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Contiguous distribution of two species of Cebus monkeys in El Tuparro National Park Colombia.

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American Journal of Primatology 8:lOl-ll2 (1985)
Contiguous Distribution of Two Species of Cebus Monkeys
in El Tuparro National Park, Colombia
THOMAS R. DEFLER
IJnnruersidad de Los Andes, Bogotd. Colombia
The geographic distribution of two congeneric monkeys (Cebus albifi-ons
and C. ape&) was studied in El Tuparro National Park in the llanos of
eastern Colombia. Extensive trips were undertaken by land and river to
collect 268 precisely located groups of these two species. The distributions
of these monkeys were generally mutually exclusive and parapatric, contrasting with their known sympatry in closed-canopy rainforest farther to
the south. The replacement of one species by the other was abrupt along the
northern water courses in the park; however, the two species’ ranges partially overlapped and contained islands of sympatry towards the southern
parts of the park, where forests are more extensive. Along the rivers, C.
albifrons was found in seasonally inundated forests and woodlands that
were seldom entered by C. apella. Such inundatable vegetation was extensive in downriver sites in the typically flat llanos geography of this part of
Colombia. Although some differential use of habitat was demonstrated,
many forests containing the two species seemed essentially identical so that
historical precedence, competition, or both may also be posited to partially
explain the distributions, although this remains to be demonstrated.
Key words: distributions, parapatry, Cebm albifrons, Cebus apella, Colombia
INTRODUCTION
The exclusion of a species from the habitat of another closely related species is
a striking pattern wherever geographical distributions are known with sufficient
detail [MacArthur, 19721. Often such ranges suggest competitive exclusion of one of
the two species. Other possibilities include subtle habitat differences or higher order
interactions with a third or fourth species [eg, Bergerud, 19671. Peripheral populations near the limit of their distribution may be particularly interesting, since they
may be at or near the limit of their available abilities for utilizing the resources for
their particular environment [Terborgh, 19741.
The present paper describes a contiguous and mutually exclusive distribution of
the two congeneric monkeys Cebus albifrons and C. apella in eastern Colombia near
the Orinoco River. The particular C. albifi-ons population is peripherally isolated
from the main population to the south. That the two &bus species are generally
Received December 2,1983; revision accepted October 5, 1984
Address reprint requests to Thomas R. Defler, Universidad de 10s Andes, Apartado Aereo 4559, Bogota,
Colombia.
0 1985 Alan R. Liss, Inc.
102 / Defler
parapatric in El Tuparro National Park is interesting, since it is known that the
two species are widely sympatric in the upper Amazon basin in closed-canopyforest
[Hawa, 1976; Neville et al, 1976; Terborgh, 1983; personal observation]. In general,
the distributions of the two species are congruent in the upper Amazon basin,
reaching the lower slopes of the Andes; but, although C. alhifrons only reaches
northern Bolivia in the south and reaches in the east to the Tapajos and Negro
Rivers in Brazil, C. apella is found to the east coast of Brazil and to northern
Argentina. In general, in the northern parts of their range in Colombia, there is a
mosaic of either C. apella or C. albifrons, and above the Vichada River the two
species seem to be distributed mutually exclusively [Wolfheim, 1983; persona1 observation]. The two species are very similar in their feeding habits, inasmuch as they
both feed on most available fruits, nuts, and small vertebrates and invertebrates
and can be characterized as omnivores [Defler, 1979a,b, 1982; Izawa, 1978, 1979;
Terborgh, 19831. They should be at least partly competitive, therefore. in any sympatric situation.
Terborgh 119831 has shown how the two species have evolved different foraging
strategies: C. albifrons travels great distances in order to exploit widely separated
patches; C. apella exploits more evenly distributed resources, traveling less to do so.
Many species of plants and animals exploited by both species have been identified
[Defler, unpublished manuscript], however, suggesting some competition.
