Red kangaroo

Name and taxonomy

Anselme Desmarest described the species in 1822 from an animal taken somewhere west of the Blue Mountains. He placed it in the genus Kangurus. John Gould moved it to Osphranter in 1842, a name later sunk into Macropus as a subgenus. A 2015 revision of Australian mammals raised Osphranter to a full genus again, and genetic work in 2019 agreed. So the red kangaroo now shares its genus with the wallaroos rather than the grey kangaroos.

The word kangaroo comes from gangurru in the Guugu Yimithirr language of north Queensland, the name of a grey kangaroo. The old story that it means I do not know, told of Cook and Banks, is false. Australians call a big male a Big Red, a female a flier and a male a boomer. No subspecies is recognised, so the species is monotypic.

Evolution and relatives

Kangaroos belong to the order Diprotodontia, along with koalas, wombats and possums. Within it, the family Macropodidae holds the kangaroos, wallaroos and wallabies. The red kangaroo sits in the genus Osphranter with the common wallaroo and its relatives. Its diploid chromosome number is 20. Like other kangaroos, it descends from small possum-like ancestors that came down to the ground as Australia dried.

Body size in the species increases with latitude, following Bergmann's rule. Blue-grey males, red females and mixed forms occur, so colour alone does not fix the sex. Genetic studies show female gene flow across distances of up to 1,000 kilometres, so populations mix widely.

Appearance

The red kangaroo is large, lean and muscular, with long pointed ears and a short square muzzle. Black and white marks line the side of the muzzle, and a pale stripe runs from mouth to ear. A male measures 130 to 160 centimetres from head to rump, plus a tail of up to 120 cm. A female measures 85 to 105 cm, with a tail of 65 to 85 cm. Males weigh 55 to 90 kilograms, about twice a female's 18 to 40 kg. Standing, a typical adult reaches 1.5 metres and a big male more than 1.8 m.

Males are brick red with pale buff underparts and limbs, and females are blue-grey with a brown tinge. In the arid zone many females are coloured like males. The fur is short and dense. Adult males often show pink staining on the chest and neck.

The forelimbs are short with small clawed paws, used to eat, groom and fight. The hind limbs are heavily muscled, and the second and third toes are fused into a grooming claw. The tail is thick enough to hold the body upright as a third leg of a tripod. The eyes give a field of view of about 300 degrees. Males grow far larger shoulders and arms than females, which helps in fights.

Habitat and range

The red kangaroo lives across western and central Australia, wherever the country is dry. It is absent from the wetter margins: the south-west of Western Australia, the east and south-east coasts, and the northern rainforest. It favours open plains where annual rainfall averages under 500 millimetres. Typical country is chenopod shrubland, mulga, brigalow, sandplain and hummock grassland, and floodout plains near ranges. It almost never enters hilly ground, and it needs scattered trees or shrubs for shade.

Density is highest in the semi-arid rangelands of New South Wales and Queensland. Two studies put density at 4.18 animals per square kilometre and at one animal per 89 hectares. Weekly home ranges in New South Wales cover 258 to 560 hectares, with the largest belonging to adult males. In arid country ranges are far bigger: 1,840 hectares for males and 3,680 for females on average. GBIF holds records from only 3 countries, which shows how confined the species is to Australia.

When grass fails and rain falls in patches, kangaroos travel 25 to 30 kilometres to fresh growth, then often return. One animal was recorded moving 216 km, and spontaneous journeys over 300 km are known. Kangaroos moved 13 to 20 km away found their way home.

Diet and feeding

The red kangaroo is a grazer that eats green grass, forbs and other flowering plants. In central Australia green grass made up 75 to 95 percent of the diet in one study, with Eragrostis setifolia alone at 54 percent. That grass stays green into the dry season. In western New South Wales the grass Enneapogon avenaceus formed 21 to 69 percent of the diet. Forbs can make up 38 to 99 percent of the food, depending on season.

The animal selects carefully, preferring grass and forbs and avoiding saltbush, bluebush and trees when it can. In drought it turns to those shrubs and to acacia, cassia and eremophila. Females in drought eat a higher share of grass and forbs than males do. It finds enough green feed even when the country looks brown.

The red kangaroo can go a long time without drinking, because its kidneys concentrate urine and it takes water from plants. It tolerates plants high in salt. In hot weather it visits water for brief drinks of about 9 to 12 minutes, mostly at dusk. Grazing fills most of its active hours, with feeding peaks 3 to 5 hours after sunset and around sunrise.

Behaviour and social life

Red kangaroos live in loose groups called mobs, most often of 2 to 4 animals. Membership changes constantly, and a group can reach 25. The usual group is females with their young, sometimes with a male. Where forage is rich, gatherings of up to 1,500 have been seen. In a bigger group each animal scans less and feeds more.

