Published online 28 September 2010 | Nature | doi:10.1038/news.2010.502

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Looking beyond the glamour of conservation

Mammal ecologists call for greater focus on non-charismatic species.

wallabyAustralia's bridled nailtail wallaby (Onychogalea fraenata) may be a more pragmatic conservation focus than seeking iconic but missing species like the thylacine.John Cancalosi/naturepl

With species going extinct at an alarming rate worldwide, scientists are calling for a more targeted approach to conservation efforts. Rather than desperately searching for surviving individuals of charismatic, but probably extinct, species such as the thylacine (Thylacinus cynocephalus), conservationists should concentrate their efforts on less-iconic species that are missing, but may still exist.

"People just haven't thought hard enough about where they should put their effort," says Diana Fisher, a mammal ecologist at the University of Queensland in Brisbane, Australia, who led the study. The findings are published in Proceedings of the Royal Society B1 today. "There is no chance that species are still alive that have been looked for 20 times or more," she says.

But there is good news. The study suggests that by no means all of the species classified as extinct have actually disappeared from the planet. When consulting the scientific literature and comparing past and present Red Lists of threatened species, compiled by the International Union for Conservation of Nature, Fisher and her colleague Simon Blomberg, a mathematical ecologist who is also at the University of Queensland, found that more than a third of mammal species thought to have become extinct since the year 1500 have in fact been rediscovered.

For example, although Guadalupe fur seals (Arctocephalus townsendi) were hunted to apparent extinction off the coast of Mexico in 1892, local fishermen rediscovered a tiny colony in 1926.

Even so, "the rate of mammal extinction is accelerating", says Fisher. Misclassifying a species as extinct when it actually still exists adds to the problem, because no conservation efforts are then undertaken to save the supposedly disappeared animals, she says.

Odds of rediscovery

The odds of 'rediscovering' a species thought to be extinct depend on the intensity of the search effort, the size of the search area, and the original population density and habitat size, as well as on the time that has passed since the animals have last been sighted.

According to Fisher's analyses, the mammal most likely to be rediscovered in Australia is the lesser stick-nest rat (Leporillus apicalis), a soft-furred desert animal last recorded for certain in 1933. On the other hand, Australia's icon of extinction, the thylacine, is extremely unlikely to be rediscovered given that very intense search efforts have been unsuccessful, she says. The last known specimen of the thylacine died in captivity in 1936, and people have been looking for it in the wild ever since.

Fisher and Blomberg also found that mammals are more likely to have disappeared for good if their 'extinction' was caused by introduced predators or diseases than if it was a result of excess hunting or habitat loss.

"That's really quite surprising," says Fisher. "Rather, we would have expected body mass and range size to affect extinction rates." The researchers had suspected that small animals living in large habitats would be able to escape and hide more easily than would large animals in shrinking habitats.

The study concludes that missing species are most likely to be rediscovered if their original population density was low, and if their habitats were once large but have shrunk in size.

Practical implications

The results are relevant for conservation practice, says Carlos Drews, director of the global species programme for the conservation group WWF.

"It is better to care about animals that are still around than about a few particularly charismatic species that probably aren't," he says.

But the 'symbolic power' of iconic endangered species, such as the Javan rhino (Rhinoceros sondaicus), of which only 60–80 specimens are estimated to still exist, remains a selling point of conservationism, vital for grabbing public awareness, says Carlos.

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"We should preserve as much of our planet's biological diversity as we can," he says. "When a species has become extinct it is gone forever."

Meanwhile, the true rate of biodiversity loss remains anybody's guess. The overall number of animal species on the planet is unknown and estimates vary wildly. And because new species are still being discovered, scientists suspect that many more are becoming extinct before anyone has ever recorded their existence.

One new species, the Caquetá titi monkey (Callicebus caquetensis), was discovered only last month in the Colombian Amazon region, an area of rapid habitat fragmentation.

"There are only about 250 of the monkeys left," says Drews. "It's our ethical responsibility to help them survive." 

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