The Brown Capuchin Monkey is a New World primate who lives in the northern Amazon rainforest of the Guyanas, Venezuela and Brazil. They are also found in eastern Colombia, Ecuador, Peru, including the upper Andean Magdalena valley in Colombia, and a population was established in the Republic of "Trinidad and Tobago". The capuchin has a head-body length of 32 to 57 centimetres and a weight of 1.9 to 4.8 kilograms and mostly eats fruit, insects, larvae, eggs, young birds, frogs, lizards, and even bats. They are also known to chase cats. They can be found in many different kinds of environment, including moist tropical and subtropical forest, dry forest, and disturbed or secondary forest. They are social, and form groups of 8 to 15 individuals that are led by an alpha male. Important natural enemies of the capuchin are large birds of prey who they are so afraid of that they even become alarmed when a harmless bird flies over. The capuchin rubs urine on its hands and feet in order to attract mates and reduce stress. They also use stones and sticks as tools. One population of this species uses stones as a tool to open hard nuts. 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 anvil rock is often pock-marked with hollows as a result of repeated use. They have also been observed using containers to hold water, using sticks (to dig nuts, to dip for syrup, and to catch ants), using sponges to absorb juice, using stones as hammer and chisel to penetrate a barrier, and using stones as hammer and anvil to crack nuts. Some of these tasks seem relatively simple by cognitive standards, but others, like cracking nuts with hammer and anvil, are only exceeded in complexity by chimpanzees and some humans.