Geographic Distribution and Habitat
The Emilia’s marmoset is only found in central Brazil, specifically in the states of Pará and Mato Grosso. Their habitat lies on the southeast edge of the Amazon Rainforest. The rainforest is characterized by regular rain and a relatively constant average temperature of about 28 ℃ (82.4 ℉). December through March are especially rainy.
The Emilia’s marmoset is also know as Snethlage’s marmoset. Both of these names are references to the German-Brazilian scientist Maria Emilie Snethlage.
Size, Weight, and Lifespan
Emilia’s marmosets have a head and body length of about 8.5 inches (21.6 cm), a tail length of about 13.4 inches (34.1 cm), and a weight of 12 ounces (335 grams). These measurements are about average for the marmoset family.
There is no recorded lifespan for the Emilia’s marmoset specifically, but marmosets typically live for about 10 years in the wild.
A part of the body that in the course of evolution, has degenerated and become functionless; the last small part that remains of something that once existed.
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The Emilia’s marmoset is a mostly white-haired monkey with a gray back. Their posture often gives the appearance of a hunchback. Their pink faces and muzzles are covered by light hair and feature large brown eyes. Their pointy ears are particularly recognizable as they often stick out beyond their fur.
These marmosets are small monkeys adapted to ascending tree trunks and climbing along thin branches. Marmosets have claws on all of their fingers and toes except for their big toes. These claws are primarily used for climbing. Marmosets have tails significantly longer than the rest of their body. Though these tails are non-prehensile, they can be used to maintain balance when traversing the trees.
The “true” marmosets are all characterized by strong, thick incisors in the lower jaw that allow the monkeys to gouge holes in tree bark and eat the tree sap inside. Marmosets have a highly developed cecum, which allows them to easily digest exudates such as gum, sap, and resin. These plant exudates make up a large portion of the Emilia’s marmoset diet, as well as fruits, nectar, and insects.
Behavior and Lifestyle
Marmosets are diurnal (active during daylight hours) and arboreal (tree-dwelling). They prefer to spend most of their time high in the trees in the upper canopy of the rainforest.
The marmoset’s family name, Callitrichidae, comes from the Greek phrase for “beautiful hair.”
Emilia’s marmosets live in groups of 4 to 15 individuals. These groups are led by a dominant male and female. The dominance hierarchy is decided by age, as opposed to sex, strength, or familial relationships. Females in the group are usually related, while the males leave the group around the time they reach adulthood. These groups control relatively small territories of 25 to 100 acres each that often overlap with competing groups.
Marmosets have a rich repertoire of visual, vocal, and scent communication.
Common facial expressions for marmosets include an open mouth stare, which indicates that the monkey wants to play. A marmoset who squints his eyes is cautious of a stranger or foreign object. Marmosets who are submitting to a dominant individual will show it by baring their teeth and flattening their ears. Marmosets also seem to communicate danger using their tail, waving it like a snake to express their fear of something.
Marmosets make regular trilling noises to stay in contact with their group during foraging. However, most vocalizations by marmosets are meant to communicate alarm. These alarm calls include rapid, high-pitched, bird-like cries, which more often relate to inter-group conflicts, while lower-pitched whining calls are meant to signal predators. Marmosets respond to these calls by freezing and relaying the calls to the surrounding area.
For primates, Emilia’s marmosets has quite a strong sense of smell, and so scent-marking plays a major part in communication. New World monkeys have a highly developed vemeronasal organ in their nose that allows them to learn much more about another monkey through their scent than humans could. We, along with the other apes of the world, have these organs, but they are vestigial and no longer work. Marmosets use a scent gland in their chest to rub their scent on branches to mark their territory. They rub their genitals on the branch during feeding to signal to their group where they’ve been and when they were there.
Marmosets are mostly monogamous, mating for life. Only the dominant male and female mate within the group. Occasionally, a subordinate female will secretly mate with a male from outside the group. Females have a gestation period of 5 months and they begin mating only a week or two after giving birth. Ideally, the dominant female will give birth twice a year, at the end of the dry season and wet season, respectively.
Mothers give birth to twins most of the time, although triplets and single offspring have been observed. All monkeys in the group including the father, assist the mother in raising the newborns. Babies are weaned at around 3 months old, are nearly independent by five months old, and enter puberty at about a year old. Females become sexually mature at around 15 months of age, but they will not mate until their social standing is adequate. Males become mature closer to their second birthday, at which point they leave their natal group to join a new group a create one of their own.
Because marmosets are so well adapted to gouging holes in tree bark, other gummivores (animals whose main diet is tree gum, sap, and resin with bugs for protein) may use marmoset-created holes to feed on the sap. Emilia’s marmosets are hunted by a wide variety of animals including wild cats, birds of prey, and members of the weasel family.
Conservation Status and Threats
Although data are sparse, the International Union for Conservation of Nature’s Red List of Threatened Species categorizes the Emilia’s marmoset as Least Concern (IUCN, 2015), stating that despite habitat reduction, the species is widespread and can smoothly adapt to new habitats. Emilia’s marmosets have been seen living relatively well in urban environments.
The biggest threat to the Emilia’s marmoset is the spreading agricultural industry, especially for cattle and soybeans, as well as the building of infrastructure to support the newly developed lands.
As one of the most important landscapes in the world, the efforts to protect the Amazon rainforest are as numerous as its threats. Top charities for the Amazon rainforest include the Rainforest Trust, which purchases rainforest land to prevent its destruction, and Rainforest Action Network as well as Rainforest Alliance, which focus on educating local groups to develop sustainable forestry techniques.
- [John Aguiar]. [Mico, emiliae, ]. © All the World’s Primates. N Rowe, M Myers, eds. (alltheworldsprimates.org)
- Guilherme Siniciato Terra Garbino “The Southernmost Record of Mico emiliae (Thomas, 1920) for the State of Mato Grosso, Northern Brazil,” Neotropical Primates, 18(2), 53-55, (1 December 2011)
Written by Eric Starr, November 2019