Navigation Links
Koalas' bellows boast about size

Koalas have a well-earned reputation for being dopey. Sleeping 19 hours out of every 24, and feeding for 3 of the remaining 5 hours, there doesn't seem to be much time for anything else in their lethargic lifestyle: that is until the mating season. 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

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.

Contact: Kathryn Knight
The Company of Biologists

Related biology news :

1. Loud and lazy but didnt chew gum: Ancient koalas
2. What can magnetic resonance tractography teach us about human brain anatomy?
3. New approach challenges old ideas about plant species and biomass
4. Scientists concerned about pesticide education funding
5. Clemson University peach specialist unveils CaroTiger, something to roar about
6. Interventional radiologists: Learn about peripheral arterial disease and get moving
7. BUSM professor authors book on how knowledge about genes and family history can save lives
8. Not so fast -- researchers find that lasting evolutionary change takes about 1 million years
9. No bones about it: Eating dried plums helps prevent fractures and osteoporosis
10. Paranoia about rivals alters insect mating behavior
11. UNC-Duke ties lead to collaborative finding about cell division & metabolism
Post Your Comments:
(Date:10/26/2015)... 26, 2015  Delta ID Inc., a company focused ... and PC devices, announced its ActiveIRIS® technology powers the ... F-02H launched by NTT DOCOMO, INC in ... second smartphone to include iris recognition technology, after a ... F-04G in May 2015, world,s first smartphone to have ...
(Date:10/23/2015)... , October 23, 2015 ... announce a mobile plug and play integration of physiological ... tasks SensoMotoric Instruments (SMI) present a ... solutions for eye tracking and physiological data registration. It ... SMI Eye Tracking Glasses 2w and physiological signals ...
(Date:10/22/2015)...  Synaptics (NASDAQ: SYNA ), a leading developer of human ... September 30, 2015. --> --> ... 66 percent over the comparable quarter last year to $470.0 million. ... million, or $0.62 per diluted share. --> ... of fiscal 2016 grew 39 percent over the prior year period ...
Breaking Biology News(10 mins):
(Date:11/24/2015)... -- --> --> ... Market by Product & Services (Primer, Probe, Custom Oligos, ... End-User (Research, Pharmaceutical & Biotech, Diagnostic Labs) - Global ... expected to reach USD 1,918.6 Million by 2020 from ... 10.1% during the forecast period. Browse 183 ...
(Date:11/24/2015)... , November 24, 2015 ... market research report released by Transparency Market Research, the ... at a CAGR of 17.5% during the period between ... Market - Global Industry Analysis, Size, Volume, Share, Growth, ... non-invasive prenatal testing market to reach a valuation of ...
(Date:11/24/2015)... ... November 24, 2015 , ... In harsh ... Insertion points for in-line sensors can represent a weak spot where leaking process ... series of retractable sensor housings , which are designed to tolerate extreme process ...
(Date:11/24/2015)... Capricor Therapeutics, Inc. (NASDAQ: ... development and commercialization of first-in-class therapeutics, today announced that ... scheduled to present at the 2015 Piper Jaffray Healthcare ... at The Lotte New York Palace Hotel in ... . --> . ...
Breaking Biology Technology: