Primates studied included the black and gold howler monkey, tufted capuchin, black-capped squirrel monkey, and Peruvian spider monkey. Monkeys, scientists found, had a secret yodelling weapon ...

The monkeys' "ultra-yodels" had frequency leaps that were five times larger than human frequency changes, often exceeding three octaves. (Human yodelers are limited to one octave.) While the monkeys' ...

In this study we wanted to assess the responses of two groups of tufted capuchin monkeys (N=11) to a 30 cm x 25 cm feeding board. The board consisted of a metal support to which plastic blades of ...