Dwarf cassowary (Casuarius bennetti)
|Weight||25 kg (2)|
Classified as Near Threatened (NT) on the IUCN Red List (1).
Cassowaries, the largest of all forest birds (3), are wonderfully peculiar animals. They are flightless; have a prominent, bony casque on top of the head (4); and a formidable claw on the innermost of its three toes (5). The dwarf cassowary, although the smallest of the three cassowary species, is hardly deserving of its name as it stands at 80 centimetres to the top of its back (6). It is largely black, except for the bare skin on the throat and neck which is coloured a brilliant blue, with striking red stripes running down the sides of the neck (6). The feathers of the dwarf cassowary are not the soft down normally associated with birds, but instead are reduced to bare, black spines, forming drooping, coarse, bristle-like plumage (3) (7). This plumage, which also covers the tiny, virtually hidden wings (5), is thought to help protect the body of the cassowary from scratches from thorns and vines as it moves through the dense forest vegetation (3) (5). The black casque, which was once thought to be a bony extension of the skull, but is now known to be made of a tough, foam-like substance (5), is quite distinct from that of other cassowaries, being flattened at the front and back and almost triangular in shape (6). Male and female dwarf cassowaries can be distinguished by the typically larger size of the female (5).
The dwarf cassowary occurs on the island of New Guinea, and the surrounding, smaller islands of New Britain, Ceram and Japen (6).
Like other cassowaries, this species is an inhabitant of forest, occurring from sea level up into the mountains, to the treeline at around 3,600 metres (8).
The dwarf cassowary is a secretive bird (5), which moves warily though dense jungle and will run for cover if disturbed (2) (5). It can run at up to 48 kilometres per hour, even through dense undergrowth, with its lowered head and casque protecting the bird from thorny vegetation (5). Surprisingly for its bulky size, the dwarf cassowary can also leap obstacles, swim rivers (5), and defend itself with a kick from its powerful, clawed feet (3).
Due to its elusive behaviour, and solitary nature (2), the dwarf cassowary is more likely to be heard than seen (5). Its call, a deep booming sound, is the world’s lowest known bird call, and is thought to be ideal for communicating with distant cassowaries in dense forest as low frequencies can penetrate vegetation (9). It has been hypothesized that the horny casque may act as an amplifier to produce these resonating calls, or assist in receiving the calls of other cassowaries (9) (10).
Foraging alone, the dwarf cassowary feeds on fleshy fruits (2). It can swallow large fruits whole, and the seeds pass undamaged through the gut, making them an important disperser of seeds in the forests in which they occur (3). The dwarf cassowary is also suspected of eating soil, a practice called geophagy, which is thought to act to bind poisonous or bitter tasting substances in certain fruits and seeds, allowing the cassowary to digest these otherwise nutritious plant parts (11)
Cassowary females typically lay three to six eggs between June and August. These large, greenish eggs, measuring 13 centimetres long, are laid onto a nest of leaves at the base of a tree (5), and are incubated entirely by the male (7). The male also takes responsibility for caring for the young chicks, in which the female plays no part (7).
The dwarf cassowary is thought to be able to tolerate some level of habitat degradation, and is fairly common over a wide range, and is therefore not currently considered to be threatened with extinction (8). However, this does not mean it is free from any threats, and the population is thought to be declining, albeit slower than populations of the other cassowary species (8). The dwarf cassowary is impacted by significant hunting pressure, and logging is exacerbating this threat as it opens up previously inaccessible areas to hunters (8). Caught in ground traps, chased down by dogs, or hunted by bow and arrow, the cassowary is caught for its feathers, large eggs, and flesh, which is considered a delicacy by some (12).
There are currently no conservation measures known to be in place for the dwarf cassowary (8). However, BirdLife International, a global bird conservation organisation, has recommended a number of measures for this species, including researching the effects of any potential threats, promoting hunting restrictions in local communities, and preventing habitat clearance (8).
For further information on the dwarf cassowary see:
- BirdLife International:
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- Casque: A helmet-like structure or protuberance.
IUCN Red List (June, 2007)
- Pratt, T.K. (1983) Diet of the dwarf cassowary Casuarius bennetti picticollis at Wau, Papua New Guinea. Emu, 82: 283 - 286.
- Primack, R.B. and Corlett, R. (2005) Tropical Rain Forests: An Ecological and Biogeographical Comparison. Blackwell Publishing, UK.
- Shuker, K.P.N. (2003) The Beasts That Hide from Man: Seeking the World's Last Undiscovered Animals. Paraview Press, New York.
- Burton, M. and Burton, R. (2002) International Wildlife Encyclopedia. Marshall Cavendish, New York.
- Roots, C. (2006) Flightless Birds. Greenwood Publishing Group, Connecticut.
- Scott, T. (1995) Concise Encyclopedia Biology. Walter de Gruyter, New York.
BirdLife International (November, 2008)
- Mack, A.L. and Jones, J. (2003) Low-frequency vocalizations by Cassowaries (Casuarius spp.). The Auk, 120(4): 1062 - 1068.
National Geographic News (November, 2008)
- Diamond, J., Bishop, K.D. and Gilardi, J.D. (1999) Geophagy in New Guinea birds. Ibis, 141: 181 - 193.
- Sillitoe, P. (2003) Managing Animals in New Guinea: Preying the Game in the Highlands. Routledge, London.