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The Galapagos Giant Tortoise is perhaps the most well-known animal on the islands and with good reason. These massive reptiles can weigh up to 550 pounds and live up to 150 years in the wild. It is the largest and longest-living vertebrate in the world but also one of the rarest.
In the past, gigantic tortoises lived on every continent but Antarctica and Australia. Sadly, only two populations of a few thousand massive tortoises are left: the Seychelles in Africa and the Galapagos Islands in South America. By contrast, the estimated population of giant tortoises that once inhabited the Galapagos Archipelago was down to 3,000 from a quarter of a million. Scientists are unsure of the exact cause of their almost total extinction. Still, they are clear that human presence and expansion have a role—particularly for those residing in the Galapagos Islands.
Origins
The Galapagos giant tortoise is the result of a process called island gigantism, which occurs incredibly frequently among island populations. The consensus among specialists is that the archipelago’s initial tortoises were around the size of an average tortoise. However, years after arriving on the islands, the tortoises grew to vast sizes, almost unrestrained by minimal competition and practically no predators. Their colossal size serves them well and makes them better adapted to thrive in erratic environments such as the Galapagos. Because their size enables them to store more fat and water for protection in times of scarcity (they have a specific water-storing region in the root of their neck), tortoises can survive for over a year without food or fresh water. Furthermore, they can expand their habitat due to the ease with which they can swim across islands because of their small surface-area-to-volume ratio. Additionally, they have greater control over their body temperature.
On your upcoming voyage aboard Yacht La Pinta, behold the Galapagos Giant Tortoise!
Conduct
Visitors are often mesmerized when a small bird sits on the enormous tortoise shells in the Galapagos, and it makes for a perfect photo opportunity. However, this is a significant part of the mutualistic relationship between Galapagos birds and giant tortoises. Vermillion Flycatchers and Darwin’s Finches often begin pecking at insects hidden in the cracks in the tortoiseshell once they land there. Additionally, they are seen circling the tortoises to get their attention. Once they have, the tortoise will stretch its neck or other appendages to allow the bird to obtain ticks from previously unreachable areas. This way, the bird gets a free dinner, and the tortoise gets a free wash.
Observe Giants Galapagos turtles feasting on a variety of flora in the elevated regions of Santa Cruz Island.
Galapagos giant tortoise adaptation and natural selection
Currently, just 11 subspecies of Galapagos giant tortoises remain in the archipelago, down from their former population of 14 or 15. However, saddleback and domed shell tortoises are the two families into which tortoises are typically divided. Whether a tortoise falls into one of these categories depends on its habitat in the Galapagos Islands. Tortoises on islands with lower rainfall rates are smaller than on islands with higher precipitation levels. In addition, their limbs are longer and thinner than those of domed shell tortoises, and their saddleback-shaped shells are raised over their necks and back legs.
These unique traits are intimately associated with the habitats that tortoises live in. Generally speaking, there is significantly less flora on Dryer Islands, typically found higher up. For example, cacti are one of the most common plant species that produce fruit near the top of the plant. The tortoise that can reach higher and gather more fruit is consequently healthier and more likely to breed because of its long legs and ability to elevate its neck. It’s remarkable to see how several subspecies on different islands have successfully adapted to these two qualities. On the other hand, the Santa Cruz highlands are rich in flora and luxuriant greenery and are home to hundreds of domed shell tortoises.
