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Behavior of the Common Marmoset

Before considering common marmoset behavior in detail, we need to understand about primate social groups and the influence of living in social groups on behavior.

Primate Social Groups

Most primates are social animals. Indeed, some are highly gregarious. They eat, sleep, and travel together in the same group all the time.

Group living provides clear benefits. Some important examples are:

  • better access to food
  • better access to mates
  • protection from predators
  • help in rearing offspring

Group living also comes with a cost which can be extreme for some low ranking or subordinate members. Examples include:

  • increased competition for food and mates within the group
  • aggression from higher ranking members of the same group

Primates can be found in several types of groups. Some provide more opportunities for social interaction than others:

  • multimale & multifemale group: Several adult members of both sexes and may grow to be quite large with some groups having 150 or more individuals.
  • polyandrous group: One mating adult female and more than one mating adult male.
  • harem group: One adult male and several adult females and offspring
  • monogamous pair: A single adult male and adult female and their offspring.
  • solitary: An adult female and her young. Adult males and females only interact to mate.

Marmoset Social Groups

Marmosets are highly social primates and may be found in monogamous, polyandrous or small multimale and multifemale social groups. In most groups, however, only one breeding couple (the dominant or highest-ranking adult male and female) is usually observed. The older offspring and other group members assist in rearing the newborn offspring of the dominant breeding female. Breeding female marmosets commonly give birth to twins, and one major benefit to them from group living comes from assistance in infant care. When, on rare occasions, infants are born to subordinate females, they often do not survive infancy.

The high level of sociality seen among marmosets and their family group structure (usually two parents and their offspring) make them a fascinating primate to study and from which to learn about primate behavior.


Observing Marmoset Behavior

Observing primate behavior can be both challenging and rewarding. For group living primates, like the common marmoset, social interactions among group members provide an ideal setting for learning primate behavior.

The common marmoset has been studied in captivity for more than 30 years and in the wild for more than 20. While this means we know a great deal about marmoset behavior, we still have a lot to learn. Common marmoset behavior shares much in common with that of other primates, but like all species, marmosets also have their own species-typical behavioral characteristics.

Listed below are some important common marmoset behaviors. These behaviors will be useful not only for observing marmoset behavior such as from using the Callicam to observe a family of common marmosets at the Wisconsin Primate Research Center, but will also help in understanding behavior of other primates.

Marmoset behaviors include:

COMMUNICATION

Primates communicate by sight, sound and smell.

Sight:

Communication by sight, or visual communication, is very important among primates, including marmosets. Examples of visual communication include facial expressions, body posture, raising body hair, and moving ear tufts. Body posture, moving ear tufts, and facial expressions become especially important during mating, aggressive and play encounters.

Examples of some important visual cues for the common marmoset are:

  • Piloerection: During piloerection, a marmoset will cause its body hair to stand on end or its body hair will erect over a specific area (such as the tail). This type of behavior is found in many primates, as well as many other animals. Piloerection allows the marmoset to give the impression of larger body size. A marmoset may piloerect during aggressive and sexual interactions or when encountering a strange object.
  • Facial Expressions: Marmosets have many different facial expressions, and they are all an important means for communicating information. Some examples include:
    • The "relaxed" face. (seen when calm or resting)
    • "Head-cock stare" (seen when observing an object, prey or another monkey)
    • "Play" face (seen during play encounters)
    • Facial submit (submissive behavior seen during aggressive encounters)
  • Body Posture: Sometimes the position in which a monkey is standing, sitting, or even holding its tail, delivers information to another individual.  Some examples of body postures seen in the common marmoset include:
    • "Leg stand" - When in this position the marmoset is standing on its hind legs. The hands may or may not be outstretched. This is used in response to a foreign object or unknown sound.  This provides the animal with better visual perspective.
    • "Cringe" - Marmosets often cringe as a submissive gesture.
  • Tail positions: In some primates, these are an important means of communication. For example, certain primates use an erect tail as an aggressive display. In the common marmoset, however, the tail is primarily used for balance during locomotion.

Sound:

Communication by sound, or auditory communication, occurs through vocalizations. Each primate species has a unique set of vocalizations. These can be used to communicate important information about (1) group location, (2) warning about a predator, (3) contestants involved in aggressive encounters, and (4) parents and offspring interactions.

