SOCIAL ORGANIZATION AND BEHAVIOR
Photo: Anne Savage
Though cotton-top tamarins have been extensively studied in captivity,
their social organization in the wild is not fully understood.
Cotton-top tamarins are found in groups of two to seven individuals, but
also live in groups as large as 13 animals (Neyman 1977; Savage et al.
1996a). These groups are composed of one or two breeding males and
females and other individuals of varying sex and age. Tamarin groups
are multi-generational, including
a dominant breeding pair and their offspring of various ages as well as
unrelated immigrant adults, but results from genetic tests have not been
published confirming the relationships of individuals within groups.
One of the core social behaviors of callitrichines, including cotton-top
tamarins, is cooperative rearing of young
(Snowdon & Soini 1988; Savage
1990; Savage et al. 1996a). Sexually mature adolescents and adults
remain in their natal groups in
order to help raise their siblings and this pattern of behavior shapes
the social structure of wild groups. Young cotton-tops do not remain in
their natal groups indefinitely and group size may fluctuate over time
as adults and subadults migrate into and out of the group for new mating
opportunities (Neyman 1977; Savage et al. 1996a; Sussman 2000). There
is no sex or age bias in migration; males and females emigrate from
their natal groups equally as frequently and the age at migration varies
(Savage 1990). Once cotton-top tamarins emigrate into neighboring
groups, they generally assume a non-reproductive role but are active
care-takers of the infants and become fully integrated into the social
hierarchy of the group (Savage 1990).
Social relationships within cotton-top tamarin groups are generally
friendly with few signs of aggression within the social group (Snowdon &
Soini 1988; Garber 1997). There is a dominance hierarchy in which the
primary breeding male and female are codominant over younger or
non-breeding animals within the group and breeding females can be quite
aggressive toward younger females (Savage et al. 1988; Snowdon & Soini
1988). The breeding female within the group is, in certain feeding
contexts, dominant over all other group members and maintains access to
food items (Garber 1997). Cotton-top tamarins are territorial, though
males and females react to intruders differently. Males are more
tolerant of female intruders and are more aggressive toward male
intruders, while females are somewhat intolerant of intruders of both
sexes and display threateningly. When neighboring groups of cotton-top
tamarins encounter each other, there is no physical contact between
members of the different groups though there may be threat displays
(Savage 1990). All members of the group react cohesively and mob
potential predators as well as defend injured group members (Snowdon &
Soini 1988). One of the behaviors that reinforces this group
cohesiveness is grooming. Cotton-top tamarins spend a considerable
amount of time grooming throughout the day during periods of rest.
Grooming is a social tool to create and maintain bonds between primates.
In cotton-top tamarins, the majority of grooming occurs between
breeding adults in a group and both sexes groom and are groomed equally
(Snowdon & Soini 1988).
REPRODUCTION
Photo: James & Suzanne Hampton
Traditionally housed in monogamous
family units in captivity, monogamy was long thought to be the breeding
pattern in wild populations. In reality, cotton-top tamarins have been
observed in seemingly monogamous groups with only one breeding male and
one breeding female but also in polygamous groups with multiple
breeding males and females (Snowdon & Soini 1988; Savage et al. 1996a).
While two pregnant females have been reported in one wild group, there
are no reports of two females producing and rearing offspring in the
same social group (Savage et al. 1996a, 1997b). The mechanism for this pattern
has been studied extensively in monogamous captive groups (Neyman 1977;
Savage et al. 1988, 1996a). In both captive and wild groups of
cotton-top tamarins, only one adult female within the social group is
reproductively active. The dominant breeding female within the group
suppresses reproduction in the other sexually mature females, which are
often her daughters, but can also be unrelated female immigrants (Savage
et al. 1988; Snowdon & Soini 1988). Suppression of reproduction, both
in wild and captive groups, is linked to the behavioral and chemical
restriction of sexual behavior within the group, delay of onset of
puberty, and general stress effects. It is possible that pheremonal cues from the dominant
female are the mechanism by which reproduction is surpassed in younger,
subordinate females within the group (Savage et al. 1988; Heistermann et
al. 1989). However, the immigration of new, unrelated males into
established groups appears to have an effect in releasing subordinate
females from this reproductive suppression. In groups with new males, there is
greater likelihood that two females will become pregnant but only one
female will give birth to live offspring (Savage et al. 1997b).
