Socioecology of the Blue Monkeys

(Cercopithecus mitis stuhlmanni)

of the Kibale Forest, Uganda

RASANAYAGAM RUDRAN

m

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY • NUMBER 249
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SMITHSONIA N CONTRIBUTION S T O ZOOLOGY • NUMBER 249

Socioecology of the Blue Monkeys

(Cercopithecus mitis stuhlmanni)

of the Kibale Forest, Uganda

Rasanayagam Rudran

SMITHSONIAN INSTITUTION PRESS

City of Washington

1978
ABSTRAC T

Rasanayagam Rudran. Socioecology of the Blue Monkeys (Cercopithecus mitis

stuhlmanni) of the Kibale Forest, Uganda. Smithsonian Contributions to Zoology,

number 249, 88 pages, 34 figures, 58 tables, 1978.—This study was conducted

between December 1972 and November 1974 and included some 2100 hours of

observation. Blue monkeys usually lived in "one-adult male" social groups that

included 13 to 27 animals (X = 20.8). The large disparity in the adult sex ratio

of these groups was partly accounted for by the emigration of young males that

lived as solitary individuals at least for a short period after leaving their parental

groups.

Blue monkeys frequently formed large mixed-species groupings with one or

more of the other primates living in the study area and these associations probably functioned in the avoidance of predation. Associations with the folivorous

red colobus (Colobus badius) probably enhanced the acquisition of invertebrate

food, while other types of associations, particularly with redtails (Cercopithecus

ascanius), may have resulted in efficient location of food resources. Polyspecific

associations seemed to be avoided during the times blue monkeys fed on plant

foods.

Blue monkeys exploited a large number of food plants but tended to be selective feeders. Fruits were usually the most frequently used plant component,

but foliar foods and invertebrates were periodically used at high frequencies.

Spearman rank correlation tests indicated (1) a significant negative correlation

between the frequency of use of fruits and indices of diet diversity computed on

the basis of the Shannon-Wiener equation, and (2) a significant positive correlation between the frequency of use of foliar foods and indices of diet diversity.

The use of food resources showed considerable intermonthly variations and depended on availability, relative abundance, and the dietary preferences of the

blue monkeys. The frequency of food intake and the composition of the diet of

four age /sex classes were found to differ. The adult male seemed to adopt a

"time minimizing" feeding strategy and exploited a larger proportion of fruits

and a smaller proportion of invertebrates than adult females, subadults, and

juveniles.

Blue monkeys of the Kibale Forest occupied relatively large home ranges. On

a daily basis, however, they used only a small portion of their home range and

the size of daily ranges varied appreciably during different sample periods. Overlaps in areas used on different days of a sample period were usually small. Thus

on the average less than 5% of the area used during a sample period was used on

all five days of the sample period, while about 66% was visited on only one day

of the sample period.

Phenological data collected during the study suggested that differential use of

the home range was affected by variations in food abundance. Spearman rank

correlation tests showed that ranging patterns were related to the location and

exploitation of abundant food resources. In addition the ranging patterns appeared to be partially affected by climatic factors and the location of areas used

for night resting.

OFFICIAL PUBLICATION DATE is handstamped in a limited number of initial copies and is recorded

in the Institution's annual report, Smithsonian Year. SERIES COVER DESIGN: The coral Montastrea

cavernosa (Linnaeus).

Library of Congress Cataloging in Publication Data

Rudran, Rasanayagam

Socioecology of the blue monkeys (Cercopithecus mitis stuhlmanni) of the Kibale Forest, Uganda.

(Smithsonian contributions to zoology ; no. 249)

Bibliography: p.

1. Cercopiihecus mitis —Behavior. 2. Social behavior in animals. 3. Animals, Food habits of.

4. Mammals—Ecology. 5. Mammals—Uganda—Kibale Forest Reserve. I. Title. II. Series:

Smithsonian Institution. Smithsonian contributions to zoology ; no. 249.

