In the last decade, increasing attention has been devoted to exploring some aspects of yawning in non-human animals. With their chin red mark, bony paranasal swellings, male large brains and long canines, drills ( Mandrillus leucophaeus ) offer a robust model for testing hypotheses on the phenomenon. We identified two yawn variants (covered, Y CT and uncovered teeth, Y UCT ) which differ in terms of recruitment of muscular act...

Predation is a major cause of mortality in non-human primates, and considered a selective force in the evolution of primate societies. Although larger body size is considered as protection against predation, evidence for predation on great apes by carnivores comes from chimpanzees ( Pan troglodytes ), gorillas ( Gorilla gorilla ), and orangutans ( Pongo spp.). Here, we describe the first encounter between wild bonobos ( Pan pa...