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Information on the morphometric measurements of Emus, including mass and body measurements, sexual dimorphism, and techniques used to determine age in adults. It also covers recommended furnishings for Emu enclosures, such as open planted enclosures, non-slip floors, and protective shelters. Additionally, the document discusses methods for capturing and restraining Emus, as well as common injuries and their causes.
Typology: Summaries
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Kelly Swarbrick 2008
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This Emu Husbandry Manual is intended to present the current scientific, experiential and practical understanding of the captive care of Emus. Some contributions lend themselves to scientific rigor, where material presented is supported by peer-reviewed literature. Other contributions are based, out of necessity, on the collective experience of professional keepers, because relevant scientific literature is scant or non-existent. The author cannot be, and is not, legally, financially or in any other way, responsible for the application of techniques described within the Manual. When undertaking any procedures or techniques outlined in the Manual, it is up to individual workers to assess the unique circumstances of their situation, apply common sense, and subsequently apply any procedures or techniques at their own risk. In all cases, the reader of this Manual is cautioned not to use this manual as an exact step-by-step guide, but rather as a starting reference point for further case-specific studies.
the risks associated with exposure to harmful UV rays.
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1 Introduction
The curious and docile nature of Emus, Dromaius novaehollandiae , brings much enjoyment to people who observe or work with them in captivity. These large, flightless birds are an Australian icon and are seen throughout zoological institutions, wildlife parks, and farms worldwide.
The relationship between man and Emus has been a rocky one; two species and one subspecies of Emu have sadly been wiped out. Emus have been regarded as a pest to farmers in the past and attempts have been made to cull numbers however luckily for the Emus, many attempts failed due to their tough constitution and ability to continue running despite injury.
The agility and speed of Emus has aided them in escaping major threats to their survival. Their bodies are built to withstand the harsh climatic conditions of Australia and their ability to locate food in a diversity of locations has definitely benefitted their survival. In fact, Emus will basically have a go at consuming almost anything and surprisingly can withstand swallowing even the harshest of objects (rubber plugs to name one).
Once considered a major threat to the farming industry, Emus are now farmed themselves in Australia and largely overseas. Emus are farmed for their meat, eggs, leather, feathers and oil. Emu oil has a long list of benefits on the human body and is used as an alternative treatment for skin problems, hair loss, arthritis and many other medical conditions.
Emus have a very interesting social structure, with males playing the major role in rearing chicks. It is the father, not the mother, who incubates the eggs and raises the young. The little bundles of creamy fluff with black squiggly stripes are irresistibly cute to anyone who encounters them.
Emus are hardy animals and this is most likely why they are so easy to care for in captivity, that is of course, if appropriate measures are undertaken to provide them with their physical and behavioural needs. Their resilience in captivity also comes as a disadvantage to them because they are able to withstand enclosures that are not entirely suitable. I have visited a handful of institutions which house Emus and found that over half of them were too small and lacked adequate enrichment furniture such as ponds in which they love to swim.
The objective of this husbandry manual is to outline the minimum standards for keeping Emus in captivity; however I urge keepers to exceed those standards. I hope that whoever reads this manual gains as much enjoyment out of it as I have had writing it.
Kelly Swarbrick
No Regional Program, Management Level 3.
Least Concern (BirdLife International 2008).
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On maturity this bird does not have a ruff or bib. It looks 'flat-chested' compared to the other two subspecies. The pendulous pouch is almost non-existent in this emu. Like D. novaehollandiae woodwardi , the metatarsus bone is long with a small diameter, making this bird taller than D. novaehollandiae novaehollandiae. The feathers are the darkest of the three subspecies. This subspecies originated in southwestern Australia (Ramey 2007).
A subspecies known as the Tasmanian Emu, Dromaius novaehollandiae diemenensis , became extinct around 1865.
Two dwarf Emu species of Kangaroo Island and King Island, Dromaius baudinianus and Dromaius ater, became extinct shortly after European settlement in the early 19th
century. (Christidis & Boles 2008)
None found. Emus are sometimes wrongly classified in the Order: Struthioniformes.
Note: Dromaius novaehollandiae , in Latin, means "fast-footed New Hollander”.
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3 Natural History
The Emu, Dromaius novaehollandiae , is a large, flightless bird placed in the Ratite group along with all other species of flightless birds: Ostrich, Rhea, Cassowary (closest relative), and Kiwi (Jeffrey 2001). Emu is surprisingly not an Aboriginal word and seems to have been derived from an Arabic word that means “large bird” (San Diego Zoo 2008).