METHODS
The study took place in the El Tuparro National Park, a 548,000 ha reserve
administered by INDERENA, the arm of the Colombian Ministry of Agriculture
that is responsible for the national park system. The park is located in extreme
eastern Colombia (Fig. 1)and is composed of typical llanos habitat, consisting of
about 80% grassy savanna and 20% forest, mostly riparian or gallery forest. A
general description of the park vegetation can be found in Vincelli [1981]. Forest
height is seldom more than 20-25 m. A distinct gradient from scrubby forest in
narrow bands along the Tomo River border proceeding to more extensive forest
along the southern Tuparro River border is evident in the space of 15-30 km.
Another 15-30 km farther south, on the south side of the Vichada River, forest cover
approaches 80%.
Average precipitation, based on climatological data from 1972-1979, was 2,400
mm in the eastern extreme of the park and 2,860 mm in the western extreme (150
km apart). Most of the forest in the park is found along the creeks and rivers and
can be divided into forest that is seasonably inundated and that which is not. The
length of the inundation or drought during the year strongly influences the plant
community and its components; communities that are not seasonally inundated
appear to be more complex and are used by more species of animals, although data
are not available to support this impression.
During trips throughout the park on trail bike in 1976-1981 and by canoe on
all navigable rivers in 1981-1982, I mapped the locations of all observations of Cebus
groups at a scale of 1:50,000. Areas of apparent sympatry between the two Cebus
species were studied more thoroughly by actively seeking contacts to determine
presence or absence of overlap between the two species. The discrete nature of the
gallery forests in this study made it rather easy to map the distributions of these
large, easily located mammals.
I classified the habitat occupied by the Cebus species along the rivers into five
categories or “habitat types”: 1) simple communities of a few plant species (especially pioneer species such as Carnpsiandra comoso, probably the most common
pioneer species in the region), which are generally low woods less than 10 m tall and
Contiguous Distribution of Two Cebus Spp / 103
we always found on a loose, sandy substrate; there are early successional communities found, for example, on the inside of a river bend; 2) low woods that are extensively inundated each year and contain several plant species up to 10-15 m, including
many spiny Bartris palms; these communities are often found on an abandoned
river bed on a substrate of clay or sand parallel to the current river bed; 3) woods
about 15 m high with much underbrush and higher plant diversity than habitat
type 2, seasonally inundated and containing many spiny Bactris palms; 4) well
developed forests 15-20 m high containing much underbrush but sometimes swampy
and flood at high water; and 5) the most developed, semi deciduous forests seen,
which reaches heights of 20-25 m; forest of this habitat type never become flooded
and often contain palms of the species Attalea regia and Jessenia polycarpa on a soil
that is loamy or clay. No attempt was made to characterize forest or habitat types
that did not abut on the rivers and that could be seen from the canoe. The abovedefined cline of vegetation or habitat types is based primarily on the extent of
inundation, with habitat type 1 being the first to become flooded and the last to be
drained during the year, whereas habitat type 4 is inundated only during high
water. Habitat type 5 is never flooded. Knowledge of inundation or lack of inundation of each habitat type is based on more than 5 years of residence in the area
during all seasons.
A high percentage of the forests in the park are located away from the rivers.
These are complexly structured, with the best Cebus habitat being synonymous with
habitat type 5, most generally described as semi deciduous freatophytic forest. Away
from the rivers, many of these forests are found alongside small creeks and are
separated from each other by wide expanses of grassy savanna (sometimes several
krn in extent), which surely restrict much primate movement between forests.
RESULTS
The locations of 268 contacts with Cebus monkey groups throughout the Park
appear in Figure 2. A line can be drawn from the Tom0 River in the north south-
104
I Defler
Contiguous Distribution of Two Cebus Spp I 105
wards to the Tuparrito River (a straight line distance of 25 km), which completely
separates the majority of contacts with the two species, The boundary zone between
the two species on the Tom0 River is characterized by a wide zone of seasonally
inundatable and low (5-10 mj bushy woodland, where no Cebus were contacted
during three exploratory trips into the area. The nearest contacts of C. apella and C.
albifrons in this area were in forests that were considerably higher and more
extensive than any habitat examined between the two contacts.
