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Ecologically differentiated patterns of aggressive and sexual behavior in two troops of Ugandan baboons Papio anubis.

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Ecologically Differentiated Patterns of Aggressive and
Sexual Behavior in Two Troops of Ugandan
Baboons, Papio anubis
Department of Anthropology, T h e University o f Calgary,
Calgary, Alberta
Two baboon troops from different ecological conditions - a
thicket savanna in Queen Elizabeth Park, and a forest edge in the Budongo
Forest - were studied during a 15 month period. Two different social structures
were found and various levels of aggressive activity were observed, both among
males and among females and juveniles. The patterns of female sexual behavior
differed widely between the two troops. These patterns are examined, and the
genetic and environmental factors involved in the determination of aggressive
and sexual behavior among baboons are discussed.
Two troops of African baboons, from
two very different ecological situations,
provided the data upon which this paper
is based. One troop lives in a protected
National Park, Queen Elizabeth National
Park, in a thicket savanna ecology on the
floor of the Albert Rift Valley, while the
other troop is resident in a forest edge
(mixed colonizing forest) and tree savanna/high grass ecology within the confines of the Budongo Forest Reserve.
The animals of both troops correspond
to the norm of "Olive Baboons," here ascribed to the species Payio anubis. The
only local population variations noted were
the presence of slightly larger, light colored
eyelid patches in the Budongo groups and
the existence of a gene for a shortened tail
noted in the QENP group.
Ecology-Queen Elizabeth National Park
Queen Elizabeth National Park lies on
the floor of the Albert Rift Valley a t the
south end of the Ruwenzori, with the study
area centered at latitude 0" 10's and longitude 30"O'E, and encloses most of the
shorelines of Lakes Edward and George.
The park encompasses two major ecological communities-the dry, deciduous Maramagambo forest, and two areas of thicket
savanna a t the north and south ends of
the park. The thicket savanna extends
from the foothills of the Ruwenzori and
the Crater Area southward to the MaramaAM. J. PHYS.ANTHROP.,38: 641-648.
gambo with only a relative increase in the
density of thicket formation and the appearance of a very few acacia trees along
the Kazinga Channel. The flora and fauna
of QENP are both rather restricted in variety. The thicket formations consist of a
total of five species of bush, three of trees,
and a number of ground plants and
grasses. The fauna is likewise deficientelephants, buffalo, hippopotamus, waterbuck, kob, bushbuck, hyenas, lions, and
the rare leopard being virtually the entire
large mammal inventory. In spite of this
the ecosystem is a balanced, savanna
type one familiar to primatologists. The
thicket savanna is only kept from proceeding to forest in the northern area of the
park by the slight overpopulation of elephants. Papio anubis is discontinuously
distributed over the park area: one troop
in the Crater Area, two troops occupying
part of the south side of the Kazinga Channel, and several troops along the edge of
the Maramagambo. The baboon population in the area seems to be limited by
the lack of adequate sleeping trees, Acacia
seiberiana being the only suitable species
in the area.
The park normally has two wet and two
dry seasons; March to May, and September
to mid-November is wet, the rest of the
year dry. Temperature averages about
22°C with fluctuations down to 10°C and
up to 3 0 t " C .
64 1
Ecology -B udongo Forest
The Budongo Forest Reserve is situated
i n Bunyoro Kingdom i n the area east of
the Albert Rift some 20 km away from
Lake Albert with the study area centered
a t latitude l”45’N. and longitude 31”28’E.
The land is a low rolling plain with many
“sentinel” hills poking up irregularly, one
of which is Busingiro Hill, the central area
of this study. These sentinel hills are
mostly rather rocky with poor soil and
hence are covered with mixed tree
savanna/high grass biome, and are surrounded by tropical rain forests of several
different types within the Budongo and
Siba Forests. Busingiro Hill seems to be
in the process of being colonized by mixed
forest; the Budongo is expanding at a
steady rate now since elephants are no
longer found i n the immediate area. Several hundred species of trees, bushes,
herbs, creepers, etc., as well as a dozen or
so species of grasses, exist i n this interface
between forest and savanna. However,
most of the nonprimate animal life has
been hunted out of the area, both in the
name of “control,” and by the nearby native agriculturists who practice poaching
whenever possible. The main nonprimate
animals are bushbuck and duikers; occasionally a warthog or buffalo is seen. This
area normally has only one dry seasonDecember to February-and one long wet
season with a slight lessening in rainfall
during July, which is also the coolest
month. Temperatures average about 22°C
with fluctuations down to 5°C and up to
30°C. Rainfall occurs to an average of
1500 mm yearly, but with considerable
variation. (Eggeling, ’47.)
