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Ex factor

Demise of snails in a New Zealand freezer is a sign of the times.

The world just got a little smaller. If you go down to the woods today in search of a western black rhinoceros (Diceros bicornis longipes) you'll be out of luck. Those at the International Union for Conservation of Nature, whose task it is to maintain the Red List of endangered species, have been looking high and low for western black rhinos for some time, but in vain. Last week, they called off the search and declared it extinct. Most of us will never have knowingly met a western black rhino. One feels a keen sense of its passing nonetheless — a sensation to which we are becoming accustomed. Rhinophiles will also, no doubt, be aware that the northern white rhino (Ceratotherium simum cottoni), a cousin of the late western black rhino, is on the brink of extinction, and that the last Javan rhino (Rhinoceros sondaicus) outside Java is also believed to have disappeared.

Conservation news is not all bad. The efforts of conservationists to rescue populations from the wild, breed them in captivity and reintroduce them, sometimes pay off. Przewalski's horse (Equus ferus przewalskii) was listed as extinct in the wild in 1996, but was brought back after a captive breeding programme, and the wild population is now believed to exceed 300. The Arabian oryx (Oryx leucoryx) is also on the up, albeit gingerly. Thanks to captive breeding and reintroductions — intentional or otherwise — the howls of wolves are heard once more where they had been absent for centuries, and wild boar (Sus scrofa) are believed to infest parts of Britain with a vigour that would shame an urban cockroach.

Less well publicized, perhaps, are the woes of endangered creatures too small, obscure or superficially revolting to attract headlines. Conservationists have long understood that the public categorizes creatures into two kinds — Cute and Yucky. The land snail Powelliphanta augusta tends, arguably, to fall into the latter class. Mature individuals grow to the size of a fist. A rapacious carnivore, it survives by sucking worms out of the ground. Clearly, it is a species that only its mother could truly love. It was discovered in 1996 in a remote mountain ridge on the South Island of New Zealand, its sole known place of residence. Unluckily for the marauding mollusc, its entire range was due to be demolished to make way for an opencast coalmine. About 4,000 snails were caught and released in another part of the area, with 1,600 being placed at their preferred temperature of 10 °C in chiller units in a government conservation-department facility. Unfortunately, a fault in a sensor plunged the temperature in one of the units to zero, and 800 of the snails — a sizeable fraction of the entire species — froze to death. The fault was not noticed immediately because it happened over a public holiday.

The incident highlights an important fact long known in conservation biology, that as species shrink in number, they become ever more vulnerable to sudden mishaps. To suffer because of, say, an avalanche or a brushfire is unfortunate — after all, species have evolved and become extinct innumerable times throughout Earth's history without the interference of Homo sapiens. So it is sad that P. augusta has come closer to extinction as a result of people's efforts to prevent such an eventuality. But one might, if one were so minded, also look askance at the decision to plonk an opencast mine on the snail's habitat. How different it might have been had the snails been able to disguise themselves as fluffy polar bear cubs or baby pandas. Conservationists can only do so much. When backed with political will, they can do much more.

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Ex factor. Nature 479, 268 (2011).

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