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Galapagos Giant Tortoise
Geochelone elephantopus
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Threats
Hunting, poisoning, reduction of prey species, human
encroachment
STATUS:
ESA -- ENDANGERED
IUCN -- VULNERABLE
SIZE:
Weight:
Males from 115 pounds
(51 kg) to as much as 600 pounds (270 kg), females somewhat smaller
HABITAT:
Galapagos Islands
POPULATION:
15,000
CURRENT RANGE:
Galapagos Islands (map shows ranges of all populations)
CONSERVATION:
Captive-breeding and restocking program in Galapagos; CITES trade restrictions
The oldest giant tortoise on record lived 152
years. Reliable records
of tortoise life spans
aren't available yet because people haven't been observing them
long enough.
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Live Long...
Charles Darwin visited the Galapagos Islands -- an archipelago in the Pacific Ocean about 650 miles (1,040 km) off the coast of Ecuador -- in 1835. Among the many fantastic creatures he saw there were giant tortoises, weighing 600 pounds or more, with shells four feet across. Galapagos giant tortoises are the largest tortoises in the world. Giant tortoises in general are the longest-lived of all vertebrates (animals with backbones). We're not sure just how long they can live, but it's possible that some of the old-timers in the Galapagos today hatched about the time of Darwin's visit.
When Darwin was there, the total tortoise population of the Galapagos was probably around 250,000. Tortoises of different islands were quite distinct -- different shell shapes, different sizes. Scientists have concluded that there isn't just one species of Galapagos giant tortoise, but many -- perhaps a dozen or more. Years after his visit, Darwin reflected on differences in shell shape when he formulated the theory of evolution by natural selection.
...And Prosper?
Today there are perhaps 15,000 Galapagos giant tortoises left in the Galapagos. Around the world, many
species of giant island tortoises have been either wiped out altogether or reduced to near-
extinction.
Throughout the 19th century, giant tortoises were valued by sailors as food supply. They discovered that these resilient animals could live for months without food or water, flipped on their backs, and stacked in the cargo hold of a ship. This gave the sailors a ready source of fresh meat between distant landfalls. Historical records show that tens of thousands of tortoises were collected from the Galapagos, Seychelles, Mascarenes, and other islands.
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The Galapagos giant tortoise is listed under
the name Geochelone nigra in the IUCN 1996 Red List.
The Galapagos giant tortoise specimen on display in the Museum's Hall of Reptiles and Amphibians may be a hybrid -- a cross between tortoise subspecies from different islands. In the past, zoos would take animals without knowing anything about which island they came from.
As a result, zoo breeding programs often mated tortoises of different subspecies. Since all Galapagos giant tortoises are closely related, hybrids are viable and fertile. Unfortunately,
such hybridization destroys the integrity of the original subspecies. This is another way in which species can become endangered.
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Giant tortoises have also fallen prey to introduced animals. Rats came to the Galapagos on 16th-century sailing ships. By 1900, there were small permanent settlements on the islands, and people brought pigs, dogs, and cats with them. All of these animals eat tortoise eggs, and some also hunt juvenile turtles. Goats and cattle -- also introduced by human settlers -- compete with tortoises for the islands' scant food resources:
nettles, leaves, fruits, and berries.
Improving the Outlook
In 1959, the Charles Darwin Foundation established a research center and rescue station on Santa Cruz, one of the Galapagos Islands. Tortoise eggs are incubated at the research center, and hatchlings are raised there until they're four or five years old -- big enough to contend with the rats, dogs, cats, and pigs. Then they're reintroduced to their native island. More than 3,500 giant tortoises have been added to wild Galapagos populations this way. In Ecuador, which owns the Galapagos Islands, laws have been passed banning the capture, harming and exportation of giant tortoises. If these laws continue to be enforced and pressures from introduced predators and tourists can be sufficiently controlled, the outlook for Galapagos tortoises in the 21st century is reasonably bright.
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