Abstract:

Long-distance calling is a distinctive vocal signal known for its loudness and long-range transmission, typically emitted by male individuals. It is often inferred to serve important socio-ecological functions, such as territory defense, protection of valuable resources, and mate attraction. The white-headed langur (Trachypithecus leucocephalus) is an endemic primate species in China, inhabiting the karst limestone forests in the southwestern of Guangxi. The role of long-distance calling in the survival and reproduction of white-headed langurs remains unclear. Between February 2023 and August 2023, we collected data on the long-distance calling locations and times of adult males from eight white-headed langur groups, as well as information on their foraging and sleeping sites, in the Banli area of the Chongzuo White-headed Langur National Nature Reserve, Guangxi. We tested the defensive function of long-distance calls concerning two important resources: food and sleeping sites. The results indicated that adult male white-headed langurs initiate their first long-distance calls an average of 38 min after the group departs from the cave, at an average distance of 43 m from the sleeping site. They make their last long-distance calls an average of 39 min before the group returns to the cave, also at an average distance of 43 m from the sleeping site. Additionally, the location of the sleeping site significantly influenced the calling location of the white-headed langurs, supporting the hypothesis that these calls serve a sleeping site defense function. However, foraging locations had no significant impact on calling locations, which did not support the food resource defense hypothesis. These findings indicate that long-distance calling in white-headed langurs is used for defending sleeping sites but not food resources. This study is the first to clarify the role of long-distance calls in defending critical survival resources in white-headed langurs. It enhances our understanding of the adaptive mechanisms and functions of vocal communication in white-headed langurs and provides scientific evidence for the conservation of rare and endangered species.

Key words: White-headed langurs (Trachypithecus leucocephalus), Long-distance call, Resource defense hypothesis, Endangered species conservation

摘要：

发声物种的长距离鸣叫是一种独特的声音信号，因鸣叫洪亮和传播距离远而著称，通常由雄性个体发出，常被推断具有宣誓领地、防御重要资源和吸引配偶等重要社会生态功能。白头叶猴 (Trachypithecus leucocephalus) 是中国特有的非人灵长类动物，栖息在广西西南部的喀斯特石山森林中，雄性成年白头叶猴经常发出长距离鸣叫，但这类叫声在其生存繁衍中的作用尚不明确。2023年2—8月，我们在广西崇左白头叶猴国家级自然保护区板利片区收集了8个白头叶猴群的成年雄性的长距离鸣叫位置和时间、觅食和过夜地信息，检验了白头叶猴长距离鸣叫对食物和过夜地两种重要资源的防御功能。结果显示，白头叶猴成年雄性在猴群出洞后平均38 min和距离过夜地平均43 m远的地点进行初次自发鸣叫，而在猴群回洞前平均39 min和距离过夜地平均43 m远的地点进行末次自发鸣叫，且过夜地的位置显著影响白头叶猴的鸣叫位置，支持过夜地防御假设。然而，觅食地点对鸣叫位置无显著影响，不支持食物资源防御假设。本研究首次阐明了白头叶猴的长距离鸣叫对防御重要生存资源的作用，将促进理解白头叶猴声音通讯的适应机制和功能，为珍稀濒危物种的保护提供科学依据。

关键词: 白头叶猴, 长距离鸣叫, 资源防御假说, 濒危物种保护