Emus have been living in Australia for an extremely long time, in fact their ancestors called Dromornithids (part of the Australian megafauna), coexisted with dinosaurs. Originally there were three different species of Emu, but unfortunately due to hunting by Europeans in the 19th^ century, there is only one species left today (Wikipedia 2008).
On one hand, humans have wiped out two species of Emu as well as the Tasmanian subspecies of Emu, and reduced Emu numbers within local wild populations on the mainland. On the other hand, agricultural development and water provided for domestic stock, has enabled the Emu to live in Australia’s Outback, which was once too dry for its survival (San Diego Zoo 2008).
In 1932, following a hot summer, wild Emus in Western Australia went on a rampage in search of food and water. Under pressure from farmers, the Australian Government sent a Royal Australian Artillery unit to Western Australia, led by Major Meredith and armed with machine guns and 10,000 rounds. It was estimated that 20,000 Emus were causing the damage. So began the Great Emu War.
Surprisingly, “the birds proved to be more adept in terms of both camouflage and strategic retreat than the soldiers themselves, and they dispersed rapidly in small groups when they were shot at” (Folch 1992).
Less than a week after the war had begun, the Defence Minister ordered a withdrawal. Only 12 Emus had been killed and onlookers were amazed at the fact that Emus could keep running once they had sustained injuries (GEA 2001). Major Meredith was quoted: "If we had a military division with the bullet-carrying capacity of these birds it would face any army in the world. They could face machine guns with the invulnerability of tanks. They are like Zulus...." (GEA 2001).
It is the biology of the Emu that aided them during the Emu War. Their ability to run at such fast speeds (up to 50km/h) is due to their extremely specialised pelvic limb musculature and powerful feet with three forward facing toes. They are the only birds to have calf muscles. Emus are also very good swimmers (Wikipedia 2008).
On very hot days, Emus pant, using their lungs as evaporative coolers, to maintain their body temperature. In cooler weather Emus breathe normally, and rely on their large nasal passages, which have multiple folds inside to recycle air and create moisture for reuse. As cool air passes into the lungs, it warms due to the extraction of heat from the nasal region. When the Emu exhales, the “cold nasal turbinates [highly folded nasal passages] condense moisture back out of the air and absorb it for reuse” (Wikipedia 2008).
Another biological aspect of the Emu, which provides protection from hot weather conditions, is its plumage. The tips of the double-shafted feathers are black, which absorbs solar radiation, and the feathers are loosely packed in a way which insulates the skin. The insulation provided by the coat prevents the heat from flowing to the skin (Wikipedia 2008).
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Note: The following measurements have been derived from data based on individual Emus therefore they are not indicative of the measurements of the overall Emu population.
Table 3.1 : Mass and Basic Body Measurements of Dromaius novaehollandiae.
Height
190cm (Simpson & Day, 1994) Length (bill to tail) 1340mm (MSU 1998) Wing Length 20cm (Billabong Sanctuary 2007)
Leg Length 1045mm995mm^ (MSU 1998)(Biewener & Main 2007) Length of Femur 244mm (Biewener & Main 2007) Length of Tibiotarsus 424mm (Biewener & Main 2007) Length of Tarsometatarsus 327mm (Biewener & Main 2007)
Foot Length
155mm 170mm
(Biewener & Main 2007) Length of skull (bill + cranium)
160mm 155mm
Length of bill 65mm 90mm
Head-body length (neck) ~570mm (Estimate from Emu at Oakvale Farm) Weight 30 to 55kg* (San Diego Zoo 2008) *I was unable to find records on the specific weights of the three subspecies.
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Figure 3.1 : Skeleton of Emu Dromaius novaehollandiae (Post 2008)
Physically, it is hard to distinguish between male and female Emus because they are similar in appearance, however the female Emu is larger in mated pairs, weighing about 5kg more than males (Ivory 1999). The female’s body plumage is darker before breeding, black feathers cover the head and neck (Simpson & Day 1994).
Emus have three toes in a tridactyl arrangement, a feature which allows them to run. Emus, along with all Ratites, differ from other birds because they lack a keel, which is a breast bone to which flight muscles are attached. Emus also lack a ‘preen gland’ therefore their feathers are dry and not oily (Wikipedia 2008).
Emus are also the only birds with “gastrocnemius muscles [calf muscles] in the back of the lower legs” (Wikipedia 2008).
The shaggy body feathers of the Emu are greyish brown in colour; the shafts and tips of the feathers are black (DEC WA 2007). A unique feature of the Emu feather is that it has two shafts, a main shaft and secondary shaft. Emus have a shaggy appearance because their shafts lack tiny hooks to bind them together; therefore they hang limply from their body (Billabong Sanctuary 2007).
