Researchers at the University of Southern Denmark Investigate the Vocal Techniques of Daubenton’s Bat.
This small mammal is found throughout Europe and Asia. The study, published in the journal PLOS Biology, focuses on the different laryngeal structures that bats use to expand their vocal range.
Bats can produce low-frequency calls thanks to the folds of their vocal cords.
Vocal Communication is essential for bats. They are known for using sound to navigate their surroundings and locate prey in a process called echolocation. These creatures also use sound for social communication.
The researchers noted that bats utilizing echolocation have an impressive vocal range of seven octaves to suit their auditory needs. In contrast, most mammals, including humans, have a vocal range of three to four octaves. Bats use extremely high-pitched sounds for echolocation; however, they employ low-frequency growls to communicate with one another.
The scientists began to investigate precisely how Daubenton’s bats maximize their vocal range. The research team monitored the larynx of five bats and recorded the organs while applying airflow to mimic natural breathing.
This allowed the scientists to directly observe the vocal membranes and the folds of the larynx vibrating at different frequencies. The researchers stated that this represents the “first direct observations” of these phonatory structures in Daubenton’s bats.
“For the first time, we identified which physical structures in the larynx vibrate to produce their different sounds. For instance, bats can produce low-frequency calls thanks to the folds of their vocal cords,” said Coen Elemans, the lead author of the study and a biology professor at the University of Southern Denmark.
The vocal cord folds are located above the actual vocal cords. Historically, these folds were thought to play no role in normal human speech. However, research has revealed that these folds are crucial for some forms of unique phonation.
The researchers found that these folds may also be the source of the low-frequency growls of bats. They did not directly observe the vibration or oscillation of the vocal cords. However, the researchers stated: “We dare to speculate that, in bats, the vocal cord folds have taken on the role of lower frequency vibrations.”
Scientists still do not know exactly what the bats are communicating when they use such growls. Study co-author and biologist Lasse Jakobsen noted: “Some seem aggressive, some may express discomfort, and some may serve very different functions.”
