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Tufted capuchin
Cebus apella

SOCIAL ORGANIZATION AND BEHAVIOR

Tufted capuchin social organization is characterized by discrete hierarchies of rank between both sexes and different age classes (Izawa 1980). Both male and female rank hierarchies are correlated with age, with the older individuals typically being higher ranked than younger individuals (Izawa 1980). Tufted capuchin groups are often small, numbering in the teens or lower twenties with only one to several adult males and around the same number of adult females (Izawa 1980; Defler 1982). It is suggested that when troop size approaches around twenty individuals, the chances of group fission increase and such fission limits group size (Izawa 1994). There is some evidence that tufted capuchin society might be matrilineal, as matrilines remain together when group fission occurs (Izawa 1994). Tufted capuchin group home ranges can overlap, often with the ranges of more than two groups overlapping the same area (Spironello 2001). This common territory is the result of the lack of territorial defense by a single tufted capuchin group (Defler 1982). When different groups encounter one another, interactions range from peaceful curiosity and tolerance of the other group to active chasing away by adult males (Defler 1982; Spironello 2001).

Photo: Kevin Schafer

The alpha male dictates group movement and activity patterns, is the focal point of group attention and functions in group cohesion (Izawa 1980). With the exception of young males, who often transfer between groups several times before settling into a new troop, group membership is stable over a number of years (Janson 1990a). The tufted capuchin dominance hierarchy serves to regulate social spacing during group foraging and thus is reflected in access to high-quality foods. Higher-ranking individuals are better placed during social foraging to attain the best and largest amounts of resources while lower-ranking individuals are marginalized (Janson 1990b). Females usually stay within their natal group excepting the occasional adult female who may migrate between troops (Janson 1990a). The earliest age at which a male emigrates from his natal group is at 6 years of age (Janson unpub. data cited in Robinson & Janson 1986).

Adult tufted capuchin males are more likely to exhibit anti-predator vigilance to protect other age and sex classes from threats and are also far better than the other classes at detecting potential threats (van Schaik & van Noordwijk 1989). Lower-ranking males tend to avoid higher-ranking males in day-to-day activities but there are strong bonds between different males nevertheless (Izawa 1980; Janson 1984). Agonistic behavior between females is seen far more than in males, probably because females do not actively avoid higher-ranking females (Izawa 1980).

Changes in the alpha male dominance hierarchy of tufted capuchin males are rarely reported (Moura 1999). In several instances in the wild however, changes in the alpha male occurred as a result of instability developing in social relationships between individuals. That is, either an infant grew large enough to threaten a previously larger individual or injuries were sustained by an individual and this caused instability in the social structure (Izawa 1990, 1997; Moura 1999). Such instability causes fighting in which serious injuries can be sustained and in which the dominance hierarchy can change (Izawa 1997; Moura 1999).

Allogrooming among tufted capuchins in captivity shows several trends that lend insight into social relationships within a troop. Further research is needed into the meanings of these trends however, before conclusions can be drawn as to their meanings. First, individuals tend to groom down the hierarchy, that is, higher-ranking individuals tend to groom those of lower rank more than those of equal or higher rank. Second, the higher the rank of an individual, the more grooming that individual was likely to perform. Finally, the dominant individual was the only rank which performed grooming on others more than receiving grooming (Parr et al. 1997).

REPRODUCTION

The tufted capuchin mating system is difficult to classify as it is multi-male/multi-female the majority of the time but can also be single-male. That is, often most males can potentially mate with most females, but under certain conditions only the alpha male will mate (Carosi et al. 2005). Perhaps the most characteristic aspect of the tufted capuchin mating system is the active female solicitation of the alpha male and female choice of mate (Phillips et al. 1994). Males solicit mating far less often then do the female tufted capuchins and seem to respond to female solicitation rather than to initiate it (Phillips et al. 1994). Female behavior is the only indication of estrus, as there are no external clues or genital swelling which might indicate an estrous state (Carosi et al. 2005). Estrus lasts from one to eight days but typically lasts around five days (Janson 1984; Phillips et al. 1994). In addition, estrus does not show any strict seasonality although it is more common in some times of the year than others and conceptions are somewhat synchronous among females (Janson 1984). Birth season varies by locale and reflects the differential rainfall, food availability and photoperiod of the habitat (Carosi et al. 2005).

