The common emu (Dromaius novaehollandiae) is a flightless bird that is part of the Dromaiidae family. It is the second tallest bird in the world, after the ostrich. The fact of being a large and heavy bird does not prevent it from traveling long distances, running at 50 km / h and making strides of almost 3 meters.
This is due, among other factors, to the fact that it has specialized muscles anatomically. The common emu is the only bird that has gastrocnemius or gastrocnemius muscles on the lower back of its limbs..
Its plumage has the appearance of wool and the feathers have double rachis, which emerge from a common trunk. Regarding the coloration, the skin has a bluish tone, which is evident in those semi-nude areas, such as the neck. The body is brown or gray in color, but it can vary to reddish or darker tones, depending on the region where it lives..
The Dromaius novaehollandiae it is endemic to Australia, where it lives in much of the continental region. The subspecies that were distributed on Kangaroo Island, Tasmania and King Island are extinct. Savanna forests and grasslands are among the preferred habitats.
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The vestigial wings of the common emu are reduced to small appendages, located in the anterior region of the body. At the tip of each of these there is a small claw. Relative to the chord of the wing, it measures about 20 centimeters.
While running, this bird flaps its wings, probably to stabilize its body during movement.
The eyes are protected by nictitating membranes. These translucent lids move horizontally from the inner edge of the eye to the outer edge. Its function is to protect the eyes from the dust and sand that abound in arid regions where the common emu inhabits..
This species has a tracheal bag, which is approximately 30 centimeters long. This structure covers a cleft that exists in the tracheal rings, ventrally. This opening is 6 to 8 centimeters long.
When the air is directed towards the bag, the skin that covers the neck expands and a loud sound is produced, which in the male resembles a growl.
The emu's head is covered with wispy black feathers. Its beak is black and is specialized for grazing. As for the neck, it is long and sparsely covered with feathers, so the tone of its skin can be seen, which is whitish blue.
The Dromaius novaehollandiae It is the second highest bird in the world, being surpassed by the ostrich. Taking into consideration the measurement from the beak to the tail, the male measures an average of 1.49 meters and the female 1.57 meters. In relation to the average weight, in the adult male it is around 31.5 and in the female it is 37 kilograms.
The emu has long limbs and, despite being a large and heavy animal, it can run at a speed of up to 50 km / h. This is due to their highly specialized musculature. In this way, this species has gastrocnemius muscles, known as calves, in the back and lower part of each limb..
Like the flight musculature in birds, the muscles in the pelvic limb contribute a similar proportion to total body mass. These particularities allow this species, when walking, to stride 100 centimeters. However, if it is galloping, it can be up to 300 centimeters..
As for their legs, they lack feathers and have thick, padded pads. In addition, they have three toes on each leg, each with a strong and sharp claw. When kicking, the common emu can inflict serious injuries to the opponent.
The plumage of the Dromaius novaehollandiae It has a woolly appearance and can range from gray to brown in color. The body absorbs solar radiation through the terminal end of the feathers, which are black..
However, this heat is not transferred to the skin, because the internal plumage works as an insulator. In this way, the emu can stay active during the hottest hours of the day..
A unique feature of feathers is that their rachis are double, both emerging from the same axis. Each one is the same length, but its texture may vary.
The coloration can vary, influenced by environmental factors. The common emu that lives in arid regions, have a reddish plumage. On the contrary, if you live in a humid habitat, it tends to have a darker tone..
In hatchling, the juvenile plumage develops around 3 months. This one is black, with a darker neck and head. The adult's own tones are acquired when the common emu is 15 months old. As the bird ages, the feathers on the face thin out, exposing the bluish skin.
-Animal Kingdom.
-Subkingdom: Bilateria.
-Phylum: Chordate.
-Subfilum: Vertebrate.
-Superclass: Tetrapoda.
-Class: Birds.
-Order: Casuariiformes.
-Family: Dromaiidae.
-Genus: Dromaius.
-Species: Dromaius novaehollandiae.
Subspecies:
-Dromaius novaehollandiae minor.
-Dromaius novaehollandiae baudinianus.
-Dromaius novaehollandiae novaehollandiae.
-Dromaius novaehollandiae diemenensis.
The Dromaius novaehollandiae It is found throughout mainland Australia. The subspecies that inhabited Tasmania (Dromaius novaehollandiae diemenensis) is extinct, being its last wild record in 1845. The lowest densities of this bird occur in the center of the island and along the eastern coast..
The common emu has a nomadic lifestyle, so it can live in almost any biome. However, it prefers grasslands and savanna forests, where areas with stagnant water generally abound.
Likewise, try to avoid highly populated regions, rainy and dense forests and those arid areas, with annual rainfall less than 600 millimeters.
If in the region where it lives there is abundant water and food, the common emu remains in it. On the contrary, if any of these factors are scarce, the bird migrates to another area. Generally, the trips are made in pairs, although it could form large flocks.
This behavior is atypical, due to their generally solitary habits. Group-like behavior arises as a response to the shared need for other sources of food. In the search for a new habitat, it can travel long distances, walking between 15 and 25 kilometers daily..
The common emu is classified by the IUCN as a species of least concern of going extinct. This is because this bird has a wide distribution range in Australia, so it does not approach the thresholds of Vulnerable, considering the criterion of habitat size..
Also, the current trend of the population is stable. However, protectionist organizations continue to fight against the threats that afflict them.
The main cause of the population decrease of the Dromaius novaehollandiae it is his hunt. After the arrival of European settlers to the Australian continent, the common emu was overhunted.
This bird is killed to obtain its red meat, low in fat and its skin, ideal in the manufacture of leather goods. Other products that are potentially commercial include eggs, feathers, bones, and manure..
