American alligators produce loud, very low-pitched vocalizations called “bellows”. These rumbling roars communicate the animal’s body size to other alligators. Alligators can use this information to avoid unpromising contests for mates and breeding areas. That’s according to a new study published in Scientific Reports on May 12, 2017
In alligators, being bigger than other alligators can have decisive benefits. Females only accept males larger than themselves as mates and larger alligators are much more likely to win territorial fights. However, direct physical confrontations can lead to lethal injuries. That’s why it’s advantageous if fights can be avoided by alligators reliably signaling their body size to potential mates and rivals early on.
That’s where bellowing comes in. A research team of cognitive biologists at the University of Vienna identified cues to body size in the alligators’ bellows.
For the study, the scientists recorded the bellows of 43 adult American alligators at the St. Augustine Alligator Farm Zoological Park in Florida. Then they measured the head and total body length of all the alligators up close with measuring tapes and hand-held laser-distance-measurement devices.
Their analysis found that the resonance frequencies of the bellows are almost perfect predictors of body size. Study co-author Stephan Reber is a cognitive biologist at the University of Vienna. Reber said in a statement:
Resonance frequencies depend on the length of the vocal tract. Larger alligators have longer vocal tracts and therefore lower resonances.
Bottom line: A study suggests that the bellows of American alligators reveal their size.
Eleanor Imster has helped write and edit EarthSky since 1995. She was an integral part of the award-winning EarthSky radio series almost since it began until it ended in 2013. Today, as Lead Editor at EarthSky.org, she helps present the science and nature stories and photos you enjoy. She also serves as one of the voices of EarthSky on social media platforms including Facebook, Twitter and G+. She and her husband live in Tennessee and have two grown sons.