The species is crepuscular and nocturnal, and it rests in shade through the day. In extreme heat it shelters under saltbush or mulga rather than in caves or rocks. It cools itself by panting, sweating, licking its forearms and digging hip holes in the shade. It can also enter torpor to save energy. The body stays close to 36 degrees Celsius.

Males are not territorial, and they fight only over females in heat. Young males box: they stand on their hind legs and jab, lock forearms or push to unbalance a rival. If a fight escalates, a male leans back on his tail and kicks with both hind feet. Red kangaroo fights involve more wrestling than those of other kangaroos. A defeated male lives alone and avoids contact. Large males rove alone through their ranges to check on the breeding state of females.

Communication and senses

Little is recorded about red kangaroo calls. Males test a female's condition by making her urinate, sniffing the stream and curling the lip in a flehmen grimace. Like most mammals, they probably rely heavily on scent for social information. Vision and hearing are excellent, and the eyes cover about 300 degrees. A kangaroo in a big group looks up less often, which suggests the group shares the watch.

Reproduction and life cycle

The red kangaroo breeds all year when conditions allow. Females mature from 15 to 20 months and males from 20 to 24 months, though drought can delay both. A female first breeds at about two and a half years in normal times, or as late as five years in drought. The dominant male guards a female in heat against up to ten rivals. Mating lasts 10 to 25 minutes, sometimes in several short bouts.

Gestation is only 33 days. The newborn is blind, hairless and about 2.5 centimetres long, weighing around 0.75 grams. It climbs through its mother's fur into the forward-facing pouch in three to five minutes and fixes on one of four teats. Within a day or two the mother mates again, and the new embryo halts at the blastocyst stage. This pause, called embryonic diapause, lasts until the pouch joey is about 204 days old or is lost.

The joey first pokes its head out at about 190 days and leaves the pouch for good at about 235 days. It suckles as a young-at-foot until about 12 months. A mother can support three young at once: one at foot, one in the pouch and one embryo on hold. The milk from each teat matches the age of the joey drinking it. In good seasons a female raises about three young every two years. Wild red kangaroos have lived up to 22 years, though most die in their first year.

Predators and threats

An adult red kangaroo is too big for most predators. Dingoes and wedge-tailed eagles take joeys, and a dingo pack or a pair of eagles occasionally kills an adult. Saltwater crocodiles take kangaroos where the two meet. A kangaroo defends itself with kicks and blows, and it swims well. If chased into water, it may hold the attacker under with its forepaws.

People are the main predator today, through hunting, culling and road kills. Livestock and rabbits compete for the same grass. Drought is the natural check on numbers, because it stops breeding and kills young. Some habitat has gone to towns and intensive farming.

Population and conservation

The IUCN rates the red kangaroo as Least Concern. It is widespread and locally common, well represented in reserves, and faces no major threat. Farm dams, cleared pasture and fewer dingoes have let it spread and grow denser in places. Nearly 3 million square miles of Australia lies inside national parks.

All Australian states regulate kangaroo hunting, and shooting on farms needs a permit in Queensland and New South Wales. Commercial harvest runs in New South Wales, Queensland, South Australia and Western Australia under national management plans. In 2000, 1,173,242 red kangaroos were killed. In 2009 the government set a limit of 1,611,216 for commercial use. In 2023 over half a million were harvested across Australia. The harvest is controversial because the animal is so popular.

Relationship with humans

Aboriginal people in central Australia have hunted the red kangaroo for food for a very long time, and still do. The kangaroo industry is worth about 270 million Australian dollars a year and employs over 4,000 people. The meat feeds people and pets, and it is lean, with only about 2 percent fat. The skins make strong leather.

Kangaroos dazzled by headlights leap in front of cars, and a strike through the windscreen can kill the occupants. Crashes peak between 5 and 10 in the evening, in winter, and after long dry spells. Kangaroo crossing signs stand along roads across the country. Graziers see the animal as a pest that eats grass meant for sheep. Yet it avoids paddocks where sheep graze heavily, while it shares ground with cattle.

The red kangaroo is protected by law like all Australian wildlife, and it is a national icon. It appears on the coat of arms and on the tail of the national airline.

In culture and myth

The kangaroo is one of the emblems of Australia, and the red kangaroo is the biggest of them. It stands with the emu on the national coat of arms, and the flying kangaroo marks Qantas aircraft. The word came into English from the Guugu Yimithirr people of north Queensland at the time of Cook's voyage. A popular tale says the locals answered I do not know, but gangurru really names a grey kangaroo.

In Aboriginal tradition the kangaroo is a food animal, and it probably features in Dreaming stories and rock art across the interior. The boxing of males is likely the origin of the boxing kangaroo image used by Australian sports fans. The blue flier and the Big Red are folk names that entered bush speech. With the koala, the kangaroo is likely the first animal most people picture when they think of Australia.