gray, with the belly being somewhat lighter-colored than the rest of the body. The hands and feet are black. The tail is prehensile: strong and can be used for grasping, as an extra limb. The tufted capuchin has a head-body length of , a tail length of , and a weight of , with the males generally being larger and heavier than the females. Behaviour and ecology The tufted capuchin is a diurnal, arboreal primate species, but it often forages on the ground to search for food or to walk longer distances between trees that are too far apart to jump. The tufted capuchin lives in groups of two to twenty or more animals. A single group usually contains at least one adult male, but mixed groups with multiple males do also occur. In that case, one of the males is dominant. He accepts only a few monkeys in his direct surroundings, mainly younger animals and a few females. The dominant male and the group members that are close to him have the privilege to eat first in case of food scarcity, while subordinate monkeys have to wait until they are ready. After a gestation period of 180 days, one young is born, or incidentally a twin. This young, which weighs only 200 to 250 grams, is carried on the back of its mother. The mother feeds her child for 9 months, but the young are sexually immature until its seventh year, which is quite late for a primate of its size. Important natural enemies of the capuchin are large birds of prey. They are so afraid of those birds that they even become alarmed when a harmless bird flies over. Diet A recently discovered characteristic of one population of this species is that it uses stones as a tool to open hard nuts. First it chooses ripe nuts from a nut palm. It uses its teeth to strip off the nut's fibrous husk. Then it leaves the nut to dry for about a week. When the nut is dry, the monkey lays the nut on a large, flat rock or fallen tree, hammering the nut with a suitable stone until the nut cracks. The hammerstones are often large enough to require lifting with both hands. The anvil rock is often pockmarked with hollows as a result of repeated use. Besides nuts, the capuchin also eats fruit, leaves, nuts, seeds,