THIRTEEN's Nature surveys the world of 'Fabulous Frogs' tonight (Wednesday, June 25, 2014) on PBS. Sir David Attenborough takes us on a journey through the weird and wonderful world of frogs, shedding new light on these charismatic, colorful and frequently bizarre little animals through first-hand stories, the latest science, and cutting-edge technology. There are more than 5,000 species of frogs and toads, and they come in all shapes, colors and sizes. Their amazing adaptations for survival have made them the most successful of all amphibians.
Fabulous Frogs uses high-speed camera techniques and graphics to illustrate the wide variety of frog anatomy, appearance and behavior.
The ancestors of today's frogs were a group of amphibians that lived around 300 million years ago, and their anatomy resembled that of a salamander. As Attenborough shows, they had long spines with ab0ut 30 vertebrae ending in a tail. Fifty million years later, an intermediate form evolved with only 15 vertebrae and almost no tail, but the hind legs were much bigger. Compare that to today's amphibian with an even shorter spine, elongated pelvis, and long, strong legs that can enable some frogs to leap at least 30 times their own body length. The reason they are able to jump so far is revealed in Fabulous Frogs.
Among the many frog behaviors singled out in the program are courtship techniques, which can involve anything from calling, waving, or changing color, to knock-down, drag-out fights for the right to mate. The female gliding leaf frog, found in the jungles of South America, listens to mating calls from all the males nearby and heads in the direction of the loudest voice. That call is her roadmap to the strongest male, and thus the best mate. Panama golden frogs employ visual signals to reinforce their courting intent. Males wave to potential rivals to warn them off, but if that doesn't work, a wrestling match ensues to determine mating rights. When the winner spots a female, he waves to show he's interested and if she returns the wave, the courtship is a success, and mating can begin.
Frog anatomy can function in all sorts of interesting ways. Frogs can't turn their heads from side to side because they don't have necks. But they solve that problem with their very big eyes, which give them an almost 360-degree range of vision. Those big eyes are also called into service to help frogs eat. As frogs swallow, they pull their bulging eyes downwards to help push food down their throats. And while a frog doesn't drink, it absorbs all the water and most of the oxygen it needs through its skin.
A frog's skin can provide camouflage or a brightly-colored warning, and can also contain deadly toxins that serve not only a defensive purpose but are a source of traditional and modern medicines, as well. However, this same marvelous membrane has also proven to be a deadly vulnerability. A frog's permeable skin is so sensitive to its surroundings that if there are environmental problems, frogs are among the first creatures to be affected. While loss of habitat and pesticides contribute to loss of their numbers, one particularly lethal pathogen called a chytrid fungus specifically attacks the cells in a frog's skin, blocking the flow of essential salts to muscles and eventually causing the heart to stop beating. A number of different species of frogs are already extinct in the wild, though some continue to be bred, studied and conserved in captivity until such time, if ever, a remedy can be found or the fungus disappears and they can be reintroduced to their original home.
Although Attenborough notes that almost a third of all amphibians are now threatened with extinction, he points out that frogs are incredibly adaptable creatures whose ability to survive even in the most improbable places is truly extraordinary and continues to offer hope in spite of the threats that face them.