Abstract:

Vocal alarm is one of the important survival strategies for animals, where habitat vegetation cover, climatic factors, noise, and call purpose may play a role in the adaptive tuning of animal calls. How the alarm calls of animals adapt to the temporal changes of habitat structure remains poorly explored. The acoustic adaptation hypothesis (AAH) suggests that animal calls should evolve in a direction that facilitates efficient transmission in their environment, but not all empirical reports support its predictions. The alarm calls of Brandt’s voles (Lasiopodomys brandtii) are an important anti-predator behavior. To detect the acoustic characteristics and functional adaptability of their alarm calls, in May, July, and September 2023, the alarm calls of Brandt's voles were collected in the typical steppe area of Xin Barag Right Banner, Inner Mongolia. These calls were then combined with the local historical climate parameters and real-time environmental noise indicators to analyze the relationship between the characteristics of their alarm calls and the habitat. The results showed that the alarm calls of Brandt’s voles exhibit both monosyllabic (13.1%) and multisyllabic acoustic (86.9%) characteristics. Furthermore, the minimum and maximum fundamental frequency were significantly positively correlated with habitat vegetation index and ambient relative humidity, respectively, but significantly negatively correlated with wind speed. The maximum fundamental frequency and fundamental frequency range were significantly positively correlated with ambient noise, while other frequency (i.e. the minimum fundamental frequency) and time (i.e. inter-note intervals of a call) domain parameter showed a negative correlation. Under the environmental conditions of relatively high temperature, abundant rainfall, and low noise in summer (July), the alarm calls of Brandt’s voles were characterized by long pulses with relatively concentrated audio frequencies and high-frequency sounds with loose syllables. In spring (May) and autumn (September), which were relatively dry, windy, and noisy, especially in September, the calls were adjusted to short pulses and broadband low-frequency sounds with dense syllables. The alarm calls of Brandt's voles responded to the seasonal changes in relative humidity, wind, and noise rather than vegetation canopy density, which did not support the acoustic adaptation hypothesis. This difference was also the result of their trade-off between anti-predator risks and benefits and was closely related to the dispersal of their offspring or family relatives. This study provides a basis for the anti-predator acoustic countermeasures related to the adaptation of Brandt’s voles to colonial and seasonal breeding life.

Key words: Lasiopodomys brandtii, Alarm calls, Acoustic adaptation hypothesis, Habitat factors, Anti-predatory acoustic strategy

摘要：

警戒鸣叫是动物重要的生存策略之一，生境植被郁闭度、气候因子、噪声和鸣叫功能等可能对动物鸣叫适应性调整发挥作用，动物警戒鸣声如何适应栖息地结构的时序变化是一个有待探究的问题。其中声音适应性假说认为动物的鸣声信号应该朝有利于在其所处环境中高效传播的方向进化，然而并非所有研究支持其预测。布氏田鼠 (Lasiopodomys brandtii) 的警戒鸣叫是其重要的反捕食行为，为检测其警戒鸣叫的声学特征和功能适应性，本研究于2023年5月、7月和9月在内蒙古新巴尔虎右旗典型草原区，采集布氏田鼠的警戒鸣叫，并结合当地历年气候参数和实时环境噪声指标，分析其警戒鸣叫特征与生境间的关系。结果发现布氏田鼠警戒鸣叫具有单音节 (占比13.1%) 和多音节 (占比86.9%) 的声学特征，且多音节鸣叫的最小基频或最大基频与生境植被指数或环境相对湿度呈显著正相关，但与风速呈显著负相关，最大基频和基频范围与环境噪声呈显著正相关，但最小基频等其他频域参数以及音节间隔与之呈负相关。夏季 (7月) 相对高温多雨、低噪声的环境条件下，布氏田鼠警戒鸣声表现为音频相对集中的长脉冲、音节松散的高频音；而在相对干燥、风急嘈杂的春季 (5月) 和秋季 (9月)，尤其是9月，鸣声调整为短脉冲、音节密集的宽带低频音，布氏田鼠警戒鸣声响应了相对湿度、风速和噪声等非植被郁闭度的季节性变化，但不支持声音适应性假说，这种差异也是其权衡反捕食风险和收益的结果，与其幼仔或家族亲缘个体扩散紧密关联。本研究为布氏田鼠适应集群和季节性繁殖生活相关的反捕食声讯对策提供了依据。

关键词: 布氏田鼠, 警戒鸣叫, 声音适应性假说, 栖息地结构, 反捕食声讯对策