All habitat along the indicated line separating the two species between the
Tom0 River and Quinvaza Creek was grassy savanna. The line separating the two
species proceeded directly south from the Quinvaza Creek to the Tuparrito River,
where it followed the Tuparrito eastward. From that point (Fig. 31, no C. apella were
ever observed north of the Tuparrito River, although south of the same river, a
complex mosaic of isolated C. albifions groups and sympatric associations of the two
congeners were discovered. This extended to a point further east, where C. apella
contacts ceased only C. albifrons were found downriver (Fig. 4).
West of the line dividing the two species on the Tuparrito, a series of small,
apparently isolated populations or groups of C. albifions were contacted along the
north bank of that river; these were surrounded by C. apella in the adjacent and
nearby gallery forests on slightly higher ground. On the Tuparro River to the south,
a point (Fig. 5 ) was identified east of which C. apella were never contacted north of
the river. Only C. apella were contacted along the south bank of the Tuparro River.
To the west of the general dividing line between the two species on the Tuparro,
some groups of C. alhifions were contacted that seemed isolated from the rest of the
population and were surrounded by groups of C. apella. Two definite cases of
sympatry on the Tuparrito River (Fig. 4) and the Tuparro River (Fig. 6) were
observed, where groups of congeners extensively overlapped in their activities both
during the wet season and the dry season.
An analysis of 70 contacts with groups of the two species along the rivers,
classifying each contact in one of the five habitat types, showed that, although there
was a broad overlap in the types of plant communities used by the two species (Fig.
71, C. albifrons also often used inundatable woods (habitat types 1 and 2) that were
seldom used by the C. apella groups. Preferences of the two species for each of the
five habitat types along the rivers showed a significant difference (F = 28.48, df =
1.69, P < 0.001) calculated from the 70 contacts mentioned.
Since the amount of inundatable forest increases downriver, it could be argued
that the significant difference seen in use of habitat type resulted from C. albifrons
being found on downriver sites (circularity). Therefore, a n analysis was made of 27
contacts with groups that were observed a t sites in which the congener was found
directly on opposite sides of the river (mainly on the lower Tuparro River). This
analysis also showed the use of habitat types by each species to be significantly
different (F = 20.59, df = 1.26, P < 0.001).
Figures 3,4,6, and 8-10 show in more detail some observed contact zones between the two species. The zones varied from a strict separation between the two
species (Fig. 3) to observed sympatry in well developed forest of habitat types 4 and
5 (Figs. 4 and 6).
I)ISCUSSION
Because many instances of sympatry are known between C. albifions and C.
apella, the parapatry seen in El Tuparro National Park is particularly interesting
106 / Defler
Fig. 3. Detail of border between C. ape& ( 0 )and C. albifrons (0)
on the Tuparrito River showing the
location of first contact there with C. alhifrons south of the Tuparrito River. East of this point only C.
alhifions were contacted on the north side of the river.
Fig. 4. Detail of area of sympatry south of the Tuparrito River. Extensive overlap of the home range
occured of a group of each of the species. The C. albifrons (0)
group used mostly the lower parts of the
gallery, closest to the river, where extensive inundation occurs during the rainy season. Further away
from the river, along the connecting gallery forest along tributary creeks, only C. apella ( 0 )was contacted.
Contiguous Distribution of Two Cebus Spp I 107
Fig. 5. Detail of area on northern bank of Tuparro River where C. apella ( 0 )is completely replaced by
C. ulbifruns (0).
The two congcners are separated by 2.5 km of passy savanna along the northern lip of
a large oxbow lakc with only a thin margin of 2-5 m-high bushy trees along the water’s edge.
Fig. 6. Detail of group of C. albifrons (0)
sympatric with C. upebla (e)in well developed forest (habitat
type 5)and a C. albifrons group in seasonally inundatable woods around a lake.
