By Carrie Flood
Giant tortoises have almost universal appeal. The slow moving, herbivorous giants are reminiscent of dinosaurs, with their fixed smiling faces and long leathery necks.
Long ago, there were giant tortoises on all but one of the continents. Today, they are limited to two populations: one on the Aldabra Islands in the Indian Ocean, and one on the Galapagos Islands off Ecuador.
The Phoenix Zoo is home to some of each, and they all recently got new homes. You’ll find the Aldabra tortoises over by the Desert Lives trail, where it intersects the Africa trail near the rhinoceros. The Galapagos have a new home just across from their old exhibit, near the covered bridge. Their old home will eventually be demolished to make room for the expansion of the elephant exhibit!
The classification of the Galapagos tortoise is constantly being modified, and species get grouped or separated based on new genetic information. Currently, there are 15 species of Galapagos tortoise alive today, and 4 species that are believed extinct. Three of these species have been gone for many decades, but the last one just went extinct a few years ago. The Pinta Island tortoise was heavily exploited by European settlers and visiting whalers in the first half of the 1800s. In the 1970s, the last Pinta Island tortoise was brought into captivity at the research station on the islands, with hopes that he might breed with females from another species. While eggs were laid, none hatched, and the male tortoise, named Lonesome George, passed away in June of 2012.
While the story of Lonesome George is heartbreaking, it also compels us to act so that we don’t have to watch the last of another species disappear before our eyes. AZA (Association of Zoos and Aquariums) member institutions across the nation cooperate with one another to match up the different species of tortoises with other members of their own species. The idea is to maintain genetically diverse populations of each species in managed care as a failsafe. The Galapagos Islands are now protected of course, but much of the habitat is still recovering from the damage sustained before protections were put in place.
The Phoenix Zoo is home to two species of Galapagos tortoise. Elvis and Lola are two of just seven Iguana Cove tortoises in AZA member institutions, while Mary and Mopey are Vulcan Darwin tortoises, which are found in only six AZA zoos in North America. Both species are dome-shelled. The dome-shelled tortoises evolved in humid areas of the islands where forage is more abundant. The other group, the tortoises, have a large upward thrust in the front of their shell that allows them to extend their necks higher. The saddle-backed species evolved in dry areas of the islands, where tortoises had to reach higher to find food.
Tortoises are important to the ecosystems of the islands where they live. They are seed dispersers, carrying seeds of plants long distances before dropping them in their dung. One study found an average of more than 400 seeds in each pile of tortoise poop! The plants have evolved to rely on the tortoises to spread their seeds throughout their range, and where the tortoises have disappeared, the ecosystems can collapse. Birds like the flycatchers and finches studied by Charles Darwin also depend on the tortoises, feeding on the ticks that live in the folds of skin on the tortoises’ necks and legs. One species of finch has been observed hopping about in front of the tortoise. This “dance” lets the tortoise know that the bird is hungry, and the tortoise will stretch out its head and neck, so the bird can access the ticks! Of course, this benefits both – the tortoise gets rid of parasites and the finch gets an easy meal. Isn’t that fascinating? I wonder which bird figured out the secret dance steps that unlocked access to the parasite buffet….
The oldest known Galapagos tortoise was more than 150 years old, and many scientists suspect that they can live even longer. The Galapagos tortoises at the Phoenix Zoo aren’t quite that old, but their wrinkly skin can still make you feel young by comparison! Next time you’re watching the giant tortoises stretch out in the sun or tuck into a giant salad, know that by supporting the Zoo you’re helping to conserve and protect these magnificent animals – and their native island habitats – for future generations. Great job!
Want to learn more about our conservation efforts and how you can help? Visit https://www.phoenixzoo.org/conservation/.