This Bolitoglossa species has a bold red stripe on its back

Video of new species

They were among some 5,000 plants and animals recorded by scientists from London's Natural History Museum during three expeditions to Central America.

Two species are nocturnal, while the third is a dwarf variety, growing to little longer than a thumbnail.

The three new finds bring the number of Costa Rican salamanders known to science to a total of 43.

Salamanders eat insects and worms, and live in water or in moist areas. They usually feed at night and hide during the day, often hibernating during the winter.

Some 300 species are known around the world, mainly in the Northern Hemisphere, but there have been few new discoveries since 1998, when five new salamanders were found in tropical east-central Mexico.

The three new salamanders were found in La Amistad National Park, a Unesco World Heritage Site on the Costa Rica-Panama border.

Two belong to the nocturnal Bolitoglossa genus; while the third, from the Nototriton (dwarf salamander) family, is a diminutive 3cm (1 inch) in length.

"Finding so many new species in one area is exciting, particularly as this is probably the only place in the world you can find these animals," said the NHM's Dr Alex Monro, who is leading the project.

The dwarf salamander is the strangest specimen found

"It shows we still have a lot to learn about the variety of wildlife in this region. We have four more expeditions planned this year - who knows what we could find when we go back?"

La Amistad National Park has few roads and treacherous terrain, so remains largely unexplored.

Scientists believe the region is a centre for diversity for these tailed amphibians. It is thought to be home to some two-thirds of all Costa Rica's native species, including hundreds of birds, mammals, reptiles and other amphibians, and thousands of plants.

The new species will be named and catalogued by scientists at the University of Costa Rica. The Natural History Museum is working alongside scientists and officials in Costa Rica and Panama on the project, funded by the UK government's Darwin Initiative to promote biodiversity conservation.