Schwartz Joshua J, Brown Robert, Turner Sarah, Dushaj Kola, Castano Marisol
Department of Biology and Health Sciences, Pace University, Pleasantville, NY 10570, USA.
J Comp Psychol. 2008 Aug;122(3):283-8. doi: 10.1037/0735-7036.122.3.283.
Male gray treefrogs call to attract females under challenging acoustic conditions. At higher chorus densities, there is considerable background noise and a good chance that a male's calls will often be overlapped by calls of other individuals. Call overlap may reduce the probability of mating because females prefer calls with internal pulse structure that is not obscured. With increases in acoustic stimulation, males lengthen call duration while simultaneously reducing call rate such that "pulse effort" changes little. In our study, we tested the "interference risk hypothesis." This proposes that males change call duration so that, on average, there will be a sufficient number of pulses and interpulse intervals clear of acoustic interference per call to attract a female. However, female choice experiments employing call alternatives of different durations, rates, intensity levels, and degrees of call overlap refuted this hypothesis. Our results leave open the possibilities that the dynamic shift in the two components of pulse effort are related to the problem of call detection in a noisy environment or are responses by males to the perceived threat of competition for females.
雄性灰树蛙在具有挑战性的声学条件下鸣叫以吸引雌性。在较高的合唱密度下，存在相当大的背景噪音，而且雄性的叫声很可能经常被其他个体的叫声重叠。叫声重叠可能会降低交配的概率，因为雌性更喜欢内部脉冲结构未被掩盖的叫声。随着声学刺激的增加，雄性会延长叫声持续时间，同时降低叫声频率，使得“脉冲努力”变化不大。在我们的研究中，我们测试了“干扰风险假说”。该假说认为，雄性会改变叫声持续时间，以便平均每次叫声有足够数量的脉冲和脉冲间隔，不受声学干扰，从而吸引雌性。然而，采用不同持续时间、频率、强度水平和叫声重叠程度的叫声替代物进行的雌性选择实验反驳了这一假说。我们的研究结果留下了这样的可能性，即脉冲努力的两个组成部分的动态变化与嘈杂环境中的叫声检测问题有关，或者是雄性对感知到的雌性竞争威胁的反应。
