The Cassowary in Captivity

Richard Perron, B.Sc. (Econ)

(First printed in the International Zoo News No. 240 Vol. 39/7 [1992])

 

Double-wattled Cassowaries

Despite almost four hundred years of captive history in European zoos, the cassowaries of Australia and New Guinea remain largely unknown to the general public, and are too often an enigma to those zoos which keep them. Only one book (Rothschild, 1899) has ever been devoted to cassowaries, and that largely concerns the morphology, distribution and taxonomic relationship between the species and imagined subspecies. Although a few good first-hand accounts of husbandry do exist in various journals, the published literature is both sparse and fragmented. Consequently, myths and misconceptions abound about these birds, as well as much lamentable ignorance.

Cassowaries are flightless and belong to the ratite group, which is probably the oldest living branch of the the birds. Although it is certain that their distant ancestors were able to fly, the lack of a keeled sternum, to which all other birds attach their wing-flapping muscles, suggests that the experiment was soon discontinued on the grounds of ergonomic unsuitability. Ratite ancestors were probably similar in size to the tinamous, to which they are related, and subsequently increased their size after losing the ability to fly. Extinct ratites include the giant elephant birds (Aepyornithidae) of Madagascar, the variously sized moas (Dinornithidae) of New Zealand and the mihirungs (Dromornithidae) of Australia. The distribution of all extant ratite species was achieved through non-flight locomotion and as a consequence of continental drift movements during the last 85 million years. The closest living relative to the cassowary is the emu of Australia, while both are near relatives of the New Zealand kiwis. There are three cassowary species in a single genus - Casuarius casuarius (Linnaeus 1758). C. bennetti (Gould 1857) and C. unappendiculatus (Blythe 1860). Each of these species is readily identifiable by the presence or absence of wattles on the front of the neck, even in newly-hatched chicks.

C. casuarius, sometimes misnamed C. bicarunculatus, is the best known of the cassowaries, and was first brought to Europe by Dutch traders in 1597, subsequently being called the "Ceram cassowary" due to its presumed island origin. In English, it is generally known as the double-wattled (two-wattled, twin-wattled) cassowary on account of its pair of pendulous fleshy wattles. It is also sometimes called the southern, or Australian, cassowary because it is the only member of the genus found in Australia; where possible, however, nomenclature should reflect some obvious and unchanging characteristic, and while the species is native to Australia (and indeed there may be grounds for accrediting subspecie status to the population) it is also widespread in New Guinea, which is where the majority of captive specimens are derived from.

C. casuarius wattles

The adult double-wattled cassowary, Casuarius casuarius, is a very large, black feathered bird with a brownish helmet, or casque, rising blade-like from its head. Height varies, according to sex (the cassowary male is always smaller than the female), from 1.4 to 1.7 metres in normal walking posture, but easily reaches 1.6 to 1.9 metres when the bird assumes an upright stance if surprised, aggrieved or in mating display. The iris is brown and the whole of the head, neck and throat are devoid of feathers in adult birds, the juvenile gradually shedding its brown feathers over three years until the skin becomes fully exposed. The bare skin of the head is whitish, blending into blue around the ears and beak, which has a thin yellow or white stripe on the lower bill. The throat and forepart of the neck are blue while the corrugated skin of the nape and shoulders is reddish, this colour extending onto the back in some birds. The lower leg has scales instead of skin and has three toes. The upper leg and thigh skin are blue beneath the feathers. The two wattles on the neck are usually red and may be joined at their base, separated slightly or wide apart, varying substantially also in length and thickness according to the individual. The colours referred to here and in describing the other species indicate the approximate area of the spectrum, rather than a fixed shade, as individuality, time of year and mood all create differences.

The great variation, both in captive birds and museum specimens, gave rise to a large number of proposed subspecies based on wattle size, helmet shape and neck coloration. After modern research, in particular recently into the Australian population around Mission Beach in Queensland, these 'subspecies' traits have been downgraded and, although the subspecies level is still erronously applied by some zoos to their captives, the diversity is now put down to the general genetic richness of the species. Trinominal status, certainly probable at the genetic level because of the isolated populations, remains a thing of the future in view of the limited sample currently available.

