The tiger (Panthera tigris) is the largest cat species, reaching a total body length of up to 3.3 m (11 ft) and weighing up to 306 kg (670 lb). It is the third largest land carnivore (behind only the polar bear and the brown bear). Its most recognizable feature is a pattern of dark vertical stripes on reddish-orange fur with a lighter underside. It has exceptionally stout teeth, and the canines are the longest among living felids with a crown height of as much as 74.5 mm (2.93 in) or even 90 mm (3.5 in). In zoos, tigers have lived for 20 to 26 years, which also seems to be their longevity in the wild. They are territorial and generally solitary but social animals, often requiring large contiguous areas of habitat that support their prey requirements. This, coupled with the fact that they are indigenous to some of the more densely populated places on Earth, has caused significant conflicts with humans.
Tigers once ranged widely across Asia, from Turkey in the west to the eastern coast of Russia. Over the past 100 years, they have lost 93% of their historic range, and have been extirpated from southwest and central Asia, from the islands of Java and Bali, and from large areas of Southeast and Eastern Asia. Today, they range from the Siberian taiga to open grasslands and tropical mangrove swamps. The remaining six tiger subspecies have been classified as endangered by IUCN. The global population in the wild is estimated to number between 3,062 and 3,948 individuals, down from around 100,000 at the start of the 20th century, with most remaining populations occurring in small pockets isolated from each other. Major reasons for population decline include habitat destruction, habitat fragmentation and poaching. The extent of area occupied by tigers is estimated at less than 1,184,911 km2 (457,497 sq mi), a 41% decline from the area estimated in the mid-1990s.
The San Francisco Zoo is a 100-acre (40 ha) zoo located in the southwestern corner of San Francisco, California, between Lake Merced and the Pacific Ocean along the Great Highway. The zoo's main entrance, once located on the north side across Sloat Boulevard and one block south of the Muni MetroL Taraval line, is now to the west on the ocean side of the zoo off of the Great Highway.
This zoo is the birthplace of Koko the gorilla, and housed 693 individual animals representing about 197 species as of 2011.