108 I Defler
5
v)
u
z
0
~
:1
Y
= 32
20
’0
o
N =3a
CEBUS APELLA
=
w
20
Lz
1 0
1
2
HABITAT
3
4
5
TY PE S
Fig. 7. Percentagc of contacts with C. alhfiuns in each habitat type compared with thc percenlage of
contact with C. apella in each habitat type.
and presents the problem of understanding this difference in their mutual distributions. Terborgh [1983),in his comparative study of five species of primates in Man6
National Park in Peru, presented a preliminary scheme for understanding how
these two closely related species. C. albifrons and C. apella. vary in their foraging
strategies in the same or similar habitat, allowing wider amplitude for alternative
niches. The area of Terborgh’s study supports a t least 13 species. Terborgh characterized C. albifi-ons as a n “opportunistic nomad” using widely separated resources
and travelling between good concentrations of fruit exploiting them until they are
used up. Terborgh showed, in contrast, that C. apella uses resources much more
evenly, with much less traveling between patches, ie, a continuous utilization of
resources as the group moves along.
The reduced forest found in the Colombian llanos and its widespread scrubby
appearance argues for a comparatively poor habitat for primates. Though few studies have been done that demonstrated species richness for gallery forests in the
llanos as compared to closed-canopy rainforest, Eisenberg [1979] showed an inverse
correlation between annual drought period and diversity of primate species. Such
annual drought periods are typical for llanos habitats. In eastern El Tuparro, there
are three sympatric primate species, in western El Tuparro, there are four. Directly
to the west a t the same latitude but in seasonally more moist piedmont forest, six
sympatric species of primates are known.
The two species in El Tuparro occupy habitats that seem identical; one species
is found on one side of the river and its congener on the opposite side, a distance of
only a few meters. However, C. albifrons also uses many inundatable sites (often
inundated at the time of the observation) that C. upella seldom enters. I have
frequently observed C. albifrons in flooded forest but never C. apella. The C. albi-
Contiguous Distribution of Two Cebus Spp / 109
(a)
Fig. 8. Detail of border between C alhifrons ((1) and C. apslla
on Quinvaza Creek in El Tuparro. The
observed groups were separated by 3.5 km of grassy savanna and a small gallery forest. Inundatable. low
(10-15 m) bushy forest along the Quinvaza Creek is continuous except for small breaks (50 in)caused by
stream cutting.
Fig. 9. Detail of' westernmost contact of C. albifrons (1 1) north of the 'hparrito River, surrounded by C.
upella (a).
This was probably one group contacted on three different days. Adjacent gallery forest along
the main river and along an affluent creek total about 100 ha.
110 I Defler
Fig. 10. Detail of C. ulbifrons (0)
surrounded by C. upella
on northern bank of tho Tuparru River,
which was possibly sympatric. The probable single group of C. albifions was Contacted in well developed
forest that was seasonally inundatable alongside the main river. The several &goupsof C upella were
contacted only i n the upland, drier forest (with some swamp).
f r o m may have been moving between two widely separated concentrations of food,
only passing incidently through flooded forest, or they may have been exploiting a
food source (for example, Inga spp) in the flooded forest itself.
Away from the rivers, however, gallery forests in the park in the areas where
each species is dominant seem essentially the same, yet a sharp boundary between
populations is maintained in many areas, especially to the north of the park where
vegetation seems to be more sparce. Such sharp boundaries of species evidently
confined by congeners are well known in the tropics leg, Diamond, 1972; Terborgh
& Winter, 19821 and might indicate that some competition exists between the two
species if there is no habitat difference or higher-order interaction with third or
fourth species. However, the effect of competition is not easy to demonstrate directly,
and such parapatric distributions could also be ascribed to historical factors. It is
interesting to note that on upriver sites on the Tuparrito and Tuparro Rivers, groups
of C. alhifrons were contacted that seemed surrounded by a population of C. upella,
whereas on downriver sites no groups of C. apella surrounded by a population of C.
albifrons were ever found. Whether the long-distance-traveling C. albifrons is simply
exploiting a habitat that includes an extensively flooded area, which C. upella is
unable to exploit, or some competition is involved remains to be proved. It is
interesting, however, t o note that Terborgh 119831 observed the two species at times
in Manu in Pacific mixed species groups, although C. alhifrons was able to consistently displace C. apella from a fruit source when any direct confrontation occurred.
