BARCELONA, Spain (Reuters) - A quarter of the world’s mammals are threatened with extinction, an international survey showed on Monday, and the destruction of habitats and hunting are the major causes.

The report, the most comprehensive to date by 1,700 researchers, showed populations of half of all 5,487 species of mammals were in decline. Mammals range in size from blue whales to Thailand’s insect-sized bumblebee bat.

“Mammals are declining faster than we thought -- one in four species is threatened with extinction worldwide,” Jan Schipper, who led the team, told Reuters of the report issued in Barcelona as part of a “Red List” of threatened species.

He said threats were worst for land mammals in Asia, where creatures such as orang utans are suffering from deforestation. Almost 80 percent of primates in the region were under threat.

Of the 4,651 mammals for which scientists have data, 1,139 species were under threat of extinction. Schipper said the data was far broader than the previous review of mammals in 1996.

Threats to species including the Tasmanian Devil, an Australian marsupial, the Caspian seal or the fishing cat, found in Asia, were among those to have worsened. At least 76 mammals have gone extinct since 1500.

“Within our lifetime hundreds of species could be lost as a result of our own actions,” said Julia Marton-Lefevre, director general of the International Union for Conservation of Nature (IUCN), which compiles the Red List and is meeting in Spain.

IBERIAN LYNX

Of the 2008 total, 188 were listed as “critically endangered,” the worst category before extinction, including the Iberian lynx of which there are just 84-143 adults left. Cuba’s rat-like little earth hutia has not been seen in 40 years.

An Iberian lynx looks from his enclosure at Cabarceno nature reserve near Santander, northern Spain, October 25, 2005. REUTERS/Victor Fraile

Habitat loss and hunting -- for everything from food to medicines -- “are by far the main threats to mammals,” Schipper and his team wrote in the journal Science. “The population of one in two is declining,” they said.

Among other threats, global warming blamed by the U.N. Climate Panel on human use of fossil fuels, was hitting species dependent on Arctic sea ice such as the polar bear.

But the report, issued during an Oct 5-14 IUCN congress, was not all gloom. Five percent of species were recovering because of conservation efforts, including the European bison and the black-footed ferret, found in North America.

The African elephant was also moved down one notch of risk, to “near threatened” from “vulnerable,” because of rising populations in southern and eastern Africa.

And a total of 349 species have been found since 1992, such as the elephant shrew in Tanzania, it said. Schipper said some species may be vanishing before they are even described.

The report focused on mammals but the situation for some other types of animals and plants is even worse, according to the IUCN, comprising governments and conservation organizations.

An updated “Red List” said that 16,928 species, or 38 percent, were threatened out of a total of 44,838. Among animals most at risk are amphibians, such as frogs and toads.

Schipper said governments urgently needed to work out ways to protect life on earth. “Conservation action backed by research is a clear priority,” he said.