Kangaroo

Kangaroos are marsupials of the subfamily Macropodinae, a name meaning large foot, and are native to Australia and New Guinea. In everyday use the word covers the largest members of the family, including the red, antilopine, eastern grey and western grey kangaroos. They have powerful hind legs, large feet built for leaping, a long muscular tail for balance and a small head. Females carry their young, called joeys, in a pouch where postnatal development is completed. Kangaroos graze, and abrasive grass wears their molars down so that they move forward in the mouth before falling out, replaced by new teeth growing in at the back.

About the kangaroo

A kangaroo is a large hopping marsupial in the family Macropodidae, native to Australia and New Guinea. The name covers the four biggest members of that family: the red, eastern grey, western grey and antilopine kangaroos. Smaller relatives in the same family are called wallaroos and wallabies, and female kangaroos carry their young in a pouch.

"Kangaroo" is a size label rather than a single branch of the family tree. The four species sit in two genera, Macropus (the greys) and Osphranter (the red and the antilopine), and the same family holds roughly 50 smaller macropods. The red kangaroo is the largest surviving marsupial anywhere in the world, while the western grey kangaroo is smaller, with a large male weighing about 54 kg (119 lb).

The body plan is built around the back half. Kangaroos have large, powerful hind legs, long feet made for leaping, a long muscular tail and a small head. Males are much bigger than females: in eastern greys, females weigh up to about 40 kg (88 lb) and males more than twice that, up to 90 kg (198 lb). Eastern greys have an almost white face, an even fur color and a black tail tip, while western greys have a darker face and a white patch on the upper thigh.

The teeth are unusual for a mammal. Lower incisors sit apart on an unfused jaw, giving a wide bite that crops grass close to the ground. Because grass is gritty with silica, the molars wear down, move forward in the mouth and drop out, to be replaced by new teeth growing in at the back. Among other mammals this kind of tooth replacement is known only in elephants and manatees.

Behavior and diet

Kangaroos are the only large mammals that use two-legged hopping as their main way of getting around. A red kangaroo cruises comfortably at about 20–25 km/h (12–16 mph), can sprint at up to 70 km/h (43 mph) over short distances, and can hold 40 km/h (25 mph) for nearly 2 km (1.2 mi). Elastic tendons in the hind legs store about 70% of the potential energy and supply most of the spring for each hop, so moving faster costs surprisingly little extra effort.

At slow speeds the animal walks on five points. It plants its forelimbs and tail, swings the hind feet forward, then repeats. Research has found that the tail pushes with as much force as the front and hind legs combined, acting as a third leg rather than a simple prop. The highest recorded jump for a red kangaroo is about 3.0 m (10 ft).

All kangaroos are strict herbivores. The eastern grey is mainly a grass grazer, while the red kangaroo eats a good share of shrubs too. Kangaroos have a single-chambered stomach, unlike the four-compartment stomach of cattle, though they sometimes bring food back up to chew as cud. Unlike cattle, they release almost no methane; the hydrogen from fermentation is turned into acetate and used for energy instead.

Many kangaroos are nocturnal and crepuscular, resting in shade through hot days and feeding in the cool of evening, night and early morning. They live in mobs that usually number 10 or more. Newcomers greet with nose touching and sniffing, and mothers groom their young. Males also hold long, ritualised "boxing" matches that may help set dominance ranks: they stand tall, lock forearms and wrestle, and balance on the tail to kick at each other's belly.

Breeding is remarkable. After a gestation of only 31–36 days, a blind, hairless joey about the size of a lima bean climbs through its mother's fur into the pouch and latches onto a teat. It usually stays in the pouch for about nine months and keeps nursing until around 18 months. A mother can pause the development of a second embryo until the pouch is free, a process called embryonic diapause, and can make two kinds of milk at once for a newborn and an older joey.

Range and habitat

Kangaroos are native to Australia and New Guinea, and each species has its own region. The red kangaroo lives in the arid and semi-arid center, with its densest populations in the rangelands of western New South Wales. The eastern grey covers the fertile east from Cape York Peninsula to Victoria, plus Tasmania, where it can reach about 100 animals per km² (about 260 per sq mi) in open woodland.

The western grey kangaroo lives across southern Western Australia, coastal South Australia and the Murray–Darling basin. The antilopine kangaroo is the far-northern counterpart of the greys, living on grassy plains and in woodland. Eastern greys use habitats from open woodland and grassland to forested mountains, usually in higher-rainfall areas.

Large kangaroos have coped with farming better than smaller macropods. Clearing land for pasture and adding stock watering points created more grazing, and the Australian government estimated 42.8 million kangaroos in the commercial harvest areas in 2019, down from 53.2 million in 2013.

Kangaroo vs wallaby

Kangaroos and wallabies belong to the same family and often the same genera. The difference is mainly size: "kangaroo" is kept for the four largest species, "wallaroo" for mid-sized ones, and "wallaby" for most of the smaller macropods, such as Bennett's wallaby. Tree-kangaroos like Matschie's tree-kangaroo are a separate, tree-climbing branch of the same family.

Conservation status

All four kangaroo species, red, eastern grey, western grey and antilopine, are rated Least Concern on the IUCN Red List in assessments from 2016. Kangaroos are relatively plentiful despite a common belief to the contrary, while many of the smaller macropods are rare and endangered.

That abundance brings conflict. Kangaroos are shot for meat and hides and to protect grazing land, and some Australians view them as pests that need regular culling. There is concern that current management may harm kangaroo welfare, biodiversity and Aboriginal culture. Kangaroos are also involved in nine out of ten animal-vehicle collisions in Australia.

Natural predators are few. Today the threat comes from dingoes and from introduced foxes, feral cats and domestic and feral dogs. In southern Queensland, about half of young eastern grey joeys do not survive to independence.