By Dr. Becker
The Galapagos Islands are known for their tortoises and represent one of only two places on the planet where these magnificent creatures still live (the other is on Aldabra Atoll in the Indian Ocean).
Around the time Charles Darwin visited the islands in 1835, there were 15 types of tortoises living on the island. That has since dropped to 11, but now we can bump it back up to 12.
Yale University researchers recently revealed that the tortoises living on the western and eastern sides of the island of Santa Cruz within the Galapagos are actually two separate species.1
Newly Identified Eastern Santa Cruz Tortoise
All the tortoises living on Santa Cruz were long thought to be of the species Chelonoidis porter. But the eastern and western tortoises have slightly different appearances, which is what tipped researchers off that perhaps they’re not the same species after all.
They ran genetic tests on about 100 tortoises from each side of the island, which revealed significant genetic differences.
Though they live just six miles a apart, the Western tortoises are Chelonoidis porterand the eastern tortoises are a new species the researchers named Chelonoidisdon faustoi (named for Galapagos National Park ranger Fausto Llerena Sánchez, who cared for endangered tortoises).
The two species turned out to be only distantly related. As reported by Live Science:2
“In fact, the two species evolved millions of years apart. The western tortoises are part of the oldest giant tortoise lineage in the Galápagos, which evolved about 1.74 million years ago.
In contrast, the eastern tortoises are much younger — they evolved less than half a million years ago.
The genetic tests showed that the eastern tortoises are more closely related to tortoises found on other Galápagos Islands than they are to the tortoises living on the western side of their own island.”
Of note, while there are about 2,000 tortoises belonging to the western species, only about 250 of the eastern species remain. The finding of the new species may help them get increased habitat protection.
As it is, giant tortoises throughout the Galapagos have significantly declined due to habitat loss, invasive species and human exploitation.3
Only About 15,000 Giant Tortoises Remain in the Galapagos
It’s thought the first tortoises arrived on the Galapagos up to 3 million years ago after drifting across the ocean from South America.4
They were once so abundant that when the Islands were discovered by Spanish sailors in the 1500s, they named the archipelago Galapagos after galápago, which is Spanish for tortoise.5
From the 17th to the 19th centuries, tortoises were hunted for food to the extent that an estimated 100,000 tortoises, or more by some estimates, were killed. According to the Galapagos Conservancy:6
“One of the giant [Galapagos] tortoise’s most amazing adaptations — its ability to survive without food or water for up to a year — was also the indirect cause of its demise.
Once buccaneers, whalers and fur sealers discovered that they could have fresh meat for their long voyages by storing live giant tortoises in the holds of their ships, massive exploitation of the species began.”
Today, there are only about 15,000 tortoises remaining on the Islands, and they’re listed as an endangered species by the Ecuadorian government.7
At least four species have already gone extinct, and the Galapagos Conservancy pointed out that many more may have already been eliminated if not for the tortoises’ long lifespan.
“The only thing saving several of the populations was the longevity of tortoises, keeping some old adults alive until conservation efforts could save their species,” the Conservancy explained.8
Galapagos giant tortoises are not only the world’s largest tortoises (growing up to five feet long and weighing up to 550 pounds); they’re also the longest-lived vertebrate. Giant tortoises average a lifespan of 100 years plus, although the oldest on record lived to be 152. According to National Geographic:9
“It is possible, though perhaps unlikely, that among the remaining giant tortoises of the Galápagos Islands, there exists an old-timer that was a hatchling at the time of Charles Darwin's famous visit … ”
Tortoises Help Island Biodiversity
Tortoises spend up to 16 hours of their day at rest, so you might wonder how they could be an active contributor to their environment. For starters, a recent study found about half of the diets of Galapagos’ tortoises is made up of invasive plant species. 10
The Islands are facing a problem with more than 750 species of such plants growing in the environment, but the tortoises have learned to live in harmony with the plants. In some cases, the invasive species may even add a nutritional boost to the tortoises’ diets.
When a group of Aldabra giant tortoises were introduced to an island called Ile aux Aigrettes in the Indian Ocean, they ate the fruit of native ebony trees, a species that had been devastated on the island. The tortoises then helped spread the seeds throughout the island, and the seeds even germinated better once they passed through the tortoises’ guts.
Even better, like on the Galapagos, the tortoises also feasted on a lot of the non-native plants on the island, representing a clear example of how wild animals can help to restore entire ecosystems.11 They also have a reciprocal relationship with the Islands’ birds, including Darwin’s finches and Vermilion Flycatchers.
The birds will “dance” in front of the tortoises when they’re looking for a meal, and the tortoises will respond by stretching out their necks to expose ticks that the birds love to eat.12
Tortoises are also an example of one of the gentlest creatures on the planet. When they’re not napping, Galapagos tortoises can be found grazing on cactus pads, grasses and fruit. Even their competitions are decidedly gentle. The Galapagos Conservancy explained:13
“Like many other species, they have ways of conveying dominance and defending themselves. Competing tortoises will stand tall, face each other with mouths agape, and stretch their necks up as high as possible. The highest head nearly always ‘wins,’ while the loser retreats submissively into the brush.”