Southern cassowary

Name and taxonomy

Carl Linnaeus described the bird in 1758 as Struthio casuarius, from a specimen collected on Seram. The species now stands as the type of the genus Casuarius. The scientific name comes from kesuari, the Malay name for the bird. English also calls it the double-wattled cassowary and the Australian cassowary. Many other scientific names were published over the years and all are now treated as synonyms.

Most authorities treat the species as monotypic today. Several subspecies were described, but none has held up. The skin colours that the descriptions rested on fade in a museum specimen. People have also traded live cassowaries for centuries, so a bird's origin may not be where it was found.

Evolution and relatives

The cassowary is a ratite, which places it with the emu, ostrich, rhea and kiwi. The emu is the sister lineage, and both sit in the family Casuariidae. Two other cassowaries are alive, the dwarf cassowary and the northern cassowary. The southern cassowary is the largest of the three and the only one with two wattles.

The wings have shrunk to almost nothing. What remains of the primary feathers is five or six long white spines. Like other ratites, the bird traded flight for size and for legs that run and kick. The casque is built from spongy bone and cartilage rather than solid horn. Scientists found in 2026 that cassowary casques glow under ultraviolet light.

Appearance

The plumage is black, stiff and bristly, so it looks more like coarse hair than feathers. The head and neck carry no feathers and show bright blue skin with red on the nape. Two red wattles hang from the throat and reach up to 18 cm long. The casque stands 13 to 20 cm high on top of the head. The bill measures 9.8 to 19 cm.

A typical adult stands 1.5 to 1.8 m tall. The largest birds on record reached about 85 kg and 2 m in height. Females are the larger sex, at 46.7 to 76 kg against 29.2 to 55 kg for males. A female also carries a taller casque, a bigger bill and brighter bare skin. Queensland hunters between 1870 and 1894 shot and weighed birds of 76 to 119 kg.

The legs are thick and the feet have three toes. The claw on the inner toe grows up to 12 cm and comes to a point like a dagger. A chick is brown, marked with black stripes that run from head to tail. They keep those stripes for three to six months and then turn plain brown. The bright neck colours arrive at about one year, and the casque takes four or five years to finish.

Habitat and range

The species lives in New Guinea, on Seram and the Aru Islands, and on Cape York in Australia. Lowland tropical rainforest is the core habitat. Birds also use eucalyptus forest, savanna woodland, palm scrub, mangroves and forested swamp. In Australia they stay below about 1,100 metres, and in New Guinea below about 500 m. The occurrence range covers about 396,000 square kilometres.

A cassowary keeps a home range and defends it against other cassowaries. Nobody has measured how much forest one bird needs. The number and kind of fruiting trees a cassowary depends on suggests the area is large. The bird swims well and crosses rivers and streams without trouble. It also jumps, and a startled bird can clear nearly 2 m from a standing start.

Diet and feeding

Fruit is the heart of the diet. The bird cannot fly, so it works the forest floor and takes what has dropped. It swallows fruit whole and can digest some fruits that would poison other animals. Fungi, insects, snails and other invertebrates go down as well. Small fish, frogs, birds, eggs, nestlings, small mammals and carrion round out the list.

Dung studies name the trees the bird eats from. Davidsonia pruriens and Syzygium divaricatum turn up often, along with palms and laurels. Members of the quandong and myrtle families appear as well. One study recovered seeds of 78 plant species from cassowary droppings. Seeds of 70 of those species still germinated after passing through the bird.

Wild and captive birds have both been seen swallowing soil when food runs short. That behaviour probably supplies minerals the fruit does not give. A single dropping can carry as much as a kilogram of seeds. Nothing else in these forests moves large seeds that far, so the bird acts as a keystone species.

Behaviour and social life

The southern cassowary lives alone for most of the year. Pairs form only in the breeding season, in late winter or spring. A bird moving slowly through the forest makes almost no sound. An alarmed bird crashes through the undergrowth at up to 50 km/h. It uses the casque to shove vegetation aside as it runs.

The bird is shy and avoids people where it can. It turns aggressive when cornered, when guarding chicks or when it expects food. Defence means jumping and kicking forward with the long inner claw. Adults appear to have no natural predator in the forest. People are the exception, because cassowaries are hunted for meat in parts of New Guinea.

Communication and senses

The voice of a cassowary is a very deep roar that travels far through dense forest. The call runs about 40 decibels above the background noise of the forest. It reaches down to about 23 hertz, which is near the lower limit of human hearing. Few birds have been recorded making sounds that low. The roars work as territory markers and tell other cassowaries where a bird is.

Researchers wonder whether the casque has a part in this. One idea is that the casque helps produce the deep calls, and another is that it helps receive them. Heat loss and visual signalling are the other explanations on offer. The ultraviolet glow found in 2026 differs between the southern and northern species, which may support a signal role.

