enrichment
Jeffrey A. French, Ph.D. & Jeffrey E. Fite, Ph.D.
Callitrichid Research Center
University of Nebraska at Omaha
for nonhuman primates
Marmosets
& Tamarins
(Callitrichids)
Marmosets & Tamarins
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Marmosets & Tamarins
Introduct�on
Nonhuman primates maintained in captivity have a valuable role in education
and research. They are also occasionally used in entertainment. The scope of
these activities can range from large, accredited zoos to small “roadside” exhib-
its; from national primate research centers to small academic institutions with
only a few monkeys; and from movie sets to street performers. Attached to these
uses of primates comes an ethical responsibility to provide the animals with an
environment that promotes their physical and behavioral health and well-be-
ing. Thus, an obligation is entailed that those individuals/institutions caring for
captive primates should make every effort to ensure adequate veterinary care and
husbandry are provided, that the animals are housed in appropriate facilities,
and that as broad a range of species-typical behaviors are able to be expressed by
the animals as is possible for the captive environment.
This book serves as an introduction to the basic behavior and environmental
enrichment of several species of nonhuman primates that are more commonly
used in education, research and entertainment. In many ways, this book is
meant to be a “how to” manual; it is not intended to be a broad scientific review
of the primate behavior and enrichment literature. The fundamental premise
taken throughout each chapter is that for an enrichment program to be effec-
tive, there must be a basic understanding of the biology and behavior of the
primate species. The species addressed in this series are: baboons, capuchins,
chimpanzees, macaques, marmosets and tamarins, and squirrel monkeys. Each
species-section can be read as a stand-alone document without need to reference
the other sections. This then allows the user to distribute the different sections
to personnel caring for the specific animals.
Each section is divided into five parts: 1) Background, comprised of the habitat
of the primate, the physical features of the primate, its psychological and/or so
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social behavior, and its mating and reproductive behavior; 2) Social World;
3) Physical World; 4) Special Cases, describing any age-related considerations
and concerns associated with individual housing; and 5) Problem Behaviors.
The content of this series has been provided by members of the Association of
Primate Veterinarians (APV) and the American Society of Primatologists (ASP)
who have special expertise in the species addressed. This book is intended to be
a primer because it is, indeed, an introduction to the subject of environmental
enrichment for primates housed in a diversity of conditions. A list of references
and/or other resources (principally on-line) is provided at the end of each chap-
ter that provide additional guidance. The use of scientific references has been
limited, but should the reader desire more information about a specific subject,
the links at the end of the sections will provide direction to obtaining additional
detailed information. Readers are also directed to the National Research Council
publication, the Guide for the Care and Use of Laboratory Animals (1996) and
the U.S. Department of Agriculture’s (USDA) Animal Welfare Regulations to
review the regulatory requirements of the Public Health Service and the USDA
for the provision of environmental enrichment.
The APV and ASP wish to thank the Office of Laboratory Animal Welfare, in
particular Ms. Carol Wigglesworth and Dr. Axel Wolff; the U.S. Department of
Agriculture/Animal Care, in particular Dr. Chester Gipson; and Ms. Dale Feu-
rer, editor, and Ms. Lori Wieder, graphics and layout production, for their as-
sistance with this project. The authors acknowledge the helpful contributions of
Dr. David J. Shepherdson, Conservation Program Scientist, Metro Washington
Park Zoo; Ms. April D. Truitt, Director, Primate Rescue Center, Inc.; and Ms.
Kathleen Conlee, Program Officer, Humane Society of the United States. Spe-
cial thanks also go to the chapter authors Dr. Christian Abee, Dr. Kate Baker,
Dr. Linda Brent, Dr. Thomas Butler, Dr. Jeffrey Fite, Dr. Dorothy Fragazy, Dr.
Jeffrey French and Dr. A. Michele Schuler, and to the reviewers from the Ameri-
can Society of Primatologists and the Association of Primate Veterinarians.
—Kathryn Bayne, M.S., Ph.D., D.V.M., DACLAM, CAAB
Editor, Working Group
This project is dedicated to the memory of Dr. Sylvia Taylor, Veterinary
Medical Officer, Animal Care, U.S. Department of Agriculture, who
was a proponent of providing enrichment to nonhuman primates and
was generous in sharing her knowledge and expertise in this regard.
