Figure 2

Correlations between individual size (total body length) and (a) the calls’ mean pitch and (b) the calls’ centroid of the frequency spectrum.

Each dot represents a single individual. Both acoustic parameters decrease with individual size, underlying that smaller individuals utter higher pitched calls with a wider frequency bandwidth⁵⁹. Alligatoridae are in dark blue (American alligator) and sky blue (spectacled caiman). Crocodylidae are in red (Nile crocodile), plum (Morelet’s crocodile) and pink (Orinoco crocodile). Regression lines are shown for the alligator and the Nile crocodile only. Slopes of the regression lines are not significantly different between both species (see results).