Cassowaries (; Biak: man suar ; ) are flightless birds of the genus Casuarius, in the order Casuariiformes. They are classified as ratites, flightless birds without a keel on their sternum bones. Cassowaries are native to the tropical forests of New Guinea (Western New Guinea and Papua New Guinea), the Moluccas (Seram and Aru Islands), and northeastern Australia..
Three cassowary species are extant. The most common, the southern cassowary, is the fourth-tallest and third-heaviest living bird, smaller only than the two species of ostrich and the emu. The other two species of cassowary are the northern cassowary and the dwarf cassowary; the northern cassowary is the most recently discovered and the most threatened. A fourth, extinct, species is the pygmy cassowary.
Cassowaries are very wary of humans, but if provoked, they are capable of inflicting serious, even fatal, injuries. They are known to attack both dogs and humans. The cassowary has often been labelled "the world's most dangerous bird", although in terms of recorded statistics, it pales in comparison to the common ostrich, which kills two to three humans per year in South Africa.
Taxonomy, systematics, and evolution The genus Casuarius was erected by French scientist Mathurin Jacques Brisson in his published in 1760. The type species is the southern cassowary (Casuarius casuarius). The Swedish naturalist Carl Linnaeus had introduced the genus Casuarius in the sixth edition of his published in 1748, but Linnaeus dropped the genus in the important tenth edition of 1758 and put the southern cassowary together with the common ostrich and the greater rhea in the genus Struthio. As the publication date of Linnaeus's sixth edition was before the 1758 starting point of the International Commission on Zoological Nomenclature, Brisson, and not Linnaeus, is considered the authority for the genus.
Cassowaries (from cognate of several related languages spoken around the Moluccas and New Guinea) are part of the ratite group, which also includes the emu, rheas, ostriches, and kiwi, as well as the extinct moas and elephant birds. These species are recognised:
Most authorities consider the taxonomic classification above to be monotypic, but several subspecies of each have been described, and some of them have even been suggested as separate species, e.g., C. (b) papuanus. The taxonomic name C. (b) papuanus also may be in need of revision to Casuarius (bennetti) westermanni. Validation of these subspecies has proven difficult due to individual variations, age-related variations, the scarcity of specimens, the stability of specimens (the bright skin of the head and neck—the basis of describing several subspecies—fades in specimens), and the practice of trading live cassowaries for thousands of years, some of which are likely to have escaped or been deliberately introduced to regions away from their origin.
The evolutionary history of cassowaries, as of all ratites, is not well known. Genetic evidence suggests that their closest living relatives are emus, and that the dwarf cassowary is more closely related to the Northern Cassowary than either is to the Southern cassowary. A fossil species was reported from Australia, but for reasons of biogeography, this assignment is not certain, and it might belong to the prehistoric Emuarius, which was a genus of cassowary-like primitive emus.
Description
Typically, all cassowaries are shy birds that are found in the deep forest. They are adept at disappearing long before a human knows they are there. The southern cassowary of the far north Queensland rain forests is not well studied, and the northern and dwarf cassowaries even less so. Females are larger and more brightly coloured than the males. Adult southern cassowaries are tall, although some females may reach . Cassowaries are heavy birds typically weighing between , Dwarf cassowaries are much smaller than northern or southern cassowaries.
Due to inhabiting the Aru islands, the southern cassowary is considered Asia's largest bird since the extinction of the Arabian ostrich. Moreover, not only is the cassowary Asia's largest bird, within New Guinea, the cassowary is the island's second largest terrestrial animal after the introduction of cervids such as the rusa deer, chital, and fallow deer.
All cassowaries' feathers consist of a shaft and loose barbules. They do not have rectrices (tail feathers) or a preen gland. Cassowaries have small wings with five or six large remiges. These are reduced to stiff, keratinous quills, resembling porcupine quills, with no barbs. The furcula and coracoid are degenerate, and their palatal bones and sphenoid bones touch each other. These, along with their wedge-shaped body, are thought to be adaptations to ward off vines, thorns, and saw-edged leaves, allowing them to run quickly through the rainforest..
Unlike the majority of birds, cassowaries lack a tongue. Their beaks are pointed, sharp and robust but not serrated, which allows them to pick up fruit more easily than the short bills of an emu or an ostrich.
Cassowaries have three-toed feet with sharp claws. The inner (first) toe has a dagger-like claw that may be long. This claw is particularly fearsome, since cassowaries sometimes kick humans and other animals with their powerful legs. Cassowaries can run at up to through the dense forest and can jump up to . They are good swimmers, crossing wide rivers and swimming in the sea..
