THE Cuban solenodon is one of the most curious animals on the planet. The small, shrewd-like creature is a mammal, but a highly venomous one - resembling the kinds of creatures that lived around the time after the dinosaurs died.

Between 1890 and 1970 there wasn't a single specimen found and it was thought to be lost forever. Then, unexpectedly three were caught just a few years later. The "extinct" species marched on.

The story of animals seemingly coming back from the dead in this fashion is not that uncommon. Forrest Galante is a wildlife biologist who's made it his life mission to search for animals that have wrongly been deemed extinct - and among the species on his list is the Tasmanian tiger.

"Animals are often declared extinct wrongly and without the proper investigation," he told news.com.au. "The process in which a species is declared extinct is very vague. It's almost impossible to say something isn't there … that difficulty of proof leads to an ease of declaring something extinct."

He has been travelling around the world searching for evidence that species like the Tasmanian tiger, pachylemur and the Newfoundland white wolf still exist.

Hundreds of species are deemed extinct worldwide annually, but the process isn't foolproof and every now and then animals are rediscovered after they were thought to be gone forever.

Forrest Galante holding a black caiman in Ecuador.

But proving an animal is still out there is no easy feat.

"It's a very serious task indeed. It is an absolute needle in a haystack and your expectations are always very low," Mr Galante said. "We have, however, had some success."

He and his team recently captured footage of a Zanzibar leopard, which has thought to be extinct for about 25 years due to persecution by local hunters in the Zanzibar archipelago, Tanzania.

He uses traditional tracking methods, eyewitness accounts and a slew of hi-tech gear including military-grade thermal imaging drones in hopes of making the huge breakthrough.

"It's what I live for man. When I found the leopard I went absolutely bonkers," he said. "I'm not a particularly emotional guy but I just lost it."

The process to capture the corroborating video - and the footage itself - will feature in a new show coming to the Discovery Channel in Australia later this month called Extinct Or Alive.

Each episode focuses on a different species thought to be extinct and the hunt to maybe prove otherwise.

HUNTING FOR THE TASMANIAN TIGER

One episode is dedicated to uncovering a thylacine, or Tasmanian tiger. But rather than heading to Tasmania, the search focused on mainland Australia - specifically Cape York where James Cook University is funding a large study into the species, following recent eyewitness stories.

"They have received funding to put out camera traps and surveys to locate a thylacine," Mr Galante said. "Upon hearing that we teamed up with them and conducted part of our survey with them."

The thylacine vanished from the Australian mainland about 3000 years ago. A thylacine population survived in Tasmania long after the demise of their mainland cousins, but a bounty was placed on their heads in the 19th century because they were believed to be responsible for sheep deaths.

A sting of reported sightings has fuelled hope the Tasmanian tiger is still out there.

The population went into rapid decline. The Tasmanian Government introduced official protection for the species in 1936, but it came too late. Just two months later, the last known thylacine died in captivity.

Some enthusiasts are adamant they have seen living tigers in recent decades, but of course any solid proof has been lacking. Mr Galante spoke with those claiming to have seen thylacines in the wild in recent years.

"These are not silly, loony people either," he said. "Some credible scientists, people who worked in natural resources, a Cape York guide who said he could see one as clear as day as his dog chased it around."

Accounts like these - which are entered into a database - have slightly bolstered the confidence of researchers who hope to rediscover the animal.

Along with looking for areas with the right environmental conditions to support the animal, Mr Galante searched for signs of predation that were different from a dingo in the effort to locate evidence of a Tasmanian tiger in the wild.

"Thylacine being one of the only marsupial carnivores has some very unique behaviour in the way that it hunted, in the way that is preyed upon animals," he said.

Mr Galante and his team spent a month in the Australian bush trying to track one down. While they may not have come away with any concrete proof, it's not the end of the hunt.

As Australian researchers continue, he hopes the program can remind people about the responsibility we have to the natural environment and the species that inhabit it.

"Whether we find the creature or we don't, what it does do is give us an understanding of what we've done wrong and what's left in the environment that we can work to save," he said.

"I think that's the most important thing - finding an extinct animal inspires hope for what could still be there even though, at the hand of man, we think we've destroyed it. What is left is worth preserving. That is the core reason I do all of this."

Extinct Or Alive premieres on Saturday, July 21 on Discovery Channel.