Many laboratory mice emit ultrasounds to communicate with each other. The ultrasounds, or ultrasonic vocalizations, cannot be heard by human ears.
In a new study led by Washington State University, researchers find that mice generate these high frequency sounds using a similar mechanism to that in ultrasonic jet engines. The finding is published in Current Biology.
Previous studies have shown that mice can generate 3 types of ultrasounds, depending on the animal’s age, its environmental conditions, and its emotional state.
Baby mice produce a 40-kHz sound when they are separated from their mothers. Adult mice emit a 22-kHz sound in anticipation of inescapable aversive stimuli. These two types of sounds reflect a negative emotional state of the animal.
In addition, mice can produce a 50-kHz sound under non-aversive conditions, and these sounds reflect a positive emotional state of the animal.
Generally, the function of ultrasounds in adult mice is likely to facilitate or inhibit social interactions.
In the current study, researchers found that mice pointed a small air jet coming from the windpipe against the inner wall of the larynx, which caused a resonance and producing an ultrasonic whistle.
Using ultra-high-speed video of 100,000 frames per second, researchers found that the vocal folds remained still while ultrasound was coming from the mouse’s larynx.
Researchers suggest that this mechanism can be found in engines in ultrasonic jets and turbines. This means mice use a very complicated and smart way to generate ultrasound.
Future research will focus on how mice use their brain to control muscles to generate these ultrasounds, and how the ultrasounds influence their behavior.
Citation: Mahrt E, et al. (2016). Mice produce ultrasonic vocalizations by intra-laryngeal planar impinging jets. Current Biology, 26: R880-R881. DOI: 10.1016/j.cub.2016.08.032.
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