It may not be long before we witness the extinction of one of the world's six species of tigers, the Amur (or Siberian) tiger (Panthera tigris altaica). As we have previously reported, Amur tiger populations have dropped precipitously in recent years to around 250 animals, and the species faces a genetic bottleneck that puts it at risk of inbreeding. Now, a mysterious illness has started spreading through the Amur population, causing the death of four adult tigers and several newborns in the past 10 months.

"We may be witnessing an epidemic in the Amur tiger population," Dale Miquelle, director for the Wildlife Conservation Society (WCS) Russia Program, told the Guardian.

The as-yet-unidentified disease seems to affect tigers' ability to hunt wild game. Left in a weakened and hungry state, the four infected tigers had started coming into human territory in search of easy food. They had to be shot as potential threats to people.

The most recent death was a 10-year-old female named Galya, which had long been tracked and studied by WCS Russia. At her healthiest, Galya was estimated to weigh 140 kilograms. When she was shot, she weighed just 90 kilograms. Galya had recently abandoned her three-week-old cubs, all of whom were found dead with no food in their bellies.

The disease was first observed in a male tiger last year. Galya and two other female tigers believed to have carried the disease had been in contact with the male.

These may not be the only tigers affected. "We are extremely concerned about the possibility of an epidemic that could be sweeping through this region," Miquelle said. "Animals we have studied extensively, and known well, have demonstrated radically changed behavior, which is extremely disconcerting."

Already facing major danger from poachers, who kill an estimated 30 to 50 Amur tigers a year, this disease represents a threat the tigers may not be able to survive. "The addition of disease-related deaths to existing sources of mortality could push this population over a tipping point," Miquelle told the Guardian.

Photo: Amur tiger, via Wikipedia