Siberian tigers are the largest felines in the world, with an average length of 11 feet. The length of the tail also averages 3 feet. Males usually weigh around 700 pounds while females are more around 400 pounds. On average, they are the largest tiger species based on weight and length. They have large feet with 5 toes on the front paws and 4 on the hind paws. Their claws are long and retractable up to 3.9 inches in length. They are also among the most at risk. It is estimated that there are only 400 to 500 Siberian (or Amur) tigers in the wild today. When it comes to their habitats, Siberian tigers are solitary animals, marking their scent on trees to keep other tigers away. Siberian tigers live mainly in the birch forests of eastern Russia, although some exist in China and North Korea. The reason these tigers are endangered is because their homes in the forests are being destroyed. It doesn't help that people hunt these tigers illegally either. Over the past hundred years, these hunters and forest destruction have reduced the overall tiger population from hundreds of thousands to perhaps 3,000-5,000. Most of the remaining Siberian tigers are in some sort of captivity, such as zoos or special parks where they are protected, but can still roam and be free. Tigers in the wild can have territories ranging from 210 to 618 square miles. Male tigers have much larger territories and will be connected to the smaller territories of several females. The size of a tiger's territory depends on available resources, and the largest territories belong to Siberian tigers. Tigers strongly defend their territory and will fight any strange tiger that strays into their range. Surprisingly a tiger finds itself in the midst of paper, fire, drought or human activity. The characteristics of a Siberian tiger are quite unique. Their skulls are characterized by their large size. It is similar to a lion's skull although it is different in the shape of the jaw. The jaw muscles are attached directly to the top of the skull, on the sagittal crest. The lower jaw can only move up and down, not from side to side. This ensures that the jaw is as strong as possible, which is ideal for its purpose in the tiger's life, such as taking down prey and tearing it to pieces. In Siberian tigers the facial region is very powerful and wide around the canines. The skull size of a male Siberian tiger ranges from 13 to 15 inches. The size of a female's skull ranges from about 11 to 12 inches. A female's skull is always smaller than a male's and never as heavy as a male's.