Galápagos Tortoise

Chelonoidis niger species complex

Reptile

Transcript:

Today on Animal Fact Files we’re discussing the Galápagos tortoise. Technically speaking, we’ll be talking about all Galápagos tortoises, but this can be a little confusing. These reptiles end up in a type of Schrodinger’s cat situation where not enough information is known to classify them in what are typically defined as “species”; they’re part of a species complex. Basically what this means is that they are all grouped together under a single scientific name but it’s understood that more information is needed to determine how they should be further classified. I mean, if you think about it, this applies to all animals. Every species name is really a hypothesis based on the information available to us at that time. We’ve talked in the past how animal scientific names can change, and the Galápagos tortoise is no exception. As it stands, there are approximately a dozen different “types” of living Galápagos tortoises.

As the common name implies, these tortoises live throughout the various Galápagos islands. This map gives you an idea of how they’re split up throughout their range, but please note that it’s not completely accurate as names have changed since its creation. The Galápagos tortoise is the largest living tortoise and one of the largest reptiles alive today. Males may be well over 600 pounds (272kg) heavy and females reach more than half this weight. They can measure up to six feet (1.8m) from head to tail. The different forms can be told apart by their shell appearance. Some are saddlebacked with the front of the shell leaving room for them to extend their neck higher into foliage. Others have domed shells. Their shells might look heavy, but they’re made of a honeycomb-like structure that makes them much lighter than they appear!

Galápagos tortoises spend part of the day basking in the sun in grassy, lowland areas. Later, they move to wetland areas with water in which to cool off and plenty of plants to eat. These reptiles are herbivores. They eat fruits, grasses, leaves, and more! When they move between habitats, they do so in groups and follow well worn paths trampled over for generations. These are known as “tortoise highways.”

The Galápagos tortoise is well known for its lifespan. An individual may live to be well over 100 years old in the wild and the oldest known living Galápagos tortoise was over 170. Mating occurs most frequently from January to August. Males fight for breeding rights and a female lays up to ten eggs in an underground nest she digs up herself. The eggs are hard-shelled and the size of a tennis ball. These incubate for three to eight months depending on location and temperature. Like the pond sliders we’ve discussed previously, temperature plays a role on the sex of the babies. Hotter temperatures produce more females, and colder temperatures more males. The babies are left to fend for themselves. It can take up to a month for them to excavate themselves from their nest. Many won’t survive to their first decade.

The Galápagos tortoises are in danger of extinction. There were once hundreds of thousands of them roaming their island home, now there are fewer than 20,000. Apart from hunting them, humans have also introduced species that wreak havoc on Galápagos tortoise nests. Rats, cats, wild pigs, and wild goats all pose a threat to these gentle giants. A well fed Galápagos tortoise can survive up to a year without eating or drinking, a trait that helps them get through the dry season on the islands.

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