The male Darwin frog from Chile and Argentina does something very strange after the female lays her eggs. He eats them.
Don’t worry, the male has a special cavity near his vocal chords. The eggs are kept there, protected from the evils of the outer world, for three days until baby frogs are ready to come out. The male then opens his moth and uses his forelimbs (his “hands”) to pull them out and release them to the world.
While the male Darwin Frog wins the Best Daddy award among frogs, there are other species who come close. In the Western Ghats of India, males of the wrinkled potter frog carefully cover eggs with mud to keep them moist and to blend them in with the sides of the stream. The African Goliath frog we met last week, keeps a careful watch on his tadpoles. If their pool is drying, he digs a tunnel and ushers them into a larger pool to keep them alive.
The small, brightly coloured strawberry poison dart frog from the forests of Central America dote on their babies. Tadpoles are born in temporary puddles that form on the forest floor after the rains. When these pools get smaller, Papa Frog keeps watch as Mamma Frog takes each tadpole onto her back. She then makes a long arduous journey up tall trees to find plants which contain a little puddle of water nestled within their leaves; there, she drops off her treasured load. She then goes back down for her next tadpole. And that’s not all. She has to make rounds afterward, to drop off eggs for each of the tadpoles to eat. Once the tadpoles turn into frogs, parents’ jobs are done.
Before producing eggs, male and female amphibians first communicate with each other and then decide to mate. This process usually takes a long time. Male amphibians have vocal chords that produce a variety of sounds from croaks to whistles to bird like calls. The vocal chords do not produce loud enough sound, so the males have air sacs on the throat. These fill with air like a balloon and act as loudspeakers that make the frog calls louder.
During the rainy season, once evening falls, forests are full of calling frogs. The chorus of males attracts females to the area, and she usually makes for the loudest male. Her logic is: the loudest male is the strongest male, so my babies will be strong too._ As she makes her way to the male of her choice, other males usually try to “steal” her away!
How amphibians avoid being eaten
Amphibians are small, with soft bodies — they make an ideal snack or meal for a variety of “predators”, like snakes and birds. Many species hide during the day and are active during night, avoiding many predators. But, they are not as defenceless as they seem. Many frogs and toads produce slimy mucous that makes it difficult for predators to get a grip on them. Others take it a step further and produce toxic secretions that make the predators spit them out. The poison dart frog from South America secretes a deadly chemical on its skin that tribes from the area use to coat their arrows!
A lot of the poisonous amphibians are brightly coloured. This acts as a warning to predators of their toxicity. Once a predator has eaten one and got a mouthful of bad taste or a reaction like vomiting, it usually remembers the colour pattern and avoids it the next time! A lot like what you do with food you don’t like. Other species rely on “camouflage” — blending in with the background — to escape the attention of predators. Some frogs and toads inflate themselves to look large and fierce.
There are two things that amphibians cannot escape from, even though they have a variety of defences. One is disease — there is a deadly fungus that is wiping out almost one-third of the world’s amphibians. It affects the skin of amphibians, preventing oxygen-carbon dioxide exchange, ultimately leading to their death__. The disease is spreading quickly throughout the world, and the first reports in India just came in last year. Another thing amphibians cannot escape from, is humans. We have cut down a lot of the world’s forests and have seriously damaged the environments amphibians live in.
Gross? Think again
Amphibians use their skin to breathe and to absorb water from the environment. This makes them excellent indicators of the health of the environment — they are the first to die from high levels of toxic pollutants. They are “ectotherms” whose body temperature is maintained by the surroundings. If there is hot water discharged from an industry, they will die out. Amphibians dying out also means the creatures they eat are getting rare; it also means the species that eat amphibians like snakes and birds could be in danger.
Some of the chemicals that amphibians produce have been shown to have medical uses. They eat a lot of insects which would be pests on our agricultural fields — a toad with a bellyful of insects is probably making sure you get fruits for your next meal. We just saw how they can “speak” to us about the health of the environment we live in. We also saw how amphibians around the world are slowly going extinct. I hope when some of you grow up, you will love amphibians as much as I do! They are not hurting you in any way, so please do not throw them away from your backyard garden and potted plants. They are helping your plants survive.
(Sandhya is a science journalist who writes about weird and wonderful creatures. You can write to her at sandysek@gmail.com or read more on her website ‘The Melting Pot’ at www.sandhyasekar.com.)
