Jaguars are one of the 36 species of wild cat in the world and one of 7 big cats. Larger males have been recorded to weigh as much as 348 lb (roughly matching a tigress and lioness), while the smallest females have low weights of 79 lb. The length, from the nose to the base of the tail, of the cats varies from 3.7 to 6.1 feet long. A short and stocky limb structure makes the jaguar adept at climbing, crawling, and swimming. The head is robust and the jaw extremely powerful, it has the third highest bite force of all felids, after the lion and tiger. A 220 lb jaguar can bite with a force of 1110 lb at canine teeth and 1556 lb at carnassial notch. This strength adaptation allows the jaguar to pierce turtle shells. A comparative study of bite force adjusted for body size ranked it as the top field, alongside the clouded leopard and ahead of the lion and tiger. It has been reported that "an individual jaguar can drag an 800 lb bull 25 ft in its jaws and pulverize the heaviest bones". The base coat of the jaguar is generally a tawny yellow, but can range to reddish-brown and black, for most of the body. However, the ventral areas are white. The cat is covered in rosettes for camouflage in the dappled light of its forest habitat. The spots vary over individual coats and between individual jaguars: rosettes may include one or several dots, and the shapes of the dots vary. The spots on the head and neck are generally solid, as are those on the tail, where they may merge to form a band. While the jaguar closely resembles the leopard, it is sturdier and heavier, and the two animals can be distinguished by their rosettes: the rosettes on a jaguar's coat are larger, fewer in number, usually darker, and have thicker lines and small spots in the middle that the leopard lacks. Jaguars also have rounder heads and shorter, stockier limbs compared to leopards. Jaguars with melanism appear entirely black, although their spots are still visible on close examination. The black morph is less common than the spotted form but, at about six percent of the population, it is several orders of magnitude above the mutation rate. Hence, it is being supported by selection. Some evidence indicates the melanism allele is dominant. Melanistic jaguars are informally known as black panthers, but they do not form a separate species. Jaguars prefer wet lowland habitats, swampy savannas or tropical rain forests. Their favorite habitat is in the tropical and subtropical forests. Jaguars also live in forests and grasslands, living near rivers and lakes, in small caves, marshland, and under rock ledges, they live in shrubby areas as well. Like all cats, the jaguar is an obligate carnivore, feeding only on meat. It is an opportunistic hunter and its diet encompasses at least 87 species. Their diet consume: spider monkeys, tapirs, caimans, peccaries, anteaters, turtles, sloths, armadillos, livestock, capybaras and will sometimes even anacondas. The jaguar is a stalk and ambush rather than a chase predator. The cat will walk slowly down forest paths, listening for and stalking prey before rushing or ambushing. The ambush may include leaping into water after prey, as a jaguar is quite capable of carrying a large kill while swimming, its strength is such that carcasses as large as a heifer can be hauled up a tree to avoid flood levels. On killing prey, the jaguar will drag the carcass to a thicket or other secluded spot. It begins eating at the neck and chest, rather than the midsection. Jaguar females reach maturity at about two years of age, and males at three or four. The cat is believed to mate throughout the year in the wild, although births may increase when prey is plentiful. Female estrus is 6 to 17 days out of a full 37 day cycle, and females will advertise fertility with urinary scent marks and increased vocalization. The gestation period lasts 93 to 105 days, females give birth to up to four cubs, and most commonly to two. The mother will not tolerate the presence of males after the birth of cubs, given a risk of infanticide, this behavior is also found in the tiger. Typical lifespan in the wild is estimated at around 12 to 15 years, in captivity, the jaguar lives up to 23 years, placing it among the longest-lived cats.