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Bear minimum

Bear minimum isolation kills. And this time it is killing bears in Spain. For one of Spain's two main populations of brown bears, extinction looms large as a very real possibility. And according to researchers, this is nothing but the result of an abnormal isolation from its compatriots for several decades.

Spain now has less than 100 of these brown bears or Ursus arctos, to boast of, compared with the several hundred that inhabited the nation during the last century. The bear population in Spain has been restricted to the Cantabrica mountains in the north, where back in 1847, a road was built. Next came a railway through the bears' habitat, and later still, a national highway was constructed - all along the same route. A ski resort has also been added recently in the vicinity. These developments, say experts, have divided the bears into a small eastern and a larger western population that, despite being just 30 km from one another, have had no contact for more than half a century now.

Scientists from the Madrid-based National Museum of Natural History and the Foundation for the Brown Bear in Santander, Spain, examined dna samples from the excrement and hair of the bears from both the eastern and western populations to check for their genetic diversity. The team found a high variability among the 70 or so animals of the larger group, while the bears from the smaller group - approximately 17 in strength - shared many of the same genes. This lack of genetic diversity, say scientists, makes a population less adaptable and therefore, less likely to survive. The smaller eastern group has already seen a marked decrease in its numbers in the past few years, and researchers have warned that very soon, they might join the already-long list of extinct species.

"In less than a hundred years, the splitting of the original population into two groups has produced serious genetic consequences for the smaller group," says Ignacio Doadrio, a biologist at the Madrid Museum. He highlights the fact that the male bear mates with four or five females and then keeps them away from other males. In a population with just a handful of members, this leads to genetic similarity. Doadrio also has a solution to counter the dwindling population of these animals. He says the best way to increase the size of these populations is to boost the larger western group by removing the traps left by hunters, and then ensuring that these bears "cross over" to the other side and reach the smaller group.

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