In the folklore of the Australian Aborigine, a bunyip is a roaring, man-eating monster that lives in lakes and swamps and billabongs, waiting in the dead of night to grab his unwary victim and drag him or her down to the bottom, where he then eats the poor wretch The bunyip loomed large in the traditional beliefs and stories of Aboriginal groups in many different parts of Australia, particularly in the eastern states, where there were large and relatively permanent bodies of water compared to the more arid areas of the western third of the continent (there are, nevertheless, also some accounts of this creature in Western Australia). Although its name might vary from tribe to tribe, the bunyip’s appearance and habits were essentially the same: it was large, black, often hairy (some versions describe the creature as furry, others as feathered).
It possessed enormous baleful, shining eyes, was given to making bellowing or booming noises in the middle hours of darkness, and preferred to emerge on moonlit nights to catch and noisily dine on whatever luckless human prey came within reach.
It possessed enormous baleful, shining eyes, was given to making bellowing or booming noises in the middle hours of darkness, and preferred to emerge on moonlit nights to catch and noisily dine on whatever luckless human prey came within reach.

Although no documented physical evidence of bunyips has been found, it has been suggested by cryptozoologists that tales of bunyips could be Aboriginal folk memory of the Diprotodon, or other extinct Australian megafauna which became extinct some 50,000 years ago, such as the Procoptodon, a Kangaroo-like animal, that had a rounded face and could lift its arms above head height, or the Quinkana, a land-crocodile. The cries of the possum or koala could likely be mistaken for the bunyip, as most people are surprised to find koalas or possums are capable of such loud roars.
The Barking Owl, a nocturnal bird that lives around swamps and billabongs in the bush is sometimes credited for making the sounds of the bunyip. The bird is known to make a call that can easily be mistaken for the cries of a woman or child. Other species of birds, such as Bitterns and Bush Stone-Curlews emit blood curdling sounds that were sometimes attributed to bunyips. However, this is unlikely as the aborigines, having lived in Australia for such a vast amount of time would know these sounds. A likely explanation for the legend of the bunyip relates to their reported locations on the Murray-Darling Basin.
Australian Fur Seals are known to swim up the river system during times of flood, subsequently becoming trapped within the river system once the flooding subsides. There have been dozens of Fur Seals killed or captured as far north as Canberra, incidentally, in close proximity to areas where a Bunyip has been heard or sighted. To an inland dwelling Aborigine, a Fur Seal, seen for the first time, would be a completely unfamiliar and frightening creature. Furthermore, many recorded descriptions of bunyips bear some commonality with seal physiology.
(Taken from many sources)
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