{"id":3037,"date":"2011-09-30T09:54:33","date_gmt":"2011-09-29T23:54:33","guid":{"rendered":"https:\/\/scienceillustrated.com.au\/blog\/?p=3037"},"modified":"2012-03-21T09:29:20","modified_gmt":"2012-03-20T22:29:20","slug":"koalas-bellows-indicate-their-size","status":"publish","type":"post","link":"https:\/\/scienceillustrated.com.au\/blog\/nature\/koalas-bellows-indicate-their-size\/","title":{"rendered":"Koalas’ bellows indicate their size"},"content":{"rendered":"
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Females are more attracted to larger mates. Image: Jen Tobey<\/p>\n<\/div>\n

A male koala’s bellow may attract mates and intimidate rivals.<\/strong><\/p>\n

Female koalas may be attracted to larger mates as they could produce larger, more competitive offspring by mating with these individuals. Male koalas appear to modify their vocal tracts to make themselves sound much larger than their actual size.<\/p>\n

According to Dr Benjamin Charlton from the University of Vienna<\/a>, Austria, the exaggerated bellows are the result of a descended larynx, which results in a longer vocal tract. Animals with longer vocal tracts are also able to produce lower resonances.<\/p>\n

“Female koalas might prefer bellows signalling larger males in mate choice contexts and male koalas could use this information on male body size to help them avoid risky encounters with larger rivals,”\u009d said Dr Charlton, lead author of the study published in the Journal of Experimental Biology<\/em><\/a>.<\/p>\n

Together with Dr William Ellis and Dr Gary Cowin from the University of Queensland<\/a> and Dr Allan McKinnon from Moggill Koala Hospital<\/a>, Dr Charlton investigated the position of the koalas’ larynx using MRI scans and post mortem examinations. The researchers discovered that the koala’s larynx has descended to the level of the third or fourth cervical vertebrae, instead of being located higher in the throat.<\/p>\n

The investigations also revealed that the sternothyroid muscle, which attaches the larynx to the sternum, was anchored very deep in the thorax and could pull the larynx even further into the chest cavity. “The low larynx position may indicate strong selection pressures to broadcast, and possibly to exaggerate body size using formants in this species,”\u009d said Dr Charlton.<\/p>\n

To examine the effects of the descended larynx on koala bellows, Dr Charlton recorded the bellows of the males at theLone Pine Koala Sanctuary<\/a> in Queensland. An analysis of the bellows revealed that koalas were able to make themselves sound as though they had 50 centimetre vocal tracts, suggesting a much larger body size than they actually possess.<\/p>\n

The bellows could provide a key to the trigger for koala mating behaviour, which isn’t currently well understood. Dr Ellis said it has been suggested that there may be a critical mass of male bellows, which could lead to oestrus in the females.<\/p>\n

In dwindling populations, if there isn’t that vocal environment, the females may not be as reproductive. “This would explain why, in some really small populations, they don’t seem to breed,”\u009d Dr Ellis said.<\/p>\n

The bellows may also enable the males to identify each other and broadcast information, allowing smaller males to avoid larger rivals. “(One way) they avoid getting beaten up all the time is to send out a call and see what happens.”\u009d<\/p>\n","protected":false},"excerpt":{"rendered":"

A male koala’s bellow may attract mates and intimidate rivals.<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7,64,45,6,8],"tags":[],"class_list":["post-3037","post","type-post","status-publish","format-standard","hentry","category-animals","category-ecology","category-environment","category-nature","category-science"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/scienceillustrated.com.au\/blog\/wp-json\/wp\/v2\/posts\/3037"}],"collection":[{"href":"https:\/\/scienceillustrated.com.au\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/scienceillustrated.com.au\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/scienceillustrated.com.au\/blog\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/scienceillustrated.com.au\/blog\/wp-json\/wp\/v2\/comments?post=3037"}],"version-history":[{"count":5,"href":"https:\/\/scienceillustrated.com.au\/blog\/wp-json\/wp\/v2\/posts\/3037\/revisions"}],"predecessor-version":[{"id":4258,"href":"https:\/\/scienceillustrated.com.au\/blog\/wp-json\/wp\/v2\/posts\/3037\/revisions\/4258"}],"wp:attachment":[{"href":"https:\/\/scienceillustrated.com.au\/blog\/wp-json\/wp\/v2\/media?parent=3037"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/scienceillustrated.com.au\/blog\/wp-json\/wp\/v2\/categories?post=3037"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/scienceillustrated.com.au\/blog\/wp-json\/wp\/v2\/tags?post=3037"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}