SOCIAL ORGANIZATION AND BEHAVIOR
Photo: Anne & Ron Carlson
Two distinct types of group organization can be observed among patas monkeys over
the majority of the year. The first type is the
group of variable numbers of females and one male. The other type is that of
all-male groups although occasionally mixed-sex groups with two adult males have
been known to occur (Hall 1965; Struthsaker & Gartlan 1970; Gartlan 1974).
During mating season, which corresponds with the summer rainy season, other
males may enter the single male group to
There is little to no intra-group mobility among females and they stay with their
for life. Most likely, females determine movements of the group and sleeping
sites because they are more familiar with the home range of the group than the
transitory males (Chism et al. 1984).
It was long debated if a defined
of female patas monkeys existed but at present, the consensus is that it does
exist. This hierarchy is not as well defined or as firm as those of other
and it is likely that the patas monkey dominance hierarchy is not kin-based
(Chism & Rogers 2002). Nakagawa (1992) supports the view of a discrete
hierarchy of female patas monkeys and suggests that the male is always at the
periphery of the group. The hierarchy of patas females remains somewhat static
once established and is maintained through submissive and aggressive actions
between the patas females. Kinship relationships between females also serve to
help keep a patas group together (Nakagawa 1992). In one captive study, when a
new group was created, the adult females formed a dominance hierarchy within
several months through
interactions (Loy & Harnois 1988). There is evidence of post-conflict
reconciliation among patas females with increases in contact between former
adversaries following agonistic interactions (York & Rowell 1988). The male
interacts infrequently with the females of his group and spends most of his
time at its periphery. It is from this position that the male spends a large
part of his time scanning the landscape for predators or males from other groups
who may challenge him (Hall 1965; Nakagawa 1992). In captivity, this model of
the sole male at the edge of the group holds, with the male aloof and
indifferent to intra-group social interactions (Hall & Mayer 1967).
Photo: Anne & Ron Carlson
Grooming plays an important role in patas social organization and can indicate
hierarchies within a group as well as relationships between
individuals doing the grooming (Rowell & Olson 1983). High status within a
patas hierarchy group is reflected by grooming frequency. Nakagawa (1992)
observed that high status female patas received more grooming than lower status
group members. Grooming also serves to facilitate
as grooming of a mother may allow the groomer access to the motherŐs infant
(Muroyama 1994). Status or rank also seems to play a role in
grooming of the adult male within a polygynous patas group. In captivity, most
of the grooming of the resident male was done by high status females (Loy &
Harnois 1988). There is evidence that the smaller the patas group, the higher
the instance of allogrooming (Chism & Rogers 2002). This higher rate of
grooming with smaller size groups most likely serves to reinforce group
cohesion as a smaller group is more vulnerable to outside interference.
The males choose to leave their natal group by puberty or are driven out when
they reach sexual maturity by the resident adult male (Gartlan 1974). Sometimes
the male will leave his natal group with a brother, a kin relation which may
help them both survive (Chism 1999). This displacement occurs typically at
around three years of age and they may remain solitary or in all male groups
until they are fully grown at around five years of age (Chism et al. 1988).
The purpose of the all-male patas group appears to be to provide safety for
young or infirm males and for protection against predators and other threats
It was long believed that patas groups organized themselves in polygynous
mating systems but now it is assumed that this type of mating system is the
exception rather than the rule (Harding & Olson 1986). One male is present
through the year with a group of females but other males infiltrate the group
during the mating season to breed with group females (Harding & Olson 1986;
Carlson & Isbell 2001). In fact, the flow of males into and out of groups
is best described as dynamic, particularly in the mating season (Chism &
Rowell 1986). In at least one study it was shown that these
are initiated by the females in the group (Ohsawa 1993). Some years, patas
groups may remain exclusive single-male mating systems while in subsequent
years the same group may be a multi-male system (Carlson & Isbell 2001).
of the single male in the polygynous groups occurs during the mating season and
serves to provide the challenger with access to mating with resident females.
Supplantation occurs when a male from another group challenges the single male
and may be accomplished through fighting and chasing (Ohsawa 2003). Depending
on the victor, either the resident male is removed from his position as the
sole male or the challenger remains peripheral. When challenged by an
extra-group male, the resident male has a higher probability of winning the
fight (Chism & Rogers 1997). Supplantation by a challenger male is
sometimes followed by a short-lived multi-male polygynous mating system in
which several males are actively breeding within a group (Ohsawa et al. 1993).
This is most likely the result of the new resident male being too preoccupied
with mating to chase other males away (Ohsawa 2003).
Photo: Anne & Ron Carlson
Patas polygynous group size is quite variable, from 20 to as large as 76
individuals (Enstam et al 2002; Ohsawa 2003). It appears that all-male groups
are typically smaller than the polygynous groups with Cameroonian all-male group
observed with 15 to as few as two individuals (Struhsaker & Gartlan 1970;
Ohsawa 2003). Inter-group encounters are typically agonistic but rarely
physical and serve to assist in group resource defense (Chism et al. 1984).
