I am greatly indebted to American cryptozoological investigator Todd Jurasek for the following information and kind permission to publish it, and also to acclaimed cryptozoological artist William Rebsamen for the wonderful artwork above.
In autumn 2002, Todd visited the village of Siawi in a remote region of Papua New Guinea roughly 18 miles east of the border with Irian Jaya just below the mountains, and approximately 6 miles from the Sepik River. During his stay there, he interviewed members of several different tribes in the hope of extracting information of cryptozoological relevance, with the aid of a missionary called Jason acting as interpreter.
He obtained some information concerning giant monitors (the apparent identity of the Papuan artrellia) and also giant snakes, as well as some more surprising testimony concerning the alleged existence here of a lion-sized cat (no feline species is known to exist on New Guinea) and also a possible large canine cryptid. But by far the most extraordinary information obtained from these interviews concerned an alleged bigfoot-like man-beast, which was described to Jason by members of both the Siawi and the Amto tribes.
According to their accounts, this New Guinea ape-man, known to the Amto people as the kayadi, was at least man-sized (i.e. about 5 ft 5 in tall, judging from the average height of most native peoples on New Guinea), hirsute, and bipedal, but also able to climb trees very rapidly, and strong enough physically to throw humans if confronted. One Amti tribesman stated that in 1981 a kayadi had been startled by his uncle while digging for eggs in a cave near his village, and another claimed that a local girl had actually been kidnapped a while back by one of these man-beasts.
Many of the major islands or island groups in the vicinity of New Guinea can lay claim to reports of man-beasts - such as the yowie in Australia, maero or macro in New Zealand, orang pendek in Sumatra, batutut in Borneo, and mumulou in the Solomon Islands. However, as far as I am aware, this is the first time that a named man-beast has been reported from New Guinea, thereby making Todd's findings a very notable contribution to cryptozoology.