Isolated Tigers

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The tiger Shere Khan was lord in Rudyard Kipling's Jungle Book, but his modern-day descendants are king no more: The big cats have seen their central Indian forests dwindle and fracture.

The remaining tigers are only surviving by moving through critical—but unprotected—corridors of land that link distant populations, a new study says.

Using hair and fecal samples, Sandeep Sharma, of the Smithsonian Conservation Biology Institute, and team studied genes from 273 individual tigers that live in four distinct locations within India's 17,375-square-mile (45,000-square-kilometer) Satpura-Maikal region.

Tigers once roamed across Asia from Turkey to the Russian Far East, but have vanished from over 93 percent of that range. (See tiger pictures.)

The 20th century was especially tough on the now-endangered beasts, when three subspecies became extinct, leaving six—all of which are at risk. (See a National Geographic magazine interactive of big cats in danger.)

At a glance the region's tigers seem to live in four populations, each occupying its own territory in what's called a designated tiger conservation landscape, or TCL. Those are Kanha-Phen, Pachmari-Satpura-Bori, Melghat, and Pench.

But the genetic study suggests otherwise: Corridors of woods and undeveloped land up to 125 miles (200 kilometers) long actually link Kanha and Pench into a single genetic unit, and Satpura-Melghat into a second.

That means the four populations of tigers are breeding as two much larger populations—and keeping their genetic diversity alive in the process.

Corridors also aid tiger survival on the ground, Sharma said, making the cats more likely to withstand many types of threats. (Related:"Tigers Making a Comeback in Parts of Asia.")

Dog Disease Infecting Tigers, Making Them Fearless

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Cats and dogs don't usually mix. But a domestic dog virus is posing a new threat to endangered tigers in the wild, experts say—partly by making them less fearful of people. (See tiger pictures.)

Forced into increasingly smaller habitats, tigers are sharing more space with villagers and their dogs, many of which carry canine distemper virus (CDV), an aggressive, sometimes fatal disease that is usually found in dogs but is also carried by other small mammals.

The virus has infected 15 percent of the 400-some Siberian tigers in the Russian Far East, and has killed at least three, according to Wildlife Vets International (WVI), a U.K.-based conservation organization. (Related blog: "Protecting Russia's Last Siberian Tigers.")


Based on odd tiger behavior on the Indonesian island of Sumatra, scientists suspect the virus is a problem there and in other countries. Many of these potentially CDV-infected tigers seem to be unfazed by people, wandering onto roads and into villages.


John Goodrich, now senior tiger program director of the conservation group Panthera, found the first known tiger with distemper in 2003 in Pokrovka, Russia: "This tiger just walked into a town and sat down. She was absolutely beautiful—a healthy-looking young tigress."


Even so, she had a fixed stare and did not respond to stimuli. "The lights were on, but no one was home," said Goodrich, who was then with the Wildlife Conservation Society.


Goodrich and colleagues anesthetized the tigress and found her positive for distemper. They cared for her in captivity for six weeks before she died.


Such fearless behavior is likely a symptom of brain damage caused by distemper, which also causes respiratory disease, diarrhea, seizures, loss of motor control, and sometimes death.


Veterinarians still don't know much about tiger distemper. It seems that the tigers "can get a mild infection that doesn't cause any problem—conversely it can be more serious than it is in the natural host," said Andrew Greenwood, a zoo and wildlife veterinarian at WVI.


Concerned by the development, WVI plans to work with the Indonesian government and veterinarians to launch the world's first tiger-disease surveillance program, which aims to find out how tigers catch distemper, identify the likely source of the virus, and determine how to best tackle it.

"If we get it right, it could help us forestall a major problem, which is the last thing tigers need in their precarious state," WVI director John Lewis said in a statement.

Conservationists estimate that only 3,200 tigers exist in the wild in 13 Asian countries—a 93 percent reduction of their historic range. (See a National Geographic magazine interactive of big cats in danger.)