Troop Structures
Troop “ A in QENP showed the now
familiar hierarchical troop social structure,
with a male dominance system employing
the nine fully adult males in a rather
straightforward unilineal sequence. The
troop was constantly in a state of tension
due to the activities of the males and the
larger juveniles, who were already intent
on the game of establishing their social
rankings and often iritruded upon the preserves of the adults. There was also a
constant state of combat among the hierarchy when females came into full estrus.
Troop “Bus-1” in Budongo evinced a
rather different social structure in that
there did not appear to be any sort of
dominance hierarchy among the males or
females. This troop was much less tense;
there was virtually no fighting-never any
over estrus females. The local human
population, often including the observer,
regularly provoked flight responses at
ranges of up to 200 m. The information
on this troop is based upon observations
made in special areas which were more
open than others, and also during hours
when these areas were frequented by the
animals. It was exceedingly frustrating to
work in this environment since the troop
when alarmed, would spread out over a
large area and move quietly along a multitude of winding tunnels through 3 m-5 m
high grass or dense forest undergrowth;
it was difficult to maintain contact since
the tolerance range of the troop was about
60 m-70 m , and the normal visual range
under these conditions 10 m-15 m.
Aggression-that is, intratroop threatening, harassing, and fighting-in troop “ A
of QENP was one of the main social activities indulged in by this group when not
pursuing primary subsistence actions. Patterns of aggression follow the well-known
sequence described by Hall (’62), Hall and
beVore (’65), Rowel1 (’66, ’69), and
Washburn and DeVore (’61, ’63), in their
papers on baboon behavior. Fighting and
chasing were regular features of each day’s
activity among all members of the group;
adult males had the most obvious and
noisy episodes, but adult females, juveniles, and larger infants were also involved. The most frequent and most violent fights between adult males occurred
in those instances when there was only a
single estrus female in the group. On these
occasions, the first two or three hours of
the day range would be nearly one continuous fight until the “consort for the day”
was decided. It was on one of these occasions that the male we named Underdog
was severely injured; his lower left lip was
torn downward from the corner and hung
loosely, and he lost the lower left canine
and one or more of the premolars. Nevertheless, the following day, Underdog man-
aged to become consort to the single estrus
female in the group.
The Budongo troop, on the other hand,
evinced a quite different pattern of aggressive behavior-virtually none at all. The
usual amount of play chasing and open
mouth threatening among the infants and
juveniles occurred but there was none of
this in the adult animals, except that
which was directed against the observer.
No intratroop fighting was over observed,
but there were three instances of intertroop combat. Three troops of baboons
have overlapping ranges on Busingiro Hill,
one of the most important overlap areas
being the feral mangoes and guavas near
Busingiro House itself. During the rains
there is no conflict between these troops;
normally they do not come on the same
days, and indeed three males migrated
from troop 1 into troops 2 and Siba-one
during October and November. This situation is much like that described by Rowel1
(’66). The intertroop conflicts occurred
towards the end of a rather prolonged dry
season in late February 1971. These conflicts were no doubt induced by the food
shortage which was affecting all of the
animals and humans in the area. This
situation somewhat resembles that described by Maxim and Buettner-Janusch
(’63). The pattern of these conflicts was
chase-counterchase between the adult and
large juvenile males of both troops, culminating in out-and-out fights between opposing adult males. Interestingly enough,
the two males involved in the fighting during the conflict between troops 1 and 2
had both been members of troop 1 during
most of the previous year.
Sexual patterns
The normal sexual pattern of female
baboons in East Africa seems to be solicitation of a male, acceptance of the mount,
head-turning over shoulder, lip-smacking,
rigid posture during the male’s ejaculatory
pause, vocalization of copulatory pants length of sequence depending upon the
male’s maturity - and finally a run away
from the male for 5m-25m. The male
makes only one mount rather than a series,
and usually follows the female and grooms
her afterwards.
This was the pattern observed among
the animals in the savanna of QENP, and
the sequence was invariable. The female
always panted and ran when a complete
or nearly complete mount was performed
upon her, even when the male was only an
infant. I n addition, mountings were only
performed on the ground; several times, a
solicitation occurred in a tree and both
baboons descended to the ground to copulate. Sexual tension was obvious in the
QENP troop, especially when only a single
female was in estrus. During the early
stages of her swelling she would solicit
from every male animal in the troop, and
accepted mounts with infants, juveniles,
and subadults, though the fully adult males
were rarely interested in her unless she
was the first estrus female to appear in
some time. In the middle phases of estrus,
the female was bound up in a daily consort
pair relationship with an adult male, and
it was at this time that most fighting was
observed. Also at this time, male masturbation was observed on two occasions, but
a possibly related action, “penis flicks” the rapid erection and loss of erection in a
two-second cycle - was often seen in consort males while being groomed.
