Kangaroos are marsupials from the subfamily Macropodinae (macropods, meaning "large foot"). In common use, the term is used to describe the largest species from this family, the red kangaroo, as well as the antilopine kangaroo, eastern grey kangaroo, and western grey kangaroo. Kangaroos are indigenous to Australia and New Guinea. The Australian government estimates that 42.8 million kangaroos lived within the commercial harvest areas of Australia in 2019, down from 53.2 million in 2013. As with the terms "wallaroo" and "wallaby", "kangaroo" refers to a paraphyletic grouping of species. All three terms refer to members of the same taxonomic family, Macropodidae, and are distinguished according to size. The largest species in the family are called "kangaroos" and the smallest are generally called "wallabies". The term "wallaroos" refers to species of an intermediate size. There are also the tree-kangaroos, another type of macropod which inhabit the upper branches of trees in the tropical rainforests of New Guinea, far northeastern Queensland, and some of the islands in the region. A general idea of the relative size of these informal terms could be:
wallabies: head and body length of 45–105 cm (18–41 in) and tail length of 33–75 cm (13–30 in); the dwarf wallaby (the smallest of all known macropod species) is 46 cm (18 in) long and weighs 1.6 kg (3.5 lb); wallaroos: the black wallaroo (the smaller of the two species) with a tail length of 60–70 cm (24–28 in) and weight of 19–22 kg (42–49 lb) for males and 13 kg (29 lb) for females; kangaroos: a large male can be 2 metres (6 feet 7 inches) tall and weigh 90 kg (200 lb). tree-kangaroos: ranging from Lumholtz's tree-kangaroo: body and head length of 48–65 cm (19–26 in), tail of 60–74 cm (24–29 in), weight of 7.2 kg (16 lb) for males and 5.9 kg (13 lb) for females; to the grizzled tree-kangaroo: length of 75–90 cm (29.5–35.5 in) and weight of 8–15 kg (18–33 lb); Kangaroos have large, powerful hind legs, large feet adapted for leaping, a long muscular tail for balance, and a small head. Like most marsupials, female kangaroos have a pouch called a marsupium in which joeys complete postnatal development.
Because of its grazing habits, the kangaroo has developed specialized teeth that are rare among mammals. Its incisors are able to crop grass close to the ground and its molars chop and grind the grass. Since the two sides of the lower jaw are not joined or fused together, the lower incisors are farther apart, giving the kangaroo a wider bite. The silica in grass is abrasive, so kangaroo molars are ground down and they actually move forward in the mouth before they eventually fall out, and are replaced by new teeth that grow in the back. This process is known as polyphyodonty and, amongst other mammals, only occurs in elephants and manatees. The large kangaroos have adapted much better than the smaller macropods to land clearing for pastoral agriculture and habitat changes brought to the Australian landscape by humans. Many of the smaller species are rare and endangered, while kangaroos are relatively plentiful, despite a common misconception to the contrary. The kangaroo, along with the koala, are symbols of Australia. A kangaroo appears on the Australian coat of arms and on some of its currency, and is used as a logo for some of Australia's most well-known organisations, such as Qantas, and as the roundel of the Royal Australian Air Force. The kangaroo is important to both Australian culture and the national image, and consequently there are numerous popular culture references. Wild kangaroos are shot for meat, leather hides, and to protect grazing land. Kangaroo meat has perceived health benefits for human consumption compared with traditional meats due to the low level of fat on kangaroos.
Terminology The word kangaroo derives from the Guugu Yimithirr word gangurru, referring to eastern grey kangaroos. The name was first recorded as "kanguru" on 12 July 1770 in an entry in the diary of Sir Joseph Banks; this occurred at the site of modern Cooktown, on the banks of the Endeavour River, where HMS Endeavour under the command of Lieutenant James Cook was beached for almost seven weeks to repair damage sustained on the Great Barrier Reef. Cook first referred to kangaroos in his diary entry of 4 August. Guugu Yimithirr is the language of the people of the area. A common myth about the kangaroo's English name is that it was a Guugu Yimithirr phrase for "I don't know" or "I don't understand". According to this legend, Cook and Banks were exploring the area when they happened upon the animal. They asked a nearby local what the creatures were called. The local responded "kangaroo", said to mean "I don't know/understand", which Cook then took to be the name of the creature. Anthropologist Walter Roth was trying to correct this legend as far back as in 1898, but few took note until 1972 when linguist John B. Haviland in his research with the Guugu Yimithirr people was able to confirm that gangurru referred to a rare large dark-coloured species of kangaroo. However, when Phillip Parker King visited the Endeavour River region in 1819 and 1820, he maintained that the local word was not kangaroo but menuah perhaps referring to a different species of macropod. There are similar, more credible stories of naming confusion, such as with the Yucatán Peninsula. Kangaroos are often colloquially referred to as "roos". Male kangaroos are called bucks, boomers, jacks, or old men; females are does, flyers, or jills; and the young ones are joeys. The collective noun for a group of kangaroos is a mob, court, or troupe.
Taxonomy and description
There are four extant species that are commonly referred to as kangaroos:
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