QL1.854 no. 249 [QL737.P93] 591'.08s [599'.82] 76-608404
Contents

Page

Introduction 1

Purpose of the Study 1

Description of the Blue Monkey 1

Description of the Study Area 3

General Field Procedures 5

Acknowledgments 5

Aspects of the Social Organization and Dynamics of Blue Monkey Groups. . 6

Methods 6

Results 7

Group Size and Composition 7

Changes in Group Composition 7

Mortality Factors 7

Periodicity of Births 8

Solitary Monkeys 8

Intragroup Social Structure 8

Intergroup Relations 12

Interspecific Relations 13

Polyspecific Associations 14

Discussion 16

Food Habits of Blue Monkeys 18

Methods and Definitions 18

Results 19

Plant Diet of Group I during an Annual Cycle 19

Selection Ratios 19

Important Components of Total Diet during an Annual Cycle 20

Food Plants Used by Blue Monkeys during the Entire Study Period. . 20

Patterns of Use of Food Resources: Intermonthly Variations 21

Patterns of Use of Food Resources: Intermonthly Similarities 22

Factors Affecting the Patterns of Use of Food Resources 24

Intramonthly Variations in Diet 27

Diet Overlap 29

Diet Diversity 29

Invertebrate Component of the Diet of Blue Monkeys 31

Monthly Importance of Plant Species and Microhabitats in Providing

Invertebrate Food Items 31

Feeding Motor Patterns Employed in the Capture and Ingestion of

Probable Invertebrate Food Items 32

Investigative Activities Related to the Ingestion of Probable

Invertebrate Food 32

Fruits as a Source of Invertebrate Food 34

Water Requirements of the Blue Monkeys 35

Vertebrate Food Eaten by Blue Monkeys 35
IV SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

Page

Intraspecific Food Niche Separation 35

Intergroup Dietary Differences 36

Discussion 40

Blue Monkey Feeding Patterns and Adaptive Significance of Diet ... 40

Intraspecific Food Niche Separation 42

Food Niche Separation between Sympatric Cercopithecines 42

Intergroup Dietary Differences 43

Interpopulational Comparisons of Blue Monkey Diet 44

The Ranging Patterns of Blue Monkeys 45

Methods 45

Results 45

Home Range Size 45

Areas Used during Different Sample Periods 46

Range Overlap between Sample Periods 48

Daily Range 51

Range Overlap between Days of the Same Sample Period 52

Distribution of Time in Space 53

Differential Use of Quadrats and Food Abundance 59

Group Spread 64

Group Movements 64

Effect of Climatic Factors on Group Movements 65

Areas and Trees Used for Night Resting 69

Quadrat Utilization Diversity 72

Intergroup Home Range Overlap 73

Discussion 74

Home Range Size 74

Factors Affecting Ranging Patterns 75

Comparison with Other Studies 77

Summary and Conclusions 77

Appendix 79

Table A.—Group I, percent of frequency of use of specific food items . . 79

Table B.—List of food plants exploited by the blue monkeys 80

Table C.—Group I, rank order (I-V) and percent of frequency of use of

top five food plants 81

Table D.—Percent of frequency of ingestion of probable invertebrates

from specific microhabitats (I-XI) 82

Table E.—Cercopithecus mitis, Groups I and II, frequency of use of

different motor patterns 83

Table F.—Group I, percent of use of specific plant food items 84

Table G.—Group II, percent of use of specific plant food items 85

Literature Cited 86
Socioecology of the Blue Monkeys

(Cercopithecus mitis stuhlmanni)

of the Kibale Forest, Uganda

Rasanayagam Rudran

Introduction

PURPOSE OF THE STUDY.—Although monkey species living in rain forests vastly outnumber those

dwelling in the savannah, the paucity of information on these species proves to be the most serious

shortcoming in clarifying the relation between the

ecology and social organization of primates. In fact

early theories on the socioecology of primates (De

Vore, 1963; Crook and Gartlan, 1966) are considered untenable mainly because they are based primarily on field studies of savannah-dwelling forms.

