The Dromaius Novaehollandiae, commonly known as the Emu is a species very similar to the ostrich or the ñandu in size as such, this species of bird is considered the second largest in height and is resident in most of Western Australia. In the following article we will learn more about this very peculiar bird.
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The Dromaius Novaehollandiae
The Emu scientifically named Dromaius Novaehollandiae is the second largest living bird by height, after its relative the ratite, the ostrich. It is endemic to Australia, where it is the largest native bird and the only extant member of the Dromaius genus.
The range of the Emu ( Dromaius Novaehollandiae ) covers most of mainland Australia, but subspecies of the Tasmanian emu and King Island emu became extinct after the European colonization of Australia in 1788. The bird is common enough to be classified as a species of least concern by the International Union for Conservation of Nature.
Emus ( Dromaius Novaehollandiae ) are soft-feathered, brown, flightless birds with long necks and legs, and can reach up to 1.9 meters in height. The Emu ( Dromaius Novaehollandiae ) can travel long distances, and when necessary can run up to 50 km.
The plumage in general consists of a sort of mixture of brown and gray, and the feathers are somewhat curled or folded at the ends in the natural state, the wings are so short that they are totally useless for flight, and in fact, these are scarcely distinguishable from the rest of the plumage, were it not for their standing out a little.
The long spines that it has and that are seen on the wings of the common kind, in this are not observable, nor is there any appearance of a tail. The legs are stout, formed much like that of the Galeated Casowary, with the addition that they are serrated or cut along their entire length posteriorly.
Systematics
The Emu ( Dromaius Novaehollandiae ) was classified for a long time, and its closest relatives were the cassowaries, in the family Casuariidae, are part of the order Rotato Struthioniformes. However, Mitchell et al. proposed an alternative classification in 2014, based on mitochondrial DNA analysis.
This divides the Casuariidae into their own order, which are the Casuariformes, and includes only the cassowaries of the family Casuariidae, placing the Emus ( Dromaius Novaehollandiae ) in their own family, which are the Dromaiidae.
There are 2 distinct species of the Dromaius that were present in the regions of Australia at the time of European colonization, and 1 additional species is known from fossil remains. The island dwarf emus, Dromaius Baudinianus and Dromaius Novaehollandiae Minor, originally present on Kangaroo Island and King Island respectively, both became extinct shortly after the arrival of Europeans.
Dromaius Novaehollandiae Diemenensis, a subspecies known as the Tasmanian Emu, became extinct around 1865. However, the mainland subspecies, Dromaius Novaehollandiae Novaehollandiae Novaehollandiae, is still very common. The population of these birds varies from decade to decade, largely dependent on rainfall; in 2009, there were an estimated 630,000 to 725,000 individuals.
Emus were introduced to Maria Island off Tasmania, and to Kangaroo Island off the coast of South Australia, during the 20th century. The Maria Island population died out in the mid-1990s. The Kangaroo Island birds have successfully established a breeding population class.
Description
The Emu ( Dromaius Novaehollandiae ) is the second tallest bird in the world, surpassed in height only by the ostrich; the largest individuals can reach up to 150 to 190 cm in height. Measured from beak to tail, the emu’s length range is 139 to 164 cm, with males averaging 148.5 cm and females averaging 156.8 cm. Emus weigh between 18 and 60 kg, with males and females averaging 31.5 and 37 kg, respectively.
Females are generally slightly larger than the males themselves and are considerably broader in the rump area.
Although flightless, Emus ( Dromaius Novaehollandiae ) have vestigial wings, the wing chord measures about 20 cm and each wing has a small claw at the tip. Emus flap their wings when running, perhaps as a means of stabilizing themselves when moving fast. They have long necks and legs, and can run at speeds of 30 miles (48 km).
When walking, this species makes a stride of about 100 cm, but at full gallop, a stride can last up to 275 cm. Its legs are featherless and under its feet are thickly padded pads. Like the cassowary, the Emu ( Dromaius Novaehollandiae ) has sharp claws on its toes, which are its main defensive attribute, and are used in combat to inflict wounds on opponents by kicking.
The tip and claw are a total of 15 cm in length. The bill is quite small, measuring about 5.6 to 6.7 cm, and soft, it is adapted for grazing. Emus have good eyesight and also excellent hearing, which allows them to detect threats at some distance.
