Cassowaries are closely related to Emu (Dromaiidae). They occur in New Zealand and northern Australia. Both families probably evolved from a common ancestor in the Pleistocene. Cassowaries (C. casuarius) reach up to 170 cm, weight 58 kg. They have a distinctive "helmet" on the head, the female’s helmet is larger. Females are also conspicuously colored and larger than males (reverse sexual dimorphism). Helmet is not elongation of cranial bones, but it is filled with foamy material. Its function is not yet satisfactorily explained. Helmet is probably used as a shield for worming dense vegetation. The helmet is fully developed only in adult individuals. Other things of interest on Cassowaries are conspicuous lobes on the neck, which are usually brightly colored. These lobes probably serve as intraspecific signals in dense dark vegetation. Cassowaries have three fingers on the back foot. The plumage is very rough, serving as protection from thorny vegetation. Hyporhachis of Cassowaries are similar to those of the emu’s, and practically as long as the main thorn. Rectrices are completely reduced, the flight feathers are reduced to 5-6 bare quills protecting the hips when crawling vegetation. Cassowaries are good swimmers, and could overcome lakes without difficulties. Toe carries up to 10 cm long claw which is an effective in defense. The adults with young chicks could be very dangerous, when alarmed. Attack is preceded by erect posture and striking deep voice. Cassowaries inhabit the rain forests, especially primary forests. C. casuarius inhabits lowlands up to middle altitudes, C. unappendiculatus is a species of lowland tropical forests and C. Bennett inhabits mountain forests at altitudes up to 3000 m. All cassowaries live solitary, except for nesting period. Their activity falls within the early morning and late evening hours, when they gather food from the ground or from low branches. The main diet is fruits, mostly families Myrtaceae and Lauraceae. A diet is sometimes supplemented by insects, small vertebrates, and also by carrion occasionally.
Nesting season begins in the period from July to October, when the greatest abundance of fruits is available. Males occupy home-ranges 1-5 km2 before the breeding season, although not aggression towards other males was identified. Once the female enters the male ward, male court to her repeatedly until the female is gradually accepting him and may be accompanied. Later, male walks around the female with erect feathers on the back, and makes the "bu-bu-bu" sounds. Male calms the female down during copulation by sifting through the feathers on his back, head cleaning, etc. Cassowaries’ males have penis similarly to other runners. After mating, the female stay in male’s territory until she lays 3-5 eggs into a nest (pre-prepared by male). Male consequently mate with another 2-3 females during the breeding season. Male incubates the eggs laid into his nest and takes care of the chicks. Incubation time is between 49-56 days. The male cares for the chicks for a period of 9 months. Juveniles mature in the third year of life.