C. unapendiculatus

Generally slightly larger, 1.5 to 1.8 metres, than the double-wattled cassowary, Casuarius unappendiculatus is the most recent of the genus to be discovered (in 1860), and is probably today the most endangered. Variously called the single-wattled, one-wattled or northern cassowary, it has been suggested that it forms a superspecies with C. casuarius. Their ranges do not overlap and the species is confined to lowland northern areas, west of the Ramu river in Morobe province through to western Irian Jaya and on Yapen Island. In the specimens I have inspected, the brown helmet tends to be larger and more open, flared to the rear, than in C. Casuarius, but I have also seen one where the helmet was compressed forward and flattened. The head, face, throat and upper neck skin is blue; front and lower rear neck, wattle and shoulders are red or yellow-gold. Two distinct colour variations in neck markings have promoted the general acceptance of two subspecies, the golden-necked and red-necked (C. u. unappendiculatus and C. u. rufotinctus respectively). Because the sample in captivity is so small, less than one-tenth that of the double-wattled cassowary, and the wild population is virtually unrecorded and unresearched, the same caution is needed in defining any subspecific status.

The smallest of the cassowaries, Casuarius bennetti, is about 1.0 to 1.4 metres high. Known generally as the dwarf cassowary, it is also called the Bennett's, mountain or little cassowary. It is the only cassowary without wattles, but does have a red, or purplish, round spot where the wattles join the neck in the other cassowaries. Its helmet is black, more triangular in form, and gives the impression of having been flattened by a blunt instrument from behind. The head and face are black sometimes with a pink cheek patch. The neck is deep blue and the shoulders red or violet. It is common in New Guinea, but is the rarest cassowary in captivity elsewhere in the world. Primarily a bird of the higher areas of New Guinea, being found up to 10,000 feet in montane forest, it leaves the lowland rain forests to its larger cousins. Although I have found both single-wattled and dwarf cassowarries in the same lowland village on the Karawari River in East Sepic province, and was assured they could both be found in the area, the likelihood is that the dwarf cassowary had been captured in the highlands and sold or traded into the region.

Instances of mixed distribution on offshore islands, such as Yapen, Aru and Ceram (where the first captive cassowary came from) are almost certainly the result of human trading rather than natural migration, as is also the dwarf cassowary population on New Britain. The trinominal situation is the same as with the other two species.

Although the cassowaries are not listed under CITES, export of these birds is prohibited by the national laws of the three countries (Australia, Papua New Guinea and Indonesia) where they are naturally found. Wild-caught birds from the New Guinea mainland, where the natives are allowed to keep and kill cassowaries for food, are often exported illegally through the traditional inter-island trading links, and appear in the Singapore bird market as locally bred. Under disinterested official scrutiny, these birds are then sold to foreign buyers as captive-bred specimens.

While being quite distinct from one another, the three species nevertheless have many physical and behavioural similarities which allow them to be treated, on the basis of current knowledge, as one entity for the purpose of captive management. Like other ratites, cassowaries have no uropygial gland for oiling the feathers, beak and scales to keep them supple and waterproof, although they habitually preen themselves like other birds. Apteria, eyelashes and a wing claw are present, but there is no alula (bastard wing), nor are there feathers under the wing. They are monomorphic; although the female is larger than the male, with a brighter coloration, and is usually the dominant bird in captivity. The male alone incubates the eggs and stays with the young birds until they are about nine months old. Adult and subadult birds of either sex are invariably aggressive to one another and usually need to be kept separated until breeding takes place; paired birds will sometimes live together peaceably (if their enclosure is large enough to allow flight?). They are diurnal, sleeping during the night, but strong moonlight and artificial light will cause them to become active.

Young birds are born without down and (remarkably similar to other ratites) have light brown feathers with wide lateral stripes of a darker brown on their backs. At about three months the stripes are moulted out, and the juvenile retains the uniform brown plumage until it starts gradually changing to the adult black from about one and a half to three years of age. In European captivity complete adult plumage is uasually attained at five years.

Observations I have made suggest that climate, housing and diet affect the speed of feather change - birds in the wild, or in suitable climatic environments, reach adult colour and sexual maturity at three years of age.

Like the Emu (their closest relative), the cassowaries have an enlarged hypopennae (afterfeather), which in most birds remains small or dormant; this results in a unique double-plumed body feather, both being replaced at the same time after the (usually annual) moult. The wing is vestigial, with the remiges (flight feathers) reduced to five or six spine-like quills ( 6.0 to 20.0 cm long in the adult), much favoured by New Guinea tribesmen for adornment in their noses and ceremonial headdresses. There is a claw on the major digit of the wing, a primitive reptilian feature, but I have never observed any use for it in cassowary behaviour. Although the wings are stretched out by an aggressively advancing cassowary and the clawed digit is at the extremity, I have never seen any movement with the wing which could be construed as anything other than an attempt to aid balance or to add to the bird's imposing size. Despite one isolated report to the contrary, I have no reason to believe - after watching many fights between captive birds and having been personally subjected to several attacks by cassowaries - that the wing is used to strike an opponent, either offensively or defensively. From its disuse, the whole cassowary wing must be considered poorly supported muscularly and easily damaged if used for leverage in restraint or any offensive action.

