Siberian (or Amur) tigers are the world's largest cats. They live primarily in eastern Russia's birch forests, though some exist in China and North
Korea. There are an estimated 400 to 500 Siberian tigers living in the wild, and recent studies suggest that these numbers are stable. Though their northern
climate is far harsher than those of other tigers, these animals have some advantages. Northern forests offer the lowest human density of any tiger habitat,
and the most complete ecosystem. The vast woodlands also allow tigers far more room to roam, as Russia's timber industry is currently less extensive than
that of many other countries.
Tigers are the largest of all wild cats and are renowned for their power and strength. There were once eight tiger subspecies, but three became extinct during the 20th century. Over the last 100 years, hunting and forest destruction have reduced overall tiger populations from hundreds of thousands to perhaps 5,000 to 7,000. Tigers are hunted as trophies and also for body parts that are used in traditional Chinese medicine. All five remaining tiger subspecies are endangered, and many protection programs are in place. Poaching is a reduced-but still very significant-threat to Siberian tigers.
Tigers live alone and aggressively scent-mark large territories to keep their rivals away. They are powerful hunters that travel many miles to find prey, such as elk and wild boar, on nocturnal hunts. Tigers use their distinctive coats as camouflage (no two have exactly the same stripes) and hunt by stealth. They lie in wait and creep close enough to attack their victims with a quick spring and a fatal pounce. A hungry tiger can eat as much as 60 pounds (27.2 kilograms) in one night, though they usually eat less.
Despite their fearsome reputation, most tigers avoid humans; however, a few do become dangerous maneaters. These animals are often sick and unable to hunt normally, or live in areas where their traditional prey has vanished.
Females give birth to litters of two to six cubs, which they raise with little or no help from the male. Cubs cannot hunt until they are 18 months old, and remain with their mothers for two to three years, when they disperse to find their own territory.
The grizzly bear is a North American subspecies of the brown bear.
These awe-inspiring giants tend to be solitary animals-with the exception of females and their cubs-but at times they do congregate. Dramatic gatherings of grizzly bears can be seen at prime Alaskan fishing spots when the salmon run upstream for summer spawning. In this season, dozens of bears may gather to feast on the fish, craving fats that will sustain them through the long winter ahead.
Brown bears dig dens for winter hibernation, often holing up in a suitable-looking hillside. Females give birth during this winter rest and their offspring are often twins.
Grizzly bears are powerful, top-of-the-food-chain predators, yet much of their diet consists of nuts, berries, fruit, leaves, and roots. Bears also eat other animals, from rodents to moose.
Grizzlies are typically brown, though their fur can appear to be white-tipped, or grizzled, lending them their traditional name.
Despite their impressive size, grizzlies are quite fast and have been clocked at 30 miles (48 kilometers) an hour. They can be dangerous to humans, particularly if surprised or if humans come between a mother and her cubs.
Grizzlies once lived in much of western North America and even roamed the Great Plains. European settlement gradually eliminated the bears from much of this range, and today only about 1,000 grizzlies remain in the continental U.S., where they are protected by law. Many grizzlies still roam the wilds of Canada and Alaska, where hunters pursue them as big game trophies.