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Common marmoset (adult and sub adults) at the enclosure at the German Primate Center Manfred Eberle

Common marmosets

Distribution

Common marmosets (Callithrix jacchus) belong to the so-called New World monkeys and are found in the northeastern Brazil. With a size of 16 to 20 centimeters, they weigh only 300 to 350 grams, making them one of the smallest species of higher primates.

 

Physical Characteristics

Aside from their small size, common marmosets are particularly notable for their long, gray-black ringed tails and the white tufts of hair around their ears. Their faces are light-colored, sparsely haired, with a white spot on the forehead. Like all members of their family, common marmosets have claw-like nails on their fingers and toes, except for the big toe, which features the typical flat primate nail. The claws allow them to hook into tree bark, enabling them climbing up and down trees in a vertical position.
 

 

Diet

Common marmosets primarily feed on plant exudates and tree gums. During the dry season, these substances make up about 80% of their diet. The availability of tree gums significantly influences the group size and survival chances of these primates. Their specialized diet reduces competition for food with other primate species, allowing them to thrive even in relatively small habitats. To access the exudates, common marmosets have evolved a unique dental structure, including enlarged, chisel-like incisors with reinforced enamel on the outer surface. The uneven wear of enamel and dentin continually sharpens the "cutting edge," which helps them gnaw through bark to stimulate the flow of exudates. During the rainy season, they consume mainly fruits, which can make up 60 to 100% of their diet. They also eat flowers, nectar, fungi, and insects like grasshoppers and locusts, as well as snails, small lizards, and tree frogs.

 

Habitat and Lifestyle

Common marmosets inhabit a variety of forest types. Thanks to their adaptability, they are found in Brazil's rainforests and coastal forests, as well as in the dry savannah known as Caatinga. They are also commonly seen in suburban gardens, agricultural plantations, and even public parks in Rio de Janeiro. Most of their day is spent foraging in trees. At night, they sleep in vines and branches in the treetops. The size of their home range is largely determined by the availability of exudate-producing trees and typically covers just two to six hectares. During their daily foraging, common marmosets travel between 500 meters and one kilometer.

 

Social Behavior and Reproduction

Common marmosets usually live in groups of three to 15 individuals, often consisting of up to four adult males and females, along with their offspring. When groups grow too large, both sexes disperse, with females leaving more frequently. These primates have a complex vocalization system that they use to communicate and even recognize each other. The group is dominated by a breeding pair, which typically is the only pair to reproduce. The other group members form a loose, age-based hierarchy around this pair. The mating system of common marmosets is quite complex and variable. Earlier studies conducted in captivity suggested a strictly monogamous reproductive system. However, in the wild, monogamy, polyandry (one dominant female mating with several males), and polygyny (one dominant male mating with several females) have all been observed. Births occur throughout the year but peak between October and December (dry season) and April to July (rainy season). The gestation period is around 145 days, and females almost always give birth to twins. The offspring are distinguished from adults by their darker ear tufts. Raising the young requires significant energy from the mother, but all group members, especially adult males, actively help care for the offspring (helper system). The young are nursed for about 10 weeks but begin eating solid food as early as four weeks old. After three to four months, they become largely independent and reach full maturity by about 15 months.

 

Common Marmosets in Research

Due to their relatively short reproductive cycles and the frequent birth of twins, common marmosets are easy to breed and play a significant role in reproduction and stem cell research. Their complex vocalization repertoire makes them useful in communication and auditory research. Additionally, common marmosets are an established model for studying Parkinson's disease, helping scientists investigate disease progression and test new therapies.