|The water boatman (Micronecta scholtzi), shown at the top left, is only 2mm long but is the loudest animal ever to be recorded, relative to its body size, outperforming all marine and terrestrial species. (Credit: Images courtesy of Dr. Jérôme Sueur, Muséum national d'Histoire naturelle, Paris)|
The frequency of the sound (around 10 kHz) is within human hearing range and Dr. James Windmill of the University of Strathclyde, explains one clue as to how loud the animals are: "Remarkably, even though 99% of sound is lost when transferring from water to air, the song is so loud that a person walking along the bank can actually hear these tiny creatures singing from the bottom of the river."
The song, used by males to attract mates, is produced by rubbing two body parts together, in a process called stridulation. In water boatmen the area used for stridulation is only about 50 micrometres across, roughly the width of a human hair. "We really don't know how they make such a loud sound using such a small area," says Dr. Windmill.
The researchers, who are presenting their work at the Society for Experimental Biology Annual Conference in Glasgow, are now keen to bring together aspects of biology and engineering to clarify how and why such a small animal makes such a loud noise, and to explore the practical applications. Dr. Windmill explains: "Biologically this work could be helpful in conservation as recordings of insect sounds could be used to monitor biodiversity. From the engineering side it could be used to inform our work in acoustics, such as in sonar systems."