Sometimes even more recent hypotheses (Struhsaker,

1969; Crook, 1970; Eisenberg et al., 1972) are found

to be deficient in explaining the social organization

of forest-dwelling primates. These problems not

only highlight the dearth of information available

from rain-forest monkeys, but also serve to show

the importance of studying them in order to fully

understand the relation between the ecology and

social organization of primates. Therefore, I conducted a field study of an African rain-forest primate, the blue monkey {Cercopithecus mitis stuhlmanni) of the Kibale Forest, western Uganda.

Prior to and during my study of the blue

monkeys, T. T. Struhsaker, J. F. Oates, and P. M.

Waser completed field investigations of other primates that lived in the Kibale Forest. We used

similar methods in our studies so that detailed and

Rasanayagam Rudran, National Zoological Park, Smithsonian

Institution, Washington, D.C. 2000S.

meaningful interspecific comparisons could be

made in order to elucidate niche separation between closely related sympatric species. Such comparisons were one of the prime objectives of our

investigations in the Kibale Forest. The comparison

between the red colobus {Colobus badius tephrosceles) and the black and white colobus (Colobus

guereza) has already been made (Struhsaker and

Oates, 1975), while the comparisons of blue monkeys

with red-tailed monkeys {Cercopithecus ascanius

schmidtii) and mangabeys (Cercocebus albigena

johnstonii), respectively, are in progress.

Although I collected data on many aspects of the

ecology and behavior of blue monkeys, in the following sections I mainly evaluate the premise that

space utilization patterns resulting from the peculiarities of food dispersion affected the social organization of primates (Eisenberg et al., 1972). Therefore, after a brief description of the study area, I

describe the social structure of the blue monkeys.

Following this I report their diet and their ranging

patterns and examine the relationship between

these aspects of the life-style of the blue monkeys.

DESCRIPTION OF THE BLUE MONKEY.—The blue

monkey is also called the diademed monkey (Dorst

and Dandelot, 1970) because it has a prominent row

of forward pointing white fur just above its brow line

(Figure 1). The upper parts of its body and tail are

frosty gray in color while its limbs are somewhat

darker in appearance. It has whitish whiskers that

are particularly well developed in adult males. The
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

FIGURE 1.—A blue monkey (Cercopithecus mitis stuhlmanni).
NUMBER 249

throat and underparts of the body are gray white.

Some young animals have indistinct russet-colored

rump patches, which I have not seen in adults. The

naked parts of the body, such as face, hands, and

feet, are black in individuals that are above two

or three weeks of age. In infants below this age,

these areas are pink. Adult males of this species

weigh over 6 kg (Kingdon, 1971) and an infant

male that I "collected" weighed 360 gm a few

hours after its birth.

The blue monkey is an extremely arboreal animal that rarely descends to the ground. This distribution of this monkey is patchy and restricted to

certain parts of Zaire, Uganda, and Rwanda. Related subspecies, however, are to be found in central and east Africa, in Mozambique, and parts of

South Africa (Dorst and Dandelot, 1970; Rahm,

1970).

DESCRIPTION OF THE STUDY AREA.—The Kibale

Forest study area (0° 34' N; 30° 21' E) is situated

close to the Kanyawara Forestry Station, which is

about 25 km east of the Ruwenzori mountains. It

is located on undulating terrain at an elevation of

approximately 1500 m and is about 3 km2 in extent. The study site is bounded by grassland on its

eastern and western sides while it is continuous

with more forest on the other two sides. Within this

area there are over 40 km of foot trails that facilitated monkey observations but in no way altered

the character of the habitat. Due to selective felling

conducted in 1969 for the removal of certain commercially valuable species, however, about a third

of the study site (referred to as Compartment 14)

remains somewhat disturbed. The rest of the study

site (Compartment 30) consists of undisturbed

mature forest.

In this area the climate is cool and temperatures

are relatively moderate. The mean minimum and

maximum temperatures are 12.7° and 25.5 °C

(Struhsaker, 1975). The mean annual rainfall of

1475 mm is relatively well dispersed throughout the

year but some months of the year are wetter than

others (Kingston, 1967). Typically, March and

April and September through November are considered wet months.

