Finger Monkeys (also known as pygmy marmoset) are incredible animals native to South America and sometimes kept as pets. The average lifespan of a finger monkey is anywhere between 15-20 years. Finger monkeys in the wild tend to live shorter lives, due to predation, disease, and accidentally falling off of trees.
“Finger monkey” is the colloquial name of the pygmy marmoset (Cebuella pygmaea), a species of monkey native to South America. They are also sometimes known as the “pocket monkey.” Closely related to other New World monkeys tamarins and marmosets, finger monkeys, as the name would imply, are most distinguished by their tiny size. On average, adults reach a body size of about 4-6 inches long and weigh about 3.5 ounces. As such, they are the smallest known species of primate and can hang comfortably off of the average adults human’s finger.
Pygmy marmosets are unique among marmosets in that they are assigned their own unique genus Cebuella, under which they are the sole species. Other marmosets fall under the Callithrix and Mico genera. There are two distinct subspecies of finger monkeys C. p. pygmaea and C. p. niveiventris. Like many primate species, they exhibit a remarkable amount of cognitive sophistication, social organization, and a robust communication system. They also occupy something of a niche market among exotic animal collectors who are drawn to their tiny size and affable appearance.
Anatomy Of The Finger Monkey
In addition to their tiny size, finger monkeys also have a prehensile tail, typically 6-9 inches long. Their fluffy fur makes them look physically more robust than they actually are and serves to discourage potential predators. Their fur is a mixture of black, gray and brownish-red, sometimes with a colored vertical stripe of fur running between their eyes.
As they are arboreal, finger monkeys have developed a number of traits for living in trees. Its tail acts as an extra appendage for grasping and climbing, while its hands and feet have sharp claws for holding on to trees. Like an owl, they are able to rotate their head 180° for maximum treetop vision. As well as having powerful legs that can launch between tree branches, they have specialized incisor teeth for feeding on tree gum and sap.
A finger monkey “family” ranges anywhere from 2-9 members, including one or two adult males and one or two adult females. Solitary individuals of both sexes have been seen in the wild as well. Generally, only one female in the group breeds, while other subdominant females help with childcare or resource gathering. Interbirth cycles range from half a year to almost 2 years and newborns stay with their group for around 2 years before setting off on their own. They do not have a preferred mating season so mating is constant, but birth rates typically peak at 2 separate times of the year, in the months of May and June, and between November and January.
Finger monkeys are a special kind of omnivore known as a gummivore; an organism that subsists primarily off of tree sap and gum. Almost 80% of their diet consists of tree sap with the other 20% coming from insects and fruit. As such, they have sharp specialized incisors meant for gouging tree bark and stimulating sap flow. They can also use these sharp teeth for self-defense. Although not know to be antagonistic, pygmy marmosets will react aggressively if they feel threatened, using their sharp teeth and claws to attack the perceived threat. Females tend to become more aggressive and less tolerant towards the end of their life.
All members of the family unit help raise newborns and both males and females seem to contribute equally to infant care. For the first two weeks of life, infants are constantly carried. After two weeks, parents will leave their infant in a secluded and relatively protected place while they go forage for food. Primatologists think that this “baby-parking” behavior is meant to decrease the burden of infant care, as constantly carrying their infants requires will expend a large amount of energy. When not being parked on top of a tree, baby finger monkeys are mostly being carried by their oldest siblings. Incidentally, playtime amongst siblings plays a crucial role in finger monkey socialization. Siblings will chase each other around and tackle each other. As with many species of animal, it has been shown that a lack of proper play-socialization while young can have a negative effect on finger monkey psychology, making them more aggressive and seclusionary.
Perhaps the most distinguishing feature of finger monkeys besides their size is their rich and multi-faceted communication system. Finger monkeys communicate using visual signs, chemical signaling, and an intricate vocal call system. There are three categories of vocalizations pygmy marmoset use: “trills”, “j-calls”, and “long calls”. Both trills and j-calls consists of a series of quickly repeated high-pitched notes and are used to signify food, danger, and location. Trills are used at short distances and j-calls over medium ranges. Long calls, on the other hand, are used during travel and facilitate communication between different groups. The long call is also used to search for a mate and sounds like “kwee-kwee-kwee…”
The more socially dominant the vocalizer, the more other finger monkeys respond. Finger monkeys seem to be able to distinguish not only the type of call being vocalized but also the individual doing the calling. Male finger monkeys respond differently to female vocalizations than males and vice versa, and both males and females can distinguish their mate’s unique vocalization from others.
Finger Monkeys As Pets? Don’t Do It!
Pygmy marmoset numbers are high and the species is not considered at risk or endangered. Some specific populations of finger monkeys are at risk though, due to habitat destruction or the exotic animal trade. It is not illegal to own finger monkeys as pets in the U.S. although in South American it is illegal to import or export the animal. These competing laws leave finger monkey ownership in somewhat of a legal gray area. As they are considered exotic, a typical pygmy marmoset costs around 4000$ and requires quite a bit of specialized care.
There is currently a controversial debate about whether or not primates should be kept as pets at all. Primates can carry foreign disease, can be unpredictable and aggressive when mature, and require a large amount of time, effort, and money to take care of. Moreover, separation of a newborn from its mother is psychologically damaging and finger monkeys need socialization with others of their kind to develop properly. Not to mention, the foreign exotic animal trade is irredeemably cruel and abusive towards primates so buying a finger monkey only gives poachers more incentive to kill adults and take their newborns. So if you are looking to buy a pet finger monkey, please forego that option and settle for seeing one in the zoo.