Located to the south-east of the island of San Cristóbal, La Galapaguera de Cerro Colorado is a tortoise reserve that was built to improve the status population of the island’s tortoises, Geochelone chatamensis. It is located within the area of Cerro Colorado, which is also one of the few places where it possible to see the Calandrinia galapagosa, a plant that is endemic to San Cristobal and is in danger of extinction.
The Galápagos tortoise is the most famous and unique fauna of the island, as well as the longest lived of all vertebrates, averaging around 100 years. They are the world’s largest tortoises and the 13th heaviest living reptile with some specimens exceeding 1.5 meters in length and weighing 150 kilograms. Larger tortoises are big enough to carry adult humans on their backs; in 1835 Charles Darwin wrote “I frequently got on their backs, and then giving a few raps on the hinder part of their shells, they would rise up and walk away; but I found it very difficult to keep my balance.”.
These giant tortoises once thrived on most of the world’s continents but now the Galápagos tortoise represents one of the two remaining groups of giant tortoises in the world (the other being the Aldabra giant tortoise). The giant tortoise population in the Galápagos archipelago was once so large that the islands were named for these huge reptiles; the old Spanish word galapago meant saddle and was used by early explorers for the tortoises due to the shape of their shells.
Tortoise numbers in the Galápagos archipelago declined from over 250,000 in the 16th century to around 3,000 in the 1970s and only ten of the original fifteen subspecies survive in the wild. On the island of San Cristóbal there were originally two populations of tortoises; one in the northeast, which remains to this day and currently consists of around 1,400 individuals, and another in the south of the island that became extinct due to the exploitation of the species for meat and oil and the introduction of non-native predators to the islands (such as goats, rats and pigs).
Despite ongoing efforts to eradicate the non-native predators, it became necessary to protect the tortoises and specimens from the northeast population were transferred to Cerro Colorado. The reserve now runs a programme to breed the tortoises in captivity before releasing them back into the wild on their ancestral home lands.
San Cristóbal tortoises mate once per year and lay between 12 and 16 eggs. The eggs are collected by park rangers and put in a dark box for 30 days and then incubated. The hatchlings are transferred to growing pens, where they remain for two years before being transported to their natural environment.
Due to this conservation programme and others like it, it is estimated that the total number of the species exceeded 19,000 at the beginning of the 21st century. Despite this increase, the species is still classified as ‘vulnerable’ by the International Union for Conservation of Nature.
The tortoises at La Galapaguera live in semi-natural conditions and visitors may follow interpretive trails through the reserve and see the young tortoises in the breeding pens. These herbivores spend their days grazing on grass, leaves and cactus, basking in the sun and napping for nearly 16 hours per day. A slow metabolism and large internal stores of water mean they can survive up to a year without eating or drinking.
The visitors centre also offers talks on the natural history of giant tortoises and the relationship and differences between the tortoises of San Cristóbal and the other tortoises in the archipelago. There is a great amount of variation in size and shape among the Galápagos tortoises, however two main morphological forms exist. The domed carapace, which is most similar to their ancestral form, and the saddle-backed carapace. The domed tortoises tend to be much larger and are generally found on higher and more humid islands, while the smaller saddle-backed tortoises evolved on arid islands as a response to the lack of available food during drought. The San Cristóbal tortoise’s shape is between both species with males having a saddle-backed shape and females and young males being wider in the middle and more domed in shape.
SOURCES:
- https://www.galapagospark.org/sitio.php?page=galapaguera_cerro_colorado
- https://animals.nationalgeographic.com/animals/reptiles/galapagos-tortoise
- https://wbd.etibioinformatics.nl/bis/turtles.php?menuentry=soorten&id=386
- https://www.galapagos.org/about_galapagos/about-galapagos/biodiversity/tortoises/