Within the study area the forest is tall, and some

emergents such as Parinari excelsa and Aningeria

altissima reach heights of over 45 m. The tree

canopy layer that usually lies between 10 and 30 m

above ground level is dense, and more or less continuous except in the selectively felled area. The

vegetation is both complex and heterogeneous. On

the undulating terrain of the study area relatively

small trees (e.g., Chaetachme aristata, Dombeya

mukole, and Diospyros abyssinica) predominate

the well-drained upper slopes, while large species

(e.g., Parinari excelsa and Mimusops bagshawei)

are found most often on the lower slopes. In the

water-logged valley bottom, trees, such as Smyphonia

globulifera and Neoboutonia macrocalyx, and semiwoody vegetation are most common. Thus, many

of the tree species within the study area exhibit a

clumped distribution (Oates, 1974; Struhsaker,

1975). The shrub vegetation is thick, particularly

in the swampy areas and in Compartment 14, where

selective felling had created some large openings

in the tree canopy layer.

The phenological activity of this forest is extremely complex. In general, species differ considerably in the pattern and timing of their phytophasic activity. For example, Balanites wilsoniana

produce young leaves only once each year during

a short period between January and March, while

Celtis durandii and Celtis africana flush throughout

the year with peaks of flush production occurring

in April-May and October-November in both

species (Oates, 1974). Olea welwitschii also produces flush throughout the year, but does not have

a peak period of flush production. Similarly, different tree species also show variability in their reproductive activity. The patterns of flowering activity of B. wilsoniana, C. durandii, and C. africana

are the same as their leafing activity, but O. welwitschii produces blossoms on a biannual basis.

Pancovia turbinata and Teclea nobilis are seasonal

in their fruiting activity, but they produce fruits

at different times of the year; in February-March

and July-November, respectively (Figure 2). In

contrast, C. durandii, C. africana, and Ficus exasperata produce fruits almost throughout the year.

On the other hand, Parinari excelsa produces fruits

with superannual periodicity. This species produced

fruits in 1973 after a lapse of nearly three years

(Struhsaker, pers. coram.). Furthermore, considerable interindividual variations in phenological activity may be noted within many species.

Due to the complex patterns of phenological activity all phytophases are available during many

months of the year but are more abundant during

certain times than during others. For instance,
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

Patterns of Fruiting Activity

4-1

3-

2-

.5

4 -i

x

C9

XJ

c

— 3

< 2

1

F. exasperata

\

y

/

\

\

C-africana P. excelsa

btk

J F M A M J

'73

S O N D J F

'74

Month

J F M A M J

'73

J A S O N DJ F M A

'74

FIGURE 2.—The mean and the range of monthly availability of fruits on selected blue monkey

food plants illustrating variations in their patterns of phenological activity. The availability

index (AI) is a subjective assessment of the abundance of fruits (based on a 0-4 scale) on trees

included in the phenological sample. Data for T. nobilis, C. durandii, C. africana, and P. excelsa

from Struhsaker (pers. comm.).
NUMBER 249

peaks of leaf and flower production occur about

one month after rainfall that follows a dry period

(Oates, 1974; see also Struhsaker, in press). Therefore, blue monkey foods can be highly variable in

their temporal as well as spatial abundance.

The faunal complement of the Kibale Forest

Study Area is quite diverse. Two hundred and

seventy-six bird species are to be found within and

around the Kibale Forest (Friedmann and Williams,

1970, quoted in Struhsaker, 1975). Mammals that

are commonly found in this area are the bush buck

(Tragelaphus scriptus), Harvey's red duiker (Ceplialophus harveyi), the blue duiker (C. monticola),

the bush pig (Potamochoerus porcus), and the

African civet (Viverra civetta). Less common are

the elephant (Loxodonta africana), the buffalo

(Syncerus cafer), the ratel (Mellivora capensis), the

crested porcupine (Hystrix sp.), the flying squirrel

(Anomalurus sp.), the serval cat (Felis serval), and

several viverrid species. Other parts of the same

forest contain the lion (Panthera led), the leopard

(Panthera pardus), the golden cat (Felis axirata),

the giant forest hog (Hylochocrus meinertzhageni),

the warthog (Phacochoerus aethipicns), and hippopotamus (Hippopotamus amphibius).

