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Dromaius novaehollandiaeemu

By George Shorter

Geographic Range

Emus (Dromaius novaehollandiae) are found exclusively in Australia and inhabits nearly the entire continent. Lower densities exist along the eastern coast and toward the center of the island. The number of individuals varies around 700,000, and is dependent on the seasonal rains. (Blakers, et al., 1984)

Habitat

Emus, with their nomadic lifestyle, will occupy nearly all available biomes in Australia. Savannah forest, grassland, and subtropical climates are preferred. Emus tend to gravitate toward areas with standing water and are seen most often in savannah areas. They avoid heavily wooded areas and desertified regions, due to water needs. (Drenowatz, 1995)

  • Range elevation
    0 (low) m
    0.00 (low) ft
  • Average elevation
    330 m
    1082.68 ft

Physical Description

Emus have many physical characteristics in common with the ostrich, which are the only birds taller than the emu. Emus can reach a maximum height of 190 cm, with the average at 175 cm. Emus feet are similar in design to other running birds, having three forward-facing toes and no rearward-facing toes. Emus have long bare legs, similar to other flightless birds Ratites. Emus are the only bird with calf muscles, making them more adapted to sprinting and long distance running. These strength adaptations allow them to sustain speeds up to 13.4 m/s, with an average 3 meter stride. The high strength of these legs allows them to perform extremely powerful kicks capable of breaking through fences or maiming predators. The average weight of an emu is 36 to 40 kilograms, with females being slightly by not significantly larger. Their plumage of shaggy dark brown feathers is not streamlined, as its main purpose is insulation from direct sunlight. This plumage has some variation due to environment, and will often reflect the general hue of its surroundings. Young emus will have additional camouflage in the form of longitudinal tan stripes on their much thinner plumage. Emus have very small vestigial wings capable of flapping, although they do not aid in mobility. They have a long, sparsely covered neck that is whitish-blue. Their heads are covered in wispy black feathers, and have a large black beak specialized for grazing. (Blakers, et al., 1984; Drenowatz, 1995)

  • Sexual Dimorphism
  • female larger
  • Range mass
    36 to 40 kg
    79.30 to 88.11 lb
  • Range length
    190 (high) cm
    74.80 (high) in
  • Average length
    175 cm
    68.90 in

Reproduction

Emus exhibit polyandrous breeding patterns, but not all females engage multiple partners. Mating season begins in December-January, which starts with the male and female emu engaging in a courtship dance. The result is dependent on the male emu's performance; if his it is unsatisfactory the female may become aggressive. Success of the male emu means up to five months of mating privileges with the courted female. Before the female emu lays her eggs, their male counterpart may court other females before being occupied with incubation. After the males begin the incubation period, the female emus will seek to mate with unoccupied males. Most female emus engage in post-mating period polygamy, however not without a cost. Female emus run the risk of losing their mate, which could mean her eggs will not be incubated. To prevent this, some will guard the male from accessing other females. In the relationship, the female emu is most responsible for keeping order in the pair formation, until incubation begins when the male becomes aggressive to all other emus. (Blanche, et al., 2000; Patodkar, et al., 2009)

When emus reach sexual maturity at 18 to 20 months, they engage in mating practices. After pairing, emus will breed until eggs are laid. From insemination, this is 48 to 56 days. Female emus are able to store sperm, allowing them to continue laying eggs every 3 days after her initial clutch. This initial clutch can range from 5 to 24 eggs. She will create more nests if necessary, which will be incubated by another male emu. A single nest may contain the eggs of several females. Male emus are responsible for egg incubation, which starts after the last egg is laid in order to minimize the incubation period. In the incubation period, male emus generally do not consume food, drink, or pass waste; they are able to survive on stored fat alone. After 48 to 56 days of incubation, the all the eggs will hatch within a period of days. The average birthweight is 500 grams. (Blakers, et al., 1984; Blanche, et al., 2000; Dzialowski and Sotherland, 2004; Patodkar, et al., 2009)

  • Breeding interval
    Emus begin their breeding cycle once yearly.
  • Breeding season
    Emus begin breeding in December to January, up to once daily. Nesting occurs around 50 days after breeding.
  • Range eggs per season
    5 to 24
  • Average eggs per season
    10
  • Range time to hatching
    48 to 56 days
  • Average time to hatching
    50 days
  • Range time to independence
    15 to 18 months
  • Average time to independence
    18 months
  • Range age at sexual or reproductive maturity (female)
    18 to 20 months
  • Average age at sexual or reproductive maturity (female)
    18 months
  • Range age at sexual or reproductive maturity (male)
    18 to 20 months
  • Average age at sexual or reproductive maturity (male)
    18 months

After female emus lay their eggs, they have little to do with them other than occasionally visiting the incubating male. Male emus are defensive toward all other emus, and takes great care in protecting the nest. Male emus find a suitable location for their mate's eggs, and will build up a bed of dead grass and foliage surrounded by larger brush. Because this nest is largely flat, male emus take special care to gather the eggs that roll away. Male emus rotate and turn the eggs every few hours to ensure consistency of incubation and hatching time. After hatching, males will protect the flock and teach them how to procure food. Males maintain their aggressive disposition toward all other emus, even the mother. This period of dependence lasts up to 7 months, after which the emus are fully grown. Emus are independent from the flock in 15 to 18 months. (Blakers, et al., 1984; Blanche, et al., 2000; Dzialowski and Sotherland, 2004; Patodkar, et al., 2009)

