History And Origins Of Emus In Australia Biology Essay

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Emu, the second largest extant flightless bird in the world is a native of Australia. People looking for an alternative to livestock are raising emus for their meat (low cholesterol red meat), hide, feathers, oil (therapeutical and cosmetic uses), to supply the breeder market or as a pet. Emu belongs to the group called ratites (Anon, 2008), which also includes Ostrich (South Africa), Rhea (South America), Kiwi (New Zealand) and Cassowary (New Guinea). The term "ratites" is derived from the Latin word "ratis" for "raft", which means a boat without a keel (Hutchins et al, 2002). The term 'Emu' is believed to have originated from the Portuguese word "ema", which means a large bird (Eastman, 1969) and the scientific name as coined by the ornithologist John Latham is Dromaius novaehollandiae (IUCN, 2010)(de Silva, de Ita, & Legorreta, 2005).

Origin of emu farming

Emus have been found in the mainland of Australia for over 60,000 years (Boland, 2003) and it was only in 1970s that the Australian Government gave permission to the Cherbourg Aboriginal Community to capture 300 wild emus for a primary breeding stock and domesticate them. The first emu farm was established in Wiluna in 1976 (Hammond et al. 2002) while Western Australia was the first State in Australia to allow commercial emu farming.

The United States first imported emus between 1930 and 1950. However, commercial emu farming in the U.S. did not begin until the late 1980's (Thompson, 1997). This industry then spread to Europe in the early eighties and then to Asia and Africa. Today emus are farmed all over the world and their current population is estimated to be around 0.7 million (2009) and their status is of "least concern" according to the Bird life International reports (IUCN, 2010). However, in the wild, emu population has not increased and has become extinct (Moon, 2008; Anon, 2009) like Tasmania and in several other parts of Australia, is considered to be endangered (Sales, 2009). Wild Emus are formally protected in Australia under the 'Environment Protection and Biodiversity Conservation Act 1999'.

All extant ratites are restricted to the southern hemisphere excluding Antarctica, and this suggests two likely theories for their evolution. It was believed previously that ratites emerged as a flightless group in Gondwanaland (Cracraft, 1974) in the Cretaceous and then as the continents drifted apart, they were widely distributed to different locations. Recent studies have confirmed that ratites are polyphyletic while also suggesting the flighted tinamous cluster within the ratite lineage (Harshman et al., 2008).

Taxonomic classification

There are two taxonomic approaches (Anon, 2010) to ratite classification: while the former combines the different groups as families in the order Struthioniformes, the latter assumes that they evolved independently and thus elevates the families to the status of orders i.e. Rheiformes, Casuariformes etc.

Literature shows two generic names for emu In his original 1816 description of the Emu, Vieillot used two generic names; first Dromiceius, then Dromaius a few pages later. Most modern publications, including those of the Australian government, use Dromaius, with Dromiceius mentioned as an alternative spelling.

Species of Emus

The current taxonomic classification (Brands, 2010) shows emu under family Dromaiidae and genus Dromaius. Currently, there is only a single living species, D. novaehollandiae and three extant subspecies in Australia (Sales, 2009) with the following distribution:

In the southeast, D. novaehollandiae novaehollandiae, (has a whitish ruff in the breeding season); in the north, D. novaehollandiae woodwardi (slender and paler); and in the southwest, D. novaehollandiae rothschildi, darker, with no ruff during breeding (Moon, 2008). Three different Dromaius species were found in Australia before originally, and one species (D. ocypus) was discovered from fossils (Eastman, 1969). D. novaehollandiae diemenensis, a subspecies known as the Tasmanian Emu, was reportedly a large emu with dark feathers. The body type was similar to that of novaehollandiae novaehollandiae and it became extinct in around 1865. The dwarf Emus Dromaius baudinianus (The Kangaroo Island Emu) became extinct around 1827 and D. ater (King Island Emu) at 4 ½ feet tall and adult weighing under 60 pounds, this black feathered emu was the smallest of the species and became extinct within around 200 years (Boles, 2001) . These birds distinctly differ in their phenotype and their pictorial representation (American Emu Association, 2009)is provided in the Appendix.

The one thing these three extinct southern Australia emus have in common is that they all had darker feathers than the mainland emus. For this reason early settlers referred to either black emu or spotted emu. Dromaius novaehollandiae is the spotted emu (American Emu Association, 2009).

Biology of the emu

Emus can grow upto 6 feet in height and could weigh upto 55 kilos. The emu has around 54 vertebraes in its axial skeleton, a flat breastbone, but no keel (Sales, 2007). The neck is very long and can be rotated a full 360 degree forming an 'S' shape (Lucas, 1965) and this aids in the combing of feathers. As the muscles of the wing are under developed, they cannot fly (Moon, 2008). The furcula is poorly developed (Maxwell, 2007) or almost absent (Anon, 2010)and they have vestigial wings that are short and end in a claw at the tip.

