A species of rat living on one tiny Philippine island and thought extinct has been rediscovered after a search that lasted more than 20 years, scientists say.

The cloud rat, endemic to only one location in the world, Dinagat Island, is a critically endangered species and was even believed to be extinct, William Oliver, of the Philippine Biodiversity Conservation Foundation Inc., told The Philippine Daily Inquirer.

However, a couple from the Czech Republic honeymooning on Dinagat observed and made a video recording of a cloud rat, Oliver said.

Zoologist Milada Rehakova, who was commissioned by the foundation, and her husband, programmer Vaclav Rehak, spotted the Dinagat cloud rat, a large, hairy gray-brown rat with a black and white tail, in the island's forest in January, he said.

The couple was combining their honeymoon with a 10-day study on tarsiers and an effort to gather information from residents on the possible existence of the Dinagat cloud rat, Oliver said.

Rehakova has been involved in the conservation of Philippine wildlife since 2007.

A single cloud rat was observed climbing and foraging in the undergrowth and tree branches on three separate occasions, enabling Rehakova and Rehak to make the first sound recordings and both still and video documentation of the rare rat, Oliver said.

The first known specimen of Dinagat cloud rat, scientific name Crateromys australis, was collected in 1975 during one of the first surveys of Dinagat Island, but has not been seen since, leading to concerns it might have gone extinct.

Even with its rediscovery, there are fears the species is unlikely to survive ongoing mining operation on Dinagat, the researchers said.