The indiscriminate capture of this species caused its extinction on several islands, including Tasmania. In the continental territory, the deforestation of forests for the use of land for agricultural and livestock purposes, on the contrary, brought benefits for the emu.
In this sense, the provision of water for livestock and the cultivation of cereals is very beneficial for the bird, as it guarantees a source of food. However, this leads to the Dromaius novaehollandiae become a threat to agriculture.
Currently, cultivated areas are protected by a wide network of fences that are resistant to the common emu, thus preventing it from entering farmland..
In this species, sexual maturity is reached after the bird is two or three years old. During courtship, both sexes ruffle their feathers and begin to walk around.
During this ritual, the male initiates a kind of mating dance around the female, slowly moving his head, simulating the movement of a snake..
If the female is not pleased with this behavior, she may become aggressive towards the male. On the contrary, if the couple consolidates, they could stay together for up to five months.
The Dromaius novaehollandiae has a polyandry reproductive pattern, however, not all females have multiple partners. The female can store the sperm in the tubules of the oviduct, and release them in a period of time known as the fertile period. In this way, he could fertilize a maximum of six eggs.
The egg measures an average of 13 centimeters × 9 centimeters and weighs between 450 and 650 grams. Externally, the eggshell is grainy and pale green.
The male is in charge of building the nest. This is almost always flat and is made up of sticks, leaves, grass and bark. It can be located in the open field or close to the bushes. In this way, the common emu has a clear visibility of the environment and can easily detect any threat..
Before the female lays her eggs, her partner can court other females. Once the eggs are in the nest, the male is the only one in charge of their incubation. While this happens, the female could mate with other males, so she could lay eggs in different nests, which will be cared for by another male..
During the incubation period, which lasts between 48 and 56 days, the male generally does not feed, surviving on the fat stored in his body..
Also, develop a brood patch. This is a bare area of feathers, where the skin is in direct contact with the eggs. Thus, it can offer them greater heat during incubation.
Because the nest is flat, the male collects the eggs that have been rolled. In addition, they rotate and rotate them from time to time, thus guaranteeing the best conditions for their development..
The male is removed from the nest shortly before the eggs hatch. Although these were laid sequentially, the chicks tend to hatch within two days of each other..
Young can leave the nest within a few days after hatching. At birth, they are approximately 12 centimeters tall and weigh 500 grams. Its plumage is characterized by having cream and brown stripes, which disappear after 3 months. This coloration provides them with camouflage, thus avoiding being spotted by predators..
The father is responsible for protecting the offspring, even from the mother herself. This can adopt a belligerent position before any other emu that threatens them. Thus, it flutters its feathers, grunts and kicks the other. It also tends to crouch over the smaller chicks, to cover them with its body. In the night, he wraps them with his feathers.
The period of dependence of the young, in which the father teaches them to obtain their food, lasts about seven months.
Experts point out that the patella represents a huge mechanical advantage for the extensor muscles that are associated with it. At the evolutionary level, this structure exhibits diverse origins in birds, mammals and reptiles..
The ontogenetic studies carried out indicate that patellar evolution has its origin in the ancestor of modern birds, a clade that contains the Hesperornithiformes and the Neornithes. In turn, the results indicate that the common emu lacks an ossified patella.
However, there is a novel finding, the patellar tendon of this species has an unusual morphology in birds. It is made up of large volumes of adipose tissue, located within a kind of network formed by collagen.
This particular characteristic may be the result of the assimilation of a periarticular pad of fat, in addition to the metaplastic formation of cartilage. Both adaptations have the function of further enhancing the tendon load.
The common emu feeds on seeds, fruits, plant shoots, but does not eat mature leaves or dry grasses, even though they are abundantly present within its habitat..
They also tend to eat arthropods and insects, such as crickets, beetles, cockroaches, grasshoppers, ladybugs, grubs, millipedes, spiders, and ants. These provide a large part of the protein requirements it needs to fulfill its vital functions..
To a large extent, the diet depends on seasonal availability. Thus, the common emu eats seeds of Acacia aneura until the rainy season begins. After this time they usually feed on the shoots of fresh grass and caterpillars.
During the winter, their diet includes Cassia leaves and pods and in the spring they consume the fruit of Santalum acuminatum and grasshoppers.
The digestive system of the common emu is characterized by having a modified distal esophagus, where food can be stored for more than 30 minutes, before entering the stomach.
This contributes to the degradation of the cellulose contained in the plant material, since this bird lacks crops that decompose food. In addition, to aid in the process of grinding and digestion of fibrous material, ingest stones up to 45 grams in weight.
The common emu generally has solitary habits, however, it can exhibit some social behaviors, provided these represent an advantage. Thus, for example, they often form groups to find new sources of food.
The Dromaius novaehollandiae it is a diurnal bird, which spends most of the day feeding. Also, they tend to groom their plumage with their beak, rest and bathe. During the night, it sleeps, but it does not do so continuously. Often wakes up multiple times as he goes into a drowsy state.
In this way, he is alert enough to react to stimuli and to wake up quickly, if necessary..
This large bird can swim, although it only does so if the area where it is found is flooded or if it requires crossing a river.
To communicate, the common emu emits various vocalizations, consisting of shuddering sounds and growls. The loud resonant sound, known to some as "booming" is created in the tracheal bag. It is used mainly by the female as part of courtship and as a threat.
If this is of high intensity it can be heard 2 kilometers away. In the case of being of low intensity, it is used to attract a partner.
As for grunts, they are basically vocalized by males during courtship, nesting and to defend their territory from other males. While mating, the female may also growl, as if she identifies a foreign element within her area..
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