Aldabra Giant Tortoise

Aldabrachelys gigantea

Reptile

Transcript:

Today on Animal Fact Files we’re discussing the Aldabra giant tortoise. As their name implies, these reptiles live on Aldabra Atoll which is part of the Seychelles located Northeast of Madagascar in the Indian Ocean. The Aldabra giant tortoise is the largest living animal on the atoll and they are some of the largest tortoises alive today. They have been introduced to other nearby islands, and they share the Seychelles with other giant tortoise species, but we'll save them for a future episode. The Aldabra giant tortoise rivals the Galapagos tortoises in size. These groups can be told apart from each other by looking at their shells. The Aldabra giant tortoise has a neck plate in the front center of its upper shell, the Galapagos tortoises do not.

In size, Aldabra giant tortoises range from 300 to over 500 pounds (136-227kg). Their shells reach three to four feet (91-152cm) in length. The males nearly double the females in size. Males also have a longer, thicker tail and a concave lower shell. This is to assist them in mating. Male Aldabra giant tortoises mount females and let out a roar while mating that sounds like this: [audio]. These reptiles reach reproductive age when they're about half their adult size, which usually occurs around 25 years of age. The breeding season lasts from February to May. A female will have a clutch of twenty eggs on average, though only a handful of these will hatch. Nests are constructed by females. Aldabra giant tortoises have sturdy claws for digging. Depending on the temperature, the eggs may take anywhere from four to six months to develop. The babies must dig themselves out and are on their own from birth. They’re about the size of a tennis ball when born!

Besides humans, these reptiles have no predators. Humans collect their eggs and meat for food, but today the Aldabra giant tortoise is protected, and their populations have increased since their near extinction at the turn of the 20th century. Their biggest threat is the climate crisis the world is currently facing. The highest point of Aldabra island is only 50 feet (15m) above sea level and rising sea levels could reduce their habitable range.

The Aldabra giant tortoise eats grasses, seeds, bark, leaves, and more. They can extend their neck up to three feet (91cm) to reach vegetation. They also eat meat when it's available. These tortoises eat carrion and will even scavenge carcasses of their own species! They have knife-like jaws that are strong enough to crush a human’s hand. Aldabra giant tortoises don't have to drink much water because they get it all from their food. They can go weeks without eating if needed.

Aldabra atoll includes scrub forests and coastal dunes surrounding a mangrove-boarded lagoon. Like elephants, Aldabra giant tortoises change their surrounding environment. They can tople small trees and create mud wallows for bathing. Their eating habits have led to the development of 'tortoise turf' where the vegetation grows low. This creates new habitat for other, smaller animals living on the island. Though they can cause this much change around them, they're also quite relaxed. Aldabra giant tortoises are only active a few hours each day. In the morning and evening they'll search out food, mate, dig, and more. Otherwise, they rest. Sometimes they sleep in mud baths to help keep mosquitoes away from their exposed skin.

The Aldabra giant tortoise is believed to be one of the oldest living vertebrates, but this isn't well documented. At the very least, they have outlived the people studying them! Scientists who previously observed these tortoises have passed away, but their records weren't complete enough to form concrete evidence on the Aldabra tortoise's lifespan! It's guessed they live to be older than 100, and some zoos claim ages over 150!

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