The Ropen is cryptid thought to be either a big bat, or more commonly, a pterosaur on New Guinea Island. It is said to produce a light, possibly to attract fish. The Ropen is a flying cryptid alleged to live in the vicinity of the Indonesian Papua province and the nation of Papua New Guinea. According to the book Searching for Ropens, it is "any featherless creature that flies in the Southwest Pacific, and has a tail-length more than 25% of its wingspan." On the Island, the word "ropen" refers to a large nocturnal creature that glows briefly as it flies. The ropen is the subject of folklore (like a man but also like a spirit) but it's believed by some natives to be a real animal. Descriptions vary, but it is often said to be batlike, and sometimes, pterosaur-like—although pterosaurs are generally accepted to have been extinct. The ropen is believed to be nocturnal and to exhibit bioluminescence. Purportedly it lives on a diet of fish, though there have been some reports of the creature feasting on human flesh, especially from grave robbery.
As is often the case with cryptids, the Ropen's true identity is subject to debate. Some believe it to be a Rhamphorhynchidae-like creature (a pterosaur with a diamond shape tail), while others suggest that the Ropen is a misidentified bat (e.g. flying foxes, which are large fruit bats than can have wingspans up to two metres (six feet), or frigatebirds). Flying lights in Papua New Guinea have been reported by not only natives but by Western visitors. Evelyn Cheesman, an entomologist, mentions them in her book The Two Roads of Papua (published in 1935): "baffling" lights that lasted "about four or five seconds."
The book Searching for Ropens says that the "ropen" light of Umboi Island lasts for about "five seconds." There is also said to be a creature called "Duah" that is said to be another kind of ropen, but according to Searching for Ropens the correct word is actually "duwas," and it is just another name, in a different language, for the same creature.