The Emu flaps its wings while running, which is believed to help the bird to balance itself. Wings also help in dissipation of heat from the body (Moon, 2008). Their lung and air sacs are similar to chicken (Maina & King, 1989) but there are no pneumatic bones except the femur. Emus tongue has serrated edges (Sales, 2007) and the beak is usually black in colour. The true conformations and guidelines for judging emus id provided by the (American Emu Association, n d)

Emus possess a diverticulum in the trachea, the tracheal cleft is peculiar to emus (Cho, Brown, & Anderson, 1984), about 6-8 cm long (Sales, 2007), leading to a tracheal sac (Fowler, 1991). The trachea is primarily composed of cartilages around 30-40 in number which form complete rings and in ratites, they are dorsoventrally flattened (Heard, 1997). This is observable in an adult female as a pouch of loose skin at the base of the neck. Adult females make a drumming or boom sound (Heard, 1997) where as the adult males "grunt." This pouch is easy to see in females during their first three years of breeding (American Emu Association, 2009), but in subsequent years does not enlarge as much. Males also have this cleft, but the membrane does not enlarge as much. This cleft is the source of the booming and grunting (Cho, Brown, & Anderson, 1984).

They have a renal-portal system (Fowler, 1991) similar to that in other birds and reptiles. Emus do not have a crop but the proventriculus is quite large with the function of mixing food with digestive juices before passing into the ventriculus (gizzard) which is the muscular stomach. The emus possess paired caeca, which are relatively short, and a short colon. The mean lengths of different parts of the digestive tract of emus are given in the appendix. The cloaca houses the Bursa of Fabricius (Fowler, 1991), which is the primary lymphatic organ of the bird involutes by three or four years ofage.

Emus are fast runners with well developed strong legs, reaching a speed of around 50 kms per hour for short distances (E. O. Wilson, 2003). Emus have a reduced number of toes (three) and associated muscles (Patak & Baldwin, 1998). All the toes are directed forward and the underside of each are flat with broad pads (Eastman, 1968) which may be thickened by calluses (Fowler, 1991). They can kick forward and backwards, and are also able to swing their legs laterally. Emus are good swimmers and they love to splash water on their body.

The gastrocnemius muscle, the most powerful muscle has four muscle bellies so also the contribution to total body mass of the pelvic limb muscles of emus is similar to that of the flight muscles of flying birds, whereas the pelvic limb muscles of flying birds constitute a much smaller proportion of total body mass (Patak & Baldwin, 1998).

Plumage

Their plumage is dark brown after the annual molt, but fades later to pale brown ( Hutchins, et al, 2002). Emu feathers are unique because both the primary and secondary feathers are of the same length. Each feather has two shafts, the main shaft and aftershaft of the feathers, which are equal in length so that every feather appears double with barbs, which are widely spaced that they do not interlock to form a firm vane; barbules and barbicels are absent (Fowler, 1991). Instead they form a loose, hair-like body covering. The shafts and tips of the feather are also black, allowing solar radiation absorption (Moon, 2008).

There is no separation of pterylae and apterylae on an emu's body. There are four types of Emu feathers: the short, black neck feathers; the downy-white fluffy chest feathers; the silvery-brown, black-tipped back feathers; and the long, bristly tail feathers (Eastman, 1968), which may be as long as 26 inches. The uropygial gland secreting preen oil (uropygiols) are absent in emus (Deeming, 1999).

Maloney & Dawson (1994) found that the emu maintains a constant body temperature within the temperature range of -5 to 450 C. They also added that during cold weather, emu regulates body temperature initially by reducing conductance and then by increasing heat production. At high temperatures cutaneous evaporative water loss in addition to panting is resorted to. The Emu's legs are devoid of feathers and they also help in thermoregulation (Maloney & T. Dawson, 1994). The bird spends most of its time walking and standing. They also prefer to sit either in the crouching position or on their sternum even while eating, drinking or preening. As a result, calluses are common in the dependent parts of the body of the bird (Fowler, 1991).

Thermoregulation in emus

Solar radiation is absorbed by the tips, and the loose-packed inner plumage insulates the skin. The resultant heat is prevented from flowing to the skin by the insulation provided by the coat, allowing the bird to be active during the heat of the day. Heat loss from the body occurs via four path ways: radiation, evaporation, conduction, and convection (Maloney & T. Dawson, 1994). Another adaptive feature of the bird is the layer of fat on its back to support the large feathers and also enhance insulation against very low temperatures (Moon, 2008).

