Thesis

Vocal repertoire and female choice in an Ecuadorian treefrog, Dendropsophus carnifex

Frogs predominantly communicate acoustically, using advertisement calls to mediate both inter- and intrasexual interactions. In many frogs, these signals comprise a single component; however, in others they are composed of distinct multiple components. Male executioner treefrogs, Dendropsophus carnifex, exhibit a multicomponent advertisement call composed of an introductory screech note followed by two or more secondary click notes. However, the vocal repertoire of this species, including spectral and temporal properties, has not been fully characterized. Therefore, the purpose of my study was to identify and characterize the different call types used by male D. carnifex, and to determine the effect of the multicomponent advertisement call on both female call recognition and choice. I conducted field recordings of calling males, and carried out three 3-choice female phonotaxis experiments. I tested (1) female phonotaxis to each call component and to a complete call, (2) female choice for differences in the number of click notes, and (3) female choice for differences in call rate. Based on previous literature on multicomponent advertisement calls, I hypothesized that females would recognize the click notes of the advertisement call as the mating signal, and that females would choose calls with more notes and at faster rates. The results demonstrate that both notes, presented separately or together as a complete call, evoked similar female phonotactic responses, suggesting that either note was sufficient to elicit a mate-recognition response. Additionally, I found that females preferred calls with greater numbers of added click notes and faster call rates. Because females preferred stimuli with greater call output, males calling with more click notes or at faster rates should experience a greater mating advantage. As calling is energetically expensive and possibly indicates male quality, selecting mates based on these call parameters may provide females with indirect benefits, such as good genes. Determining female phonotaxis towards multicomponent calls and call preferences is important in understanding the evolution of signal complexity in light of sexual selection.

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