Other sounds appear to fill out the range. A thunderous call belongs to the mating season, and hissing and rumbling serve the rest of the year. A courting male gives a booming call while he swells his throat. Chicks whistle and chirp at a high pitch to keep in touch with their father.

Reproduction and life cycle

The female runs the mating system in this species. She pairs with two or three males in a season and starts a new nest with each one. Breeding falls in the southern winter, from about June to July, when fruit is plentiful. The male builds the nest, a mat of plant material on the ground. It is 5 to 10 centimetres thick and up to 100 cm across, so water drains away from the eggs.

A clutch holds three to five eggs. Each egg is 11.8 to 15.8 cm long and 8.2 to 10.2 cm wide, and weighs 567 to 634 grams. The shell has a grainy surface and starts bright pea green before it fades. The male alone incubates, for about 50 days. The female takes no part in the sitting and moves on to her next mate.

Chicks hatch fully feathered and can walk and explore within hours. The father raises them alone and teaches them where to find food. They become independent at nine to twelve months old. Adult plumage and a full casque take four to five years to develop. Captive birds have lived 20 to 40 years, and the wild lifespan is not known.

Predators and threats

Habitat loss is the largest threat to the species. Logging and land clearing probably break the forest into patches that a bird cannot cross safely. Road building brings traffic into the range, and vehicle strikes kill many birds. Feral pigs and dogs disturb nests and eat eggs and chicks. Hunting still takes birds in parts of New Guinea.

Feeding by people makes the danger worse in Australia. Fed birds move towards houses and roads, where cars and dogs are waiting. Queensland trialled a system that uses artificial intelligence to spot birds near a road and warn drivers. Fatal crashes may have dropped by up to a third, though a lower speed limit came in at the same time. Animal Diversity Web reports a decline of about 30 percent over thirty years.

Population and conservation

The IUCN assessed the southern cassowary as Least Concern in 2018. A 2002 study put the world total at 10,000 to 20,000 birds. Between 1,500 and 2,500 of those lived in Australia. A federal draft recovery plan in June 2023 gave an Australian figure of about 5,000 birds. Naturalists have logged 3511 observations of the species on iNaturalist.

Australia appears to treat the bird far more seriously than the global list does. The national population is Endangered under the federal EPBC Act. Queensland listed the northern population as vulnerable and the southern one as endangered in November 2022. Land clearing in Australia has now largely stopped, which helps.

A 2021 study found that large reserves had allowed the species to recover. A paper in March 2023 listed 23 Australian species that no longer meet the threatened criteria, and this bird was one. The team judged the population stable, or falling slower than the threshold. Zoos around the world breed the species, including White Oak Conservation in Florida.

Relationship with humans

The cassowary has a reputation as the most dangerous bird alive. Guinness World Records gave it that title in 2004. Deaths are in fact very rare, and only two have been reported since 1900. A 2003 study of 221 attacks found that 150 of them were against people. Three quarters of those came from birds that people had fed.

The attack pattern appears to be mostly bluff. The bird chased or charged in 71 percent of cases and kicked in 15 percent. Food explained 73 percent of the attacks, and defence of chicks or eggs explained 7 percent. The first recorded death was on 6 April 1926, when two boys attacked a bird with clubs in Queensland. A kick opened a 1.25 cm wound in the neck of the older boy, who died soon after.

The second death happened in Florida on 12 April 2019. The bird's owner, a man of 75 who had raised it, fell over and was clawed. People in New Guinea have taken cassowary chicks and reared them in villages for centuries. Feathers went into headdresses, quills became nose ornaments and the grown bird became meat. Cassowaries have been traded through Southeast Asia for more than 500 years.

In culture and myth

The cassowary appears to matter more in New Guinea belief than any other bird. For the Kalam people a cassowary is a relative, and it is not classed with birds at all. They switch to a special speech register while eating cassowary meat. The Maring of Kundagai sacrificed cassowaries in certain rituals. Highland groups keep half-tame birds for ceremonial gifts and for food.

Some archaeologists argue this makes the cassowary an early case of bird keeping. Collecting eggs and rearing the young may predate the keeping of chickens. The trade in live birds may also explain cassowary populations on islands away from New Guinea.

In Australia the bird may sit behind a famous story. Aboriginal Australians tell of the bunyip, a spirit of the water, and Robert Holden recorded nine or more regional forms. Ngarrindjeri people call it the Mulyawonk, and it punished anyone who took more fish than they needed. Karl Brandt suggested in 2017 that meetings with cassowaries helped shape the bunyip. An 1845 account of the bunyip describes deadly claws and a head like an emu, which fits the bird.