Birds
Southern Cassowary
Casuarius casuarius · also called double-wattled cassowary, Australian cassowary
The southern cassowary is a giant, prehistoric-looking bird of the tropical rainforest — a blue-necked, black-plumed ratite the size of a person, with a bony helmet and a claw like a knife. It has a fearsome reputation, but its real importance is quieter: it plants the forest it lives in.
Overview
Southern cassowaries inhabit dense tropical rainforest in New Guinea, on some Indonesian and Australian islands, and in a narrow strip of northeastern Queensland. They are solitary except when breeding, occupy large home ranges, and move along regular paths through the forest, following the fruiting of different trees through the year. They are shy and usually heard — as a deep, resonant boom — before they are seen.
Physical characteristics
A cassowary has a coarse, drooping black body plumage that looks more like hair than feathers, tiny vestigial wings tipped with bare quills, and thick, powerful legs. The head and upper neck are bare and vividly coloured in blue and red, with two red wattles hanging from the throat, and topped by the tall brown casque. Each foot has three toes, the innermost bearing a straight, sharp claw up to 12 cm long.
Diet and the forest’s gardener
Cassowaries are primarily frugivores, eating the fallen fruit of hundreds of rainforest plants, supplemented with fungi, invertebrates, small animals, and carrion. Because they swallow large fruit whole and travel widely, they are the principal seed disperser for many trees — including species whose seeds are simply too big for anything else to move. Ecologists consider the southern cassowary a keystone species: remove it, and the composition of the forest changes over generations.
Reproduction
Breeding roles are reversed. The larger female holds a territory overlapping those of several males, mates, lays a clutch of large pale-green eggs in a simple nest of leaf litter, and then departs. The male incubates for around seven weeks and raises the boldly striped chicks by himself for the better part of a year.
Threats and conservation
Globally the species is Least Concern, but the Australian population is Endangered, numbering only a few thousand. The main pressures are rainforest clearing and fragmentation, vehicle strikes on roads through cassowary habitat, dog attacks on chicks and adults, and the effects of feeding by people, which draws birds toward roads and houses and causes aggressive encounters. Recovery efforts focus on habitat corridors, road warning zones and speed limits, and public campaigns against feeding wild cassowaries.
Southern Cassowary: common questions
Is the cassowary the most dangerous bird in the world?
It is often called that, and it can be dangerous, but attacks are rare. A cassowary defends itself by leaping and kicking with both feet, and the long inner claw can cause deep wounds. Almost all serious incidents involve birds that have been fed by people and lost their fear, or birds cornered, provoked, or defending chicks. There is one confirmed human death in Australia, in 1926, and one in Florida in 2019 involving a captive bird. Given a way out, a wild cassowary will run rather than fight.
What is the casque on its head for?
The tall helmet-like crest is made of a stiff keratin shell over a spongy, flexible core. Proposed functions include pushing through dense undergrowth, signalling age and dominance to other cassowaries, amplifying or receiving the bird's very low-frequency calls, and shedding heat. Recent studies suggest thermoregulation may be an important role. It likely does several jobs at once, and it keeps growing throughout the bird's life.
Why is the cassowary important to the rainforest?
It is a keystone seed disperser. Many Australian and New Guinean rainforest trees produce fruit with seeds too large for any other surviving animal to swallow and carry. The cassowary eats the fruit whole, walks long distances, and deposits the intact seeds in a pile of its own dung, often far from the parent tree and with a ready-made fertiliser. Some plant species would decline sharply or disappear without cassowaries.
Which cassowary parent raises the chicks?
The male, alone. After a female mates and lays a clutch of three to five large green eggs in a ground nest, she leaves — often to breed with another male. The male incubates the eggs for about 50 days, barely eating, then guards and leads the striped chicks for around nine months to a year, teaching them what to eat, before driving them off to establish their own territories.