Black feathering occurs on the Emus face and on the back of their necks. The sides of their neck are blue in colour (Alderton 2004). Emus have short black bills and eyes that are reddish in colour (Alderton 2004) (Figure 3.2).
Tarsometatarsus
Femur Tibiotarsus
Wing
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Figure 3.3 : Adult Emus (top) and Juvenile Emu (bottom)
Emu chicks are downy and cream in colour with dark brown to black body stripes (Figure 3.4). The stripes are arranged in a “squiggly pattern on top of the head” (Billabong Sanctuary 2007). When viewed from above, the colouration of the Emu chick helps break up the outline of the body, making it harder for predators to spot them (Billabong Sanctuary 2007).
F igure 3.4 : Emu Chicks
Kelly Swarbrick 2008
Kalma 2007
Kelly Swarbrick 2008
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Emus occur naturally in all states on the Australian mainland (Billabong Sanctuary 2007). A subspecies known as the Tasmanian Emu, Dromaius novaehollandiae diemenensis , once inhabited Tasmania, however it soon became extinct after the arrival of Europeans (AMO 2001). Also extinct are two dwarf subspecies of Emus that lived on Kangaroo Island and King Island, Dromaius baudinianus and Dromaius ater (AMO 2001).
Despite these major losses, Emu numbers have increased since European settlement due to the abundance of man-made watering holes for domestic stock as well as the Emu’s ability to reproduce rapidly. “It is estimated that the wild Emu population is 625,000-725,000, with 100,000-200,000 in Western Australia and the majority of remaining populations in New South Wales and Queensland” (AMO 2001).
Simpson & Day’s Field Guide to the Birds of Australia (2004) maps the distribution of the three extant subspecies of Emu, Dromaius novaehollandiae novaehollandiae (in the southeast), Dromaius novaehollandiae woodwardi (in the north), and Dromaius novaehollandiae rothschildi (in the southwest) (Figure 3.5).
A = Race novaehollandiae E B = Race rothschildi E C = Race woodwardi E North-south annual migrant in Western Australia
Figure 3.5 : Distribution of the three extant Dromaius subspecies
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In the wild, Emus live for an average of 5 to 10 years (Billabong Sanctuary 2007). They have been recorded to live for up to 19 years (maximum) (ASDP 2008).
Emus have a much longer life expectancy in captivity, up to 35 years (San Diego Zoo 2008). They have been recorded to live for up to 40 years (maximum) (ASDP 2008).
There are no known techniques used for determining the age of adult Emus however it is possible to tell the difference between juvenile Emus and adult Emus (refer to section 3.1.3 (Figure 3.2)).
Emus are fully-grown at twelve to fourteen months of age and do not reach sexual maturity until they are approximately two years of age. This fact may also enable you to roughly determine the age of an adult because if the Emu is fully-grown and not breeding, you can assume it is between 1-2 years of age. (San Diego Zoo 2008).
Although unreliable, the weight of an Emu could possibly indicate their stage of development. “The body weights of emus have been reported to be about 40 kg at 64 weeks of age, 40.6 kg at 70 weeks of age, and approximately 55 kg at maturity” (Dunk et al. 2003).
Skulling is a technique used to determine the age of birds and is based on “the extent of pneumatization in sections of the skull overlying the brain (the frontals and parietals)”. A young bird’s skull consists of a single layer of bone; skull pneumatization is the gradual formation of another layer of bone beneath the original layer of bone. Depending on the species, this process may take from four to twelve months.
Recognisable patterns are produced in the distribution and extent of air pockets and small visible columns of bone developing between the two layers of bone. These patterns can actually be seen through the thin layer of skin on top of a bird’s head by brushing aside the crown feathers using water (Figure 3.6).
Figure 3.6 : Two common sequence patterns of skull pnematicization (a) periferal pattern (b) medial line pattern.
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Various studies have been carried out in order to determine the age of different bird species. Jannett (1983) conducted a study on ‘A Quantitative Method for Age Determination of Adult Birds’. Jannett (1983) hypothesised that the differential growth of bones would provide a means for identifying ages of adult birds. White Leghorn chickens of two different age cohorts were used for the study and the variables were the weights of different bones within the body. Jannett (1983) concluded that: “the technique provides a means of separating adult classes of birds hitherto not distinguishable on the basis of plumage”.
The all-time best method for determining the age of adult birds, no matter what the species may be, is good record keeping! Records of Emus should be kept from hatching. It is the most reliable way to determine the age of adult Emus. Other techniques for determining the age of birds can create confusion and are also very time consuming compared to looking up a record.