Sexual maturation is a prolonged process rather than a single event in
the life of a primate (Tardif 1984). Puberty occurs between 15 and 18
months of age in cotton-top tamarin females, and though they may reach
sexual maturity by this age, they do not exhibit normal ovarian cycles unless the proper
social environment is present (Tardif 1984; Ziegler et al. 1987). As
has been shown in laboratory studies, young females do not cycle while
in their natal groups because of suppression by the dominant female, but
as soon as they are removed and placed with an unrelated male, young
cotton-top tamarins exhibit normal fertility and begin to cycle
regularly (Ziegler et al. 1987). If the dominant breeding female is
removed from the social group, the oldest and highest-ranking daughter
within the group becomes fertile and successfully suppresses fertility
in younger, subordinate females (Heistermann et al. 1989). Hormonal
analyses reveal that ovarian cycles in cotton-top tamarins last about
15.5 days and there are no apparent physical signs of estrus (Tardif 1984; Snowdon & Soini
1988). Mating occurs throughout the ovarian cycle with peaks during
presumed estrus. Gestation lasts six months
(183 days) and within five months after parturition,
cotton-top tamarins resume cycling. The interbirth interval is about 48 weeks
in the wild but in captivity, cotton-tops give birth every 28 weeks
(Savage 1990; Savage et al. 1997). In captivity, they experience
immediate postpartum estrous,
unlike wild cotton-tops that do not exhibit ovulation for
five to six months after parturition (Achenbach & Snowdon 2002; Savage et
al. 1997b). Like all callitrichines, cotton-top tamarins exhibit highly seasonal
birth patterns with the peak season lasting from two to three months during
the early half of the rainy season, between April and June (Snowdon &
Soini 1988; Savage et al. 1997b). The timing of the birth season is
linked to the period of highest fruit abundance. Given that cotton-top
tamarins give birth to twins more frequently than singletons,
the energetic requirements of nursing and caring for infants is extremely
energetically taxing on the mother and one adaptation to this physical
stress is to time births with periods of highest availability of food
resources (McGrew & Webster 1995).
PARENTAL CARE
Photo: Anne Savage
Cooperative infant-care in tamarin social groups is essential to the
survival of infants (Savage et al. 1996b; Garber 1997). A single pair
of tamarins would not likely be able to successfully rear twins in the
wild and are therefore dependent on the help of other group members
(Savage et al. 1996b). Furthermore, parental behavior is not
instinctual but learned, and both males and females that are
inexperienced are unsuccessful caregivers. If a cotton-top tamarin of
either sex has no experience carrying infants, its own offspring are
likely to be rejected or abused (Bardi et al. 2001; Savage et al.
1996b). Finally, one of the most important functions of group care and
cooperative parenting is to increase predator detection through
vigilance (Savage et al. 1996b).
Born weighing 15 to 20% of their mother's body weight, to carry
even one of the twins is an energetically demanding feat (Savage et al.
1996b). They mature rapidly in their first few months and are usually
carried dorsally as a pair
throughout the first month of life (Garber 1997). In the wild, males
and females of all ages carry and exchange food with the infants, even
if they are not related to the twins. The mother is the primary carrier
for the first week of life, when the twins are nursing constantly. As
the mother decreases the amount of time spent carrying the infants over
the first eight weeks of life, other group members, especially males,
increase the amount of time spent carrying the twins (Savage et al.
1996b). Infant cotton-top tamarins are carried exclusively for the
first month after which they gradually decrease the amount of time they
are carried by group members. By week 10 the infants move independently
about 50% of the time (Savage et al. 1996b). After 14 weeks of age
they are rarely seen being carried.