Cassowaries are precocial, and within two or three days of hatching the young bird is able to fend for itself. It will imprint easily on humans, becoming very tame and following its keeper everywhere. It is lively, inquisitive and dependent; it needs draught-free warmth (30oC for the first three weeks, and then reducing 1oC every three days until a minimum of 20oC is reached, which should be maintained until the twelfth week), comforting, lots of water to drink and a high-calcium, protein-rich diet such as Mazuri Ratite Chick Foods. Newly hatched chicks may need to be stimulated with live mealworms to eat in the absence of parental example. Chicks, like older birds, will appreciate small cubes of apple, pear, banana, tomato and other soft fruit (not citrus fruit, pinapples or kiwi fruit), with the occasional piece of raw beef or ox heart thrown in.

A young adult will eat up to ten kilos of this kind of fruit salad every day if given the chance. Although the cassowary is the world's largest frugivore, its natural diet in the wild often does not reflect our conception of fruit, and most items included would be viewed as dry, tough and tasteless. In fact, a very high percentage of what the cassowary normally eats is excreted whole, having passed visibly untouched through its unique digestive system. It seems that the cassowary, which spends most of its time in the rain forest searching for food, requires the bulk input simply to gain a minimum quantity of useful energy and vitamins for survival; its digestive system retains what it can, the rest being quickly discarded. This has four side-effects: cassowaries will often pick through their own droppings for useful morsels, they are less susceptible to impactation than other ratites, they act in the wild as vital dispersers of forest plants, and in captivity they appear to be constantly suffering from diarrhoea because the food eaten contains little indigestible bulk. Any balanced pellet diet feed, such as Mazuri Zoo Diet A, will be reduced to a liquid stream if the birds have adequate water (ten litres a day) to drink. The sign of a healthy cassowary is a loose bowel; solid faeces are a sign of trouble.

Sexing is easiest when the cassowary is young and examination physically practicable. There are a number of methods, including eversion of the cloaca as in waterfowl (which is suitable for chicks up to two weeks old), or the use of endoscopic speculums and optic fibre scopes, but the simplest, quickest and least traumatic for the older bird is direct palpation of the penis. The bird should be forced to the ground so it is in a crouching position with both feet underneath the body. One person, at least, will be needed to keep the bird in this stance while another, using a lubricated surgical glove, can then try to explore, after the spasms have ceased, into the cloacal region for the presence of a penis or tiny clitoris. Sexually mature male cassowaries (and emus) can be easily identified using this method because the penis is large, but immatures and out of condition birds can lead to confusion. Feeding Valium tablets inserted into grapes or other soft fruit two hours before the examination will minimise the bird's panic and outrage. An alternative method of sexing is to take a blood or tissue sample for analysis at one of the available expert laboratories. If you do not want to try any of these methods, you will have to wait until the first fertilised egg to be absolutely sure.

As the young cassowary grows, an eleven-fold increase in the first three months levelling off to about 30 kilos body-weight at one year and as much as 60 kilos at three years, its wattles and helmet will slowly enlarge, continuing to increase in size well after adulthood has been reached. The helmet is composed of a keratinous skin over a core of firm cellular foam-like material which grows above the skull and not out of it. It is relatively soft, not hard and bony as is often supposed, and can be bent sideways, squeezed and deformed. This may help to explain the wide variety of shapes evident in wild and captive-bred birds which in headlong flight may have hit small trees and bushes with some force thereby distorting the helmet shape. Crome & Moore (1987) suggest that the helmet has shock-absorbing qualities and has developed as a protective device for these rainforest birds. Since neither the Australian nor the New Guinea populations have serious predators apart from humans, and humans have only been around for at most 70,000 years in this region, they wouldn't do much charging about in the undergrowth in their absence and further research is needed on this subject. Certainly, the aggressive behaviour indicates some historical competitors and/or predators.

