Cryptozoology is the study of "hidden" animals. Those animals that have never previously been recognised by the scientific community and rediscovered animals that were thought to be extinct but show up again, often unexpectedly, in their original habitat.

As 2010's International Year of Biodiversity (IYB) comes to an end, the Earth Times asked leading cryptozoologist Dr Karl Shuker what he thinks the prospects are for new and rediscovered species in the 21st Century.

Dr Shuker was intrigued by stories of strange, unidentified animals from a young age. And like many cryptozoologists it was a book by a Belgian zoologist that got him started: "I'd always been interested in reports of mysterious creatures, but when I was around 13 or 14, my mother bought me the paperback edition of Dr Bernard Heuvelmans's classic cryptozoology book, On the Track of Unknown Animals, and from then on I was totally hooked!"

On The Track of Unknown Animals (1958), and its companion piece In The Wake of Sea Serpents (1968) are scrupulously researched works taking their readers through a long list of animals that eyewitness accounts suggest may exist. There are tales of encounters with dinosaur-like beasts, ape-men and long-necked sea serpents. At the heart of Heuvelmans work and that of all cryptozoologists is the belief that there is still a lot left to discover in the natural world, including new, and often very large, species of animal.

Many people are surprised to learn quite how many new species of animal have been discovered in the last 50 years, varying from small insects and bizarre marine creatures living by ocean vents to rare tree kangaroos. What does Shuker consider the most significant zoological discovery or rediscovery of the last 50 years?: "Possibly the Vu Quang ox or saola of Vietnam Pseudoryx nghetinhensis. An extraordinary animal the size and body-shape of a buffalo but with long slender antelope-like legs and horns, which was totally new to science (but not to local hunters - a recurring theme in relation to cryptozoological discoveries), constituted the largest new land mammal for several decades, and is dramatically different from any other known species on the planet today."

But what other species, whose existence has yet to be proved does he believe might emerge on closer investigation? Shuker thinks it might be a particularly exciting discovery: "The orang pendek or 'short man' of Sumatra is promising, thanks to unidentifiable hair samples and footprints that have been documented and analysed. Some believe it to be a terrestrial form of ape, others a small bipedal hominid, and there may even be both out there in the dense jungles of this large yet little-explored Indonesian island."

Shuker, like many cryptozoologists, is hopeful that with successful conservation of habitats and initiatives to protect them (like the IYB) it won't just be new species emerging but that some previously thought lost for good will reappear: "The most surprising and unexpected animals have a knack of reappearing. Possible examples include the ivory-billed woodpecker, whose alleged reappearance several years ago was doubted by some experts, the Asian pink-headed duck, and perhaps even the thylacine or Tasmanian wolf, which has been dubbed the world's most common extinct animal on account of the numerous unconfirmed sightings of it that have been reported on Tasmania as well as the Australian mainland and even New Guinea."

As conservationists fight for the survival of many of the world's species it seems there is hope that some of the animals previously thought to be extinct may just be hiding away discretely. And that there may be some animals we haven't even dreamt of yet.

Dr Shuker's latest cryptozoology book, Karl Shuker's Alien Zoo, packed with cryptozoological news reports is available on Amazon and by order from all major bookshops.