Emu

Name and taxonomy

The scientific name of the emu is Dromaius novaehollandiae. Dromaius comes from a Greek word for a runner, and the species name is the Latin form of New Holland. New Holland was the European name for Australia when John Latham described the bird in 1790. The whole name therefore reads as the fast-footed bird of New Holland.

Nobody is certain where the English word emu came from. One account traces it to an Arabic word for a big bird that Portuguese sailors applied to the cassowary. Another points at the Portuguese word ema, used for an ostrich or a crane. Australian languages had their own names, among them barrimal in Dja Dja Wurrung and murawung in the Sydney basin. Arthur Phillip's book of 1789 first put the bird in print, under the name New Holland cassowary.

Evolution and relatives

Emus are ratites, the group of flightless birds that also holds ostriches, rheas, kiwis and cassowaries. The cassowaries are the nearest living relatives of the emu. A study of mitochondrial DNA in 2014 moved the emu into a family of its own, Dromaiidae. That work left the cassowaries alone in Casuariidae and placed both families in the order Casuariiformes.

Australia held more than one emu when Europeans arrived. Dwarf forms lived on Kangaroo Island, King Island and Tasmania, and all three died out in the 1800s. The Tasmanian bird was gone by about 1865. The mainland bird remains common, and the plumage differences across the continent probably reflect soil and rainfall rather than separate races.

Appearance

An emu stands 150 to 190 centimetres tall and weighs 18 to 60 kilograms. Males average about 31.5 kg and females about 37 kg, and females are broader across the rump. The plumage is shaggy and grey-brown, with black shafts and black feather tips. Each feather carries two shafts from one base, which is unusual among birds. Dark tips soak up the sun while the inner down keeps the heat off the skin.

The neck is pale blue and the sparse feathers on it hide little. The legs carry no feathers and the feet have three toes with thick pads beneath. Each toe ends in a claw, and the toe and claw together run to 15 cm. The wings are stubs about 20 cm long, each with a small claw at the tip. Birds on red desert soils look rusty, while birds in damp country look darker.

Habitat and range

Emus range across nearly all of mainland Australia, inland and near the coast. They do best in savanna woodland and in dry sclerophyll forest. They are scarce in crowded districts and in country with under 600 millimetres of rain a year. Bores and dams sunk for livestock have carried the bird deeper into the interior. The east coast, where emus were once ordinary, now holds few of them.

The bird travels to find feed, and it can cover hundreds of kilometres in a season. The Australian Museum records daily movements of 15 to 25 kilometres during such journeys. Western Australian birds run north in summer and south in winter. Birds on the east coast wander with no clear pattern that anyone has found. Pairs are the usual unit, and a large mob forms only where food draws many birds together.

Diet and feeding

The emu is an omnivore that feeds by day and takes whatever the season offers. Acacia seed, casuarina and fresh grass make up much of the plant food. Grasshoppers, crickets, beetles, ants, spiders and moth caterpillars supply most of the protein. Wheat and orchard fruit go the same way, and a hungry emu climbs a high fence to reach them. The bill is small and soft, and it suits grazing rather than tearing.

There is no crop to hold food, so the bird swallows small stones to grind it in the gizzard. One stone may weigh 45 grams, and a bird may carry 745 g of them at once. Emus also swallow charcoal, and nobody has explained why. They drink about once a day, and they inspect the water in a group before they kneel to it. An undisturbed bird may drink for ten minutes, and it can then go several days without water.

Behaviour and social life

Emus are active by day and spend it feeding, preening, dust bathing and resting. They swim well but enter water only in a flood or to cross a river. Sleep comes in short pieces, and a bird wakes about every ninety minutes to feed or to pass droppings. Deep sleep folds the neck into an S and lowers the body to the ground. The shape of a sleeping emu is thought to pass for a low mound at a distance.

Heat holds no terror for the bird, because panting turns its lungs into a cooling system. Cold air warms in the folded nasal passages, and moisture is taken back out of each breath. An emu keeps a steady body temperature from minus 5 to 45 degrees Celsius. Curiosity is strong, and a wild emu will follow a person to see what happens. Captive birds peck another animal and then run off, which probably works as play.

Communication and senses

The emu booms, drums and grunts, and it makes no song of any kind. An inflatable pouch in the throat produces the boom, and the bird sets the pitch by the size of the opening. The pouch runs more than 30 centimetres long and swells in the breeding season. A loud boom carries about 2 kilometres across open country. Females do most of the booming, in courtship, in holding ground and in threatening a rival.

