Ingo Arndt / Close up of foot of Chimpanzee {Pan troglodytes} note opposable toe

Ingo Arndt / Orang utan hand holding branch close-up {Pongo pygmaeus abelii} Sumatra, Indonesia

Andy Rouse / Mountain gorilla (Gorilla beringei beringei) close up of feet showing toe curled around branch, Volcanoes NP, Virunga mountains, Rwanda

Ingo Arndt / Orang utan holding twig and feeding {Pongo pygmaeus abelii} Gunung Leuser NP, Sumatra