Jaguars (Panthera onca) are large members of the cat family native to South and Central America. They are closely related to the lions, tigers, and leopards of the Old World, and are the largest species of the cat family found in the Americas.

They vary from 1.1 to almost 1.9 metres in length, stand around 70 cm tall at the shoulder, and weigh between 57 and 113 kilograms. The jaguar has the strongest jaw structure of any feline.

Although jaguars look very much like leopards and are closely related to them, their ecological role and behaviour is more akin to that of the tiger.

Their habitat ranges from the rain forests of South and Central America to more open country, but they are rarely seen in mountainous areas. Known for their strong swimming and climbing abilities, they often prefer to live by rivers, in swamps, and in dense forest with thick cover for stalking prey. Jaguars, on rare occasions, are seen as far north as the southwestern United States, particularly in Arizona The historic jaguar range actually extended as far north as Southern California and Western Texas. At this point in time it is unclear whether these encounters reflect transitory or permanent populations.

Jaguars are solitary hunters that do not associate with one another outside the breeding season. They typically take large prey: their very strong jaw equips them to hunt deer and peccaries, but they are great opportunists and will take anything from frogs and mice to birds, fish, and domestic livestock. A jaguar will usually bite and pierce the skull of its prey, thereby killing it and demonstrating the strength of the jaguar's jaw muscles. Jaguars can run quite quickly, but do not have much endurance and rarely engage in long chases.

Jaguars mating. Notice the melanistic female.

The background of the coat is usually an orange-yellow in colour, with numerous rings or rosettes on the flanks and spots on the head and neck. It is possible to distinguish this cat from a leopard by the presence of spots inside its rosettes. A condition known as melanism can create jaguars that appear entirely black (although the spots are still visible if one looks closely). These are known as black panthers, but do not form a separate species.

Young jaguar males reach sexual maturity at about 3 or four years of age, females about a year earlier. Females give birth to as many as four cubs after a 90 to 110 day gestation, but raise no more than two of them to adulthood. The young are born blind and can see after two weeks. They remain with their mother for a long time, up to two years, before leaving to establish a territory for themselves, which can be anywhere between 25 and 150 square kilometres in size (depending on the availability of suitable prey). In captivity, jaguars can live for up to 20 years.

The word jaguar comes from the South American Tupi-Guarani language. According to one early European explorer, jaguara meant a beast that kills its prey with one bound. The original and complete amerindian name is "Jaguarete". Curiously, "Jagua" means dog in Guarani.

Their wide range means that the jaguar will not be in danger of becoming extinct for the forseeable future. They have declined in number in some areas, however, mainly due to habitat loss, especially in rain forests and grassland turned into cropland.