WHAT IS THE WORLD'S RAREST ANIMAL?

by Whit Gibbons

January 11, 2009

Q. What is the world's rarest animal?

A. This question needs to be qualified if you expect to get anything like consensus from scientists. For example, you might restrict the question to types of animals (such as bird, fish, or frog) or to a location (such as within the United States, or within Alabama, or in the desert). Even then, you are unlikely to get a single answer on which all scientists would agree.

Part of the difficulty lies in establishing what is meant by "rare." Marble salamanders, which 99.44 percent of the people in the southeastern United States have never heard of and even fewer have seen, are not rare in the sense of being scarce. Amphibian biologists know that marble salamanders spend most of their lives in the woods under logs, leaves, rocks, or even underground. They come onto the surface when they breed in the fall, almost always at night when it is raining. To anyone other than an amphibian biologist they would be perceived as rare because the average person has never observed them in their natural habitat. By that definition, most animals, as well as plants, are rare.

The more common perception of what makes something rare is that not many of them are known to exist. The Grand Cayman blue iguana indisputably qualifies as one of, if not the, rarest lizard in the world. These turquoise or pale blue lizards, which are restricted to Grand Cayman in the Cayman Islands south of Cuba, can get more than five feet long and live more than half a century. The record longevity in captivity is 67 years. Blue iguanas qualify for the rarity category because so few are left on the island. And their odds of survival look grim. Some lizard biologists have predicted that the species will be extinct by the year 2020, except for a few animals in captivity.

Like the blue iguana, one of the rarest turtles in the world also reaches an enormous size and probably lives for decades. The Yangtze (also called Shanghai) softshell turtle is considered to be the rarest turtle in the world by most turtle biologists. Two of these turtles, a male and a female, that are in zoos in China are purported to be more than 80 years old each. One giant softshell turtle is known to inhabit a large lake in Hanoi, Vietnam, and one was found in another Vietnamese lake, but sightings in the wild over recent decades have been few. Females, which get larger than the males, can reach lengths of more than four feet and are estimated to weigh more than 400 pounds. Attempts have been made to breed the remaining pair in captivity, but so far no fertile eggs have survived.

Many ornithologists consider the rarest bird in the world to be a small honeycreeper known as the po`ouli, which is native to rainforests on Maui. According to recent reports, only three surviving individuals are known to exist. The U.S. Fish and Wildlife Service consider the species endangered (if they didn't, we should certainly wonder why not) and is attempting to protect the habitat. Efforts are also being made to get a pair to mate (assuming that both sexes are represented among the remaining individuals).

Rarity among animals, as well as plants, is not a new development. Of the millions of species that have gone extinct through the ages, a point was reached when only two or three were left. Then there were none. To that extent, rarity, even extinction, is a natural biological phenomenon. What is not natural is when we (human beings) are responsible for the rarity of a species, including the three mentioned above, because we have destroyed their habitat.

Perhaps we have reached a turning point in our stewardship of Earth. If, as I believe, most people value Earth's biodiversity, then maybe we are ready to recognize the right of other species to inhabit this planet and to set ourselves a goal for the second decade of this millennium: Let us strive to ensure that being a victim of habitat destruction is itself a rarity.

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