Frequently, a patas monkey will continuously scan its environment and monitor
its surroundings both
and, if available, will seek out a high vantage point to do so (Rowell &
Olson 1983; Chism 1999; Enstam & Isbell 2004). This important behavior
serves several purposes. The scanning alerts the patas in a group to predators
and to non-group patas (Hall 1965; Nakagawa 1992). In addition, the scanning
may serve as a social monitoring process and help with group coherence
(Rowell & Olson 1983). Patas scan not only the landscape but also each
other so that they are constantly aware of other patas' actions which may serve
to reduce agnostic encounters. This may also assist with the maintenance of
acceptable distances between patas individuals which avoids agonism (Rowell &
Olson 1983; McNelis & Boatright-Horowitz 1998). Because the patas monkey
is a relatively silent species compared to other monkeys, the constant visual
monitoring of the landscape as well as each other can serve as a type of
communication in that most individuals will notice quickly if something is
amiss with another individual (Rowell & Olson 1983).
Patas monkeys have a clearly defined conception and birth season. Typically
conception occurs in the summer wet season and births occur in the winter dry
season (Struhsaker & Gartlan 1970; Nakagawa et al. 2003; Chism et al. 1983).
Patas are able to obtain more nutrition in the dry season than in the wet and
this may be one explanation for the seasonality of their reproduction (Nakagawa
2000). Another potential reason for such profound birth seasonality may be the
availability of food during the breeding season which allows the prior year's
infant to be weaned, enabling the mothers to become pregnant again (Chism et al.
1984). In captivity, the patas monkey does not display this reproductive
seasonality (Sly et al. 1983). In addition, wild patas monkeys typically give
birth during the day which may be an adaptation to reduce the risks associated
with nocturnal predators. Patas monkeys are vulnerable to nocturnal predators
and rely on concealment at night to avoid said predators (Chism et al. 1983).
Photo: Anne & Ron Carlson
The patas monkey in some cases participates in
in which a male and female will attend to, stay in close proximity to, and
monitor one another. A consortship, as described above, lasts more than thirty
minutes. During the course of this association, the male and female patas
monkey will copulate. In addition, if other patas individuals approach, the
two patas in consort will move even closer together (Harding & Olson 1986).
These pairings may allow unfamiliar patas to assess one another's reproductive
fitness and allow the pair of monkeys to size each other up (Harding &
In captivity, the average
period for a female patas monkey is 167 days (Sly et al. 1983). As a patas
juvenile is fully able to take care of itself from six to seven months of age,
this allows females to be ready to bear young again by the next breeding season
and to essentially reproduce at the maximum rate possible (Chism et al. 1984).
The age at first conception in females in both the wild and in captivity is
approximately 2.5 years resulting in the first birth at around three years of
age (Chism et al. 1984; Nakagawa et al. 2003). The male matures slightly later
and can sire offspring at four years old, but rarely is able to do so due to
his inability to access females (Rowell & Chism 1986). The average
ovarian cycle of the captive patas female is 30 to 33 days and a degree of
has been observed in a specific patas group (Rowell 1976; Loy et al. 1978;
Rowell & Hartwell 1978).
A marked color change in the facial hair of female patas is observed during
pregnancy. This has been observed in two separate studies in captivity. The
facial hair begins to lighten in the second trimester of pregnancy and is at its
maximum lightness between 1.5 and 2.5 months postpartum (Loy 1974; Palmer et
al. 1981). Approximately three months
a darkening process begins returning the face to close to its pre-pregnancy color
(Loy 1974). This color change may be the result of hormonal changes associated
with pregnancy and may have a use in delineating the reproductive histories of
females as the face does not always completely revert to pre-pregnancy
coloration (Palmer et al. 1981). The bright blue color of the patas scrotum
appears to play some role in competition for access to females, but its color
exhibits no correlation with season, age, or health (Bercovitch 1996).
As to which sex initiates copulation, it appears that this is related to what
type of mating system is in operation at any given time. In years when a
multi-male/multi-female mating system is in place, males are much more likely to
initiate copulation than in polygynous years. Females showed the converse,
initiating copulation at a much higher rate during single-male mating years
than in multi-male system years (Carlson & Isbell 2001). The female
solicitation posture consists of the female placing herself in front of a male
facing away from him in a crouching position and looking back at him while
blowing air into her cheeks. She also may drool and curl her tail (Chism et
Photo: Anne & Ron Carlson
There has also been at least one instance of probable
by a patas male observed in the wild (Enstam et al. 2002). The reason for this
killing is probably to increase mating opportunities for the male because he
may then subsequently mate with the mother. Hrdy (1974) suggests that
infanticide is beneficial when a male may only have a short time to mate
before being supplanted by another male and when access to females is limited.