Female tufted capuchin behavior changes noticeably during estrus and they become skittish, with consistent grimacing and characteristic estrus vocalizations resembling a whistle or a whine (Janson 1984). In addition, during the first several days of estrus, the alpha female will approach and follow the alpha male and constantly and actively solicit him. These solicitations are similar to overall estrus behavior and take the form of vocalizations, distinctive submissive postures, grimaces, and rapid touching and fleeing (Janson 1984). The alpha male's response is initially indifferent and deterrent but after several days he becomes receptive and copulations, up to one per day, will occur (Janson 1984; Carosi et al. 2005). Sexual solicitation by females of alpha males is extremely adaptable, changing focus almost immediately when a formerly subordinate male attains alpha status (Carosi et al. 2005). In other words, when a male attains alpha status, females will immediately start soliciting him when they previously ignored him due to his subordinate status. Toward the end of estrus, females will stop soliciting and mating with the alpha male and will mate with several other lesser-ranked group males in a short period of time (Janson 1984). Copulations involving an alpha male will typically last much longer than those involving subordinate males (Janson 1984). There is little male-male or female-female aggression during tufted capuchin mating behavior, probably resulting from the active solicitation of males by females and because of alternation between those females soliciting the same male (Janson 1984; Phillips et al. 1994).

Female solicitation postures can take several forms including the female facing the male, grimacing at him, and spreading her thighs or the second posture which has her facing away from the male and looking back over her shoulder at him. Following this posturing, copulation will occur and can last up to four minutes (Janson 1984). Post copulation, a sperm-plug is formed as a means for a tufted capuchin male to increase his chances of producing offspring (Carosi et al. 2005).

Photo: Luis Claudio Marigo

The menstrual cycle in the captive tufted capuchin female averages 20.8 days (Nagle & Denari 1983). Average gestation in captivity is 153 days (5 mos) but can range from 149-158 days (4.9-5.2 mos) (Wright & Bush 1977). In the wild, females attain reproductive maturity at around four years of age but in captivity this number is around five years (Fragaszy & Adams-Curtis 1998; Carosi et al. 2005). Male reproductive maturity has not been ascertained in the wild but in captivity, males are fertile by about four and a half years of age (Fragaszy & Adams-Curtis 1998; Carosi et al. 2005).

PARENTAL CARE

The average weight of a captive tufted capuchin at birth is 210 g (7.4 oz) (Fragaszy & Adams-Curtis 1998). At birth and for the subsequent three weeks in the wild, the infant will cling dorsally to its mother and not move independently (Calle 1990). In addition, for the first two weeks of life in the wild, the majority of the mother's resting time is spent suckling and grooming the infant (Calle 1990). Transportation in the first month is provided by the mother, who also provides food for the infant for the first two months (Valenzuela 1994). After the fourth week of life, 20-70% of the infant's time is spent with alloparents of all demographics which is an indicator of strong group cohesion (Valenzuela 1994). Carrying by other group members occurs predominantly while the mother feeds and while the group is moving (Escobar-Páramo 1989). By the third month, infants move independently except in situations in which the group must move very quickly (Valenzuela 1994). As wild infant capuchins gain independence and are capable of solitary movement, they typically gravitate toward and stay near the alpha male (Escobar-Páramo 1989). Their affiliative bond of the infant with the alpha male is stronger and more evident than with subordinate group males (Calle 1990).

At around nine months, infant facial coloration lightens above the eyebrows. In addition, contrasts in pelage color become more profound between the shoulders and the rest of the body (Escobar-Páramo 1989). Because females produce offspring only about once every two years, it is assumed that complete weaning takes place into the second year as having a dependent infant precludes reproduction at the one year mark (Robinson & Janson 1989). Wild weaning has been estimated at around 16.5 months and captive weaning at 13.7 months (Fragaszy & Adams-Curtis 1997).

