Unusual aspects of anuran sexual behavior as seen in the red-legged frog, Rana aurora aurora

Abstract

When clasped by a male frog, the release behavior of an unreceptive female Rana aurora is more extensive and elaborate than that described for other anuran species. A female R. aurora cannot gain her release from a persistent male by uttering a release call which is accompanied by abdominal vibrations, the behavior effectively used by unreceptive females of other species of Rana. Instead, she extends her back legs and rolls to one side, finally remaining on her side with body and limbs stiff and outstretched.A male Rana aurora vocalizes while in amplexus with the female, and increases the speed, intensity, and repetition rate of his calls whenever the female attempts to displace him. This call by amplectic males is distinct from the normal male mating call.The advantage of an elaborate female release behavior in Rana aurora, and possible functions for the calls given by amplectic males, are discussed.