This week's programme in the series on Man and Science Today.

Dr Stanley Rand really does communicate with frogs. At the Smithsonian Tropical Research Institute on an island in the middle of the Panama Canal he learnt their language while investigating their surprisingly complex mating calls. For Stanley Rand and his fellow biologists the dense forest of the island has become a huge open-air laboratory, raising intriguing questions for biologists.
Why, for example, is the sloth so slow? Why do some tropical animals have thick fur coats? How is it that so many different species of birds have developed songs that are so similar?
But as Horizon visited Panama, bigger problems were looming up: pollution by the oil tankers that funnel through the canal, and the large-scale destruction by man of the tropical forest itself.
(Colour)