On the Track of Unknown Animals (French: Sur la Piste des Bêtes Ignorées) is a 1955 cryptozoological book by Belgian-French zoologist Bernard Heuvelmans. Although not the first book to deal entirely with undescribed animals, its publication is regarded as the founding moment of cryptozoology, and it established Heuvelmans as the "Father of Cryptozoology". Translations and revised editions have been published in 1958, 1972, 1982, 1995, and 2014.
The book begins with a refutation of "Cuvier's rash dictum," a statement made by eminent pioneering palaeontologist Georges Cuvier to the effect that no medium or large mammals remained to be discovered, and that animals known only from fossils are especially unlikely to be found alive. Heuvelmans details several largely-unexplained regions where large animals could still survive; the discoveries of a number of large mammals in recent years; and the discoveries of animals, such as the coelacanth, previously known only from fossils.
The first section to deal entirely with cryptozoology, "The Man-Faced Animals of Southeast Asia," covers, as its name implies, the various hairy hominids of Southeast Asia, including the nittaewo, the orang-pendek, and the several varieties of yeti.
The next part, "The Living Fossils of Oceania," begins with a description of the known animals of Australia, which were widely considered to be hoaxes when they were first discovered, and goes on to describe some still-unrecognised animals, including the bunyip, "giant rabbits" which Heuvelmans believed may be surviving giant marsupials; the Queensland tiger, and the moa.
Part four, "Riddles of the Green Continent," covers South American cryptids, including possible living ground sloths in Patagonia, alongside Patagonian water tigers such as the iemisch and yaquaru; giant anacondas and "other inland sea serpents" such as the minhocão; and various apes or large primates, including the mapinguari.
Part five, "The Giants of the Far North," deals with only one cryptid: the woolly mammoth of the Siberian taiga, and also describes the history of the discovery of that animal.
The sixth section, "The Terrors of Africa," covers "three large pygmies," the forest rhinoceros, water elephant, and marozi; the Nandi bear; "little hairy men" including the agogwe; and "Congo dragons," including supposed living dinosaurs and pterosaurs, mystery crocodilians, and water lions. Heuvelmans' coverage of the Nandi bear was especially significant, as sightings of that cryptid had hitherto been considered to refer to a single known or unknown animal: Heuvelmans, examining the features of each sighting individually, revealed that they seemed to refer to different animals, both known and unknown.
The final chapter, "The Lesson of the Malagasy Ghosts," deals with the relict animals of Madgascar, particularly giant lemurs. Many of these animals are believed to have gone extinct in historical times before being wiped out by human activities without even being studied, and Heuvelmans ends by writing:
- "Tomorrow we may know one of our other relatives: the abominable snowman, for instance, who is surely a shy and gentle great ape; or perhaps an even more human primate like the tiny agogwe or the elusive orang pendek. I hope with all my heart that when he is captured there will be no needless murder. Have pity on them all, for it is we who are the real monsters."
- Sur la Piste des Bêtes Ignorées by Bernard Heuvelmans, Libraire Plon, 1955
- On the Track of Unknown Animals by Bernard Heuvelmans, trans Richard Garnett, Rupert Hart-Davis, 1958
- On the Track of Unknown Animals by Bernard Heuvelmans, Paperback – Abridged, MIT Press, 22 May 1972, ISBN 0262580209
- Sur la Piste des Bêtes Ignorées by Bernard Heuvelmans, 2nd edition, 1982
- On the Track of Unknown Animals by Bernard Heuvelmans, Kegan Paul, 3rd revised edition, 1995 ISBN 0-7103-0498-6
- On the Track of Unknown Animals by Bernard Heuvelmans, Routledge, 3rd edition, Kindle format, 10 July 2014