Male koalas use a distinctive resonant donkey-like bellow to convey their dominance during mating season.
This one, at the Lone Pine Koala Sanctuary in Brisbane, seems to come out of a nap to mark its presence.
The Lone Pine sanctuary: [ Ссылка ]
More on koala conservation and biology at Dot Earth:
A Conservation Challenge Down Under: Koalas, Chlamydia, Culling [ Ссылка ]
A research paper on the phenomenon:
Free-Ranging Male Koalas Use Size-Related Variation in Formant Frequencies to Assess Rival Males
Benjamin D. Charlton,1,* Desley A. Whisson,2 and David Reby1
Claudio Ricardo Lazzari, Editor
[ Ссылка ]
Koalas are marsupial mammals that inhabit the Eucalyptus forests of eastern Australia [27]. The koala’s solitary nature and conspicuous vocal activity during the breeding season [28-30] indicates that vocal communication is likely to be important for coordinating this species’ reproductive behavior, and makes the koala well suited for studying the function of vocal signals in mammal sexual communication. Recent work has revealed that the formant frequency spacing of male koala bellows is a reliable acoustic cue to the caller’s body size [6]. In addition, playback studies, using re-synthesis techniques to shift formants in male bellows, have shown that estrous female koalas move preferentially towards male bellows with lower formants simulating larger callers [25], and also confirmed that male koalas perceive formant shifts in male bellows corresponding to the natural variation in body size between a large and small adult male [31]. Taken together, these findings indicate that inter-sexual selection pressures will favor individuals able to produce lower formants in their bellows, and also suggest that size-related formant information could be functionally relevant to male koalas.
Nevertheless, because these previous studies were conducted on captive animals, the response of koalas to size-related formant information in their natural environment remains to be investigated. Indeed, whereas captive male koalas do not display differential looking responses to male bellows simulating different size callers [31], other behavioral responses to size-related formant information (such as differences in vocal behavior) may become apparent in free-ranging males that are actively competing for females during the breeding season. Signaling body size is important for determining the outcome of agonistic interactions between males in several terrestrial vertebrates [e.g. 18,32,33] and the male koala’s permanently descended larynx certainly suggests strong selection pressures for callers to elongate their vocal tracts and lower formants [6], in order to maximize the acoustic impression of their body size conveyed to receivers [34]. Thus, because formants are salient to male koalas [31] it is reasonable to predict that they use these acoustic cues to assess the body size of prospective rivals, allowing them to avoid escalating contests with larger, and potentially more dangerous individuals.
