Inter-signal interaction and uncertain information in anuran multimodal signals

Abstract

Disentangling the influence of multiple signal components on receivers and elucidating general processes influencing complex signal evolution are difficult tasks. In this study we test mate preferences of female squirrel treefrogs Hyla squirella and female túngara frogs Physalaemus pustulosus for similar combinations of acoustic and visual components of their multimodal courtship signals. In a two-choice playback experiment with squirrel treefrogs, the visual stimulus of a male model significantly increased the attractivness of a relatively unattractive slow call rate. A previous study demonstrated that faster call rates are more attractive to female squirrel treefrogs, and all else being equal, models of male frogs with large body stripes are more attractive. In a similar experiment with female túngara frogs, the visual stimulus of a robotic frog failed to increase the attractiveness of a relatively unattractive call. Females also showed no preference for the distinct stripe on the robot that males commonly bear on their throat. Thus, features of conspicuous signal components such as body stripes are not universally important and signal function is likely to differ even among species with similar ecologies and communication systems. Finally, we discuss the putative information content of anuran signals and suggest that the categorization of redundant versus multiple messages may not be sufficient as a general explanation for the evolution of multimodal signaling. Instead of relying on untested assumptions concerning the information content of signals, we discuss the value of initially collecting comparative empirical data sets related to receiver responses

A systems approach to animal communication

“…The temporal coordination between the acoustic components and visual cues associated with calling (visible inflation of a vocal sac) also influences female responses [46]. Research on the squirrel treefrog, Hyla squirella, found similar cross-modal interactions [47]. Starnberger et al [29] provide an excellent review of additional anuran signalling examples, including those in which temporal coordination among signal elements influences element function.…”

Female gray treefrogs, Hyla versicolor, are responsive to visual stimuli but unselective of stimulus characteristics

“…Furthermore, the results of the visual cues in chorus noise experiment demonstrate that even with the auditory stimulation of a mating chorus, females showed phototaxis but failed to discriminate between visual stimuli. There are many other combinations of auditory and visual stimuli that could be tested, and interactions between these modalities are known to be important in anurans (Narins et al, 2003;Taylor et al, 2011). However, the primary aim of our study was to determine whether females responded to, and discriminated between, visual stimuli alone.…”

Robots in the service of animal behavior

“…Receiver responses can be modulated by interactions among signal components in nonhuman animals as well, sometimes in unexpected ways 2 . Adding to the confusion is that traits conspicuous to humans are sometimes surprisingly unimportant as signal components in nonhuman animals 3 , 4 . Controlling aspects of one perceptual modality and not another would be useful when investigating animal behavior, but is often impossible when working exclusively with living organisms.…”