In high temperatures, Emus start panting to maintain their body temperature, while their lungs act as evaporative coolers. Emus are particularly resistant to alkalosis caused by low levels of carbon dioxide in the blood (Maloney And Dawson, 1994). Emu's lung has shown that they are poorly adapted for gas exchange when compared with lungs of other birds (Maina and King, 1989). The capillaries required for gas exchange are covered by granular epithelial cells, and hence the interphase between blood and the gas is extremely thick. Emu's poor ability for oxygen intake and its large body size is assumed to point to the fact that they evolved in a warm environment with few predators. If there were few predators, the Emu would not have had a selective pressure for highly efficient lungs for flight for fast escapes (Moon, 2008).

As much as 40% of the total heat produced by emus can be dissipated via the unfeathered areas which accounts for 17.5% of total surface area in the emu (Phillips & Sanborn, 1994). For breathing in cooler weather, they have large, multifold nasal passages. Cool air warms as it passes through into the lungs, extracting heat from the nasal region. On exhalation, the Emu's cold nasal turbinates condense moisture back out of the air and absorb it for reuse. The body temperature of emus is lower than other birds (Maloney, S .K And Dawson, 1994)

Hide

The leather is soft and supple with an intriguing pattern resulting from the removal of the feathers. The leather is usable wherever a soft, piece-work display is desired, such as for pillows, vests, purses or business card holders. The feathers are used in the automotive and electronic industries as feather dusters, and by fishermen for tying flies.

The Emu has sharp vision and hearing. The eyes of an Emu are protected by nictitating membranes which are translucent, and used as a protective covering for eyes from dust.

Ecology and behaviour

They are also known to be curious animals, which might approach handlers and observe them carefully. Emu spends much of its time combing its plumage with the beak (Eastman, 1965).

Ratite farming in various countries is regulated by codes of practice, but these often only apply minimum requirements and are often not best practice. The welfare issues concerning ratites have been examined in details (P C Glatz & Miao, 2008) based on achieving the five freedoms. Some of the major welfare issues which can be a concern for ratite breeders are a proper feeding, water and shelter for emus under varying weather conditions, injuries from aggressive birds, freedom of movement and space near feeding areas.

Ratite farming in various countries is regulated by codes of practice, but these often only apply minimum requirements and are often not best practice. The welfare issues concerning ratites have been examined in details (P C Glatz & Miao, 2008) based on achieving the five freedoms. Some of the major welfare issues which can be a concern for ratite breeders are a proper feeding, water and shelter for emus under varying weather conditions, injuries from aggressive birds, freedom of movement and space near feeding areas.

Nutrition

Emus are omnivores, the time taken for food to pass through the digestive tract is calculated to be 4.5 to 6 hours ( Herd & Dawson, 1984)on an average but for intact wheat grains it may take up to two days. Shell grit would be retained for a much longer period in the gizzard to help in the maceration of food. Most ratite growers feed a diet that is between 17-24 per cent crude protein during feeds are available (Hermes, 1996).

Emus have a low requirement for protein after 40 weeks of age and cost effective low protein finisher diets can be fed. O'Malley & Snowden (1999) reported the physiology of appetite in the emu are not dependent on those for sexual expression and aggression. Restricting the feed intake until 2 - 3 months prior to slaughter (12-16) months resulted in better fattening of birds. Production parameters from the study are listed below.

Emus forage in a diurnal pattern consuming a variety of plants, vegetables and grains (Eastman, 1965). They also eat insects which contribute to their protein requirement. The pH of emu proventriculus and gizzard are 2.8 and 2.5 respectively (Herd, 1984). Emus serve as an important agent for the dispersal of large viable seeds in the wild, which contributes to floral biodiversity.

Emus are curious birds and might eat anything shiny, marbles, pieces of fences, nails, nuts and bolts. Emus drink at infrequent intervals, but ingest large amounts when they do so. They are observed to prefer kneeling on solid earth while drinking, and often drink continuously for 10 minutes, unless disturbed (Eastman, 1965).

Emus can digest between 35% to 45 % neutral detergent fiber (NDF) in diets with 26%-36% NDF and they digest hemicellulose better than cellulose or lignin (Herd & Dawson, 1984).

Farming of emus

Farming of emus has great potential that almost every item from this bird can be utilized. The female begins to breed between 18 months and three years of age, and may continue to produce eggs for more than 15 years. It is the male who incubates the eggs which hatch in about 50 days. Regulations for management and farming of emus are already in place in South Australia (Department for Environment and Heritage, 2000), Queensland (Kent, 2000).

