THE EFFECT OF CHANGES IN THE RELATIVE TIMING OF SIGNALS DURING FEMALEPHONOTAXIS IN THE REED FROG, HYPEROLIUS-MARMORATUS

In anurans the properties of individual males' calls can change marked ly during a single bout of calling. Females will therefore be confront ed with an array of signals that change in relative attractiveness ove r time and, consequently, may be stimulated to approach several males before initiating amplexus. This would increase the time spent in the chorus and therefore, the costs associated with finding a mate. These costs may be minimized if, at some point of 'decision', a female's res ponse to a male becomes irreversible, such that any subsequent changes in dynamic call features are ignored. To test this females were prese nted with two identical calls in a leader-follower call pattern and th en the timing of the calls after the initiation of a response to the p referred leader was switched. If call timing was switched when females were within 2 m of the leader, they changed course and tracked the so urce of the leading call. However, when calls were switched when femal es were 2 m away, only some females changed course. A second experimen t tested whether females 'lock into' static features such as dominant frequency. When a high frequency leading call was switched to a follow er and a low frequency call to a leader, females tracked the source of the leading call, disregarding call frequency. The tendency was weake r when a high frequency follower was switched to a leader. The idea th at the initiation of a response to a male renders females less respons ive to more attractive calls that may arise is not supported.