Other parts of the cassowary that grow are the feet with their three toes; all the distal phalanges are sheathed completely inside keratinous nails, especially the very long, sharply-pointed inside ones which may eventually reach 18 cm. By the time these weapons reach a respectable length, the cassowary inconveniently goes through a behavioral change, probably induced by puberty. The actual age varies from eighteen months to two and a half years, but when the time comes the puppy-dog adherence to humans changes to violent aggression against all and sundry - even the hand that feeds it. Despite long-term attempts to keep the birds tame, nothing I have been able to do has prevented hand-raised birds from turning into uncontrollable beasts. A fully-grown adult female double-wattled cassowary may weigh 80 kilos, can run at thirty miles (fifty kilometres) an hour, can jump five feet (1.5 m) into the air and simultaneously kick with it's foot, directing the dagger-length toe towards any chosen objective. A swift downward slash of the foot can easily slit open the side of a dog or the stomach of a man. Their inclusion in the British Dangerous Wild Animals Act (1976) is wholely justified and their potential to injure, maim and even kill should never be underestimated.

Such 'pets' require special housing and well planned enclosures. A strong plastic-coated chain-link (50mm x 50mm) fence, at least two metres high, with firmly cemented stout posts or metal tubes at three metre intervals on the outside, has proved adequate to contain even the most aggressive birds, and saves them from damaging themselves against the fence supports. Water moats separating birds from each other or from the public should be used with caution, since cassowaries are excellent swimmers who enjoy a bathe now and again. Apart from a small pool for both drinking and bathing, grass with several low shrubs and shady trees, preferably of a (non-poisonous) fruiting variety, will do much to enhance the quality of captive life. It is not advisable to place other birds or mammals in the same enclosure with cassowaries, although rats and arboreal species will probably survive - rats and swallows co-exist in my own huts.

An outdoor enclosure size of 600 m2 for a lone bird and 1,000 m2 for a compatible breeding pair should be considered a minimum. Indoor accommodation of at least 20 m2 for single birds and 36 m2 for pairs is recommended for the winter months in cold climates, with a smaller self-contained room which can securely sealed off adjacent to the double one if breeding is anticipated. Access doors to each room should contain a small window (not glass) and be made of strong material and lockable with bolts. Water and food supply should be installed to work automatically or be replenished from outside the rooms; containers are best fixed firmly to the walls and not loose somewhere in the room where they may cause injury. The cassowary drinks by scooping water up in a forward motion, so small-diameter containers, such as buckets, are not suitable. Some sort of heating to keep temperatures above freezing is necessary (8oC stops most discomfort and avoids colds), although short below-zero periods do not appear to cause injury. Emus seem quite capable of surviving prolonged exposure to -15oC, but I have not trusted their close genetic affinity to the extent of allowing my own cassowaries to try out their endurance.

Birds intended for breeding should be housed in neighbouring enclosures to become familiar with each other. The choice of when to allow birds to occupy the same enclosure must be dependent on the circumstances - some birds remain fiercely aggressive to one another right up to the mating display, while others live quite happily together all the year round. Like a lot of animals in captivity, which do not have to search for their food, the cassowary will often appear lethargic and listless. Females tend to be more active, wandering about along the perimeter fence to establish their territory, while the adult male will find a secluded spot and just sit there for most of the day, looking about and sometimes preening himself. Leading up to breeding time tension will rise and the male will become more active and aggressive at any provocation, but will still find time to sit at his favoured 'nesting' spot to show his parental suitability. Both birds will arch and concertina their necks, bow down and emit a deep booming grunt which vibrates the air for several hundred yards. At the same time the naked skin of the neck and the cheek are inflated, while the whole body trembles. They will do this display sometimes to intruders before attacking. When mating time comes, the two birds will circle each other and spring about in a way reminiscent of cranes, occasionally bumping against each other with the chest, until the male, with spits and hisses, succeeds in mounting the submissive female from the rear. Each egg must be individually fertilised in this way. The female will lay her eggs (virtually all months of the year have been recorded, but April to September seems to be the favourite period in Europe) at the spot the male has already chosen. Once the male begins to sit after the last egg has been laid, the female must be housed separately and not allowed near the incubation area.

Although the minimum breeding age is about three years, few birds in northern climates can be expected to reproduce before they are five or six. Both natural and artificial incubation have been successfully achieved in zoos and private collections for all species since the first dwarf cassowary in 1863. Clutch sizes vary between three and six dark green eggs (average size 90mm x 135mm, weight about 550g), but egg removal can induce much larger numbers (twenty and more). Egg laying frequency varies between four and six days, with about 50% fertility in captivity.

