The critically endangered red-eyed stream frog, or Duellmanohyla uranochroa, has become a symbol for the global decline of amphibians. The nocturnal frog was once common in Costa Rica and Panama, but has suffered severe population declines due to habitat loss and fungal disease. An estimated 165 amphibian species have died out in recent years.

The chytrid fungus is a major killer of amphibians worldwide. Chytridiomycosis disease destroys amphibians' delicate skin, which they also use to breathe through. It is believed to have come from the African clawed frog, which was used for human pregnancy testing throughout the world in the 1950s. The fungus spread and devastated many species, including these harlequin toads of the genus Atelopus.

Gliding frogs, like this one in Panama, are known for their spectacular leaps through rainforest canopies. But their territory is being threatened by logging - habitat destruction, such as deforestation and draining wetlands, is endangering the world’s amphibians. Climate change and the overuse of pesticides are other factors that scientists agree are making it harder for many species to survive.

Amphibians are thought to be good indicators of how healthy the planet is. Because they absorb substances from the water and air during their lifecycle, they are more sensitive to the environment than most other animals. They have thus been described as "canaries in the coalmine," meaning they can provide early warnings of a deteriorating environment.

Frogs, toads, salamanders, newts and caecilians - they all play a vital role in the food web. They eat insects and are in turn eaten by snakes, birds, and even humans. In medical research, some amphibians have been found to produce chemicals with the potential to cure human diseases. The frog pictured here secretes poison that native peoples have long applied to darts.

While many amphibian populations are endangered or extinct, new species are still being discovered. Last year, this bright "yellow dyer" frog, which colors your fingers yellow when you touch it, was discovered in the mountains of western Panama by Germany-based biologist Andreas Hertz. Its scientific name is Diasporus citrinobapheus.

Scientists specializing in amphibians and reptiles are called herpetologists - PhD student Andreas Hertz is one herpetologist on a mission to document rare amphibians in Latin America. Since 2007, a global project called "Amphibian Ark" has been underway, in which species are collected from the wild and put in quarantine before the deadly chytrid fungus can reach them.

The Hula painted frog was thought to be extinct for the past six decades - until one was found hopping across a road in northern Israel in 2011. Since then, more have been discovered, and there are believed to be up to 200 living in the Hula Valley. As an organism that has kept the same form over millions of years, it's considered a "living fossil."

A victim of the pet trade and tourism, the strawberry poison dart frog is still classified as a species of "least concern" on the IUCN Red List. This tiny frog measures about 2.5 centimeters and is found in Costa Rica, Nicaragua, Panama and Puerto Rico. The venom from these frogs is less harmful to humans than that of other poison dart frogs, but can still cause discomfort.

The Bornean flat-headed frog (Barbourula kalimantanensis) is among the frog and salamander species with no lungs at all - they breathe exclusively through their skin. It lives in cold, fast-flowing rainforest streams on the island of Borneo in Indonesia. Listed as endangered, this very rare frog's environment is under threat from pollution and the toxic byproducts of illegal gold mining.