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Marmosets & Tamarins
Background
Hab�tat
In the wild, marmosets and tamarins inhabit diverse habitats, ranging from
Costa Rica to southern Brazil and Bolivia. They are principally tree-dwelling
animals.
Phys�cal Features
Marmosets and tamarins belong to the New World primate family Callitrichi-
dae, which is characterized by unique morphological and reproductive traits.
Callitrichids, among the smallest (.5 to 1.3 lbs.) of the New World primates,
often are brightly colored monkeys with little, if any, gender differences in body
size or coloration.
Other distinguish-
ing morphological
features of marmo-
sets and tamarins
include claws instead
of nails on all digits
except for the oppos-
able hallux, and two
molars on either side
of each jaw.
Cotton-top tamarin (Saguinus oedipus) with nestbox and perches
(photo by K.Bayne).
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Behav�or
Marmosets and tamarins have rich
communicative behavioral repertoires
that help individuals communicate
within their group and with other
groups. Chemical communication
via scent marking is one important
aspect of callitrichid social and sexual
behavior. Scent marking increases
when marmosets and tamarins are
exposed to unfamiliar animals. Cal-
litrichid primates have specialized
glands (found in the anogenital, su-
prapubic, sternal, and perhaps facial
areas), which produce oily secretions
that are mixed with urine and de-
posited on branches and, to a lesser
degree, other surfaces. These scents contain information on species, subspecies,
and individual identity, as well as reproductive status, social rank, and the age
of the marking. Scents are also thought to facilitate reproductive suppression of
subordinate females in some callitrichid species.
Marmoset (Callithrix geoffroyi ) parents sitting with their infants (photo by H. A. Jensen).
Adult Geoffroy’s marmoset, Callithrix geoffroyi
(photo by H. A. Jensen).
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Mat�ng and Reproduct�on
The social behavior of callitrichids within groups, in many ways, revolves
around two aspects of callitrichid reproduction: reproductive suppression, which
prevents subordinate males and females from engaging in sexual behavior, and
extended residence of offspring in the natal family group. Subordinate females
and adult-aged daughters living in their natal family group do not typically
engage in reproductive activity and, in most cases, nonbreeding females are
endocrinologically suppressed and do not ovulate. Likewise, subordinate males
and adult-aged sons typically do not engage in sexual behavior. Reproductive
suppression is known to be lifted from subordinate individuals when a new
breeding male is introduced and following the death or illness of a breeding
male or female.
Cooperative care is another important component of callitrichid social life.
Marmosets and tamarins typically produce fraternal twins that are cared for by
all group members, including both male and female non-reproductive individu-
als. This is particularly important because, at birth, litters weigh approximately
15 – 25 percent of adult body weight. Numerous studies have demonstrated
that subordinate individuals provide a significant amount of care to infants born
into the group. Indeed, the breeding male has been shown to participate less in
carrying behavior when there are multiple helpers (e.g., adult offspring), with
a concomitant increase in his survivability. The expression of competent care-
giving behavior, however, requires experience with infants (either one’s own or
siblings). It is suggested, then, that individuals remain within their natal groups
during the rearing of the next one or two litters.
Soc�al World
The social lives of marmosets and tamarins are unique among primates. Marmo-
sets and tamarins are the only primates known to exhibit a cooperative breed-
ing system, characterized by extended residence of offspring within the family
group, breeding that is mostly limited to a single breeding pair, and care of
offspring provided by group members other than the parents.