By far the most conspicuous members of the

mammalian fauna of the Kibale Forest study area

are the primates. These include the black and white

colobus (Colobus guereza occidentalis), the red colobus (Colobus badius tephoroscles), the blue monkey

(Cercopithecus mitis stuhlmanni), the red-tailed

monkey (C. ascanius schmidtii), the lhoest's monkey

(C. I. Ihoesti), the mangabey (Cercocebus albigena

johnstoni), and the chimpanzee (Pan t. troglodytes).

Sometimes, the olive baboon (Papio anubis) may

be seen within the study area. Other primate species found here are the small nocturnal forms, such

as the potto (Perodicticus potto), the dwarf galago

(Galago demidovi), and a larger galago believed to

be G. inustus.

GENERAL FIELD PROCEDURES.—My study of the

blue monkeys of the Kibale Forest began in December 1972 and ended in November 1974. During

the first two months of my investigations, I conducted a pilot study in order to (1) become familiar

with the fauna and flora of the area and (2) standardize my methods of data collection with those

used in the investigations of other primate species

found in the Kibale Forest. From February 1973,

I began intensive data collection from two groups

of blue monkeys (i.e., Group I and Group II). I

collected these data on a monthly basis during five

consecutive days of dawn to dusk observations of

each group. During some months each of these

groups was observed for two 5-day periods (in the

following text I refer to each 5-day period as a

sample period). Thus, Group I, which was investigated for 16 months, was contacted during 23 sample periods, and Group II, which was observed during 18 months, was contacted during 20 sample

periods (Table 1). Three other groups were also

periodically contacted during the study.

I have given the details of the methods of collection of socioecological data in the appropriate sections. In general, however, methods of data collection were by and large predicated by the generally

poor visibility conditions within the forest. Because

of this it was usually not possible to keep all or

even one member of a group under continuous

surveillance for more than a few minutes. This

precluded the possibility of conducting longitudinal

sampling of the group. Therefore, much of the data

were collected either in a systematic manner by

sampling group activities during predetermined

10-minute periods of observations or on an opportunistic basis. The 10-minute periods of systematic

observations (referred to as scan periods) were centered at the hour, at the half hour, at a quarter to,

and a quarter past the hour.

ACKNOWLEDGMENTS.—I acknowledge the financial

support given me by the New York Zoological

Society, the National Institutes of Mental Health

of the United States (Grant No. 1 RO1 MH23008-

01 awarded to Dr. Thomas T. Struhsaker), and

the Smithsonian Institution. I also thank the

President's Office of Uganda and the Uganda Forestry Department for permission to conduct my

research in Uganda and in the Kibale Forest. The

National Research Council of Uganda is thanked

for acting as my local sponsor during my stay in

Uganda.

Several people helped me in many ways during

various stages of my research on the blue monkeys.

I am most grateful to all of them. As in the past,

Dr. John F. Eisenberg, my adviser, inspired and

encouraged me through all stages of my project.

Through him I met Dr. Thomas T. Struhsaker,

who gave me the opportunity to conduct field research in Uganda and shared with me the fruits

of his field experiences. To these two people I
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

TABLE 1.—Monthly schedule of fielchvork in Kanyawara in sample periods of usually

