Offspring from long-callers grew faster and survived better as tadpoles, were larger at metamorphosis (the time when tadpoles turn into frogs), and grew faster after metamorphosis. Since male gray tree frogs make no contribution to offspring except for sperm, females can get no direct benefits from choosing a long-calling male. This test strongly suggests that a long call is the sign of a healthy male with good genes, and that females who choose those males produce genetically superior offspring.
