The primate I have decided to study this week is the pygmy marmoset. Pygmy marmosets belong to the suborder Haplorrhini, family Cebidae, subfamily Callitrichinae, and genus Callithrix. Pygmy marmosets are the smallest monkeys in the world, weighing on average 119g and measuring, on average 136mm. Males and females are very similar in size, although females tend to be slightly heavier. There are few morphological difference between the subspecies and may only differ slightly in ventral pelage color. They have brownish-gold fur with black ticking on their shoulders, backs, and heads, while ventral fur is light yellow to white. Infants are born with different pelage than adults but by the end of the first month, they lose this coat and resemble adults.
Pygmy marmosets move quadrupedally, running up and down tree trunks, vertically clinging to trees as they feed on sap. Their small body size allows them to use very slender supports and allows them to leap up to five meters. Pygmy marmosets are able to turn their heads 180 degrees, an adaptation which allows them to scan for predators while clinging to trees. Pygmy’s also have claw-like nails which are different from the flat nails seen in other primates probably as an adaptation to a life spent mostly in the tress. The shape of their lower incisors is narrow and elongated which allows them to gnaw into trees and stimulate sap flow more efficiently. They also have a enlarged cecum which allows extended time for the breakdown of plant gums. It is also common for pygmy marmosets to give birth to none identical twins.
Characteristics such as elongated, sharp incisors and claw-like nails are adaptations to the very specific diet of the pygmy who are exudativore-insectivores who spend the majority of their time gouging holes into tress or vines with their sharp lower teeth then eating the gum, sap, resin exuded. Insects also make up the other important part of the diet and grasshoppers are especially coveted.
Pygmy marmosets use sleeping sites, or roosts, each night, which are generally made of dense tangles of vines. Each group generally has two or three sleeping sites but use one on a regular basis. Each morning the group will leave and travel directly to their primary exudate tree where the marmosets feed for 30-90 minutes. After feeding the activities shift to more social things such as huddling, grooming, and playing. A pygmy marmoset group, ranging in size from two to nine individuals, utilizes a primary exudate tree in its home range until the exudate yield declines at which point they gradually move to a new area.
Pygmy marmosets are found in Peru, Ecuador, Colombia, Bolivia, and Brazil. They occupy mature evergreen forest in and at the edges of periodically inundated river floodplains and are commonly found in highest densities in river-edge forests. Pygmy’s are rarely found at the top level of the canopy. The understory where pygmy’s are usually found is composed of reeds, tall grasses, few herbaceous plants, vines, shrubs, and saplings.
Other primates that are found in the habitats occupied by pygmy marmosets include, the saddleback tamarin, mustached tamarin, black-mantel tamarins, golden-mantle saddle-back tamarins, collared titi monkey, dusky titi monkey, squirrel monkey, and the owl monkey. Because of their extremely small body size, pygmy marmosets are subject to predation by raptors and climbing snakes. In some cases, they exhibit mobbing behavior in which the entire group flocks to an intruder, loudly vocalizing and attacking the intruder until it retreats, other times they remain frozen until the threat has passed.
Given their tiny body size an the type of forest in which they are found, wild pygmy marmosets have been poorly studied and there is a lack of detailed behavioral and ecological data.
Cawthon Lang KA. 2005 June 30. Primate Factsheets: Pygmy marmoset (Callithrix pygmaea) Taxonomy, Morphology, & Ecology . <http://pin.primate.wisc.edu/factsheets/entry/pygmy_marmoset>. Accessed 2014 February 2.