Male vocal competition is dynamic and strongly affected by social contexts in music frogs
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Male–male vocal competition in anuran species is critical for mating success; however, it is also highly time-consuming, energetically demanding and likely to increase predation risks. Thus, we hypothesized that changes in the social context would cause male vocal competition to change in real time in order to minimize the costs and maximize the benefits of competition. To test this hypothesis, we assessed the effect of repeating playbacks of either white noise (WN) or male advertisement calls on male call production in the Emei music frog (Babina daunchina), a species in which males build mud-retuse burrows and call from within these nests. Previous studies have shown that calls produced from inside burrows are highly sexually attractive (HSA) to females while those produced outside nests are of low sexual attractiveness (LSA). Results showed that most subjects called responsively after the end of WN playbacks but before the onset of conspecific call stimuli although call numbers were similar, indicating that while males adjusted competitive patterns according to the biological significance of signals, their competitive motivation did not change. Furthermore, these data indicate that the frogs had evolved the ability of interval timing. Moreover, when the inter-stimulus interval (ISI) between playbacks was varied, the subjects preferentially competed with HSA calls when the ISI was short (<4 s) but responded equally to HSA and LSA calls if the ISI was long (≥4 s), suggesting that males allocate competitive efforts depending on both the perceived sexual attractiveness of rivals and the time available for calling. Notably, approximately two-thirds of male calls occurred in response to HSA calls, a preference rate comparable to that previously found for females in phonotaxis experiments and consistent with the idea that the mechanisms underlying both the male’s competitive responses to rivals and the female’s preferences toward potential mates coevolved under the same selective pressure.
KeywordsMale–male competition Advertisement call Competitive strategy Sexual attractiveness Interval timing Frog
This work was supported by the grants from the National Natural Science Foundation of China (No. 31372217 to Guangzhan Fang and No. 31270042 to Jianguo Cui), from the “Hundred Talents Program” of Chinese Academy of Sciences (KSCX2-YW-R-077) to Yezhong Tang and from the Youth Professor Project of Chengdu Institute of Biology (Y3B3011) and Youth Innovation Promotion Association of Chinese Academy of Sciences (Y2C3011, KSCX2-EW-J-22) to Jianguo Cui.
Conflict of interest
The authors declare that they have no conflict of interest.
Animal procedures were approved by the Animal Care and Use Committee of the Chengdu Institute of Biology.
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