Table_2_Syntactic properties of male courtship song in the lesser short-tailed bat, Mystacina tuberculata.XLSX

Bats (Mammalia: Chiroptera) have sophisticated acoustic abilities adapted to many uses, including both echolocation and social vocalisations. Social vocalisations are used in a wide variety of contexts and vary greatly in acoustic arrangement and complexity. Among the most intricate are the courtship songs that males of certain species use to attract mates and advertise their qualities. To date, however, few studies have examined the phonological construction of bat songs or made a detailed assessment of the syntax used to combine different song elements. Here, we examine the syntactic construction of courtship songs in the New Zealand lesser short-tailed bat, Mystacina tuberculata, a highly vocal, lek-breeding species with exceptionally high song-output rates. We hypothesised that song construction in this species is both hierarchical and non-random, and demonstrates a high degree of individual variation, potentially allowing for individual recognition. We recorded the courtship songs of nine male bats and used manual classification of song components to examine the song structure. Here we examine whether the deployment of different song components is dependent on their position, and also determine the transition probabilities between different components. We find that the frequency of song-element production and the distribution of elements within songs are non-random at both the individual and population level, and that the number of elements used per phrase differs between individuals. Overall, we demonstrate that M. tuberculata songs are hierarchically constructed and employ phonological syntax to build syllables and phrases. We further show that bats employ high structural similarity and conservatism in the construction of syllables, while retaining a capacity for versatility and innovation that allows for considerable individual variation and, likely, individual recognition.

蝙蝠（哺乳纲：翼手目（Mammalia: Chiroptera））具备适配多元用途的复杂声学能力，涵盖回声定位（echolocation）与社交发声（social vocalisations）两类核心功能。社交发声的应用场景宽泛多样，其声学编排模式与复杂程度均存在显著差异。其中构造最为精巧的，是部分物种雄性个体用以吸引配偶、彰显自身特质的求偶鸣曲（courtship songs）。然而截至目前，鲜有研究探讨蝙蝠鸣曲的音系结构（phonological construction），也未对组合不同鸣曲元素所遵循的句法（syntax）规则开展细致评估。本研究聚焦新西兰小短尾蝠（Mystacina tuberculata）的求偶鸣曲句法结构展开分析，该物种为高发声性、采用求偶场繁殖（lek-breeding）的类群，鸣曲产出率极高。我们提出研究假设：该物种的鸣曲构建兼具层级性与非随机性，且个体间差异显著，这一特征或可支持个体识别行为。我们录制了9只雄性蝙蝠的求偶鸣曲，通过人工分类鸣曲组分的方式解析鸣曲结构。本研究旨在验证不同鸣曲元素的使用是否与其所处位置相关，并明确不同元素间的转移概率。研究结果表明，无论是在个体层面还是种群层面，鸣曲元素的产出频率以及元素在鸣曲中的分布均呈现非随机性；且不同个体每短语所使用的元素数量存在显著差异。整体而言，本研究证实M. tuberculata的鸣曲为层级式构建，并通过音系句法组合形成音节与短语。我们进一步发现，蝙蝠在音节构建上呈现出较高的结构相似性与保守性，同时保留了灵活性与创新性，这使其能够产生显著的个体差异，进而大概率实现个体识别。