Yukihiro Fukuda / Japanese macaque (Macaca fuscata) searching for nuts with young watching, Jigokudani, Joshinetsu Kogen NP, Nagano, Japan

Pete Oxford / Brown Capuchin (Cebus apella) stabilizes itself with its prehensile tail while using a heavy rock hammer to crack open palm nuts placed in small pits in the anvil rock surface, Cerrado habitat, Brazil

Pete Oxford / Brown Capuchin (Cebus apella) stabilizes itself with its prehensile tail while using a heavy rock hammer to crack open palm nuts placed in small pits in the anvil rock surface, Cerrado habitat, Brazil

Pete Oxford / Brown Capuchin (Cebus apella) pair using rock and anvil to crack open Piassava Palm (Attalea funifera) nuts, Cerrado habitat, Piaui State, Brazil

Chien Lee / Long-tailed Macaque (Macaca fascicularis) troop feeds on oil palm nuts washed downriver from a plantation, Kinabatangan Wildlife Sanctuary, Sabah, Borneo, Malaysia

Luciano Candisani / Black-striped Capuchin (Sapajus libidinosus) using rock to crack open nuts while juvenile watches, Piaui State, Brazil

Yukihiro Fukuda / Japanese macaque / Snow monkey {Macaca fuscata} feeding on pine nuts in autumn, Jigokudani, Nagano, Japan

Rod Williams / Allen's swamp monkey {Allenopithecus nigroviridis} male feeding on peanuts, captive, from Congo

Pete Oxford / Brown Capuchin (Cebus apella) pair using rock and anvil to crack open Piassava Palm (Attalea funifera) nuts, Cerrado habitat, Piaui State, Brazil

Pete Oxford / Brown Capuchin (Cebus apella) stabilizes itself with its prehensile tail while using a heavy rock hammer to crack open palm nuts placed in small pits in the anvil rock surface, Cerrado habitat, Brazil

Pete Oxford / Brown Capuchin (Cebus apella) stabilizes itself with its prehensile tail while using a heavy rock hammer to crack open palm nuts placed in small pits in the anvil rock surface, Cerrado habitat, Brazil

Pete Oxford / Brown Capuchin (Cebus apella) using a heavy rock hammer to crack open palm nuts placed in small pits in the anvil rock surface, a second monkey eats the opened palm nuts, Cerrado habitat, Brazil