By Susana Madera
Galapagos Islands, Ecuador, (EFE).- For the past 50 years, the Galapagos Islands (Ecuador) have been at the heart of a restoration and conservation program involving the rearing and reintroduction of almost 9,500 giant tortoises to their natural habitat. This has breathed new life into their unique ecosystem.
This initiative began in 1965 with the implementation of the Land Tortoise Captive Breeding Program by the Galapagos National Park (GNP) in response to the drastic decline in the populations of these chelonians, particularly on Española and Pinzón Islands, mainly due to the introduction of invasive species.
It is believed that there are at least 15 different species of Galapagos giant tortoise. Three are already extinct, and the objective is to prevent the remaining 12 from suffering the same fate.
According to the Galapagos National Park, repatriation did not begin until around 1970, after captive breeding and the completion of other processes.
The program began with two populations: the Pinzón population, comprising 22 individuals (Chelonoidis duncanensis), and the Española population, including 13 tortoises (Chelonoidis hoodensis).
Diego, the tortoise who fathered hundreds of offspring
The arid, small, and easily accessible island of Española, located in the southeast of the archipelago, lost almost all of its tortoises years ago, mainly to pirates and whalers who used the refuge as a food source, taking the giant tortoises on their ships, despite them being able to “survive up to a year or more without eating or drinking.”
According to the Galapagos National Park, it was precisely from Española that a tortoise was transferred to the San Diego Zoo in the United States in 1933, where it remained for 40 years until it was repatriated to the breeding center on Santa Cruz Island, the most populous island in the archipelago, to participate in the captive breeding project for around 40 years.
The specimen, named after the zoo, waited 87 years to return to Española in 2020, bringing with it a lineage of 800 specimens.
Diego was one of 15 tortoises of the species Chelonoidis hoodensis, which helped to save the species. The population of this species now exceeds 2,300 in Española and 1,000 in Pinzón.
More than numbers
Although these numbers may seem modest compared to other species, the National Park said that the health of populations is not assessed solely by their numbers but by population structure and reproductive capacity.
Census data showing populations of males, females, juveniles, and newborns reveal a constant and healthy renewal process. To ensure the continuity of the program, Galapagos National Park maintains three breeding centers on San Cristóbal, Isabela, and Santa Cruz Islands.
The tortoises reproduce “favorably” in the wild in these centers, but they also ensure constant reproduction in captivity. This facilitates the reintroduction of these individuals to their islands of origin.
Repatriations have taken place on eight islands:
National Park records show that Isabela tops the list for repatriated tortoises of different species (3,467), followed by Española (1,911), Santiago (1,360), Pinzón (1,121), Santa Cruz (751), Santa Fe (742), San Cristóbal (124) and Floreana (19).
The repatriation project began with the of the Charles Darwin Foundation (CDF) and now involves numerous other organizations. These efforts have been ed by programs aimed at eradicating introduced and invasive species, including pigs, goats, donkeys, and rodents.
Pinzón Island is a success story, as the natural hatching of a tortoise was documented there for the first time in over a century following the eradication of rodents.
“Ecological engineers”
As large herbivores, land tortoises disperse seeds and clear vegetation, creating open spaces that favor the germination of new plants. They act as “ecological engineers,” shaping the landscape and contributing to the ecological balance of the islands.
Although their population is currently in a good state, the presence of invasive species remains their main threat, despite ongoing efforts to control them, since the size of the islands makes total eradication unfeasible.
However, illegal species trafficking is an emerging threat that also affects land iguanas in the archipelago. This archipelago was declared a UNESCO World Heritage Site in 1978 and inspired the English scientist Charles Darwin to develop his theory of evolution. EFE
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