Also, C. apella groups permit a wide overlap of groups, whereas C. ulbifrons are
much less tolerant of neighboring groups of the same species [Defler, 1979, 1982;
Contiguous Distribution of Two Cebus Spp / 111
Terborgh, 19831. This may support the hypothesis that C. albifrons is able to outcompete C. apella under certain conditions.
Although the similarity of some feeding habitats in the two species is thoughtprovoking, it is not possible to say whether or not, in fact, such a distribution is due
at least partially to competition, though the pattern suggests that C. albifrons has
retreated to a habitat patch where it has a competititve edge over C. apella in this
part of Colombia. It is, of course, equally possible that C. apella is gradually replacing C. albifrons and that the process is ongoing. The absence, however, of a key
resource for one or the other species or the presence of a particular predator might
also account for a species’ absence as a n alternative to a hypothetical competitive
displacement pattern [Cody, 19741. Dietary preferences and habitat needs of both
species must be examined much more closely before competition can be used to
explain the current distribution of these congeners.
North of the closed-canopy forest of the Colombian Amazon, there are at least
two disjunct populations of C. albifrons, both separated from the main (2. albifrons
population by C. apella [Hernandez & Camacho & Cooper, 19761. Obviously, at one
time these isolated populations of C. albifrons must have been unified. Apparently,
some historical change has taken place that has allowed C. apella to invade areas
that previously must have supported populations of C. albifroris. Since C. albifions
in El Tuparro uses inundatable, successional types of vegetation in the llanos much
more successfully than C. apella, it seem logical that the historical change that has
taken place, perhaps allowing C. apella to successfully invade and replace previous
populations of C. albifrons, must have been a drying out of formerly flooded and wet
conditions, conditions in which C. alhifrons seems to have an advantage over its
congener. There have been several periods in the recent Pleistocene and Holocene of
the Colombia llanos when vast areas were inundated. The most recent such period,
during the climactic optimum of 5000-6000 BP, probably created conditions in wide
areas of the llanos similar to the extensive downriver seasonally flooded forests
found today [ Brown, 19821. Perhaps these periods created conditions in the llanos
that were more favorable to expansion by C. ulbifrons. A foraging strategy requiring
groups of C. alhifions to travel wide distances looking for locally available concentrations of food as supported by Terborgh’s 119831 evidence, might be the best
adaptation for traveling over great expanses of flooded forest, a situation C. apella
seems to avoid. Such a n adaptation, perhaps taking place in a vast, flooded llanos,
could have served as a preadaptation to the niche the species now enjoys in the
richly complex, closed-canopy rainforest.
ACKNOWLEDGMENTS
I thank Ernest0 Barriga, Jorge Hernandez, and many employees of INDER-
ENAs park system for various types of help during my stay in El Tuparro National
Park. Parts of the study were supported by the Peace Corps and World Wildlife
Fund; U.S. maps of the regions were supplied by Sam Allen of the Interamerican
Geodesic Service in Bogota. Comments on a n earlier draft of this paper were kindly
supplied by John Robinson.
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Izawa, K. Frog-eating behavior of wild blackcapped capuchin (Cebus apella). PRIMATES
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Izawa, K. Foods and feeding behavior of the
wild black-capped capuchin (Cebus upella).
PRIMATES 20:57-76,1979.
MacArthur, R.H. GEOGRAPHICAL ECOLOGY. New York, Harper & Row, 1972.
Neville, N.; Castro, N.; Marmos, A. Censusing primate populations in the reserved area
of the Pacaya and Samiria Rivers, Department Loreto, Peru. PRIMATES 17:151-181,
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Terborgh, J. Preservation of natural diversity: The problem of extinction prone species. BIOSCIENCE 24:715-722,1974.
Terborgh, J. THE BEHAVIORAL ECOLOGY
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‘rerborgh, J.; Winter B. Evolutionary circumstances of species with small ranges, pp.
587-600 in BIOLOGICAL DIVERSITY IN
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