By Susan Milius
Male frogs in a mountain pond sneak their sperm directly onto egg masses of a female who’s already mated with another male, an extra effort at fatherhood that scientists haven’t reported before in amphibians, says an international team. In the study population, original matings fertilized on average only about three-quarters of the eggs.
A widespread European species called the common frog (Rana temporaria) engages in standard frog-mating behavior. Males firmly grasp a female and eject sperm while she releases a soft mass of eggs. As is typical for frogs, fertilization occurs in the water rather than inside the mother’s body.