Emu chicks emerging › Nature Features (ABC Science)

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Emu chicks emerging

Across inland Australia, thousands of striped emu chicks are beginning to appear. While most birds wait for longer days in spring before breeding, for Emus it’s reversed. It’s shortening days that switch on their reproduction instincts. And that’s not the only reversal. It’s broody males that spend uncomfortable winter weeks on the nest, without food or drink, before doing sole parent duty for the next year and a half.

Emus belong to an ancient group of flightless birds known as ratites, which includes the cassowary, the kiwi, the ostrich and rhea. Ratites are one of the earliest offshoots in bird evolution so have a special place in evolutionary studies.

The emu is common throughout much of inland Australia except for dense rainforest and areas that are waterless or highly urban.

The most likely place to see them, though, is open pastoral country. They’re very inquisitive birds and are the source of many tourist stories about the swallowing of keys and bits of cameras.

In Queensland, around the Warrego and Bogan rivers, Aboriginal hunters would lure emus by climbing a tree, lowering a ball of emu feathers and rags and twirling it rapidly. The fascinated emus would gather near the tree and be speared from above. They need to be lured because there’s no way to catch up with an emu. At speeds of up to 70 km/hour, emus really can “run the pants off a kangaroo”.

Emus are also good swimmers. They love water and on a hot day like nothing better than a cool dip in the creek, the dam, the horse trough or even under the sprinkler.

Fact file:

When: Male and female emus start pairing up around December or January – anytime after the summer solstice on December 21-22.

Where: East coast of Australia

Pairing up

Emus in wandoo woodlands, Western Australia (Source: Kip Venn /)

Male and female emus start pairing up around December or January – anytime after the summer solstice on December 21-22. Emu courting is a lively affair. The sound alone is said to be unforgettable. The birds, particularly females, fill their throat pouches with air to make a drumming sound, which can be heard hundreds of metres away.

Feathers are fluffed and there’s a lot of dipping and ducking, grunting and bobbing around. The males may also fight, chasing each other away from females by powerful frontal kicks.

Broody blokes

Around April, as the days get noticeably shorter, mating begins. In some parts of the country, mating is also timed to start just before the rainy season. If the rains are late then the emus will delay breeding. The reason for this link is yet unknown.

Emus are very seasonal. University of Western Australia researchers have found that short days (photoperiod) depress the birds appetites, particularly the males, and trigger hormones that stimulate their breeding.

The pair mate every day or so, with the female laying an egg every two or three days, until a clutch is formed. Most clutches have about 8 to10 eggs but can go as high as 20.

After about seven eggs the male gets ‘broody’ and sits on them for the entire incubation period. It takes eight weeks (56 days) to hatch an emu chick! During this time he doesn’t eat or drink, just living off his fat and any nearby dew on the grass. The only time he stands up is to turn the eggs, which he does 10-12 times a day. The father also stays and looks after the chicks for up to 18 months, leading them to feeding areas and showing them what to eat.

Shabby female behaviour: the girls take off

As soon as the male goes broody the female stops mating with him, although she often continues to lay eggs in the nest. These eggs, however, can be fertilised by other male emus. One survey of 106 chicks showed 51 per cent were not fathered by the nesting male! Eventually the female leaves the first male altogether. She may mate with one or two other males after the first one and can have up to three nests per season, especially if the rains have been good.

Male emus seem to be able to count to about seven (Source: Graeme Martin/)

Masculine sacrifice

The broody male loses up to a third of his body weight and becomes increasingly dazed and forlorn. It’s thought he could be in a state of ketosis – when the body’s metabolism burns only fat it produces ketones which are toxic.Incubating males also experience a rapid fall in testosterone. By midsummer, though, males are able to aggressively protect their young.

As to the advantages of breeding in autumn-winter, this means that the chicks will hatch two months later in spring, when the weather is warmer and there is the best chance of food being around.

The chicks begin to hatch as early as June and as late as the beginning of September. July and August are generally the peak times. In the wild there is a very high predation rate on the eggs but scientist Stephen Davies says if the chicks manage to hatch out they then have about a 70-80% chance of reaching adulthood.

Chicks grow very quickly putting on 1 kg/week at first. They reach their full height when they’re about a year old, but don’t breed until their 2nd year, at about 20 months.

Emus are well adapted to Australian conditions (Source: Kip Venn/)

Survival in a hot dry land

Emus are well adapted for living in a hot dry land. Unlike other animals such as kangaroos, emus remain active even in the hottest parts of the day, foraging and walking. Scientists Shane Maloney and Terry Dawson have found that the emus two-tone plumage gives them very clever protection from the sun. The trick is in the colour.

The black tips of emu feathers absorb large amounts of heat from the sun, but the rest of their plumage then keeps that heat away from the bird’s skin. Only about two per cent of the solar radiation that hits an emu gets through to the skin. Any wind then convects the heat in the feather tips away from the bird.

