRI for Galapagos Conservancy and leader of the expedition, confirmed that crews marked 1,745 females, 1,794 males and 1,184 juveniles. Data suggest that this is a healthy population: in nature, a population of such a large size, with many older as well as younger individuals, and that has one male for each female — as is the case of the Alcedo volcano tortoises — is considered a completely viable population.
“Although we have much data yet to process, I estimate that the population exceeds 12-15,000 tortoises total in this region,” Tapia said.
Other positive data from the expedition include the discovery of two new tortoise nesting areas located on a northwestern plateau and on an eastern slope.
Danny Rueda, director of the Galapagos National Park Directorate (GNPD), indicated that the expedition revealed that this is the population of giant tortoises in the best condition in Galapagos. However, it is not free of threats, as invasive species such as rats and feral cats were also found.
“Finding such a large number of tortoises on Alcedo Volcano confirms that the management programs implemented in that environment have been successful. The eradication of goats and donkeys in 2006 has allowed the giant tortoise population here to flourish. In addition, abundant vegetation was found, which guarantees a permanent source of food for this species,” added Rueda.
As a result of the management actions implemented by the GNPD and its collaborators during the last six decades, Galapagos is likely home to around 60,000 giant tortoises including populations of the different species — a number that, according to Tapia, is still low considering that more than 200,000 tortoises were removed from the Archipelago in previous centuries.
About Galapagos Conservancy: For the past 35 years, Galapagos Conservancy has helped protect the unique biodiversity and ecosystems of Galapagos by supporting research, conservation, outreach, and building a sustainable society. Galapagos Conservancy is the only US-based organization focused on protecting the Galapagos archipelago. The Giant Tortoise Restoration Initiative is a collaborative effort of Galapagos Conservancy, Inc. and the Galapagos National Park Directorate.
Images: Available at https://www.flickr.com/gp/galapagosconservancy/U4tub8; all images must be credited to: Joshua Vela / Giant Tortoise Restoration Initiative (Galapagos Conservancy)
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