Study reports bad news for world's mammals

At least one-quarter of the world's known mammal species are at risk of becoming extinct, and about half are declining in population, a global survey released Monday morning has found.

The study – which took 1,700 experts in 130 countries more than five years to complete – was conducted as part of the International Union for Conservation of Nature's Red List of Threatened Species and will be published this week in the journal Science. It covers all of the 5,487 wild-mammal species known to humans since the year 1500, and is the most thorough study of its kind since 1996.

According to an article in Science magazine, which like the journal of the same name is published by the American Association for the Advancement of Science, the study lacked sufficient data for about 15 percent of the world's mammal species.

For some species, data were quite detailed, down to individual breeding rates. But many others remain virtually unknown.... Particularly sparse were data on some rodents and bats, several of which are known just from single museum specimens collected from remote regions. In all, 836 species were so poorly studied that it was impossible to tell what their conservation needs might be.

That means that the number of species actually threatened could be as high as 36 percent.

The most vulnerable species are primates (excluding humans, of course) and marine mammals. The threatened mammal species are being killed off by a variety of human activities, as the Washington Post's Juliet Eilperin notes:

Land and marine mammals face different threats, the scientists said, and large mammals are more vulnerable than small ones. For land species, habitat loss and hunting represent the greatest danger, while marine mammals are more threatened by accidental killing through fishing bycatch, ship strikes, and pollution.

While large species such as primates (including the Sumatran orangutan and red colobus monkeys) and ungulates (hoofed animals) may seem more physically imposing, the researchers wrote that these animals are more imperiled than small creatures such as rodents or bats because they "tend to have lower population densities, slower life histories, and larger home ranges, and are more likely to be hunted."

Primates face some of the most intense pressures: according to the survey, 79 percent of primates in South and Southeast Asia – including the Hainan gibbon – are facing extinction.

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