Bearded sakis specialise in eating the young seeds from inside unripe fruits (2) (8). Their robust canines (8), along with the other upper teeth that jut forward over the lower teeth like a macaw’s beak, are perfect for cracking open the hard shells of some fruits and nuts, enabling them to reach the soft kernels within (4). Their remarkably strong jaws and teeth are capable of breaking open fruits that humans would be unable to achieve without the aid of a hammer (4). Bearded sakis supplement this diet of seeds and fruits with arthropods, including spiders and insects (9), and, unusually, soil. The habit of eating soil, also known as geophagy, may be done for a number of reasons, such as for minerals, to absorb toxins, or to alleviate gastrointestinal upsets (10).
Seeking out trees with the best seeds and fruits is a time consuming activity for the bearded saki (6), undertaken in groups of around 30 individuals (4). The gestation period in this monkey lasts for five months, with just a single young born at a time. The bearded saki becomes sexually mature at four years of age and can live for more than 18 years (4).