Cebuella niveiventris

Geographic Distribution and Habitat

The eastern pygmy marmoset, also known as the white-bellied pygmy marmoset, is found in the northwestern Brazilian states of Amazonas and Acre, eastern Peru, and northern Bolivia. Within their range, they inhabit gallery forests (those formed along riverbanks that flow into otherwise open areas, such as deserts or savannas) at elevations ranging from 295-394 feet (90-120 m).

The species and their western pygmy marmoset (C. pygmaea) counterpart are separated in range by the Amazon River (Solimões River) and Maranon River. The eastern pygmy marmoset has recently (as of April 2021) been confirmed, through the use of DNA testing, to reside in the country of Ecuador, hundreds of kilometers north of the Maranon River!


The eastern and western pygmy marmosets were believed to be one species. In the early 2000s, they were separated into two species on the basis of the eastern pygmy marmoset possessing a more white, pale color (more to be explained in Appearance). However, in 2018, a study confirmed this division between the two species is actually based on their DNA and skull structure (rather than simply their fur color.) 

Eastern pygmy marmoset range, IUCN 2023

Size, Weight, and Lifespan

The eastern pygmy marmoset ranges in head-to-body length from 4.61-5.98 inches (117-152 mm), with a tail length ranging between 6.77-9.02 inches (172-229 mm). There is sexual dimorphism (noticeable physical differences between genders) only in terms of weight, with males weighing in at 3.77-4.41 ounces (107-125 g), while females weigh 4.44-4.97 (126-141 g). The eastern pygmy marmoset is one of the smallest primate species in the Americas!

Their lifespan in the wild is 10-12 years.


The eastern pygmy marmoset is covered in a fawn and gray fur coat, with yellow and/or black markings on the back and head. Their underparts, including their arms and legs, are whiteish; the throat and chest area have more orange-to-white coloration. The non-prehensile tail (not used for grabbing or grasping, but instead, for balancing among the tree branches) is marked with black bands down the length. Cheek markings and a vertical stripe down the nose are white in color and are likely used for visual communication. 

Babies, meanwhile, initially have gray heads and yellow fur covered with black markings. They begin showing the adult pattern by their first month of life.

Like their western cousins, the eastern pygmy marmoset sports longer hairs around the face and neck which gives them the appearance of a lion’s mane (and thus, the nickname of “lion monkey”). In addition, both species have longer rear limbs compared to their forelimbs (the better to jump around the trees with), and all nails, except for the big toenails, have claws—for gripping vertically onto trees and poking holes in them in search for food—as opposed to flat nails.

Photo: © alonsolopezph/iNaturalist/Creative Commons

Like the western pygmy marmoset, the eastern pygmy marmoset has a unique, high-quality, and rare diet. The majority of their diet consists of plant exudates, in other words, tree sap, tree gum, and latex. At times, they also eat insects and even fruits for some extra nutrition.

Due to this particular diet, pygmy marmosets have dental and nail adaptations to gnaw and dig into trees to get at their sticky favorite foods. With regard to their teeth, they have large lower incisors and a strong V-shaped lower jaw perfect for chewing into trees.

Behavior and Lifestyle

Eastern pygmy marmosets are diurnal (most active during the day) and arboreal, spending their time in the trees. After a day spent foraging, at night, group members will roost in a sleeping tree, either gathering into a tree cavity or a nest. Nests will especially be made for the young on thin branches. These thin branches are preferred as they cannot support the weight of [natural] predators, such as cats, birds of prey, and snakes. Their roosting spots are strategically chosen near their food source(s). Upon waking up in the morning, group members depart to forage soon after sunrise. They move about the trees on all fours with remarkable agility, and prefer to stay in the higher parts of the trees (but rarely the canopy).

Upon reaching the primary exudate tree, the pygmy marmosets will feed for 30-90 minutes on the sappy secretions. After this time period, there is a shift in focus to social activities, including grooming, playing, and huddling. After this brief rest period, exudate foraging (alongside snacking on insects) continues until midday, upon which there is another social break. Foraging and feeding begin yet again in the late afternoon until the group travels back to roost at night.

Like their western brethren, their small size, agility, and camouflage coloring make them tricky to observe in the wild. They are also naturally shy, and would rather hide than fight when confronted by threats from other species, so their behaviors are said to be “cryptic” (in other words, secretive). Should you ever find yourself within their forested domain, one reliable way of finding and observing them would be to find their distinct feeding holes in tree bark. Pygmy marmosets repeatedly visit the holes to feed, so if you’re patient and wait near a tree with some recent feeding holes, there is a good possibility you will see a group of these monkeys. In addition, to get a reliable estimate of how many eastern pygmy marmosets there are in a given region, your best bet would be to find their roosting tree, watch them gather in one place, and count!

Other predator-avoidance strategies besides nesting on thin branches include sounding an alarm call followed by beating a hasty retreat and using a rather owl-usual (sorry… bad pun) method for being alert to potential predators seeking to make them their next meal (more on that in the Fun Facts section).