  • Parental Investment
  • male parental care
  • pre-fertilization
    • protecting
      • male
  • pre-hatching/birth
    • provisioning
      • male
    • protecting
      • male
  • pre-independence
    • provisioning
      • male
    • protecting
      • male
  • extended period of juvenile learning

Lifespan/Longevity

When in captivity, under a regular hydration and feeding schedule, emus are able to live up to 20 years. Emus in the wild experience many more stresses, including dry periods and starvation, which reduces their lifespan to a max of ten years. (Blakers, et al., 1984)

  • Range lifespan
    Status: wild
    5 to 10 years
  • Average lifespan
    Status: wild
    7 years
  • Range lifespan
    Status: captivity
    15 to 20 years
  • Average lifespan
    Status: captivity
    16 years
  • Typical lifespan
    Status: wild
    5 to 10 years
  • Average lifespan
    Status: wild
    7 years
  • Typical lifespan
    Status: captivity
    15 to 20 years
  • Average lifespan
    Status: captivity
    16 years

Behavior

Emus are generally solitary birds, but exhibit social behaviors whenever advantageous. Examples include sharing nests and searching for food. In these instances large groups will migrate all at once to the next food source. During incubation periods emus no longer display nomadic tendencies. Emus are strictly diurnal. When they do sleep, they wake very often due to predatory threats and hydration needs. Emus exhibit a playful curiosity with each other and to other animals, noted particularly in captive environments. An example would be pecking or biting another animal and running away, simply to elicit a response. Emus will swim when presented the opportunity, and are adept at doing so. (Blakers, et al., 1984; Patodkar, et al., 2009)

  • Range territory size
    5 to 10 km^2
  • Average territory size
    7 km^2

Home Range

The home range of emus are 5 to 10 square km. This area is dynamic, as they are always on the move in search of water and food. (Blakers, et al., 1984; Drenowatz, 1995; Patodkar, et al., 2009)

Communication and Perception

Emus have the ability to communicate by using an inflatable neck sack, and can create sounds loud enough to be heard 2 km away. The name "emu" resembles its signature call, heard as "e-moo". Translating these calls is the main form of receiving communication, aside from visually interpreting body language. During courtship, the emu male and female participate in a dance consisting of struts and snake-like head movements. Males must make the correct moves, otherwise the female can rapidly change her mind and become aggressive. (Patodkar, et al., 2009)

Food Habits

Emus primarily feed on fruits, seeds, insects, and small animals. Emus will also feed on animal droppings, and will reject leaves and dry grasses. Emus have no crop for storing or breaking down food, but instead have a modified esophagus that is able to store food upwards of 30 minutes before entering the stomach. Since emus may experience starvation for weeks, they are able to store large amounts of fat in preparation. Emus are able to lose more than half their body mass during these long starvation periods. This adaptation also allows the male emus to endure an entire encubation period without food. (Blakers, et al., 1984; Patodkar, et al., 2009)

  • Animal Foods
  • mammals
  • amphibians
  • reptiles
  • insects
  • terrestrial non-insect arthropods
  • Plant Foods
  • wood, bark, or stems
  • seeds, grains, and nuts
  • fruit
  • Other Foods
  • dung

Predation

The primary predator of emus are dingoes. Dingoes mainly threaten the nests, consuming the eggs. One dingo will distract the incubating male, so that the nest becomes exposed. When attacking emus, predators will target the head and neck. To defend against dingo attacks, emus exploit their height by quickly leaping away. Emus will leap to put distance between the dingo's mouth and their neck. This is often accompanied by a kicking defense, which can be lethal for the dingo. Against eagles and hawks, emus have little practical defense. The wedge-tailed eagle, will attempt to break their neck by tackling them after a dive. Emus can only run wildly and unpredictably, seeking cover (a rarity in their habitat). (Blakers, et al., 1984)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Emus disperse seeds of many low growing plants over wide ranges, because of their nomadic migratory patterns. Some seeds have a specialized coating that, after digestion, increases their chances of sprouting. The emu can impact farmlands that are not fenced in, due to the herd growing nature of migrating emus searching for food. Many small insects fall prey to the emus, who will eat opportunistically. Emus are often hunted by dingoes and hawks. Internal parasites have been documented in emus. Roundworms have caused illnesses and deaths of captice emus via cerebrospinal nematodiasis. Lungworms inhabit respiratory organ and nematodes infect the brains of emus. (Blakers, et al., 1984; Kazacos, et al., 1991; Law, et al., 1993; Rickard, et al., 1997)

  • Ecosystem Impact
  • disperses seeds
Commensal/Parasitic Species
  • roundworms (Baylisascaris procyonis)
  • lungworms (Cyathostoma variegatum)
  • nematodes (Chandlerella quiscali)

