The giggling sounds of a hyena contain important information about the animal’s status, say scientists.
In the first study to decipher the hyena’s so-called “laugh”, they have shown that the pitch of the giggle reveals a hyena’s age.
What is more, variations in the frequency of notes used when a hyena makes a noise convey information about the animal’s social rank.
Details of the US-based research are published in the journal BMC Ecology.
The volume of air in your lungs is a good indicator of strength ( hence age , genes + health as well) .In moments of fear , like a clash over food or a mate , the exertion would lend itself to a display of audible lung volume ( a growl , howl ) . The nuances of the growl would indicate the intention of the growler ( read the post about the body as emotional store two posts back ) as the viscera are moved around a musculature and affect the timbre of the growl ( confident or sensing failure signals) .
All this helps to stop a senseless fight getting too far ( the signals are received , one loses and one wins ).The loser has helped not to weaken the winner too much but enough to determine his mating rights.
Its not a big step up to passively communicating this information in a non-confrontational way as these Hyenas are doing so that a hierarchy can be formed .