Capuchins are the most intelligent New World monkeys – perhaps as intelligent as chimpanzees. They are noted for their ability to fashion and use tools. For instance, they have been observed using rocks to crack open nuts. ADAPTATIONS They are mainly arboreal but do forage on the ground. They are diurnal and feed all day with a short rest at midday. They have semi-prehensile tails that help them stabilize movement or act like a brake. They have opposable thumbs and big toes. They can also walk upright so that they can carry food; they fashion and use objects as tools and to manipulate food. They are considered to be very intelligent, some think as intelligent as chimpanzees.