14 DAY TRIAL // A team of investigators with the University of Sussex, in Brighton, UK, was recently able to determine why koala bears are capable of producing the super-bass, ultra-low sounds they make, which are extremely unusual and deep for creatures of their size.
In a paper published in the December 2 issue of the esteemed scientific journal Current Biology, the group says that koalas only produce these noises when they are in matting season. The sounds are generated by an organ in the throat that the team led by biologist Benjamin Charlton discovered.
It is possible, the expert comments, that previous studies simply did not look at the role that this throat structure may have in vocalization. Apparently, it is responsible for enabling koalas to produce sounds that are no less than 20 times lower than what would be expected of creatures of their size.
Only elephants and other very large mammals can make sounds with such a low pitch, the research group adds. Charlton was part of a team that discovered a descended larynx in koalas, back in 2011.
This location of this structure, which holds the vocal cords, gives the animals a vocal tract very similar to our own. In addition, the descended larynx is also responsible for producing the other types of resonant calls that the koalas are famous for, Nature reports.
“The first time I heard a koala bellow, I was genuinely amazed that an animal this small could produce such a sound,” Charlton says. However, discovering the peculiar location of its larynx did not go a long way towards explaining the bass sounds, since the vocal cords within were much too small.
The answer was found to lie within the much larger folds that span an opening between the oral and nasal cavities located in the koalas' pharynx. This organ is located above the larynx, and represents the upper part of the throat. These folds have never been described before, the team says.
With the conclusions of the new study, koalas become the first terrestrial mammals that feature a specialized structure for noise production other than the larynx. The findings were made possible through the dissection of ten dead koala males, performed by Charlton, his team, and colleagues at the Leibniz Institute for Zoo and Wildlife Research, in Berlin.
“For an animal that spends so much of its time resting, the bellow is perhaps the most interesting thing the koala regularly does. Yet we are only just figuring it out,” concludes University of Queensland in Brisbane wildlife ecologist William Ellis, who was a member of the 2011 study team.