The ability to climb is very important for pygmy marmosets, because tree sap is their favorite food. They scamper up and down trees headfirst, clinging to the side of a tree trunk and gouging a hole in the bark with their sharp lower teeth, using an up-and-down sawing motion. When the sap puddles up in the hole, they lap it up with their tongue.
Pygmy marmosets have certain trees they like within their 2.5-acre (1 hectare) territory; they can make up to 1,300 holes in each one! Sometimes they lie in wait for insects, especially butterflies, which are attracted to the sap holes. They also eat some nectar and fruit.
At the San Diego Zoo, the pygmy marmosets are fed yams, carrots, leaf eater biscuits, bananas, apples, grapes, crickets, and mealworms.