The Emu, Dromaius novaehollandiae, is the largest bird native to Australia and the only existing member of the genus Dromaius. It is also the second largest bird in the world by height, after the ostrich. The Emu is common over most of mainland Australia, although it avoids heavily populated areas, dense forest and arid areas. There are three existing subspecies in Australia:
- In the southeast, D. novaehollandiae novaehollandiae.
- In the north, D. novaehollandiae woodwardi.
- In the southwest, D. novaehollandiae rothschildi.
The soft-feathered, brown, flightless birds reach up to 6.5 feet in height and weigh up to 100 pounds. Emus have brown to grey-brown plumage of shaggy appearance. The shafts and the tips of the feathers are black. Solar radiation is absorbed by the tips, and the loose-packed inner plumage insulates the skin. The resultant heat is prevented from flowing to the skin by the insulation provided by the coat, allowing the bird to be active during the heat of the day. A unique feature of the Emu feather is its double rachis emerging from a single shaft. The sexes are similar in appearance.
Emus can travel great distances at a fast, economical trot and, if necessary, can sprint at 31 mph for some distance at a time. They are nomadic and may travel long distances to find food. They feed on a variety of plants and insects. They have small vestigial wings and a long neck and legs. Their ability to run at high speeds is due to their highly specialized pelvic limb musculature. Their feet have only three toes and a similarly reduced number of bones and associated foot muscles; they are the only birds with gastrocnemius muscles in the back of the lower legs. On very hot days, Emus pant to maintain their body temperature.
Emus form breeding pairs during the summer months of December and January, and may remain together for about five months. Mating occurs in the cooler months of May and June. During the breeding season, males experience hormonal changes, and their testes double in size. Males lose their appetite and construct a rough nest in a semi-sheltered hollow on the ground from bark, grass, sticks and leaves. The pair mates every day or two, and every second or third day the female lays up to 20 very large, thick-shelled, dark-green eggs.
The male becomes broody after his mate starts laying, and begins to incubate the eggs before the laying period is complete. From this time on, he does not eat, drink or defecate, and stands only to turn the eggs, which he does about 10 times a day. Over eight weeks of incubation, he will lose a third of his weight and will survive only on stored body-fat and on any morning dew that he can reach from the nest. Some females stay and defend the nest until the chicks start hatching, but most leave the nesting area completely to nest again. An Emu may nest three times in a single year.
Incubation takes 56 days, and the male stops incubating the eggs shortly before they hatch. Newly hatched chicks are active and can leave the nest within a few days. They stand about 10 inches tall and have distinctive brown and cream stripes for camouflage, which fade after three months or so.
The male stays with the growing chicks for up to 18 months, defending them and teaching them how to find food. Chicks grow very quickly and are full-grown in 12″“14 months. They may remain with their family group for another six months or so before they split up to breed in their second season. In the wild, Emus live between 10 to 20 years, captive birds can live longer than those in the wild.
Their calls consist of loud booming, drumming and grunting sounds that can be heard up to 1.25 miles away. The booming sound is created in an inflatable neck sac. Emus forage in a diurnal pattern. They eat a variety of native and introduced plant species. They also eat insects, including grasshoppers and crickets, ladybirds, soldier and saltbush caterpillars and cotton-boll moth larvae and ants. Emus may serve as an important agent for the dispersal of large viable seeds, which could contribute to the maintenance of floral biodiversity.
Wild Emus are formally protected in Australia under the Environment Protection and Biodiversity Conservation Act 1999. Although the population of Emus on mainland Australia is thought to be higher now than before European settlement, some wild populations are at risk of local extinction due to small population size. Threats to small populations include the clearance and fragmentation of areas of habitat, deliberate slaughter, collisions with vehicles, and predation of the young and eggs by foxes, feral and domestic dogs, and feral pigs.
Emus are farmed primarily for their meat, leather and oil. Emu meat is a low-fat, low-cholesterol meat. Despite being avian, it is considered a red meat because of its red color and pH value. The best cuts come from the thigh and the larger muscles of the drum or lower leg. Emu fat is rendered to produce oil for cosmetics, dietary supplements and therapeutic products. There is some evidence that the oil has anti-inflammatory properties as well. Emu leather has a distinctive patterned surface, due to a raised area around the hair follicles in the skin; the leather is used in such small items as wallets and shoes, often in combination with other leathers. The feathers and eggs are used in decorative arts and crafts.