The common marmoset has its own set of vocalizations. Learning to recognize the individual sounds takes patience and a careful ear. Individual sounds have been identified for the common marmoset and are named according to how they sound:

  • Nga; erh-erh; trill; twitter; trill phee; phee
    • Nga: An infant cry to obtain attention. Also a submissive call in adults.
    • Erh-erh: Aggressive vocalization.
    • Trill, twitter, trill phee, phee: All thought to be involved with establishing and maintaining contact between animals within, and sometimes between, social groups.
  • To hear these vocalizations, visit the web page of the Lab of Auditory Neurophysiology at Johns Hopkins at: http://www.bme.jhu.edu/~pistorio/vocal.html

Smell:

Smell is an important means of communication for all primates, including humans. Marmosets have a better developed sense of smell than humans.

Communication by smell is called olfactory communication. The most common type of olfactory communication is scent marking. Marmosets and many other primates' scent mark by rubbing their scent glands (located in the chest and anogenital regions) over an area they want to mark. Other marmosets will then sniff or lick these markings to obtain the "message".

Scent marks identify an individual, its sex, species and many other attributes, including fertility status, or even if it recently had a fight. Scent marks by marmosets in the same social group may help to identify their group's territory.

PLAY

Play is a common and important behavior that occurs not only in primates, but in many other animal species as well. While play behavior is seen more frequently among the younger animals, adults may also play.

It is usually very easy to recognize when primates are playing. Play, however, involves many different behaviors and can occur among many different combinations of group members.

For younger primates, play may help in the development of social and motor skills and it often involves patterns of behaviors which will become important in adulthood.

Marmosets exhibit three types of play:

  • Play with an object
  • Solitary play
  • Social play

When engaged in play a marmoset often displays a "play face" with its mouth open and relaxed -- the teeth are obvious, but the lips are not retracted. The "play face" is observed in many primate species.

While playing together, marmosets may chase one another, pounce on one another or wrestle with one another. Sometimes they may even bite one another. The biting, however, is inhibited, non-wounding and non-aggressive.

It is important to distinguish play behavior from aggression and submission. When marmosets are acting aggressively or submissively, they do not exhibit a "play face". Instead they often have their teeth bared (the lips are retracted) and will cackle, scream or squeal. Additionally, the biting and wrestling in fights causes wounding.  Such disputes occur in both free-living and captive groups and are a normal part of primate social life.

AGGRESSION AND SUBMISSION

Aggression and submission in marmosets occurs under many different circumstances and includes a variety of aggressive and submissive behaviors.

Aggression and submission commonly involves competition over resources (mates, food, territory) and the establishment or maintenance of social rank. While low-level, vocal aggression can be common in some primate species, all-out fighting is rare. Fighting often leads to serious injury to one or all contestants and is therefore very costly. For this reason, primates are more likely to rely on threats and displays more often than actual physical combat.

The common marmoset, like many other primate species, is not particularly aggressive and fighting is rare. When aggression does occur, it is usually associated with both aggressive and submissive behaviors and vocalizations.

Aggressive behaviors include:

  • Piloerection
  • Frown stare
  • Biting
  • Ear-tuft flick

Submissive behaviors include:

  • Facial submit
  • Animals avoiding each other
  • Ear-tufts flattened

Two common vocalizations associated with aggressive encounters are nga (which is submissive) and erh-erh (which is aggressive).

GROOMING

Grooming is a very important behavior among all primates. Marmosets, like other primates, groom each other ( allogrooming) and themselves ( self grooming). Grooming serves two functions:

  • Hygienic grooming allows primates to remove dead skin, debris, and parasites living on the skin.
  • Social grooming is an important form of social contact. It helps to strengthen and form social bonds among group members and may even be used to ease tense interactions.

Common marmosets groom frequently. However, each episode usually lasts for a few minutes.

In addition to grooming, other types of social contact are important for common marmosets. They may often be seen nuzzling, hugging, licking or huddling with one another.

INFANT CARE

Young primates are very dependent. Marmosets are no exception. Infants must be nursed, carried and watched until they are old enough to take care of themselves. For some primates, this may be an extensive period. In the common marmoset this period lasts approximately four to eight weeks.

In most primate species, the mother is the sole provider of care for the young. The common marmoset differs from most primates except mammals, lesser apes and its close relatives (tamarins) because the father and other group members, including older offspring, regularly carry young infants. The mother will also hold and carry the young, but she devotes much of her time and energy to nursing rather than just carrying.