In the Budongo troop the situation was
somewhat different. The complete female
sexual response pattern was deficient. The
females rarely panted during a copulation,
no matter what the maturity of the male,
and the running away phase was often
abbreviated to either a single step away or
an immediate turning around to groom the
male. Consort pairs were never formed but
a “pseudo-consort’’ relation was noted occasionally. On three occasions, an estrus
female and her pseudo-consort left the
vicinity of the troop during the day range,
and separated from it by up to 500 m ; on
these excursions it was always the female
who did the leading, the male tagging
along submissively. This pseudo-consort
relation did not evince the intensive and
repeated sexual activity which the consort
relation did in the savanna troop, in that
copulation was rather infrequent on these
sorties. There was, other than on these
pseudo-consort occasions, no portion of a
female’s estrus period during which she
was reserved to the adult males. Even at
the height of her swelling, she would
accept mounting attempts by large infants,
juveniles, and subadults, and the adult
males did not seem to be interested in preventing such activity. Most copulatory behavior occurred during the early hours of
the day, 0700 to 1000 hours, and was performed high in trees. Pairs never came
to the ground merely to copulate. Most
observed copulations occurred in end
branches at altitudes of 10 m to 20 m .
Some nursing females of the Budongo
troops came into regular estrus when their
infants were at the transitional phase,
changing from black to brown coat color.
This is rather different from previously
described sequences of female estrus
cycles (Hall, ’62; Saayman, ’ 7 0 ) , and
would tend to reduce the period between
births to about one year. I a m at a loss to
explain this phenomenon except to postulate that perhaps it is social synchrony of
estrus occurring in a n environment which
permits it, since infant two’s are normally
weaned and existing on their own in juvenile groups in this troop by the time they
are a year old. This estrus synchrony may
be analogous to the heat synchrony of the
In both areas there seemed to be a pronounced birth peak and a definite period
of about three months when almost all of
the females in the troops came into estrus
Fig. 3
and were bred. It was during this period,
February to April, that the above-mentioned nursing females came into estrus
in the Budongo, though the phenomenon
was not observed i n the QENP troop.
Each troop of baboons examined showed
very different mannerisms, attitudes, and,
to some extent, variations in social structure. In the process of trying to understand
the reasons behind these differences it
was determined that the differences could
not be held at the foot of “genetic” distinctions, purely learned differences, nor even
the differences in environment. In the end,
the ethological view of behavior as expressed by Eibl-Eibesfeldt (’70, ’72) was
eagerly seized upon and slightly modified
to form a model (fig. 3 ) for the generation
of variance in behavior sequence sets. In
this model, the basic level is of species
specific, genetically determined behavior
sets, the features that all baboons of the
Papio anubis type show in common. There
is also a conditioning or modulating factor
in the ecological environment which acts
like a filter between the genes and the observable behavior. The ecology can modify
the genetic behavior program by appropriate deletion or emphasis of some aspect of
Behavioral model.
a behavior sequence - all according to the
requirements of successful adaptation to
the particular ecosystem. The third portion
of the model is that of group history and
learned behavior, which puts the final
idiosyncratic troop specific details onto the
behavior sequence. This is the “proto-cultural” behavior which is individually
learned and may or may not be passed on
through observational learning to other
members of a troop.
It is also possible that new patterns of
behavior can be engendered by a combination of learning capabilities and the ecological requirements which could then be
inserted into the behavioral repertoire of
the species. This flexibility would be particularly important to a species during the
invasion of a new environment or during
ecological change. Such malleability is
obviously part of the capacity of Papio
anubis and of Homo sapiens, since both
have survived quite drastic ecological
modification, and also have spread
throughout numerous environments across
It is felt that this model fully accounts
for the differentiation of behavior sequences between these two troops, and
with further work and cogitation, it could
become a useful model for all other
Eggeling, W. J. 1947 Observations on the
ecology of the Budongo Rain Forest, Uganda.
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Eibl-Ebesfeldt, I. 1970 Ethology: The Biology
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New York.
1972 Love and Hate: The Natural History of Behavior Patterns. Holt, Rinehart, and
Winston, New York.
Hall, K. R. L. 1962 The sexual, agonistic, and
derived social behavior patterns of the wild
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Hall, K. R. L., and I. DeVore 1965 Primate
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Rowell, T. E. 1966 Forest living baboons in
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1969 Long-term changes in a population of Ugandan baboons. Folia Primat., 11:
Saayman, G. S. 1970 The menstrual cycle and
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aggressive, anubisa, two, behavior, baboons, patterns, differentiation, uganda, sexual, papio, troops, ecological
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