Fun Facts

Remember those differences in skulls between the eastern and western pygmy marmoset? Scientists believe they might nibble on different kinds of tree species with different kinds of bark, which makes this adaptation necessary.

Want another idea of just how small these primates are? Pygmy marmosets are also called “finger monkeys” due to their teeny-weeny size.

That’s no owl: Eastern pygmy marmosets have the ability to turn their head 180º in order to be on the lookout for predators.

Daily Life and Group Dynamics

Groups are composed of two to nine individuals, with one or two adults of each gender, and the dominant female’s offspring. The dominant male usually restricts breeding access of other males to the dominant female of the group. Upon reaching maturity, offspring may leave their natal (birth) group to start one of their own or they may stay to help raise newer babies. 

The home range consists of 0.25-0.99 acres (0.1-0.4 ha), and their daily feeding is usually concentrated on one or two trees at a time. When those trees get “sucked dry” of exudates, the group will move to a new set of trees. Home ranges are maintained by scent boundaries made from scent glands, signaling neighboring groups to stay away and keep within their own territories.

The eastern pygmy marmoset is sympatric with (occurs in the same area as) the saddleback tamarin (Leontocebus fuscicollis) in part of their range. Wildlife biologists believe that such mixed-species associations may be a strategy for protection from predators (with “safety in numbers”).


Eastern pygmy marmosets communicate with one another primarily by chattering and trilling in high-pitched voices. They can make sounds so high in pitch, that humans can’t even hear them! A few distinguishable calls have been documented:

• Trills: short-distance, high-pitched contact calls

• “J calls”: a high-pitched ringing trill used as a medium-distance contact call

• Long calls: a series of 2-7 high-pitched long notes used as a long-distance contact call

• Warning calls: an alarm call used to warn others of predators, mainly raptors

Like humans, the eastern pygmy marmoset also makes faces (aided by their distinctive cheek markings and white stripe down the nose) to express emotions such as contentment, fear, or surprise. This is done by moving lips, eyelids, ears, and the hair around the face. What cute, little, expressive monkeys they are!

Grooming is another social activity that the eastern pygmy marmoset partakes in. In doing so, not only do they rid each other of dead skin and parasites, but they reinforce social bonds within the group.

Reproduction and Family

Eastern pygmy marmosets are monogamous, with a breeding pair producing one to three offspring every year (up to 80% of births resulting in twins). They do not have a specific breeding season. Rather, the dominant pair breeds at any time of the year. The dominant female has a gestation (pregnancy) period of 4.5 months, and births young at intervals of 5-6 months. Dad even helps with the birthing process, cleaning the babies as soon as they are born. Breeding between the pair occurs during the female’s postpartum estrus (after birth physical readiness), around three weeks after giving birth to the previous offspring. She signals her readiness for mating using secretions from her scent glands.

Raising the young is a family affair, with group members displaying a cooperative system of infant care. Dad will carry his babies piggyback style for the first two weeks of life, and bring them back to Mom to nurse. When the young are a bit older, the babies will hide while the rest of the family forages until they are strong enough to travel with the group. Young are weaned from Mom’s milk at around three months of age, and reach sexual maturity (and thus, independence) between 15 and 17 months of age.

Photo: © alonsolopezph/iNaturalist/Creative Commons
Ecological Role

As some of their diet consists of fruit, the eastern pygmy marmoset aids in the regeneration of their forest habitat by dispersing seeds through their feces as they move around their habitat. As a prey species, they also play a role in feeding local predators within the habitat. Finally, they may also be considered pest controllers through their consumption of insects.

Conservation Status and Threats

The International Union for Conservation of Nature lists the eastern pygmy marmoset as Vulnerable (IUCN, 2015), appearing on the IUCN Red List of Threatened Species.

The primary threats facing the eastern pygmy marmoset are habitat loss (both in size and quality) due to human activities including deforestation, mining, palm oil cultivation, settlement expansion, as well as hunting for meat and the pet trade.

Conservation Efforts

The eastern pygmy marmoset is listed in Appendix II of the Convention on International Trade in Endangered Species (CITES), an international agreement between governments whose goal is to ensure that international trade in specimens of wild animals and plants does not threaten their survival.

The eastern pygmy marmoset is found in numerous protected areas within their range, including (but not limited to):

Bolivia: Manuripi Health Nature Reserve 

State of Acre:

  • Serra do Divisor National Park
  • Cazumbá-Iracema Extractive Reserve
  • Chandless State Park

State of Amazonas:

  • Abufarí Biological Reserve
  • Jutaí-Solimões Ecological Station 
  • Serra Três Irmãos Ecological Station
In order for the eastern pygmy marmoset to stop moving along the path to endangerment and extinction, conservation actions needed include proper land/water and site/area management, as well as better enforcement against the pet trade and hunting for bushmeat. In addition, further monitoring of the eastern pygmy marmoset’s population trends, as well as research on their population size, distribution, trends in life history and ecology, and threats are crucial if the species is expected to survive in the years to come.
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  • https://animals.sandiegozoo.org/animals/pygmy-marmoset
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Written by Sienna Weinstein, May 2024