Caring for infants is a particularly large investment in time and energy for the marmoset. The "family structure" of the marmoset social group is important for successful infant rearing as large groups rear more infants than smaller ones. While infant marmosets develop in a relatively short time, and thus the length of time involved in infant care by marmosets may seem less than observed in other primates, the intensity of marmoset infant care is more than is observed in most other primate species (expect in tamarins).

When infants are present, specific activities involving their care may be observed. Of these, carrying, transferring, accepting, rejecting and rubbing-off are most easily seen.

  • Carrying: All group members participate in this activity and may carry one or both infants. Because the infants have yet to grow the characteristic white ear tufts and because their fur blends with that of the adults, they are not easily distinguished while being carried. As the infants get older and more active it becomes easier to see them.
  • Transferring & Accepting: After being carried for a period of time, the infants are transferred from one group member to another. When infant transfer occurs, the infants will crawl from one individual to another. The marmoset accepting the infants will position itself so that the transfer is easier for the infants. If an infant is not being carried it will cry ( nga) to signal that it wants to be carried. When this happens, the accepting adult will again position itself so that the infant can crawl on. So, while infant marmosets are aided onto a carrier, they are not picked up and held during transfer and acceptance.
  • Rejecting & Rubbing-off: As infants get older and larger, they are encouraged to become more independent and are carried less frequently. An infant is rejected when an adult refuses to carry the infant as it attempts to climb on. Rejecting may involve non-wounding biting and cuffing by the adult to further discourage the infant. If the infant is already being carried by the adult, it may try to remove the infant by rubbing the infant off as a sign of rejection. The infants may cry frequently and persist in their efforts to be carried. When infants become large enough to be more independent, rejection by older carriers becomes commonplace and is a natural and important part of the infant's development.

FEEDING & DRINKING

For all primates in the wild, searching for and consuming food takes up a large portion of the day. The common marmoset is no exception. In their natural habitat, a marmoset may devote up to 50% of the day searching for and feeding on foods such as insects, fruits and tree gums and saps. Like other forest-dwelling primates, marmosets do not come down to the ground to drink. Instead they rely on water collected in the trees.

For captive marmosets, food is provided at specific times, usually once or twice a day. These times may be marked with heightened activity among group members. At the Wisconsin Primate Research Center, marmosets are fed once a day between about noon and two in the afternoon. They are very active at this time, but by four o'clock they begin to settle down for the night.

In captivity, marmosets usually do not have a natural source of tree gums and saps. However, they may still exhibit tree gnawing behavior if an appropriate substrate is available.

For many captive primates feeding time may also be a period of heightened aggression with individuals attempting to secure the most food and/or the most desirable selection. Marmosets are rarely aggressive. However, with preferred foods, such as grapes, marshmallows, or bananas, marmosets may display some aggression.

LOCOMOTION

Strictly speaking, locomotion involves the movement of an animal from one location to another. Locomotory behavior is important for animals because it determines how they travel from one location to another and it may also provide information to an observer as to why the animals are moving.

Animals are restricted in locomotion by their body size, the habitat in which they live, and possibly by the strength of their tail. For example, a smaller primate (like the common marmoset) is able to run along the tops of branches using its tail for balance whereas a larger primate (like the spider monkey) must suspend itself below the branch with its arms and/or tail. Unlike the spider monkey, the marmoset's tail is not prehensile; it cannot be used as an additional limb, such as in hanging from a branch. Very large primates (like gorillas) often spend most of their time on the ground.

Primates living in areas with very low tree cover, such as the African savannah, are primarily terrestrial, or ground dwelling. Those living in the forests, such as marmosets, are primarily arboreal, or tree dwelling. The different types of locomotion between primates reflects their terrain differences.

In the common marmoset, locomotory behavior is relatively easy to observe and may involve behavior necessary to move between trees:

  • leaping/jumping from one structure to another
  • walking/running along a branch or other support
  • climbing

It may also be important to understand why or to where an animal is moving. For example, is the animal being pursued?

When a marmoset is approaching or retreating from another monkey or object, their pace is often faster and may appear as a "bouncing gait". Marmosets move about by walking, running, climbing, leaping or jumping when they are not approaching or retreating from another object or monkey.

RESTING

Just as humans rest, so too must other primates. Marmosets spend a large part of their day involved in this activity. A marmoset is said to be resting when it is not moving and is not engaged in any activity.

When resting, the marmoset may be awake and alert. During these times the monkey may be sitting or lying on its stomach with its tail in a relaxed and uncoiled position.

Marmosets will rest both in and out of physical contact with other group members.


Text and design by Kara Lascola.

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