London: Scientists have identified a species of frog in which the male and the female remain faithful for life.
The size of the pool in which they lay tadpoles is the only reason that prevents the amphibian`s from straying, the researchers claimed.
Genetic tests of male and female of mimic poison frog -- a species of Peruvian poison frog found in the rainforest of South America -- has showed that they are monogamous.
For their study, a team led by biologist Dr Jason Brown, then of East Carolina University, sampled the DNA of a dozen pairs of adult frogs and the subsequent generations of
tadpoles they produced.
Of 12 frog families, 11 had males and females that remained continually faithful to one another, together producing all their offspring. In the twelfth family, a male
frog mated with two females.
"Others have found evidence of social monogamy in amphibians where parents remain paired, however they didn`t look at the genetics of these couples and their offspring to
confirm this," Dr Brown was quoted as saying by the BBC.
"Or they have looked at the genetics and observed that they are actually promiscuous."
So that makes the mimic poison frog the first confirmed monogamous amphibian, he said.
As per the details of the frog`s sex life published in the journal The American Naturalist, after mating, a female mimic poison frog lays eggs on the surface of leaves.
The male frog transfers the tadpoles -- which hatch from the eggs -- to pools of water which collect in bromeliad leaves high up in the branches of trees and looks after them.
When the tadpoles become hungry, the male calls to his female partner who arrives to lay a non-fertile egg in each pool, which the tadpole eats as food.
When the researchers moved tadpoles into different sized pools, they found that they grew quickly in the larger pools -- which contained more nutrients, but could not survive alone in smaller ones.
Overall, the researchers believe they have found convincing evidence of an evolutionary chain of causation: changing the breeding pool size forced the mimic poison frog
to change its system of parental care, with males and females working together. That then culminated in social and genetic monogamy.
If the pools were bigger, the frogs wouldn`t have to remain faithful, as they wouldn`t be tied by their need to work together to raise their brood.
"This is the first discovery of a truly monogamous amphibian. These frogs are truly devoted to their offspring, and to each other," said Dr Brown, who is now studying at Duke University in Durham, North Carolina, US.