The croaking sounds of frogs are made for the specific purposes of effecting reproduction and caring for the tadpoles until matured enough to be independent as miniature frogs!!
The vocal sounds of the frogs is usually that of a matured female seeking the notice of makes to mate with , resulting in laying of thousands of eggs. But these eggs can't survive drought of any kind. They must be enmeshed completely in water medium to ensure their hatching!!
The rains provide such water mediums as in ponds, gutters, swamps etc.This accounts for their croaking during the rains.
These amphibious animals are of high fecundity; producing and hatching thousands of eggs per time. These hatchlings are known as tadpoles. They look like fishes more than frogs at this stage. But later they transforms gradually to become miniature frogs which jumps out of their birth place in the water to surrounding land to live independent life.
At maturity, they must return to a water body to procreate.
Yes!, they are wonderful animals, dominating both their land and water habits.