All patas females participate in
At present, it is not obvious
what the benefits of allomothering are, although they may be related to social
hierarchy based on who receives allomothering and who does the allomothering
(Muroyama 1994; Nakagawa 1995). This behavior may also be related to an
relationship between adult females (Nakagawa 1998). On at least
one occasion in Cameroon, patas females of one group were observed to kidnap
an infant from a different group, allomother it for a while and eventually
abandon it (Nakagawa 1995). Allomothering may also serve to strengthen social
interactions and group cohesion. In captivity, infant patas females were
observed to receive significantly more allomothering from non-kin females that
the male patas infants (Loy & Loy 1987). This preference to allomother female
infants serves to integrate and reinforce relationships within the female natal
group and to drive the males to their position at the periphery of the group.
In captive studies, patas adult males seldom interact with mothers with infants
and their behavior could even be described as avoidant (Chism 1986).
Patas monkeys demonstrate one of the shortest
Cercopithecine, averaging about one year between births (Chism et al. 1984;
Nakagawa et al. 2003). The patas infant must be fully independent by one year
of age as it will be displaced by a new infant. Orphaned patas infants have
been observed to survive in the wild without being adopted as early as seven
months of age (Chism et al. 1984).
In captivity, from birth until the fourth month of life, male and female infants
receive comparable amounts of grooming and attention from their mothers. After
this period of time, there is a marked increase in grooming and attention paid
to female infants while grooming of the male infants remains the same (Loy &
Loy 1987). This again shows the strong
bonds between adult females. After the fifth month of life, contact between
the mother and her infant of either sex decreases steadily (Chism 1986). During
this time the infant will continue to nurse at night, but represents only a
small energetic cost to the mother. This nursing is merely a supplemental
food source as the infant is quickly learning how to forage on its own.
Complete weaning of the infant only occurs when the mother gives birth to a new
infant, typically around one year of age (Chism 1986).
Photo: Anne & Ron Carlson
Patas infants are born completely black in color and remain so for the first
three months of their lives. In the subsequent three months, the
will begin to fade to the reddish coat of the adult (Palmer et al. 1981). In a
specific captive study, patas infants were observed to typically start eating
solid food around the seventh week, exhibit play behavior in the eighth week, and
bipedally scan at the third month. For the first several months, the
predominant posture of an inactive mother with a young infant is that of
cradling which starts to steadily decrease in the third month. This may assist
the infant in its suckling posture and to keep it warm (Chism 1986). In a long
term study, the mortality rate of infants and one year-old juveniles averaged
20% (Nakagawa et al. 2003).
Patas vocalize infrequently and tend to move quietly (Chism & Rowell 1988).
They are a relatively silent species with few physical cues that rely on visual
communication to avoid agonistic interactions within groups (McNeilis &
Boatright-Horowitz 1998). Visual contact serves to transfer information about
important occurrences within the patas environment quickly through constant
monitoring of not only the environment, but other patas within a group as well
(Rowell & Olson 1983). Patas rely on an "adaptive silence" and prefer not
to give away their locations to predators (Hall 1967). Patas exhibit a low
between individuals which may be as a result of the open nature of their habitat
which facilitates visual contact instead (Nakagawa 1992).
Patas alarm calls are the best documented of their vocalizations. These calls
are directed to warn other patas of a threat and are uttered mainly in response
to mammalian predators. There are various alarm calls which in many cases are
predator specific however males only utter the "bark grunt" in response to all
predators. This type of grunt is also vocalized by males in response to the
approach of extra-group male patas (Enstam & Isbell 2002).
Patas monkeys other than adult males exhibit several
discrete alarm calls which they use to warn the group of danger. In response
to jackals and wildcats, a "cough" alarm call is uttered. "Loud chutter" is
the alarm call associated with baboons, domestic dogs, jackals and wildcats.
A "nyow" alarm call is the response to baboons, domestic dogs and lions.
Finally, a "quiet chudder" or a "gecker" are calls both associated with snakes
and the "gecker" may also be used to warn of raptors (Enstam & Isbell 2002).
Other types of vocalization used by patas monkeys are those used in
allomothering interactions. These consist of the allomother's "moo" and the
infants' "want" call. The infant's "want" call serves to attract related,
unrelated, and even unfamiliar allomothers. The allomother's "moo" is
typically uttered when approaching the infant to be allomothered (Nakagawa 1998).
Another type of possible communication is that of
communication. In captivity, patas were observed to occasionally approach
another individual and perform a discrete "nose to mouth" gesture with the
ostensible purpose of ascertaining what the other individual had been eating
(Rowell & Olson 1983).
One documented captive patas communicative display is that of the Grimace-Gecker
in which the patas displays its teeth to another. Originally suggested to be
a submissive/appeasement signal, this display has been argued not to convey
such a message. Regardless, the display appears to be discrete and to serve
some unknown communicative purpose (Jacobus & Loy 1981; Loy et al. 1993)
Content last modified: December 18, 2006
Written by Kurt Gron. Reviewed by Karin Enstam.
Cite this page as:
Gron KJ. 2006 December 18. Primate Factsheets: Patas monkey (Erythrocebus patas) Behavior . <http://pin.primate.wisc.edu/factsheets/entry/patas_monkey/behav>. Accessed 2014 September 16.