Habitat and Distribution
Once common on the east coast of Australia, Emus ( Dromaius Novaehollandiae ) are now rare; conversely, the development of agriculture and the provision of water for livestock in the interior of the continent have increased the range of Emus in arid regions. Emus inhabit diverse habitats throughout Australia, both inland and near the coast. They are most common in savanna woodland and sclerophyll forest areas, and less common in densely populated districts and arid areas with annual rainfall of less than 600 mm.
Emus primarily travel in pairs, and while they may form large herds, this is an atypical social behavior that arises from a common need to move towards a new food source. Emus ( Dromaius Novaehollandiae ) have been shown to travel great distances in order to reach abundant feeding areas.
In Western Australia, the movements of the Emu ( Dromaius Novaehollandiae ) follow a sort of seasonal pattern distinctly north in summer and south in winter. On the east coast, their wanderings seem to be more random and apparently do not appear to follow a set pattern.
Geographic Range
Emus ( Dromaius Novaehollandiae ) occur exclusively in regions of Australia and inhabit almost the entire continent. The lowest densities exist along the east coast and towards the center of the island. The number of individuals tends to vary by about 700,000 and depends on seasonal rainfall.
Behavior
Emus ( Dromaius Novaehollandiae ) are birds with a diurnal lifestyle and spend all day feeding, preening their plumage with their beaks, bathing and also resting. They are usually gregarious birds apart from the breeding season, and while some of them are foragers, others remain vigilant for their mutual benefit. They may swim when appropriate, but rarely do so unless the area is flooded or they have to cross a river.
Emus ( Dromaius Novaehollandiae ) begin to settle at dusk and usually sleep during the night. They do not sleep continuously but rise several times during the night. When they do fall asleep, emus first squat on their tarsi and enter a state which may be called drowsiness during which they are alert enough to react to stimuli and quickly return to a fully awake state if disturbed.
As they fall into a deeper sleep, their necks tilt closer to the body and the eyelids begin to close. If there is no disturbance, they fall into a deeper sleep after about 20 minutes.
Feeding
The Emu ( Dromaius Novaehollandiae ) forages in a diurnal pattern and eats a diverse array of native and introduced plant species. The diet of this bird depends on seasonal availability with plants such as Acacia, Casuarina and grasses favored.They also tend to eat insects and other types of arthropods, including:
Cotton – boll moth larvae
This provides a large part of its protein requirements. In regions of Western Australia, food preferences have been observed in roaming emus; they also tend to eat the seeds of Acacia aneura until the rainy seasons arrive, after which they switch to fresh grass shoots and caterpillars; in the winter they feed on the leaves and pods of Cassia and, in the spring season, they consume grasshoppers and the fruit of Santalum acuminatum, which is a species of quandong.
It is also understood that they feed on wheat, and any fruit or other crops they can access, climbing easily over high fences if necessary.
Reproduction
Emus ( Dromaius Novaehollandiae ) exhibit polyandrous breeding patterns, but not all females breed to multiple mates. The mating season begins in the month of December and the month of January, which starts with the male and female emu engaging in a sort of courtship dance. The outcome of this depends on the performance of the male Emu; if it is unsatisfactory, the female may simply become aggressive against him.
Male Emu success means up to 5 months of mating privileges with the female that has already been courted. Before the female emu lays her eggs, her male counterpart may get to court other females before they engage in incubation. After the males begin the incubation period, the females will look for ways to mate with unoccupied males.
Most female emus engage in post-mating polygamy, but not without a cost. Female emus run the risk of eventually losing their mate, which could mean that their eggs will not be incubated by a male who will take over.
Breeding
Emus ( Dromaius Novaehollandiae ) form breeding pairs during the summer months of December and January, and may remain together for approximately 5 months. During this time, they remain in an area a few kilometers in diameter and are believed to locate and defend territory within this area. Both males and females gained weight during the breeding season, with the female weighing slightly between 45 and 58 kg.
Mating usually takes place between April and June; the exact timing is determined by the weather as the birds nest during the coolest part of the year. During the breeding season, males undergo certain hormonal changes, including an increase in luteinizing hormone and testosterone levels, and their testes double in size.
The males are in charge of building the rough nest which is in a semi-sheltered hole in the ground, using elements such as bark, grass, branches and leaves to line it. The nest is almost always a flat surface rather than a segment of a sphere, although in colder weather conditions the nest is taller, and tends to measure up to about 7 cm and is more spherical to provide some additional heat retention.
