Cassowary
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 Southern Cassowary
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Casuarius casuarius |
Cassowaries (genus Casuarius) are very large flightless birds native to the tropical forests of New Guinea and northeastern Australia. Some nearby islands also have small cassowary populations, but it is not known if these are natural or the result of the New Guinea trade in young birds. They are frugivorous; fallen fruit and fruit on low branches is the mainstay of their diet. They also eat fungi, snails, insects, frogs, snakes and other small animals. Recently, they have also been observed to attack humans, though this usually only occurs in self-defense when humans intrude upon the birds' territory or cause them to feel threatened.
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[edit] Taxonomy and Evolution
Cassowaries (from the Indonesian name kasuari) are part of the ratite group, which also includes the emu, rhea, ostrich, moa, and kiwi. There are three species recognized today:
- Southern Cassowary or Double-wattled cassowary C. casuarius of Australia and New Guinea.
- Dwarf Cassowary C. bennetti of New Guinea and New Britain.
- Northern Cassowary C. unappendiculatus of New Guinea.
The evolutionary history of cassowaries, as all ratites, is not well known. A fossil species was reported from Australia, but for reasons of biogeography this assignment is not certain and it might belong to the prehistoric "emuwaries", Emuarius, which were cassowary-like primitive emus.
[edit] Description
The Northern and Dwarf Cassowaries are not well known. All cassowaries are usually shy, secretive birds of the deep forest, adept at disappearing long before a human knows they are there. Even the more accessible Southern Cassowary of the far north Queensland rain forests is not well understood.
The Southern Cassowary is the second-largest bird in Australia and the third-largest remaining bird in the world (after the ostrich and emu). Adult Southern Cassowaries are 1.5 to 1.8 m (5 to 6 feet) tall, although some may reach 2m (6 feet 8 inches), and weigh about 60 kilograms (130 pounds). Females are bigger and more brightly coloured.
A cassowary's three-toed feet have sharp claws; the dagger-like middle claw is 120 mm (5 inches) long. This claw is particularly dangerous since the Cassowary can use it to kill an enemy, disemboweling it with a single kick. They can run up to 50 km/h (32 mph) through the dense forest. They can jump up to 1.5 m (5 feet) and they are good swimmers.[citation needed]
All three species have a horn-like crests called casques on their heads. These consist of "a keratinous skin over a core of firm, cellular foam-like material".[1] Several purposes for the casques have been proposed. One possibility is that they are secondary sexual characteristics. Other suggestions include that they are used to batter through underbrush, as a weapon for dominance disputes, or as a tool for pushing aside leaf litter during foraging. The latter three are disputed by biologist Andrew Mack on the basis of personal observation.[2] However, the earlier article by Crome and Moore say that the birds do lower their heads when they are running "full tilt through the vegetation, brushing saplings aside and occasionally careering into small trees. The casque would help protect the skull from such collisions."[1] Mack and Jones give a further speculation: that the casques play a role in either sound reception or acoustic communication. This is related to their discovery that at least the Dwarf Cassowary and Southern Cassowary produce very-low frequency sounds, which may aid in communication in dense rainforest.[2] This "boom" is the lowest known bird call, and is on the edge of human hearing.[4]
Females lay three to eight large, pale green-blue eggs in each clutch. These eggs measure about 9 by 14 cm (3½ by 5½ inches) — only ostrich and emu eggs are larger. The female does not care for the eggs or the chicks; the male incubates the eggs for two months, then cares for the brown-striped chicks for nine months.[citation needed]
[edit] Conservation Status
Southern and Northern Cassowaries are threatened species because of habitat loss; estimates of their current population range from 1,500 to 10,000 individuals. About 40 are kept in captivity in Australia. Habitat loss has caused some cassowaries to venture out of the rainforest into human communities. This has caused conflict particularly with fruit growers. However, in some locations such as Mission Beach, Queensland, tourism involving the birds has been launched.
[edit] Interactions with humans
The 2004 edition of the Guinness World Records lists the cassowary as the world's most dangerous bird. Normally cassowaries are very shy but when disturbed can lash out dangerously with their powerful legs. During World War II American and Australian troops stationed in New Guinea were warned to steer clear of the birds. They are capable of inflicting fatal injuries to an adult human. Usually, attacks are the result of provocation. Wounded or cornered birds are particularly dangerous. Cassowaries, deftly using their surroundings to conceal their movements, have been known to out-flank organized groups of human predators. Cassowaries are considered to be one of the most dangerous animals to keep in zoos, based on the frequency and severity of injuries incurred by zookeepers.
More recently, Cassowaries have been known to lose their natural fear of people. As a result, large areas of Australian National Parks have been temporarily closed to avoid human contact with the bird.
[edit] Role in Seed Dispersal and Germination
Cassowaries feed on the fruits of several hundred rainforest species and usually pass viable seeds in large dense scats. They are known to disperse seeds over distances greater than a kilometer, and thus probably play an important role in the ecosystem. Germination rates for seeds of the rare Australian rainforest tree Ryparosa were found to be much higher after passing through a cassowary's gut (92% versus 4%).[3]
[edit] References
- ^ a b Crome, F., and L. Moore. 1988. The cassowary’s casque. Emu 88:123–124.[1]
- ^ a b *Mack AL, Jones J. 2003. Low-frequency vocalizations by cassowaries (Casuarius spp.). The Auk 120(4):1062–1068 [2]
- ^ Webber, B.L. and Woodrow, I.E. Cassowary frugivory, seed defleshing and fruit fly infestation influence the transition from seed to seedling in the rare Australian rainforest tree, Ryparosa sp. nov. 1 (Achariaceae). Functional Plant Biology 31: 505-516. [3]
- Stay in Touch, Philip Clark (ed), The Sydney Morning Herald, 5 November 1990. Cites "authorities" for the death claim.
- Underhill D (1993) Australia's Dangerous Creatures, Reader's Digest, Sydney, New South Wales, ISBN 0-86438-018-6
- Readers' Digest, June 2006 issue.
[edit] External links
- C4 - Cassowary Conservation based in Mission Beach
- The Cassowary Bird
- ARKive - images and movies of the southern cassowary (Casuarius casuarius)
- Cassowary videos on the Internet Bird Collection
[edit] See also
