The rutting vocal display of male impala Aepyceros melampus is unique for its complexity among ruminants. This study investigates bouts of rutting calls produced towards potential mates and rival males by free-ranging male impala in Namibia. In particular, a comparison of male rutting and alarm snorts is conducted, inspired by earlier findings of mate guarding by using alarm snorts in male topi Damaliscus lunatus. Rutting male impala produced 4–38 (13.5 ± 6.5) rutting calls per bout. We analyzed 201 bouts, containing in total 2709 rutting calls of five types: continuous roars produced within a single exhalation-inhalation cycle; interrupted roars including few exhalation-inhalation cycles; pant-roars distinctive by a pant-phase with rapidly alternating inhalations and exhalations; usual snorts lacking any roar part; and roar-snorts starting with a short roar part. Bouts mostly started and ended with usual snorts. Continuous roars were the shortest roars. The average duration of the exhalatory phase was longest in the continuous roars and shortest in the pant-roars. The average fundamental frequency (49.7–51.4 Hz) did not differ between roar types. Vocal tract length, calculated by using measurements of the first four vocal tract resonances (formants), ranged within 381–382 mm in all roar types. In the studied male impala, rutting snorts within bouts of rutting calls were longer and had higher values of the upper quartile in the call spectra than alarm snorts produced towards potential danger. Additional inhalations during the emission of the interrupted and pant-roars prolong their duration compared to the continuous roars but do not affect the fundamental frequency or the degree of larynx retraction while roaring. Alarm snorts are separated from one another by large intervals, whereas the intervals between rutting snorts within bouts are short. Sometimes, rutting snorts alternate with roars, whereas alarm snorts do not. Therefore, it is not the acoustic structure of individual snorts but the temporal sequence and the occasional association with another call type that defines snorts as either rutting or alarm snorts. The rutting snorts of male impala may function to attract the attention of receptive females and delay their departure from a male’s harem or territory.

中文翻译：

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雄性黑斑羚（Aepyceros melampus）发出发情声音并与警报背景重叠

雄性黑斑羚（Aepyceros melampus）的发情声音展示因其复杂性而在反刍动物中独一无二。这项研究调查了纳米比亚自由放养的雄性黑斑羚向潜在配偶和竞争对手发出的发情叫声。特别是，受到早期发现的雄性发情和报警鼻息的比较，通过使用雄性topi Damaliscus lunatus中的报警鼻息来保护配偶。发情的雄性黑斑羚每回合发出 4–38 (13.5 ± 6.5) 发情叫声。我们分析了 201 次，总共包含 2709 次发情叫声，分为五种类型：在单一呼气-吸气周期内产生的连续咆哮；间歇性吼叫，包括很少的呼气-吸气循环；喘气咆哮的特点是吸气和呼气快速交替的喘气阶段；平常的鼻息声，没有任何咆哮的部分；以及以短吼声开始的咆哮声。比赛大多以通常的鼻息开始和结束。连续的吼叫是最短的吼叫。呼气阶段的平均持续时间在连续吼叫中最长，在喘息吼叫中最短。不同吼叫类型的平均基频（49.7-51.4 Hz）没有差异。通过测量前四个声道共振（共振峰）计算得出的声道长度，在所有吼叫类型中都在 381-382 毫米之间。在所研究的雄性黑斑羚中，发情呼声中的发情呼声比对潜在危险产生的警报呼声更长，并且呼声谱中上四分位数的值更高。与连续咆哮相比，在发出间断咆哮和喘息咆哮期间进行额外的吸气会延长其持续时间，但不会影响咆哮时的基频或喉部收缩的程度。警报性的鼻鸣声彼此之间间隔很大，而一轮中的发情性鼻鸣声之间的间隔很短。有时，发情的鼻息声与咆哮声交替出现，而警报的鼻息声则不会。因此，将鼻鼾声定义为发情鼻鼾声或警报鼻鼾声的不是单个鼻鼾声的声学结构，而是时间序列以及与另一种呼叫类型的偶尔关联。雄性黑斑羚的发情喷鼻可能会吸引雌性黑斑羚的注意，并延迟它们离开雄性的后宫或领地。