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In captive settings, cal-
litrichid primates are
commonly housed in
groups comprised of a
single breeding adult male
and female, along with
the independent (subadult
and juvenile) and depen-
dent (infant) offspring of
the breeding pair. Cap-
tive groups generally do
not contain unrelated
individuals, because social
groups containing unre-
lated same-sex individuals are likely to be unstable. Studies of captive and wild
populations of callitrichid primates, however, have revealed that there is some
degree of intra-specific variation in social structure that can remain stable over
long periods of time. In fact, a variety of different social structures have been
found to result in stable social groups, including the following:
• fathers with offspring
• mothers with offspring
• same- and opposite-sex siblings (note: opposite-sex sibling groups are not
recommended for cotton-top tamarins)
• same-sex pairs or small groups of unrelated or unfamiliar individuals
• single same-sex or opposite-sex individuals of different species
Intra-group aggression is generally directed toward non-breeding individuals by
their same-sex sibling or same-sex parent. Displacement, threat behavior, chas-
ing, and minor injuries often precede the eviction of an individual from a social
group. The victim is easily identified because he/she will often separate from the
group, show fearful behavior when approached by group members (especially an
aggressor), and generally remain closer to the floor of the cage than other group
members. Temporary separation for a period of hours or days may allow an
individual that was in the process of being evicted to be reintegrated into a social
group. These aggressive events within families are often triggered by periods of
fertility in the dominant female, and special care should be taken to monitor
group relations in the two to three weeks after the birth of infants, when the
dominant females are likely to be ovulating.
Subadult male marmoset (Callithrix kuhlii ) carrying
infant sibling (photo by C. N. Ross).
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Introducing an adult male and female is quite easy. Generally, a brief period of
limited contact through mesh or a “howdy cage,” followed by a brief period of
close observations once full contact is allowed, is all that is needed. Successfully
introducing same-sex unrelated individuals or new adults into breeding groups,
however, often is more difficult. In fact, the likelihood of failure increases with
the age of the same-sex individuals already present in the group. For these intro-
ductions, much longer introduction and observation times are necessary.
Phys�cal World
Hous�ng
An ideal captive environment for callitrichid primates promotes good physical
health, allows for successful reproduction and rearing of offspring, and facilitates
the acquisition of skills that the animals would need to survive in the wild. Al-
though there are no clear specifications for optimal habitat size, habitats should
be large enough, and rich enough, to allow and promote a full range of natural-
istic behaviors, social interactions, and locomotion patterns. The general rule for
callitrichid housing is that no housing is too large. Also, as callitrichids are tree-
dwellers and range up to 10 meters above the ground in their natural habitats,
vertical space is extremely important. If space is limited, narrow, tall housing is
preferred to wide, low housing.
Cages often are constructed of wood or polyvinyl chloride (PVC) frames with
steel or wire mesh. Many zoological parks also are constructing callitrichid hous-
ing from textured rockwork with glass or wire fronting. The primary furnish-
ing for callitrichid housing should be natural tree branches and other surfaces
on which the monkeys can climb, leap, and run. Branches should be arranged
to provide a network of pathways by which the animals can move about their
home. Branches are particularly important because marmosets and tamarins
use these as the normal substrate for scent marking. If natural branches are not
provided, the monkeys will scent mark on smooth, nonabsorbent substrates, and
the marks may soil their fur.
Marmoset and tamarin group members sleep huddled together, so a nest box,
placed high in the cage should be provided. Floors should be covered with wood
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chips or shredded paper; this provides padding for young animals, which are
most likely to fall from a branch onto the floor, and it also encourages animals
to forage through the bedding. Food and water should be made available on a
feeding platform or in a bowl placed high in the cage in a location that prevents
contamination by urine and feces.
Since wild marmosets and tamarins are highly territorial under most conditions,
visual and auditory contact between different social groups should be limited.
When multiple groups are housed in close proximity to one another, and when
overcrowding occurs within social groups, increased aggressive behavior is not
uncommon. Further, chronic arousal associated with prolonged exposure to
unfamiliar animals can lead to abortions and infant loss. Visual barriers, and
sometimes sound absorbing materials, should be used to prevent territorial and
aggressive displays between groups.
In light of the important role scent marking plays in social and sexual behavior,
it is often suggested that husbandry practices maintain a sanitary, but smell-
intact, environment by sanitizing cages less frequently and/or allowing some
scent-marked items (e.g., nest box, perch, branches, etc.) to remain unsanitized
and, thereby, retain their odor. However, some practical experience suggests that
Golden Lion Tamarin (Leontidius sp.) using a rope crossing between trees (photo by K. Bayne).
