(Balls) Size Matters For Howler Monkey Mating Calls | Video

A new study of the species Alouatta caraya has revealed that the deeper the vocalization, the smaller the testicals. This also led to the conclusions that howler monkeys with low-pitch vocalization tended to live in "single-male groups with a harem of a few females," according to University of Utah professor Leslie Knapp.

credit : La Senda Verde Animal Refuge, Bolivia