The emu is a declared pest of agriculture under the provisions of the Agriculture and Related Resources Protection Act 1976, administered by the Western Australian Department of Agriculture and Food. This declaration allows for the approval and implementation of a management program in various areas of the State.

As a native species, the emu is protected under the provisions of the Wildlife Conservation Act 1950, administered by the Department of Environment and Conservation (DEC). Emus can only be destroyed on private land after a damage licence has been issued by DEC, except where a restricted open season has been declared in the event of a build-up of birds along the barrier fences. Export of emu products is controlled by the Commonwealth Environmental Protection and Biodiversity Conservation Act 1999, which requires that products are from animals bred in captivity.

Situation in Canada and around the world

Statistics Canada reports that there has been a drastic reduction in the farming of emus in Canada in the past decade (Statistics Canada, 2008). While the number of emus witnessed a decline of 72%, the emu farms were 62 % less and the average herd size was also reduced by 26%. Unless there are sustained efforts to strengthen this industry, the future might not be bright.

The emu bubble

Ratites were introduced to Canada in the early 1990s, over 300 Ontario farmers embarked on this venture expecting exaggerated profits (Turvey & Sparling, 2002). Many producers invested more than $30,000 per pair to purchase breeding stock; and made heavy investments in infrastructure.

Initially it was just a breeders market, both production and sales volume were low and competition was limited and for sometime the industry looked promising. In 1991-92 the market for chicks and eggs emerged while in 1992-1993 the yearling market emerged further pushing the prices up. The breeder market being extremely speculative and with limited supply, the price for breeding pairs went up to more than $40,000 during 1994-1995 (Turvey et al, 1998). The prolific reproduction rate of emu and the inability to develop an end market led to an oversupply of birds (chicks) more quickly than anticipated, and the bubble burst.

Emus and emu products were expected to be marketed through the Canadian Emu Cooperative (CEMU) but they were not successful in establishing a retail distribution network (Turvey et al 1998). By 1995-1996, insufficient consumer demand led to overcapacity in the industry. Producers were forced to find buyers for emu products on their own, resulting in fierce competition among many niche players. There was no quality control for the products and there was no defined market at the retail level or as specialty meats.

Due to the labelling regulations, Health Canada never certified the properties of emu oil and hence the demand stayed low. "The industry life cycle was very short, with slow entry, explosive growth, maturation within three years, and a rapid decline within five years and collapsed in 1995-1997 (Turvey & Sparling, 2002).

Reproduction

There is very little sexual dimorphism in emus that it is extremely difficult to identify the sexes. During the breeding season, the males are comparatively lighter than females.

Generally emus are breedable from around 18 months of age however this period can go up to two years. Emu is a seasonal breeder, breeding in winter for around six months. Emus start pairing from October and there are instances where, they start laying as early as in November. The pair mates every day or two, and every third or fifth day the female lays eggs, which might continue till April (Hermes, 1996).

Males lose their appetite and construct a rough nest in a semi-sheltered hollow on the ground from bark, grass, sticks, and leaves. Once the male starts brooding, the female mates with other males and would continue to lay. Emu chicks are precocious and have distinctive brown and cream stripes which would fade after three months.

A well managed female emu lays up to 30 eggs in a year. Emu's eggs are dark green in colour weighing around 500-700 grams. Female emus may lay eggs every 3 or 5 days. Emus are peculiar in that the male incubates the eggs and some times during the process would lose upto 20- 30% of its body weight. Male emus are so protective of the eggs that they stop eating and drinking and go into a phase similar to hibernation. Emu has longevity of around 40 years. Under good management conditions, an emu may lay eggs for up to 25 years (Lance, 2001).

Emu has the longest incubation period among ratites which is around 52-54 days. The conditions of incubation are widely varied around the world; still a probable one is given in the Appendix.

Emu farming is complementary to agriculture, eco friendly and is likely to be a profitable business for several reasons. Emu is a sturdy bird with an efficient immune system and the ability to survive in extremes of weather. Almost every part of the emu's body is commercially valuable. Emu is capable of surviving any type of climate and adversities. It is a comparatively less aggressive bird which does not require special structures for their stay neither do they need large chunk of land. Only one acre of land is needed to raise 100 to 150 birds. A single person can easily manage an emu farm with 100 birds in it.

Housing of emus

Chicks and Juveniles are often housed in groups, but must be separated at seven to eight months of age, as there would be lot of fighting at that age. Adult emus may be housed in pairs or in groups. Pens should be spacious with around ----- space per bird. Visual barrier may sometimes be needed between emu breeder pens at times as some emus might spend lot of time displaying for other emus.

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