The southern cassowary (Casuarius casuarius johnsonii) is the largest fruit-eating bird in the world. It is native to the tropical forests of Papua New Guinea, nearby islands and north-eastern Australia. The southern cassowary is an important rainforest gardener, spreading the seeds of rainforest trees. Sometimes the seeds are so large that no other animal can swallow and disperse them.

Did you know?

The southern cassowary is Australia’s heaviest flightless bird, but the emu is taller.

Home range

• Home range fluctuates, depending on the availability of food and mating season.
• Home range is estimated to be between 0.52km² to 5km² in coastal lowlands, but up to 12km² in upland regions.
• Home ranges overlap both within and between the sexes, though the overlap between males and females is greater.
• Females’ home ranges usually overlap with those of several males.
• They only exclude other birds during the mating season when they can aggressively defend a mating territory.

Distribution

• Found in north-eastern Australia, Papua New Guinea and the Aru and Seram Islands.
• Cassowaries are found in three broad populations in north-eastern Australia:
  1. Cape York (far northern population): far northern Cape York Peninsula, centred on the much less extensive vine forests of Lockerbie and McHenry Uplands. The Lockerbie Scrub population is possibly extinct with no cassowary having been seen there since the early 1980s.
  2. Cape York (northern population): the vine forests of the McIlwraith and Iron Ranges.
  3. Wet Tropics (southern population): extends from Big Tableland, south of Cooktown to Paluma, north of Townsville. Distribution of the Wet Tropics population is naturally fragmented but has been reduced due to forest clearing on the Atherton Tableland and coastal lowlands. Currently, 89 per cent of the remaining habitat is in protected areas such as national parks and the Wet Tropics World Heritage Area.

Description

The cassowary forms part of a group known as ratites — large, flightless birds also including the emu, rhea, kiwis and ostrich. There are three species of cassowary: dwarf or Bennett’s cassowary (C. bennettii, with two subspecies); northern or single-wattled cassowary (C. unappendiculatus), both found in Papua New Guinea; and the southern cassowary, the only one found in Papua New Guinea and Australia.

Adult cassowaries are striking in appearance, with a tall brown casque (helmet) on top of the head, a vibrant blue and purple neck, red wattles and glossy black plumage. The purpose of the casque is unknown, but hypotheses include that it indicates dominance, protects the bird’s head when running through the forests (unlikely given it is quite fragile), helps keep the head warm and shed water in its wet habitat, and aids in hearing the low vibrating sounds made by other cassowaries. They possess small vestigial ‘wings’ with 5–6 bare quills and a long claw at the tip of the wing.

Southern cassowaries can grow to a height of 2 m, with males weighing up to 55 kg and females up to 76 kg. Each foot has three claws, better described as nails, with the medial, blade-like nail reaching up to 120 mm in length.

Cassowary chicks differ in appearance, with a striped brown and cream pattern. After 3 to 6 months, the stripes fade to the brown sub-adult plumage. This is retained until 12 to 18 months of age after which the bird begins to take on adult characteristics. Maturity is reached at 3.5 years of age for females and 2.5 years for males.

Signs

• Large dung piles:
• full of seeds but may also contain invertebrates and plants.
• most visible on rainforest walking tracks and roads.
• Three-toed footprint in soft soil or mud (approximately 180 mm for adults).
• Deep rumbling sound used to indicate presence and response to threats.

Habitat

• Tropical rainforests of north-eastern Queensland, Papua New Guinea and Seram and Aru islands.
• Also found in melaleuca swamps, mangrove forests, and sometimes grassland, savanna and palm forest not far from rainforest vegetation.

Life history

• Females and sub-adults are usually solitary, while males are frequently with chicks or young sub-adults). They are generally intolerant of other cassowaries except during mating and when fallen fruit is abundant.
• Females appear socially dominant.
• Life span of approximately 30 years in the wild and between 18 to 50 years in captivity.

Ecology

Breeding

• Mating season is from early June to September.
• Females may mate with more than one male in the season.
• Females lay three to five olive green eggs between June and October.
• Male incubates eggs for approximately 50 days.
• Male raises chicks alone.
• After approximately 9 to 18 months, with the onset of the next breeding season, the juveniles leave the male and begin to fend for themselves.

Food

• Primarily fruit, known to feed on the fruits of more than 240 plant species.
• Will consume invertebrates, plants, fungi, and carrion, as well as small vertebrates when available.
• Cassowaries play an important role in the ecology of rainforests. They are one of only 4 seed-dispersing animals that can disperse the seeds of large (up to 6 cm in diameter) rainforest fruits, and can do this over longer distances than the other dispersers of large seeds.
• Consume an average of 2.9 kg of fruit per day in captivity.

Recovery actions

• Recovery Plan for the Southern Cassowary 2007
  • Actions to secure long-term protection of cassowary populations.
  • Includes improving the protection of habitat and corridors, minimising road kills and dog attacks, establishing a monitoring program in key habitats, and involving the community.
• Approximately 89 per cent of habitat in the Wet Tropics population is protected in national parks and the Wet Tropics World Heritage Area and additional areas are being added.
• Residents in local cassowary regions are creating nurseries of cassowary food plants so rainforest trees can be planted to replace cleared land, and corridors can be planted to join remaining patches of vegetation.
• Road signs and traffic calming devices indicate cassowary habitat and areas where cassowaries may crossroads, especially in the Mission Beach area.

Overall outlook

• Cassowary populations in the Wet Tropics have a positive future given the high proportion of their remaining habitat protected to a high level.
• As long as habitat can be maintained, and vehicle strikes, dog attacks and human interactions can be controlled, the Wet Tropics population is likely to have a good long-term outlook.
• The far-northern Cape York population is less secure and thus more likely to become extinct due to its tiny area of occupancy.
• The northern population currently faces fewer pressures but occupies a smaller area and appears to be at a lower density, suggesting that any increase in threats will have a more rapid and severe impact.

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