The emus walking speed, about one to two metres per second, provides just the right amount of breeze to remove this absorbed heat. Without their feathers the heat load on an emu on a hot day would be more than they could dissipate and they would soon succumb to heat stroke.

Why you can’t see emus breathing on a cold morning

Emus noses are well-adapted for saving water. They have large highly folded passages called nasal turbinates. Cool air breathed in, passes through these passages and is warmed on its way to the emus lungs. But warming up the air causes the emus nose to get colder. So, when the emu breathes out warm air, it travels back through the emus cold nose, gets cooled and water condenses. The water is then reabsorbed into the body.

In the hot times of the year emus often use a different strategy ñ panting ñto keep cool. They increase the rate of their breathing which in turn increases the amount of water evaporated from the emu into the air. This cools them, but does mean the emu must drink regularly.

Emus can pant for hours without getting light-headed from low levels of carbon dioxide (alkalosis). Humans trying the same thing would quickly be out for the count.

Their diet in the wild varies quite widely. They like green autumn shoots, winter herbs, seeds, and some fruits and flowers. They’ll eat insects when they’re available, such as grasshopper plagues. Green shoots of wheat and later on ripe wheat are also regarded favorably. They need to drink every day.

Emu Farming

Emu farming took off in Australia in 1988 when the West Australian government permitted the Aboriginal owners of Willuna Station to sell emu chicks to the public. (Emus are protected and no one is allowed to take birds from the wild.)

With a legal supply of chicks, both Aboriginal and non-Aboriginal people began to develop emu farms and find markets for emu products. In the early 1990s the industry boomed but high set up costs and limited market outlets have since cut the industry back to a much smaller size. There are around 160 emu farms in Australia, with a total of about 32,000 emus.

Emu farmer, Kip Venn, says 5000–7000 emus makes a reasonable sized farm. Also, Kip says that with a stocking rate about 5 emus/acre, they’re so easy on the land you can’t see where they’ve been.

Some farms like Kip’s are free range – the emus are allowed room to roam. He has 20 emus per one four-acre pen, and lets them choose their own mate. Initially some farms farmed more intensively and ‘force paired birds’ but high food and labour costs have lead to a more open range approach.

On the Venn’s farm about 80&38211;90 per cent of eggs successfully hatch. Rather than the male sitting on the eggs, many farms incubate the eggs and rear the chicks separately. Foxes and other pests can be a problem if eggs are left in open.

Emu products include meat, oil, leather and feathers. Most Australian states have at least one specialist emu abattoir.

White settlers in Australia used to hunt emus for their meat and their oil, which they used in lamps. Outback housewives made omelettes from their eggs, which they first broke into a basin and let stand overnight so they could skim off the oil which rose to the top. The eggs weigh about 650 grams. If you’re cooking with them the rule of thumb is one emu egg equals about 10–12 normal chicken eggs.

Emus were made extinct in Tasmania in 1865 by settlers and sealers who killed large numbers for food. They’re also extinct on Kangaroo Island and King Island.

How many emus?

There’s an average of about 500,000 emus in the wild in Australia, but this varies highly depending on the season. Numbers can rise towards a million, and fall to about 200,000. Even then the population seems to be able to bounce back quickly, probably because the females can produce three clurches of eggs in good years. Emu numbers never reach the 6 million like kangaroos. Kangaroos can time their reproduction much more precisely to fit in with the rains.

With large soft feet, emus can be very gentle on the land (Source: Kip Venn/)

Emus on the move

Emus move to keep contact with food supplies. Some people call them migratory but ‘roaming’ or ‘nomadic’ is more appropriate.

In Western Australia there’s a definite movement of emus southward in winter and northward in summer. At this time emus will travel 900-1000 km This is most probably tied to rainfall – they follow the green grass. West Australian scientist Stephen Davies, thinks they may use cloudbanks to navigate.

All birds move except incubating males. Barriers like rabbit and emu proof fences have made these migrations much more difficult. However by adding extra watering sites for domestic animals in more arid areas, pastoralists have probably helped emus to stay longer in some areas before going south. When they’re on the move emus don’t like to travel in big flocks. It’s unusual for them to be in groups of more than 20, except when they hit artificial barriers.

Migrations in Eastern Australian don’t seem to be as easily defined, although eastern emus certainly do travel in response to seasons. In the drought of 1992 there were many reports of emus swimming across the Murray River!

Emus love the water (Source: Graeme Martin/)

Wheat farmers v emus

Wheat trampling by emus is a problem. When wheat is ripe it’s less flexible. Western Australia has a 1100 km emu proof fence stretching from around Esperance in the south to north of Geraldton which keeps them out of the wheat belt. It was built in 1901 and occasionally when emus move out of the pastoral areas south westward in winter they mass along the fence. As many as 70,000 emus have been known to die at the fence.

