New Tortoises Latest Addition to Kids' Discovery Area
The North Carolina Zoo's new kids' discovery area, "kidZone," will have two new additions this season. But most visitors won't notice the subtle change. Tort, a Galapagos tortoise and one of the highlight attractions of "kidZone," will be back for another season, but joining him this year will be two new female Aldabra tortoises. The Aldabra species is second only to the Galapagos species as the biggest land tortoise in the world.
The two females arrived from the Philadelphia Zoo and will be at the park on loan until October. Retort, the female Galapagos tortoise that shared the spotlight with Tort last year, is currently at the Riverbanks Zoo in Columbia, S.C., with two other males as part of a breeding program there. The breeding has been recommended by the Association of Zoos and Aquariums (AZA), the accrediting agency for member facilities.
The tortoise breeding is part of an AZA Species Survival Plan (SSP) for tortoises. The SSP serves as a means to manage the populations of captive tortoises and other species.
The Aldabra tortoise (Geochelone gigantea), also known as the Aldabra giant tortoise, comes from the islands of the Aldabra Atoll in the Republic of Seychelles, about 950 miles east of mainland Africa and northeast of Madagascar in the Indian Ocean.
An average male weighs about 550 pounds, but a male at the Fort Worth Zoological Park, in Texas, has weighed in at almost 800. And, as is the case with the Galapagos species, females are smaller than males, averaging about 330 pounds.
Aldabras are the second-largest tortoise species and among the longest-living animals on the planet. Some are thought to be more than 100 years old, but this is difficult to verify because they tend to outlive their human observers.
One of four Aldabras brought by British seamen from the Seychelles in the 18th century eventually came to the Kolkata (formerly Calcutta) Zoo in India in 1875. At its death in March 2006, the tortoise is reputed to have reached the longest life span of any creature ever measured -- 255 years. It should be noted, though, that the accuracy of its age is disputed due to a lack of contemporary records. Today, the official record for the longest living tortoise is 170 years by an Aldabra.
Aldabra tortoises are thought to reach sexual maturity when they attain about half their full size. Their sexual maturity is determined by size, it seems, and not by age. Typically, a female Aldabra will lay between nine and 25 eggs between February and May, less than half of which are fertile. Females can produce multiple clutches of eggs each year, with an incubation that can take as long as 8 months, after which the tiny, independent young hatch.
In the wild, they are primarily herbivorous (planting-eating) but sometimes eat crabs, carrion and the carcasses of dead tortoises. They mainly graze but also browse to about three feet up. In their native Seychelles, during the rainy season (May to October), they feed mostly on dead leaves and grasses.
Aldabra tortoises are doing much better than Galapagos tortoises in the wild. Aldabra populations are estimated to be more than 140,000 on Aldabra Island alone, with an additional 1,500 captive animals in the United States. With only about 9,000 wild Galapagos tortoises, it's easy to see why that species is classified as "endangered," while the Aldabra is classified as "threatened."
The biggest problem now facing the survival of the Aldabras is the fact that wild populations are so concentrated -- more concentrated, in fact, than any other wild tortoise species. This concentration leaves the entire population extremely vulnerable to being wiped out by disease or natural disaster, such as a tsunami or volcanic eruption.
Luckily, this beautiful species is the subject of a captive breeding and reintroduction programs by the Nature Protection Trust of the Seychelles.
Tom Gillespie works for the public affairs office at the N.C. Zoo.
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