Conservationists must protect tiger populations in a few concentrated breeding grounds in Asia instead of trying to safeguard vast, surrounding landscapes, if they want to save the big cats from extinction, scientists have said.

Only about 3,500 tigers are left in the wild worldwide, less than one third of them breeding females, according to one of the authors of the study, John Robinson of the Wildlife Conservation Society.

Much has been done to try to save the world’s largest cat — threatened by hunting, habitat loss and the wildlife trade — but their numbers have continued to spiral downward for nearly two decades.

That’s in part because conservation efforts are increasingly diverse and often aimed at improving habitats outside protected areas, according to the study, published in Tuesday’s issue of the peer-reviewed PLoS Biology journal.

Instead, efforts should be concentrated on the areas where tigers live — most are clustered in just 6 percent of their available habitat — and especially where they breed.

“The immediate priority must be to ensure that the last remaining breeding populations are protected and continually monitored,” it says, adding if that doesn’t happen, “all other efforts are bound to fail.”

The WWF and other conservation groups say the world’s tiger population has fallen from around 5,000 in 1998 to as few as 3,200 today, despite tens of millions of dollars invested in conservation efforts.

The cats have been lost largely to poachers, who cash in on a huge market for tiger skins and a belief, prevalent in east Asia, that eating or applying tiger parts enhance health and virility.

The new study — to which researchers from the conservationist group Panthera, the World Bank, the University of Cambridge and others also contributed — identifies 42 key areas that have concentrations of tigers with the potential to grow and populate larger landscapes.

Eighteen are in India — the country with the most tigers — eight in Indonesia, six in Russia’s Far East and the others scattered elsewhere in Asia.

The price tag for the plan — which would require greater levels of law enforcement and surveillance — would be around $82 million a year, the study says.

The bulk of that is already being provided by state governments and international support.

Similar efforts have been successful in the past — especially in India.

The Malenad-Mysore landscape in southern India has 220 adult tigers, one of the largest populations in the world, thanks largely to intensive protection of its “source site,” the Nagarahole National Park, in the 1970s.

Those high densities have now been maintained for 30 years, the authors wrote, pointing to similar success stories with the African rhinoceros.

Alan Rabinowitz, president of Panthera, said focusing on breeding grounds is “absolutely necessary right now if we are to save tigers in the wild.”

But he stressed that in the long-term, it is important that tigers be able to move in surrounding landscapes to maintain genetic and demographic viability.

“Otherwise we are boxing ourselves into a corner that would allow only for contained, managed populations.”

Michael Baltzer, leader of the WWF Tiger Network Initiative and independent of the study, agreed, saying conservationists need to be careful not to create “wild zoos.”

Online- www.plosbiology.org