Infant survival in the first year of life is higher in the wild than in
captivity (Price 1990). Eighty-six percent of infants born in
appropriate environmental conditions will survive in wild populations
(Savage et al. 1996b). This higher survival rate may be attributed to
more experienced helpers because of dispersal between groups. In
captivity, there is limited opportunity for young tamarins to gain
parenting experience through carrying, while in the wild, natural
patterns of migration allow young cotton-top tamarins to gain this
valuable parenting experience (Savage et al. 1996b). Larger groups are
also a contributing factor for higher survivability of infants and in
the wild, infant survivability approaches 100% in a group of five
(Savage et al. 1996b). In the wild, larger groups can forage more
efficiently, have higher likelihood of detecting predators, and are more
able to spread out the energetic costs of carrying infants than smaller
groups (Savage et al. 1996b). Energetic costs of carrying infants has
been studied by comparing pre- and post-birth weights of males in
captive groups, showing that males lose significant amounts of weight
during the period of most infant carrying (Achenbach & Snowdon 2002).
All caregivers spend less time feeding, foraging, moving, or engaging in
social activities while carrying infants and spend more time in
concealed areas (Price 1992). Caregivers obviously sacrifice
energetically when they carry and protect new infants, but they
certainly reap benefits from this relationship. They may ensure the
survival of the infants and increase their direct or indirect fitness, acquire a position
in a new group, learn how to be a successful parent, secure affiliative
bonds with the younger animals that may help when they begin to breed,
and gain access to future mating opportunities (Price 1992; Garber 1997;
Achenbach & Snowdon 2002).
COMMUNICATION
Small-bodied and living in dense vegetation, cotton-top tamarins do not
rely heavily on visual signals for communication, but are more attuned
to chemical and auditory signals (Snowdon & Soini 1988). There are some
visual signals that are important for close-up interactions between
animals. Tongue flicking is a unique tamarin behavior used in many
different contexts including aggression and mating. Piloerection is another important
visual signal that is used in displays of aggression; the white fur on
the head can be raised and lowered creating a striking fan display
(Snowdon & Soini 1988). Other visual behavior patterns seen in
cotton-top tamarins include grimacing/teeth baring displayed by a
high-ranking female to a subordinate, head flicking during aggressive
displays, frowning to demonstrate hostility, and head lowering as a sign
of appeasement by subordinate animals (Snowdon & Soini 1988). Often,
vocal communication accompanies these postures to convey a message to
other animals. Vocal communication between tamarins serves primarily as
group defense, group cohesion, alarm calling, and close contact
communication. All callitrichines use "chirp" or "chuck calls" and
"slicing screams" during mobbing attacks of predators or intruders or
during feeding (Snowdon & Soini 1988). Cotton-top tamarins use "long
calls" in response to calls from distant animals and "quiet long calls"
and "trills" in close communication (Snowdon & Soini 1988).
LISTEN TO VOCALIZATIONS
While visual and vocal communication is seemingly simplistic in
cotton-top tamarins, chemical communication is complex and factors into
many facets of social structure and relationships between animals. Some
important information conveyed by chemical cues in cotton-top tamarins
includes species identification, individual identity, and timing of
ovulation (Washabaugh & Snowdon 1998). Males and females possess scent
glands around their anus and genitals, but females have more highly
developed glands which they use more often than males (Snowdon & Soini
1988). Females use their well-developed scent glands to mark surfaces
10 times more frequently than do males (Washabaugh & Snowdon 1998).
One reason females have such well-developed scent glands and scent-mark
so often compared to males is they mark surfaces to signal sexual
receptivity. Chemical cues signal to other group members, especially
males, that a female is ovulating. These chemical cues left by
ovulating females may also be a factor in reproductive suppression of
subordinate females (Ziegler et al. 1993; Washabaugh & Snowdon 1998).
Content last modified: May 18, 2005
Written by Kristina Cawthon Lang. Reviewed by Anne Savage.
Cite this page as:
Cawthon Lang KA. 2005 May 18. Primate Factsheets: Cotton-top tamarin (Saguinus oedipus) Behavior . <http://pin.primate.wisc.edu/factsheets/entry/cotton-top_tamarin/behav>. Accessed 2010 February 9.
