Then the males begin bellowing. Benjamin Charlton from the University of Vienna, Austria, explains that they probably bellow to attract females and to intimidate other males. But what messages could these rumbling bellows communicate about their senders? Charlton and an international team of collaborators publish their discovery that the koalas are boasting about their size in the Journal of Experimental Biology at http://jeb.biologists.org.
According to Charlton, they could be telling nearby listeners about their size. He explains that there was a possibility that koalas may be one of the few animals that have a descended larynx, which makes the vocal tract longer. Also, because all pipes – including vocal tracts – have frequencies where the air inside them vibrates naturally and amplifies sound, larger animals with longer vocal tracts produce lower resonances, giving their voices a more baritone quality. So, the longer vocal tracts of the largest koalas should produce deeper resonances to tell the listening koala audience just how big they are. Intrigued, Charlton, Tecumseh Fitch and their colleagues decided to find out whether male koalas have descended larynxes.
Teaming up with Allan McKinnon at Moggill Koala Hospital and Gary Cowin and William Ellis at the University of Queensland, Australia, Charlton investigated the anatomy of the marsupial's vocal tract. Using MRI and post-mortem studies, the team found that the koala's larynx had descended to the level of the 3rd and 4th cervical vertebrae, instead of being high in the throat. They were also surprised to find that the muscle that attaches the larynx to the sternum was anchored very deep in the thorax and they suggest that it could be involved in pulling the larynx even further down into the chest cavity.
But what effect does the koala's deeply descended larynx have on the acoustics of their bellows? Travelling to the Lone Pine Koala Sanctuary, home to 140 koalas, Charlton patiently recorded their rumbling bellows. He also measured the animals' head sizes, with the help of Jacqui Brumm and Karen Nilsson, as skull size is a good proxy for body size.
Back in the lab, Charlton analysed the bellows' spectra and found that the largest males always had lower resonances than the smaller animals. More surprisingly, when Charlton calculated the koala's vocal tract length based on their acoustics, he was astonished to find that the koalas were able to make themselves sound as if they had 50-cm-long vocal tracts, nearly the entire length of the animal. In fact, the diminutive animals sound even larger than bison. Charlton suspects that koalas use the resonances of the oral and nasal tracts simultaneously to sound much larger than they are.
So, koala males are able to communicate their size, with the largest animals producing the richest baritone bellows. Charlton also suspects that the males' boastful bellows could have driven the evolution of their descended larynxes. 'Individuals that could elongate their vocal tracts by lowering the larynx may have gained advantages during sexual competition by sounding larger, and this would drive the evolution of laryngeal descent,' he says.
IF REPORTING ON THIS STORY, PLEASE MENTION THE JOURNAL OF EXPERIMENTAL BIOLOGY AS THE SOURCE AND IF REPORTING ONLINE, PLEASE CARRY A LINK TO: http://jeb.biologists.org
REFERENCE: Charlton, B. D., Ellis, W. A. H., McKinnon, A. J., Cowin, G. J., Brumm, J., Nilsson, K. and Fitch, W. T. (2011). Cues to body size in the formant spacing of male koala (Phascolarctos cinereus) bellows: honesty in an exaggerated trait. J.Exp. Biol. 214, 3414-3422.
This article is posted on this site to give advance access to other authorised media who may wish to report on this story. Full attribution is required, and if reporting online a link to http://www.jeb.biologists.com is also required. The story posted here is COPYRIGHTED. Therefore advance permission is required before any and every reproduction of each article in full. PLEASE CONTACT email@example.com
Symbiotic bacteria: from hitchhiker to beetle bodyguard
28.04.2017 | Johannes Gutenberg-Universität Mainz
Nose2Brain – Better Therapy for Multiple Sclerosis
28.04.2017 | Fraunhofer-Institut für Grenzflächen- und Bioverfahrenstechnik IGB
More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.
Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...
Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.
"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
28.04.2017 | Event News
20.04.2017 | Event News
18.04.2017 | Event News
28.04.2017 | Medical Engineering
28.04.2017 | Earth Sciences
28.04.2017 | Life Sciences