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Marmosets & Tamarins
sanitizing these items
routinely does not result
in adverse effects on the
health or reproductive
capacity of the animals.
Regardless, most guide-
lines allow for the main-
tenance of scent-marked
branches in cages for
periods of several weeks
to several months.
Environmental enrich-
ment items and devices
also are a necessary part
of callitrichid hous-
ing. Not only do they
promote the develop-
ment of behavioral and
logical skills and mental
and sensory stimulation,
but they can prompt
naturally occurring
behaviors in the animals.
The amount, type, and presentation of enrichment should be varied to prevent
boredom. Foraging devices, artificial gum trees, cardboard boxes and gallon milk
jugs with large holes cut in them, paper towel and toilet paper, are commonly
used for enrichment.
Feed�ng
Meeting the nutritional needs of callitrichid primates is essential to their health
and well-being in captivity. The diets of wild marmosets and tamarins include
tree exudates (sap or gum), fruits, buds and flowers, nectar, insects, and small
vertebrates. Since proportions vary between and within species, only general nu-
tritional issues will be covered here. However, it is important to avoid over-feed-
ing these animals with food treats such that they do not consume a nutritionally
balanced diet. Further detailed information can be found in the Callitrichid
Husbandry Manual.
Example of basic cage with ladder/swing and polyvinyl chloride
(PVC) nestbox. Branches can be added for scent-marking
(photo by K.Bayne).
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Young monkeys begin to beg for and eat solid food between three to five weeks
of age. Approximately 20 percent of the diet of wild marmosets and tamarins is
protein. A canned marmoset diet, which is now commercially available, should
provide the foundation of the diet. New World primate biscuits also should
be offered, along with an assortment of fresh fruits and vegetables. Two fruits
and two vegetables should be offered daily. Cooked and uncooked cereals, and
cooked pasta, are ideal sources of carbohydrates. Treats can include gum arabic,
marshmallows, raisins, crickets, mealworms, and waxworms.
In the wild, callitrichids spend nearly 60 percent of their day foraging for food.
Live food or highly preferred food items hidden in bedding simulates a natural
situation and provides an additional opportunity for enrichment. A foraging box
can be easily made by placing highly preferred food items into small holes that
have been cut into a cardboard box filled with bedding. Callitrichids also enjoy
food items suspended from branches, and treat cups with lids and peek holes.
Spec�al Cases
Age-related Cons�derat�ons
Healthy marmosets and tamarins maintain good abilities to forage and move
about well into their old age. The only major issue with older animals is difficul-
Golden Lion Tamarin (Leontidius sp.) perching on a branch (photo by K. Bayne).
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Marmosets & Tamarins
ty in chewing solid food because of tooth wear and loss. In these cases, soaking
food in liquids prior to feeding or provisioning animals with softer diets are two
easy solutions.
In terms of normal social development, most institutions that rear marmosets
and tamarins have a policy of keeping young individuals in their family groups
until they have had exposure to and experience with one or more sets of younger
siblings. It is assumed that this experience will increase the likelihood of success
in rearing young when the animals are placed in a position where breeding is
possible. As mentioned above, however, older siblings are sometimes involved
in mild to serious fights with same-sex siblings, and may need to be removed
from the group. Decisions about removing an individual from a group should
be made in light of the need for normal experience with siblings and the serious-
ness of the aggression.
Rejection of infants by parents and the inability of infants to maintain contact
with caregivers are fairly regular occurrences in captive marmosets and tamarins.
In some cases, lack of infant success is associated with infant health and vigor
(e.g., low birth-weight infants are unable to maintain a grip on their parent’s
fur). In other cases, parents (particularly mothers) may actively reject and fail
to carry and nurse their infants. A number of zoos and research facilities have
reported some success in hand-rearing infants. Specific details of hand-rearing
protocols can be found in the Callitrichid Husbandry Manual.
It is important to note that hand-rearing is associated with a variety of behavior-
al problems, particularly as the hand-reared individuals reach reproductive age.
Therefore, decisions about hand-rearing rejected infants should involve a careful
consideration of the animal’s purpose in the facility as an adult. A