by Whit Gibbons

March 25, 2012

Q. When we hear about animals that are on the verge of extinction or that have gone extinct in modern times, most are birds or mammals. We all know about the dinosaurs, but have any reptiles gone extinct recently? Are any seriously endangered? What environmental threats do reptiles face today?

A. You are correct that birds and mammals get most of the attention when talk turns to the plight of wildlife and the environmental threats to their existence. Nonetheless, many critically endangered reptiles around the globe are circling the drain of extinction. And one need not go back to the time of the dinosaurs to find examples of reptiles that have gone extinct.

Probably the most publicized group of imperiled reptiles are the sea turtles, of which six species are listed as critically endangered. Five species of the 23 living species of crocodilians are also at risk. The Chinese alligator, closest kin to the American alligator, was once thought to be extinct in the wild in its native home along the Yangtze River. Today only 150 individuals are known to exist in the wild.

The World Conservation Union is an international organization that rates the conservation status of species globally based on the best available research and population assessments. Defining extinction for a plant or animal is relatively straightforward--no living member of the species exists anywhere. But proving that something no longer exists is not always easy.

One group of reptiles that clearly seem to have gone extinct are some of the giant tortoises that once lived on oceanic islands visited by early European adventurers. Take, for example, the island of Mauritius. Less than a century after it was discovered by European explorers, one of its avian denizens, the dodo bird, had completely disappeared, and by the early 1700s the Mauritian tortoise that inhabited the island had also been driven to extinction. The demise of the tortoises on Mauritius and other islands is believed to have been the result of overexploitation by the first human visitors to the region.

Lizards are another group of reptiles in which some species have disappeared in modern times. As if extinction of the dodo and the tortoise were not enough to lay at the feet of Mauritius's discoverers, a lizard known as the Mauritianus giant skink disappeared during the 1600s. Virtually all lizard species confirmed to have gone extinct have not been seen in at least a half century and most not since the 1800s. Some were once found on Caribbean islands, including Jamaica and Navassa Island near Haiti. The introduction of mongooses to Jamaica is considered by some authorities to be a contributing factor in the demise of several lizard species. Specimens of the now-extinct lizards were preserved in museums long ago thus confirming that they once existed.

Another group of reptiles, the snakes, are so secretive that countless species have probably gone extinct without our even knowing that they existed in the first place. Others that we were aware of have disappeared. A snake known as the Round Island burrowing boa was last reported from the island in the Indian Ocean in the 1970s. Goats and rabbits brought to the small island by settlers are the presumed cause of its disappearance. Like that of the dodo and the giant tortoise, the fate of the Round Island Burrowing boa adds another mournful note to the sad ballad of human-caused extinction.

Clearly, dinosaurs are not the only reptiles that have gone extinct; extinction in modern times has occurred. Of course, the likelihood of people discovering a new island and subsequently causing the extinction of its native wildlife is close to nil. But a far greater threat exists: environmental complacency--the mistaken belief that the world's animals and plants are doing fine. They are not. And the time to protect the environment and preserve natural habitats is not when a specific plant or animal is endangered or borders on extinction. The time to act is now.

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