CALL RATE VARIABILITY AND FEMALE CHOICE IN THE AFRICAN FROG, HYPEROLIUS-MARMORATUS

1. Two-choice phonotaxis experiments were used to investigate female r esponses to short-term variation in call timing in the African painted reed frog, Hyperolius marmoratus. The number of calls produced per st imulus in each choice test were equalised over either 10 or 20 seconds . 2. All alternative stimuli were tested against a regular stimulus wi th an invariant inter-call interval (ICI = duration between the onset of successive calls). There were three categories of alternative call timing; bouts of rapid calling (short ICI) where the period of silence between bouts was shorter than the bouts of calling; bouts of rapid c alling where the period of silence between bouts was longer than the b out of calling; and irregular calling (variable ICI) without prolonged periods of silence. 3. The only stimuli females discriminated against were rapid bouts of calling with prolonged periods of silence. Female s showed significant differences in the number of responses when prese nted with two stimuli that differed in call timing over as short a per iod as 10 seconds. 4. We also calculated variability in the ICI of 25 males in the field. There was a significant negative relationship betw een mean call rate (calls/min) and variability in the ICI. Faster call ers showed lower variability in ICI. 5. The phonotaxis experiments did not show a female preference for regular versus irregular call timing . So female mate choice of males with higher call rates in the field i s not due to a preference for males with less variability in ICI.