Data from: Grasshopper mice employ distinct vocal production mechanisms in different social contexts

Functional changes in vocal organ morphology and motor control facilitate the evolution of acoustic signal diversity. Although many rodents produce vocalizations in a variety of social contexts, few studies have explored the underlying production mechanisms. Here, we describe mechanisms of audible and ultrasonic vocalizations (USVs) produced by grasshopper mice (genus Onychomys). Grasshopper mice are predatory rodents of the desert that produce both loud, long-distance advertisement calls and USVs in close-distance mating contexts. Using live-animal recording in normal air and heliox, laryngeal and vocal tract morphological investigations, and biomechanical modelling, we found that grasshopper mice employ two distinct vocal production mechanisms. In heliox, changes in higher-harmonic amplitudes of long-distance calls indicate an airflow-induced tissue vibration mechanism, whereas changes in fundamental frequency of USVs support a whistle mechanism. Vocal membranes and a thin lamina propria aid in the production of long-distance calls by increasing glottal efficiency and permitting high frequencies, respectively. In addition, tuning of fundamental frequency to the second resonance of a bell-shaped vocal tract increases call amplitude. Our findings indicate that grasshopper mice can dynamically adjust motor control to suit the social context and have novel morphological adaptations that facilitate long-distance communication.

发声器官形态与运动控制的功能性重塑，推动了声学信号多样性的演化历程。尽管诸多啮齿类动物可在多样社会情境中发出发声信号，但针对其底层发声机制的探索仍相对匮乏。本研究以草原蝗鼠（蝗鼠属，Onychomys）为对象，阐述其可听声与超声发声（ultrasonic vocalizations, USVs）的产生机制。草原蝗鼠为栖息于荒漠的肉食性啮齿类，既能发出洪亮的长距离广告鸣叫，也会在近距离交配场景中产生超声发声。本研究通过正常空气与氦氧混合气环境下的活体录音、喉部与声道形态学检测，以及生物力学建模，发现草原蝗鼠存在两种截然不同的发声机制。在氦氧混合气环境中，长距离鸣叫的高次谐波振幅变化表明其采用气流诱导组织振动的发声机制；而超声发声的基频变化则证实其采用哨声发声机制。发声膜与薄层固有层分别通过提升声门效率与支持高频振动，助力长距离鸣叫的产生。此外，将基频调至钟形声道的第二共振峰，可有效提升鸣叫振幅。本研究结果显示，草原蝗鼠能够根据社会情境动态调整运动控制模式，同时具备新颖的形态学适应性特征，以支撑长距离通信需求。