Males do most of the grunting, and they use it in defence of a territory and while the female lays. Both sexes call when a strange object appears. Eyesight and hearing are both sharp, and a bird spots trouble a long way off. Clear inner eyelids sweep sideways across the eye and keep blown dust out of it. Body language matters in courtship, and the birds strut with snaking movements of the head and neck.

Reproduction and life cycle

Pairs form in the Australian summer, in December and January, and may hold together for about five months. Mating follows between April and June, in the coolest part of the year. Females do the courting, and they fight each other for a male more often than males fight. A contest over an unattached male can run for five hours. Bare skin below the eye turns turquoise-blue in a courting female.

The male scrapes a flat nest in a sheltered hollow and lines it with bark, grass, sticks and leaves. The female lays one very large green egg every second or third day, for a clutch of 5 to 15. An egg measures about 13 cm by 9 cm and weighs 450 to 650 grams. The shell is about 1 millimetre thick and dark green, and it bleaches white in the sun if it never hatches. Several females may add eggs to one nest, so a nest can hold 15 to 25 in all.

The male sits for 56 days and turns the eggs about ten times a day. He does not eat, drink or pass droppings, and he lives on stored fat and on dew. He loses a third of his weight over the eight weeks. Chicks hatch striped brown and cream, stand about 12 centimetres tall and weigh half a kilogram. The father guards them for up to seven months, and they reach full size in five or six.

Predators and threats

The dingo is the main predator of a grown emu, and it goes for the head and neck. An emu answers by jumping and kicking down at the dingo as it lands. The jump is well timed, because a dingo cannot spring high enough to reach a raised neck. The wedge-tailed eagle is the only bird that can take a full-grown emu, and it stoops at the head. Against an eagle the jump fails, so the emu runs in the open and swerves to shake the bird off.

Eggs and small chicks are the vulnerable stage, and dingoes, foxes, feral pigs, dogs and monitor lizards all take them. The guarding male drives attackers off with grunts, raised feathers and kicks. Vehicles kill emus on outback roads, and cleared and broken habitat costs the bird more. Lice, ticks, mites and several roundworms infect the species, though farmed emus carry fewer parasites than ostriches.

Population and conservation

The IUCN Red List rates the emu as Least Concern. A census in 1992 put the total at 630,000 to 725,000 birds. Numbers rise and fall with the rain from one decade to the next. The occupied range covers between 4,240,000 and 6,730,000 square kilometres.

Mainland numbers are probably higher now than they were before European settlement. Some local populations are still at risk, and New South Wales lists the north coast birds as endangered. Killing was once official policy, and culls in Western Australia reached 57,000 birds in the 1930s. Wild emus now have legal protection under Australian environment law. Naturalists have logged 12574 emu observations on iNaturalist.

Relationship with humans

Aboriginal Australians hunted the emu for meat and used every part of the carcass. Fat became oil for skin, tools and paint, bones became knives and tendons became string. Hunters speared birds at waterholes, netted them, or drew them in by imitating their calls. A ball of rags hung from a tree worked as bait, because the bird came to look. The rule was to kill only from need, and hunting for any other reason met disapproval.

European settlers ate emus and burnt the fat in lamps. In 1932 the Australian army took machine guns to birds raiding wheat in Western Australia. The emus scattered and mostly escaped, and the episode is remembered as the Emu War. Commercial farming began in Western Australia about 1970, and farms now run in North America and elsewhere. The birds yield meat, leather, feathers, eggs and oil, and about 95% of a carcass is used.

In culture and myth

Many Aboriginal groups read a giant emu in the dark clouds that break up the Milky Way. Its head is the Coalsack, the black patch beside the Southern Cross, and the body trails towards Scorpius. The Wiradjuri call that figure Gugurmin, and it served as both a calendar and a guide for travel. The Yuwaalaraay of New South Wales tell how the sun began when an emu egg was thrown into the sky. A Western Australian story turns a man into a flightless emu after a small bird cuts off his arms.

The Kaurna of the Adelaide region hunt the emu, kari, in the Tjilbruke story. Emus appear in Sydney rock engravings and in Aboriginal dance. The bird stands beside the red kangaroo on the coat of arms of Australia and on the 50-cent coin. Around six hundred gazetted Australian place names contain the word emu. Rod Hull's puppet emu made the bird a comic figure on British television for years.