The marmosets have the sharpest claws of any callitrichid. They also spend more time clinging to and feeding on vertical supports.
Marmosets have strong jaw muscles. However, compared to other marsupials, that strength is only average.
Marmosets live in mixed sex groups of up to 13 individuals. Only the head male and female will produce offspring. The mechanism that supposedly suppresses reproduction in lower-ranking females is still being studied.
These monkeys use their specialized claws to establish a firm grip on tree trunks and gnaw little holes in the bark with their lower incisors and canines. This causes the tree to produce more sap, which is used to seal injuries to the bark. This tree sap is a valuable source of carbohydrates and minerals.
Pygmy marmosets are only about six inches tall as adults. The tail may add another nine inches. They are gumivores, which means they supplement their diet with the sap, or gum, from certain forest trees.
The pygmy marmoset has an eclectic diet. They eat fruits, insects, birds, and bird eggs.
A longer mane of hair surrounds the face, covering the ears of the pygmy marmoset. White marks at the edges of the mouth and a white vertical line on the nose are thought to make communication through facial expressions more conspicuous in the dim light of dense forest.
It is a fairly quiet monkey, but can produce a variety of vocalisations for communicating. Its communications include a high, sharp warning whistle and a clicking sound to indicate threat
Pygmy marmosets have brownish-gold fur with black ticking on their shoulders, backs, and heads, while their ventral fur is light yellow to white. Infants are born with a lemon-yellow color with black ticking over their bodies while the head is a dark grey with yellow fur on and around their ears.
Pygmy marmosets are the smallest monkeys in the world, weighing a mere 119 g on average and measuring, on average, 136 mm. Males and females are very similar in size, though females are slightly heavier.