All three species have a keratinous, skin-covered casque on their heads that grows with age. The casque's shape and size, up to , is species-dependent. C. casuarius has the largest and C. bennetti the smallest (tricorn shape), with C. unappendiculatus having variations in between. Contrary to earlier findings, the hollow inside of the casque is spanned with fine fibres. In 2026, scientists discovered that casques on both living and deceased cassowaries glow in ultraviolet light. Scientists further discovered that "different species glowed in similar colors, but in distinct patterns across their casques. The dwarf cassowary, which has a jet black casque, did not fluoresce at all, whereas the southern and northern cassowary, which have casques with dull greens, yellows, and browns, glowed in different places."
Several functions for the casque have been proposed. One is that they are a secondary sexual characteristic. Other suggested functions include batting through the underbrush, as a weapon in dominance disputes, or pushing aside leaf litter during foraging. The latter three are disputed by biologist Andrew Mack, whose personal observation suggests that the casque amplifies deep sounds. This is related to a discovery that at least the dwarf cassowary and southern cassowary produce very low-frequency sounds, which may aid in communication in dense rainforests. The "boom" vocalization that cassowaries produce is the lowest-frequency bird call known and is at the lower limit of human hearing. Recent study suggests that casque acts as a thermal radiator, offloading heat at high temperatures and restricting heat loss at low temperatures.Eastick, Danielle L., et al. "Cassowary casques act as thermal windows." Scientific reports 9.1 (2019): 1966. After the 2026 discovery that cassowary casques glow under ultraviolet light, scientists analyzed the ultraviolet wavelengths reflecting from the casques and found that the reflected wavelengths were between 365-385 nanometers, meaning cassowaries might be able to see them. This discovery gives further weight to the hypothesis that cassowary casques play some role in visual display and signaling.
The average lifespan of wild cassowaries is approximately 18–20 years, with those held in captivity living up to 40 years.
Behaviour and ecology Cassowaries are solitary birds except during courtship, egg-laying, and sometimes around ample food supplies. Males and females each maintain separate territories that overlap, of a size of approximately 3 square kilometres in one study.Bentrupperbaumer, Joan (1997). R eciprocal ecosystem impact and behavioural interactions between cassowaries, Casuarius casuarius, and humans, homo sapiens: exploring the natural-human environment interface and its implications for endangered species recovery in North Queensland, Australia (phd thesis). James Cook University. Section 2 Page 154 (thesis) or 60 (pdf) While females move among satellite territories of different males, they appear to remain within the same territories for most of their lives, mating with the same, or closely related, males over the course of their lives. Section 3, page 114(pdf) 208(on-page numbering).
Courtship and pair-bonding rituals begin with the vibratory sounds broadcast by females. Males approach and run with their necks parallel to the ground while making dramatic movements of their heads, which accentuate the frontal neck region. The female approaches drumming slowly. The male crouches on the ground, and the female either steps on the male's back for a moment before crouching beside him in preparation for copulation, or she may attack. This is often the case with the females pursuing the males in ritualistic chasing behaviours that generally terminate in water. The male cassowary dives into water and submerges himself up to his upper neck and head. The female pursues him into the water, where he eventually drives her to the shallows, where she crouches making ritualistic motions of her head. The two may remain in copulation for extended periods of time. In some cases, another male may approach and run off the first male. He will climb onto her to copulate, as well.
Both male and female cassowaries do not tolerate the presence of others of the same sex, but females are more prone to fight than males, which will generally flee when encountering another male. While males and females may also be territorial and confrontational, this decreases during the mating season
Reproduction
The cassowary breeding season starts in May to June. Females lay three to eight large, bright green or pale green-blue eggs in each clutch into a heap of leaf litter prepared by the male. The eggs measure about – only ostrich and emu eggs are larger.
The male incubates those eggs for 50–52 days, removing or adding litter to regulate the temperature, then protects the chicks, which stay in the nest for about 9 months. He defends them fiercely against all potential predators, including humans. The young males later go off to find a territory of their own.
The female does not care for the eggs or the chicks, but rather moves on within her territory to lay eggs in the nests of several other males. Young cassowaries are brown and have buffy stripes. They are often kept as pets in native villages (in New Guinea), where they are permitted to roam like barnyard fowl until nearing maturity. Caged birds are regularly bereft of their fresh plumes.
Diet
Fruit from at least 26 plant families has been documented in the diet of cassowaries. Fruits from the laurel, podocarp, palm, wild grape, nightshade, and myrtle families are important items in the diet. The poisonous cassowary plum takes its name from the bird. The bird avoids the poisons of these fruits due to the presence of their incredibly short gastrointestinal tract, the shortest of all ratites in relation to their size. The cassowary's incredibly short and simple digestive tract leads to a short gut retention time which allow seeds to remain unharmed during the comparatively soft digestion process and allows them to consume fruits that contain toxins such as cyanogens.