Once in 1932 the army was also sent out with machine guns to decimate the numbers. In the past, Queensland emus were thought to aid the spread of prickly pear and many were shot there too.

Links

• Emu research projects
  University of Western Australia, Animal Science
• American Emu Association
• Kia Opala
  West Australian emu products
• Everything you need to know about carving emu eggs

References

• The Ratite Encyclopaedia, edited by Claire Denowatz, Ratite Records Inc, San Antonio, Texas, USA, ISBN 0-9642940-2-8
• Blache, D., Barrett, C.D. & Martin, G.B. (2000). Social mating system and sexual behaviour in captive Emus, Dromaius novaehollandiae. Emu 100 (in press).
• Blache, D., Malecki, I.A., Williams, K.M., Sharp, P.J. & Martin, G.B. (1997). Reproductive responses of juvenile and adult emus (Dromaius novaehollandiae) to artificial photoperiods. In: Advances in Comparative Endocrinology ó Proceedings of the 13th International Congress of Comparative Endocrinology, Yokohama, Japan (Eds.: S. Kawashima and S. Kikuyama) pp. 445-450 [Monduzzi Editore: Bologna, Italy].
• Blache, D. & Martin, G.B. (1999). Day length affects feeding behaviour and food intake in adult male emus (Dromaius novaehollandiae). British Poultry Science 40, 573-578.
• Maloney SK and Dawson TJ (1995). The heat load from solar radiation on a large, diurnally active bird, the emu (Dromaius novaehollandiae). Journal of Thermal Biology 20: 381-387.
• Maloney SK and Dawson TJ (1998). Changes in patterns of heat loss at high ambient temperature caused by water deprivation in a large bird, the emu. Physiological Zoology. 71: 712-719.
• Malecki, I.A., Martin, G.B., O’Malley, P.J, Meyer, G.T., Talbot, R.T. & Sharp, P.J. (1998). Endocrine and testicular changes in a short-day seasonally breeding bird, the emu (Dromaius novaehollandiae), in southwestern Australia. Animal Reproduction Science 53, 143-155.
• Malecki, I.A., Williams, K.M., Martin, G.B. & Sharp, P.J. (1997). Effects of season and incubation on reproduction in the male emu (Dromaius novaehollandiae). In: Advances in Comparative Endocrinology ó Proceedings of the 13th International Congress of Comparative Endocrinology, Yokohama, Japan (Eds.: S. Kawashima and S. Kikuyama) pp. 431-437 [Monduzzi Editore: Bologna, Italy].
• Sharp, P.J., Malecki, I.A., Williams, K.M. & Martin, G.B. (1997). Neuroendocrine control of broodiness and incubation behaviour in ratites. In: Advances in Comparative Endocrinology ó Proceedings of the 13th International Congress of Comparative Endocrinology, Yokohama, Japan (Eds.: S. Kawashima and S. Kikuyama) pp. 417-422 [Monduzzi Editore: Bologna, Italy].
• Skadhauge E, Dawson TJ, Prys-Jones R and Warui CN (1996). Role of kidney and gut in ratite osmoregulation. pp116-122 in Improving Our Understanding of Ratites in a Farming Environment. Ed. Deeming DC, University of Manchester.
• Sharp, P.J., Talbot, R.T., O’Malley, P., Tan, N.S., Williams, K.M., Blackberry, M.A. & Martin, G.B. (1996). Neuroendocrine control of incubation behaviour in the emu. In: Improving our understanding of ratites in a farming environment (Ed.: D.C. Deeming) pp. 162-164 [Ratite Conference; Oxford Print Centre].
• Taylor, E.L., Vercoe, P.E., Cockrem, J., Groth, D., Wetherall J.D. & Martin G.B. (1999). Isolation and characterisation of microsatellite loci in the emu, Dromaius novaehollandiae, and cross-species amplification within the Parvclass Ratitae. Molecular Ecology 8, 1963-1964.
• Taylor, E.L., Blache, D., Groth, D., Wetherall, J.D. & Martin, G.B. (2000). Genetic evidence for mixed parentage in nests of the emu (Dromaius novaehollandiae). Behavioral Ecology and Sociobiology (6 pp. in press)
• Williams, K.M., Blache, D., Malecki, I.A., Sharp, P.J., Trigg, T.E., Rigby, R.D.G. & Martin, G.B. (1998). Growth, sexual development and carcass composition in intact and surgically or hormonally gonadectomised male and female emus. In: “Ratites in a Competitive World” ó Proceedings of the Second International Ratite Congress, Oudtshoorn, South Africa (Eds.: F.W. Huchzermeyer, H. Lambrechts, D. Swart, S.W.P. Cloete, T.S. Brand and D.J. Verwoerd) pp. 75-80 [De Jongh’s: Strand, South Africa].

Published 01 August 2000