The study revealed that ghost bats exhibit dialects for the first time: their social calls vary depending on the location of the colony. Some signals change freely with distance, while echolocation and similar calls are strictly regulated by evolutionary mechanisms to ensure survival.

Features of Bat Vocal Communication

Bats use sounds for two main purposes: echolocation and communication. Echolocation allows these animals to navigate in the dark and find prey using ultrasonic signals that bounce off surrounding objects. Social calls serve to attract mates, warn of danger, and facilitate interactions between mothers and their young.

Research Subject

The Australian ghost bat was chosen for the study because this species lives in colonies in caves and mines in northern Australia, with colonies sometimes located far apart. Exchange of individuals between distant colonies is rare, and the species’ vocal repertoire is highly diverse.

Research Methods

In five colonies, tissue samples were collected for genetic analysis, and body measurements were taken: forearm length, ear length, tragus length, and noseleaf height. Acoustic recordings were also made in each colony. From the variety of sounds, four types of signals were identified: three social calls in the audible range (chirp-trill, quarrel, and ultrasonic social call), as well as the classic echolocation signal. For each signal, seven acoustic parameters were measured to determine whether signals differed between colonies and whether these differences were linked to genetics, geography, or body structure.

Main Results

The analysis showed that different types of signals are governed by different evolutionary mechanisms. For two social calls in the audible range (chirp-trills and quarrels), acoustic differences between colonies were associated with geographic distance. Population isolation led to the formation of dialects. Genetic data confirmed that the link between dialects and genetics was weak.

The ultrasonic social call and the echolocation signal also differed between colonies, but these differences were not related to genetics or geography. Bats from distant colonies could produce similar signals, while neighboring colonies sometimes had distinct ones.

Evolutionary Mechanisms

These features are explained by the action of stabilizing selection. The echolocation signal is a survival tool, not a means of communication. Any random deviation in the signal can reduce hunting efficiency or lead to collisions with obstacles, so such signals must remain stable to preserve the species. The ultrasonic social call is structurally similar to the echolocation signal and is likely produced by the same acoustic “instrument,” so it is also subject to the same constraints.