For natural incubation it is essential to furnish a room where the male will not be disturbed by the female or any intruders. If the male chooses to sit outside in the enclosure, measures to reduce visual, as well as physical, disturbance will be necessary. Inside, a floor covered with soft material, such as peat or composted grass cuttings, should be heated to about 24oC, using an underfloor heating system, to closely reflect natural conditions. The highest attainable rate of humidity, using sprinklers and pre-incubation floor soaking, is also recommended. During the whole of the 50-52 days' incubation period the male will not leave the nest area and will protect the clutch against all comers. In the wild, an incubating bird will not eat or drink and somehow is able to restrain all bowel activity. In captivity, food and drink may be made available, but are probably not essential for hatching or the well-being of the bird. Disturbances of any kind (e.g. cleaning etc.) can lead to serious injury and the breaking of eggs. Observation, preferably with video cameras, should be unobtrusive.

Successful artificial incubation temperatures range from 36.1oC to 36.4oC, and wet bulb from 27.3oC to 28.9oC, with 65% humidity. Bearing in mind the altitude at which artificial incubation takes place, more account should probably be taken of the natural habitat of the species being incubated; birds from mountain regions require different conditions from their cousins living at sea level. Hatch rates vary enormously, but are not usually above 50%. Newly hatched birds should be left in the incubator, or transfered to a brood box, for 24 hours until they are dry before being moved to a rearing pen. In the first two or three days of life the chick will loose weight as it internally consumes the rest of its yolk sac, and during this period the external yolk sac area should be sprayed with an antibiotic. Great care should be taken to fence off all water areas, including large drinking bowls, to protect very young chicks from drowning. Survival rates of both naturally and artificially incubated chicks are low compared with those of other ratites, and few become adults. Some first-generation captive-bred C. casuarius from Edinburgh and Whipsnade have been used for breeding with wild-caught mates, but only Whipsnade has succeeded in breeding from a pair of captive-bred birds. The first second-generation chick was hatched in June 1988 and is now on loan to Edinburgh Zoo, the second (August 1989) is now at Calgary Zoo. Both chicks came from clutches of four eggs with a hatch rate of only 25%. In recent years neither C. unappendiculatus nor C. bennetti has been bred in captivity.

Cassowaries are likely to reach a great age; 20 years is quite common, and 39 is the record in modern times. At some stage during its life the cassowary will have to be handled for transport or medical reasons. Young birds can be firmly grasped from behind by the legs and held against the body, but there is no easy way to handle a large adult bird and one should always watch out for the feet. Do not use hoods with cassowaries, because the artificial darkness does not calm them down, they get up and charge about blindly instead. A stealthy approach in the dark is also likely to meet with determined adult aggression, although young birds can be approached in this way. Coordination among the handlers, with clear instructions as to the plan to be followed, will avoid messy accidents. Cricket pads, on the legs and tied around the chest and abdomen, will help to protect the human at close quarters.

The first step should be to calm the bird down with drugs; I prefer Valium/Diazepam, using 2mg tablets, in grapes, for every estimated two kilos of body weight every 18 hours until they are groggy, because other animal tranquillisers never worked very effectively for me. Since the Valium stays in the body for 24 hours, feeding repeated doses every 18 hours effects a continuous build-up of the drug, allowing relatively easy and precise control of the necessary dose. The time sequence is a problem, however, if you are in a hurry. Once sedated, the best way is to entice the cassowary into a solid horse-box or movable cage so that no force need be used. Using large padded plywood sheets as shields, it may be possible to steer the cassowary where it is wanted. As a last resort, a large net should be thrown over the bird and three or four hefty individuals should pin it to the ground while its legs are hobbled together (leave about 20 cm of rope between the legs so that the bird can still move), wrapping sacking around the legs first to prevent chafing. A cradle, in the style of a parachute harness, made from canvas webbing is then an effective aid to assisted movement. This is essential for treatment and post-operational care if a leg is injured. Birds with broken legs should be put down immediately because I have yet to hear of a successful recovery by any ratite which suffered a broken leg.

Because of its digestive system, which does not possess a strong valve to prevent the return of food from the stomach, it is imperative that the bird be kept in an upright position to avoid choking; being trussed up and left on its side for any length of time could easily prove fatal for a cassowary.

