Sneaker Males

A female frog targets the territory of the wonderful voice she hears. But when she finally sees the male frog, she may get a ringer. Some male frogs don’t call at all. Instead they silently invade a strong caller’s territory, hoping to intercept a female as she approaches. For all the female knows, she’s found the owner of both the beautiful voice and the territory. Such so-called satellite males may not mate often, but the strategy at least gives males that can’t call competitively a fighting chance to pass on some genes.

Satellite mating works for males who don’t meet the usual strict standards of females. But what is a female frog’s best strategy? Mac F. Given, a biologist at Neumann College in Aston, Pennsylvania, found that unlike most frogs and toads, female carpenter frogs have their own call, and he suspects they use these calls as a way of double-checking before they mate.

Male carpenter frogs sing a short song of up to ten notes to advertise their territory and availability, and they continue to call and defend their territory for up to three months. Another male may respond to this long call by a single-note chirp that Given calls the aggressive call. This triggers a train of aggressive calls and responses until the territory owner grapples with the intruding male. The intruder usually gives in, chirping a release call. Then he splashes on his way.

A female carpenter frog responds to the male song just like a male, inciting the same seek-and-fight behavior in the male. But she never gives the release call, and the “wrestling” match turns into amplexus, during which the male clings to the female’s back in position to fertilize the eggs she lays. Considering the risk the female runs in possibly attracting a predator, Given wondered what the female gains. He thinks she may call to stymie satellite males. A satellite male dare not return her chirp for fear of attracting the territorial male. So by calling back and forth, the female makes sure she mates with the real prince, not a sly, silent impostor.