Proximity‐dependent Response to Variably Complex Mating Signals in Túngara Frogs (Physalaemus pustulosus)

Abstract

The plasticity of animal behavior allows individuals to maximize fitness in a wide range of contexts. Both production of and preference for mating signals are context‐dependent according to internal factors such as hormonal state, and external factors such as predation risk. In many species, male‐to‐female proximity also defines an important context for mating communication. Males often possess short‐distance courtship signals, and females often exhibit distance‐related variation in signal response. Such variation in response may occur when a signal’s relevance changes with male‐to‐female distance, but it may also result from perceptual constraints that are unrelated to fitness. Túngara frogs produce variably complex advertisement calls, and sexual selection theory predicts that females should prefer calls of greater complexity. Preference tests, however, have not demonstrated consistent trends for preference between calls of variable complexity. We tested whether proximity to males influences female response to variable signal complexity and found that both preference and memory for signal complexity are proximity‐dependent.

Choosing a Mate in a Cocktail Party‐Like Situation: The Effect of Call Complexity and Call Timing between Two Rival Males on Female Mating Preferences in the Túngara Frog Physalaemus pustulosus

“…Akre & Ryan () also found that female túngara frogs exhibit a repertoire of movements when in close proximity to males which increase the probability that males add complexity to their calls. Interestingly, Akre & Ryan () had found that when females are ‘close’ to males (a situation modeled through increasing call intensity), a stronger preference for more chucks occurs. The results of my study open the issue of whether female preferences for call timing might influence male vocal behavior at close range.…”

“…Specifically, under typical ideal experimental conditions (i.e., without conspecific interference), females prefer one, two, or more chucks over no chuck but do not discriminate between one and two chucks. Therefore, for decades, the role of multichuck whines puzzled researchers (but see recent findings in, Akre & Ryan , ; Akre et al. ).…”

“…In this study, I tested the hypothesis that the randomizing effect of call overlap can be reduced when the calls of one of the two rivals have chucks, specifically more chucks than those of the rival. I further explored the ideas that the value of multichuck calls vary with the acoustics context (e.g., Akre & Ryan , ; Akre et al. ).…”

“…The whine and the chuck stimulate different auditory organs in the inner ear (Rand et al 1992), the amphibian papilla and basilar papilla, respectively. The whine is always present and is necessary and sufficient for female choice and male competition (Ryan 1985); the chuck alone does not elicit female phonotaxis, and it is an opportunistic element that males append at the end of the whine when other males (or females) are present at the chorus; solitary males usually do not utter chucks (see Ryan 1985;Bernal et al 2009;Akre & Ryan 2010). The attractiveness of the whine is modified by the presence of chucks, with females preferring whines followed by and also those followed by more chucks among the available, although the preference is not linear (Bernal et al 2009).…”

“…In this study, I tested the hypothesis that the randomizing effect of call overlap can be reduced when the calls of one of the two rivals have chucks, specifically more chucks than those of the rival. I further explored the ideas that the value of multichuck calls vary with the acoustics context (e.g., Akre & Ryan 2010, 2011. I evaluated whether a two-chuck whine, otherwise as attractive as one-chuck whine, can be chosen when overlapped with a one-chuck whine, and whether the preference for one chuck over no chuck is preserved.…”