As with many captive animals, the first obvious indication of a health problem in cassowaries is when the bird lies dead on the floor! Diagnosing illness is particularly difficult because of their aggressive behaviour and unmanageable size, so daily attention to behavioural and physical changes is essential, along with regular microscopic inspection of the faeces. The cassowary has a habit of sneezing, or emitting nasal noises, which can be misconstrued as signs of a cold; this behaviour occurs at all ages and is a low-key warning sign. Physical injuries, particularly to the legs, are not uncommon, and care should be taken that loose wires, and buckets and other containers, are not left in the enclosures or huts.

Fortunately, primary infectious diseases are quite rare, although Newcastle disease, tuberculosis, anthrax and aspergillosis have all been recorded. Rhinitis infections, particularly in young birds, due to stress, damp and cold affecting the nasal passages and breathing, are more common, as is bacterial enteritis. Nutritional disorders are frequently encountered in young and imported birds, perosis due to manganese deficiency and rickets caused by shortages of vitamin D or phosphorus. Coccidiosis, feather lice and mites are possible parasitic problems, and older birds may suffer from arteriosclerosis and gout. Stress itself, often a contributary factor in many diseases, is not as much of a problem with cassowaries as with some other ratites, such as rheas, but fights, bad housing, cramped conditions, poor diet and physical handling will all create traumatic conditions in the birds and may cause or aggravate other problems.

The precise status of cassowaries in captivity worldwide is a matter of speculation. Although ISIS maintains a record of those animals kept by its responding zoos, about 550 at the moment, these institutions represent much less than half of the probable total of cassowary keepers. Research in Germany (Perron, 1992) substantially confirms this and would indicate a minimum world captive population, outside Papua New Guinea and Irian Jaya, approximately as follows :

Germany Survey 1992 ISIS members March 1998 Estimated total world captive population
C. casuarius
36
141
260
C. unappendiculatus
5
3
14
C. bennetti
1
4
10
Total
42
87
284

 

A studbook for the double-wattled cassowary is kept by Edinburgh Zoo.

 

References

 

Anderson-Brown, A.F. (1979): The Incubation Book. World Pheasant Association.

Arnall, L., and Keymer, I.F. (1975): Bird diseases. T.F.H. Publications, New Jersey.

Benntruperbaumer, J. (1991): Consultative Committee for Casuary Preservation, Mission Beach, Queensland. Personal communication.

Birchard, G.F., Snyder, G.K., Black, C.P., Schmitt, E., Lyvere, P., and Kane, B. (1981): Humidity and successful artificial incubation of avian eggs: hatching the cassowary. International Zoo Yearbook Vol.22, pp. 164-167.

Bruning, D.F. and Dolensek, E.P. (1986) Zoo and Wild Animal Medicine. W.B. Saunders, London.

Coates, B. (1985): The Birds of Papua New Guinea (Vol.1). Dove Publications, Queensland.

Crome, F.H.J. and Moore, L.A. (1987): The cassowary's casque. Emu No. 88, pp 123-124.

Deeming, D.C. and Ferguson, M.W.J., Edit. (1991): Egg incubation; Its effects on embryonic development in birds and reptiles. Cambridge University Press, Cambridge.

Fisher, G.D. (1968): Breeding Australian cassowaries at Edinburgh Zoo. International Zoo Yearbook Vol. 8, pp 153-156.

Hickman, D. (1992): Whipsnade Zoo. Personal communication.

Kummerfeld, N. (1986): Tierärztliche Hochschule, Hannover. Personal communication.

Lee, A.R. (1991): Management Guidelines for the Welfare of Zoo Animals: Ratites. Federation of Zoological Gardens, London.

Lincoln, T. (1988): Dakota Zoo. Personal communication.

Perron, R. (1992): Captive Ratites in Germany; 1992. Unpublished survey.

Pycraft, W.P. (1899): Dissertation on the morphology and phylogeny of the Palaeognathae and Neognathae. Transactions of the Zoological Society of London Vol. 15.

Rundel, R.S. (1992): California. Personal communication.

Rothschild, W. (1899): A monograph on the genus Casuarius. Transactions of the Zoological Society of London Vol. 15.

Stevenson, M. (1992): Edinburgh Zoo. Personal communication.

Whitehead, M. and Masson, G. (1984): Notes on the double-wattled cassowary at Twycross Zoo. Proceedings of the ninth annual Symposium of the Association of British Wild Animal Keepers, pp. 51-55.

Young, H.G. and Kilkenny, M. (1984): Breeding history and husbandry of twin-wattled cassowary at Edinburgh Zoo. International Zoo News, Vol. 31, No.4. pp 10-14.