While development in captivity is better recorded than in the wild, it is suggested that infant development in wild populations of tufted capuchins is faster than of those in captivity because of the difficulties of a wild existence versus a captive one (Valenzuela 1994). Up until the fifth week of life, sleep predominates in the daily activity of the captive infant tufted capuchin (Byrne & Suomi 1995). In captivity, infants begin to explore their surroundings between three and eight weeks of age (Byrne & Suomi 1995). In addition, an infant will constantly remain in contact with its mother until the second or third month of life (Byrne & Suomi 1998). From two to six months of age, the proportion of time spent alone grows as time spent with the mother decreases and by six to seven months more time is spent alone than with the mother (Byrne & Suomi 1995). Captive allomothering commences in the eighth week of life (Fragaszy et al. 1991). After the third month of life, adult males in captivity are also approached preferentially by infant capuchins with the male being approached more often than all the females combined save for the mother (Fragaszy et al. 1991). Social play is first seen after 14 weeks of life between the infant capuchin and other infants, juveniles and adults, particularly the adult males (Fragaszy et al. 1991). By one year of age, fine motor control is almost completely developed at the adult level and by 15 months of age, truly independent foraging is seen (Fragaszy & Adams-Curtis 1997).

COMMUNICATION

Vocal communication in the captive tufted capuchin consists of several calls which serve specific purposes. Contact calls are either the "mik" or "ik" vocalizations and to reestablish contact with the group when separated, a "fueh" call is given (Dobroruka 1972). Warning and alarm vocalizations include "e-c-k-g," "i-tsch-g-k," and "ik-a" sounds. Upon utterance of alarm vocalizations, the entire troop will flee (Dobroruka 1972). The four to five second "p-ru-pju-uiu-uiu-uiu-u" call is possibly given to signal intent to establish a new group as only females responded to this call uttered by a male who was separated from the group (Dobroruka 1972).

LISTEN TO VOCALIZATIONS

Cebus apella: contact noises (ECOSARA Biodiversity Database)

Photo: Irwin Bernstein

Urine washing and chest rubbing are several types of olfactory communication exhibited by the tufted capuchin. Both of these behaviors could be scent-marking behaviors (Carosi et al. 2005). Urine-washing consists of an individual urinating upon its extremities and rubbing them against one another (Carosi et al. 2005). There is no evidence of urine-washing serving any purpose in reproductive communication (Carosi et al. 2005). However, tufted capuchins can discriminate between groups and recognize their species versus another based on the differential odor created by urine-washing (Ueno 1991; 1994). This, coupled with evidence of differential responses to scent by sex, indicates that there is some sort of socially communicative role played by urine-washing (Ueno 1994).

There is a gland on the chest of the male tufted capuchin which plays a role in scent-marking (Epple & Lorenz 1967). The dominant captive male is observed to use this gland, rubbing it on a substrate to scent-mark it while other age and sex classes rarely, if ever, show this behavior (Dobroruka 1972). Urine marking is also seen in captivity in which males and females mark specific surfaces in their cages (Dobroruka 1972).

Captive tufted capuchins have a repertoire of 7 discrete facial displays; relaxed open-mouth, silent bared-teeth, open-mouth threat, lip-smacking, open-mouth silent bared-teeth, protruded lip, and scalp lifting (Visalberghi et al. 2006). Of the facial expressions, the silent bared-teeth and relaxed open-mouth display are the most common. The silent bared-teeth display is used in affiliative or positive interactions with higher ranking individuals and in play and courtship with other group members (Visalberghi et al. 2006). The relaxed open mouth display signals non-aggression and is commonly used in play. Scalp lifting accompanies other facial expressions and serves to accentuate the meaning of the other display in addition to being possibly an affliative expression (Weigel 1979; Visalberghi et al. 2006). Lip-smacking signals reassurance to other tufted capuchins (Weigel 1979).

A characteristic display of the tufted capuchin is the male reunion display. When separated for a time, males will approach one another quickly, embrace, and loudly vocalize (Matheson et al. 1996; Phillips et al. 2005). This behavior is not observed in females nor is it aggressive in nature (Matheson et al. 1996). Such reunion displays have been observed between adult males and between adult males and infant males and serve to reinforce affinitive relations and bonds between tufted capuchin males (Matheson et al. 1996; Phillips et al. 2005). Other displays include the oblique head tilt in which a capuchin will move its head side-to-side to gain the attention of another capuchin and the penile display where a male will stand bipedally in front of a female and display his genitals (Weigel 1979). Both sexes of brown capuchin will wag their tails when extremely excited (Dobroruka 1972).

Content last modified: April 10, 2007

Written by Kurt Gron.