Economic Importance for Humans: Positive

Emus produce oil that has been used for medicinal purposes for hundreds of years. A short list of therapeutic effects include lowering cholesterol, treating allergies, preventing scarring and stretch marks, and treating headaches. Tests suggest statistically that emu oil is a superior skin cream to mineral oil-based products. Emus have also been hunted for meat by aboriginal people and contemporary Australians. (Blakers, et al., 1984; Zemstov, et al., 1996)

Economic Importance for Humans: Negative

If given the opportunity, emus will forage on crops. Farmers now install tall fences so emus cannot access farmland. In the early 1930s, a large migration of emus to an agricultural town ended violently. The emus spoiled or consumed vast wheat fields. The military was called in to eradicate the emus in what some call the "Emu War". However the operation was unsuccessful. The emus have natural camouflage and ability to flee, which allowed them to avoid detection. (Blakers, et al., 1984; Johnson, 2006)

  • Negative Impacts
  • crop pest

Conservation Status

The emu lives in abundance in mainland Australia. In Tasmania however, the population was decimated when it was hunted by European settlers.

Contributors

George Shorter (author), Radford University, Karen Powers (editor), Radford University, Kiersten Newtoff (editor), Radford University, Melissa Whistleman (editor), Radford University, Laura Podzikowski (editor), Special Projects.

Glossary

Australian

Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.

World Map

acoustic

uses sound to communicate

agricultural

living in landscapes dominated by human agriculture.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

coprophage

an animal that mainly eats the dung of other animals

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

diurnal
  1. active during the day, 2. lasting for one day.
drug

a substance used for the diagnosis, cure, mitigation, treatment, or prevention of disease

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

food

A substance that provides both nutrients and energy to a living thing.

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

frugivore

an animal that mainly eats fruit

granivore

an animal that mainly eats seeds

herbivore

An animal that eats mainly plants or parts of plants.

insectivore

An animal that eats mainly insects or spiders.

island endemic

animals that live only on an island or set of islands.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

male parental care

parental care is carried out by males

migratory

makes seasonal movements between breeding and wintering grounds

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nomadic

generally wanders from place to place, usually within a well-defined range.

omnivore

an animal that mainly eats all kinds of things, including plants and animals

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

sperm-storing

mature spermatozoa are stored by females following copulation. Male sperm storage also occurs, as sperm are retained in the male epididymes (in mammals) for a period that can, in some cases, extend over several weeks or more, but here we use the term to refer only to sperm storage by females.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

visual

uses sight to communicate

References

Blakers, M., S. Davies, P. Reilly. 1984. The Atlas of Australian Birds. Melbourne, Australia: Melbourne University Press.

Blanche, D., C. Barrett, G. Martin. 2000. Social mating system and sexual behaviour in captive Emus Dromaius novaehollandiae. The Journal of the Royal Australasian Ornithologists' Union, 100/3: 161-168.

Coddington, C., A. Cockburn. 1995. The mating system of free-living emus. Australian Journal of Zoology, 43/4: 365-372.

Drenowatz, C. 1995. Ratite Encyclopedia: Ostrich, Emu, Rhea. United States: Ratite Records, Inc.

Dzialowski, E., P. Sotherland. 2004. Maternal effects of egg size on emu Dromaius novaehollandiae egg composition and hatchling phenotype. The Journal of Experimental Biology, 207: 597-606.

Johnson, M. 2006. Feathered foes: Soldier settlers and western Australia's emu war of 1932. Journal of Australian Studies, 30/88: 147-157.

Kazacos, K., S. Fitzgerald, W. Reed. 1991. Baylisascaris procyonis as a cause of cerebrospinal nematodiasis in ratites. Journal of Zoo and Wildlife Medicine, 22/4: 460-465.

Law, J., T. Tully, T. Stewart. 1993. Verminous encephalitis apparently caused by the filarioid nematode Chandlerella quiscali in emus (Dromaius novaehollandiae). Avian Diseases, 37/2: 597-601.

Panigrahy, B., D. Senne, J. Pearson. 1995. Presence of avian influenza virus (AIV) subtypes H5N2 and H7N1 in emus (Dromaius novaehollandiae) and rheas (Rhea americana): Virus isolation and serologic findings. Avian Diseases, 39: 64-67.

Patodkar, V., S. Rahane, M. Shejal, D. Belhekar. 2009. Behavior of emu bird (Dromaius novaehollandiae). Veterinary World, 2/11: 439-440.

Rickard, L., L. Steinohrt, S. Black. 1997. Subclinical cyathostomiasis and unidentified helminthiasis in a juvenile emu (Dromaius novaehollandiae). Avian Diseases, 41/4: 993-996.

Roderick, M., A. Stuart. 2010. The status of threatened bird species in the Hunter Region. The Whistler, 4: 1-28.

Zemstov, A., M. Gaddis, V. Montalvo-Lugo. 1996. Moisturizing and cosmetic properties of emu oil: A pilot double blind study. Australian Journal of Dermatology, 37/3: 159-162.

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