Predation
There are few natural native predators of the Emu ( Dromaius Novaehollandiae ) still alive. Early in its species history, it may have faced numerous terrestrial predators that are now extinct, including the:
And probably other carnivorous marsupials, which may explain its apparently well-developed ability to defend itself against terrestrial predators.The main predator of Dromaius Novaehollandiae today is the dingo, which was originally introduced by Aborigines more than thousands of years ago from a stock of semi-domesticated wolves.
Dingoes attempt to kill emus by attacking them directly in the head. The Dromaius Novaehollandiae normally tries to repel the dingo’s attack by leaping into the air and kicking the dingo on its way down. The emu jumps as the dingo barely has the ability to jump high enough to threaten its long neck, so a jump that is timed correctly to coincide with the dingo’s lunge can keep its head and neck out of danger.
Despite the possible prey-predator relationship, the presence of predatory dingoes does not seem to influence emu numbers much, with other natural conditions just as likely to cause high mortality. Short-toed Eagles are the only avian predator capable of attacking large, fully-grown emus, although they are more likely to take smaller specimens or juveniles. Eagles attack emus by swiftly descending at high speed and aiming for the head and neck.
Among the predators are those mentioned above of which 2 are extinct and the other 2 are alive today and are:
The Giant Megalania Lizard
The Tilacino
The Dingo
The Eagle or Short-toed Eagle
Longevity
When in captivity, under a regular hydration and feeding program, Dromaius Novaehollandiae can live up to 20 years. Emus in the wild experience many more stresses, including dry periods and starvation, reducing their lifespan to a maximum of 10 years.
Parasites and Diseases
Dromaius Novaehollandiae can suffer from external as well as internal parasites, but in breeding conditions they are more free from parasites than Ostriches or rheas. External parasites include the louse called Dahlemhornia Asymmetrica and various other lice, ticks, mites and flies.
Chicks sometimes suffer from intestinal tract infections which are caused by coccidian protozoa, and the nematode Trichostrongylus tenuis which infects emus, as well as a wide range of other birds, causing a kind of hemorrhagic diarrhea.Other nematodes are found in the trachea and bronchi; Syngamus trachea causing hemorrhagiatracheitis and Cyathostoma variegatum causing severe respiratory problems in juveniles.
Relationship with People
Emus were used as a food source by indigenous Australians and early European settlers.
Emus are inquisitive birds and have been known to approach humans if they see unexpected movement of a limb or article of clothing. In the wild, they may even follow and observe people.
Aboriginal Australians used a variety of techniques to catch birds, including spearing them while drinking at watering holes, trapping them with nets and luring them by mimicking their calls, or arousing their curiosity with a ball of feathers and rags hung from a tree. Pitchuri thorini ( Duboisia hopwoodii), or some poisonous plant that is similar, could be used to contaminate a waterhole, after which disoriented emus were easy to catch.
Economic Importance to Humans in a Positive Way
The Emu ( Dromaius Novaehollandiae ) produces oil that has come to be used for certain medicinal purposes for hundreds of years. A brief list of therapeutic effects includes:
Evidence goes so far as to suggest statistically that emu oil is a superior skin cream to mineral oil based products. Emus have also been hunted for their meat by Aboriginal and contemporary Australians.
Economic Importance to Humans in a Negative Way
If given the opportunity, Emus ( Dromaius Novaehollandiae ) will forage for crops. Farmers now install some high fences so that emus cannot get access to farmland. In the early 1930s, a large migration of emus to an agricultural town ended violently.
The emus spoiled or consumed the large wheat fields. The army was called in to eradicate these birds in what some call the “Emu War”. However, the operation was not successful. Dromaius Novaehollandiae possess natural camouflage and the ability to flee, which allowed them to avoid detection.
Communication
Emus have the ability to communicate through the use of an inflatable neck pouch, and can create sounds that are loud enough to be heard 2 km away. The name “Emu” resembles their signature call, which is heard as “e – moo”.
The translation of these calls is the main way of receiving communication, in addition to the visual interpretation of body language. During courtship periods, emus, both males and females, engage in a dance consisting of struts and head movements much like those of snakes. Males must make the correct movements, otherwise the female may quickly change her mind and become aggressive against him.
Status and Conservation of the Species
In John Gould’s Handbook for the Birds of Australia, which was first published in the year 1865, he lamented the loss of the Tasmanian emu, where it had become rare and has since become extinct; he noted that emus were no longer common in the vicinity of Sydney and proposed that the species be granted protected status.
In the 1930s, emu killings in Western Australia peaked at 57,000, and culls were also mounted in Queensland during this period due to rampant crop damage.
