They are the second largest flightless birds in the world, next to the ostrich. Their calls consist of loud booming, drumming and grunting sounds that can be heard up to two kilometres away. The soft-feathered, brown birds reach up to 2 metres in height and weight up to 45kg. They can travel great distances at a fast, consistent trot and can sprint at 50km/hour (31mph).
The female lays an average of 11 very large, thick-shelled, dark-green eggs. Each egg is roughly equivalent to 10-12 chicken eggs in volume and weight. The male becomes broody and begins to incubate the eggs. From this time on, he does not eat, just drinks occasionally 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. Newly hatched chicks are active and can leave the nest within a few days. They stand about 25 centimetres 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 then and teaching them how to find food.
They have great eyesight and hearing. Emu are farmed for their meat, oil and leather. Through time, they lost the ability to fly as this skill was no longer necessary for their survival. They developed long, strong, powerful legs instead.
The natural enemies of emus are wedge-tailed eagles, and dingoes that take young emus. Nest robbers such as various lizards, mammals and birds will raid unguarded nests. Black-breasted buzzards will drive the male emu off the next and then drop stones on the eggs to break them.