five consecutive days of observations

Month

and year

Jan 73

Feb 73

Mar 73

Apr 73

May 73

Jun 73

J u l 73

Aug 73

Sep 73

Oct 73

Nov 73

Dec 73

Jan 7k

Feb 7k

Mar 74

Apr 7k

May 7k

Jun 7k

J u l 7k

Aug 7k

Sep 7k

Oct 7k

Total

Schedule

Number

of days

13

19

? 1

21

19

2 1

1 7

? 1

lU

13

2 2

18

13

1U

1 1

2 1

1 1

7

1

9

18

2 0

3kk

Number

of hours

lilt

169

215

206

190

? 0 3

153

193

133

129

?06

162

1 2 3

125

65

128

55

38

16

83

120

128

2971*

Contact

Number

o f

sample

periods

_

1

2

2

p

2

p

p

1

1

2

1

1

1

1

1

1

-

-

-

-

-

23

with Group I

Hours

during

sample

periods

_

U6.25

95.25

9U.00

91.75

97.50

117.50

U5.25

51-25

5^.75

llU.50

60.50

56.00

56.50

20.75

25.50

18.00

-

-

-

-

-

1118.25

Hours

during

other

times

21.00

-

2.00

2.00

-

1.00

2.00

2.50

2.50

-

5.00

1.50

1.25

0.50

_

13.75

-

-

-

-

-

-

55.00

Contact

Number

o f

sample

periods

_

1

1

1

1

1

-

1

1

1

1

1

1

1

1

1

_

1

-

1

2

2

20

with Group II

Hours

during

sample

periods

.

1+3-75

50.50

1+6.50

U7.75

1+8.25

-

39-75

59.25

55.00

Ug.75

59.75

51.50

1*3.00

36.75

52.50

I

1

*. 75

-

50.00

82.75

53.00

881*. 25

Hours

during

other

times

12.50

1.00

1.50

2.00

1.50

6.75

0.75

6.00

2.50

2.00

2.00

1.50

-

0.75

-

-

2.00

-

9.25

12.50

1.25

67.75

Contact

(hours)

with other

groups

36.50

30.75

3.75

-

-

-

-

-

-

-

-

5.50

-

-

-

1U.75

19.25

-

6.00

-

l*.00

33.50

151+.00

owe an immense debt of gratitude for helping me

mold my professional career.

The members of my committee, Drs. Ed Buchler,

John Eisenberg, Douglas Gill, Douglass Morse,

Eugene Morton, and Jane Potter, and my colleagues Drs. Wolfgang Dittus, John Oates, John

Seidensticker, Tom Struhsaker, and Peter Waser

read part or all of several drafts of the manuscript.

Their coments, which vastly improved the quality of this dissertation, are gratefully acknowledged.

The Nairobi Museum and Mr. A. B. Katende

of the Makerere University Herbarium are thanked

for identification of plant specimens. Dr. Charles

Roberts of the Smithsonian Institution is thanked

for helping me with statistical analyses. Mrs.

Wyotta Holden typed the final draft of this paper.

I am extremely grateful to her for this and for her

competence and kindness. Thanks are also due to

Mr. Chris Triolo, who helped in the final preparation of the manuscript.

I also wish to thank Mr. and Mrs. Bruno Illi,

Dr. and Mrs. Lance Tickell, and Dr. Peter White

for their warm hospitality, which made visits to

Kampala extremely pleasant, and the people of

Kanyawara, who made my East African sojourn

a memorable one. Lastly, but by no means the

least, I wish to note my appreciation to my wife,

Ranji, and to Bobby. I am indebted to Ranji, who

endured the hardships of a bush life for two years,

for her patience, understanding, and secretarial

help and to Bobby for his companionship.

In Appendix Table B, Metcalfe and Chalk

(1950), Eggeling and Dale (1951), Lawrence (1951),

Struhsaker (1975), A. B. Katende of the Department of Botany, Makerere University, and S. P.

Kibuwa of the East African Herbarium, Nairobi,

were consulted for the identification and nomenclature of the listed food plants.

Aspects of the Social Organization and Dynamics

of Blue Monkey Groups

METHODS

I used interindividual distances between group

members as a way of illustrating the social structure of blue monkeys. These distances were obtained by successively considering each group member who was visible during a scan period as a focal

animal and noting its neighbors. Neighbors were
NUMBER 249

operationally defined as animals within 10 m of

the focal animal, with whom their spatial relationship remained unaltered for at least five seconds. Intraspecific and interspecific social interactions were recorded throughout the day.

Polyspecific associations formed by blue monkey

groups were defined using the following criteria.

I considered a blue monkey group to be in association with another primate species if during a

scan period (1) a single blue monkey was 5 m or

less away from an individual of another species,

or (2) when three individuals of different species

(including at least one blue monkey) were no more

than 10 m from each other, or (3) when four or

more individuals of different species (including at

least one blue monkey) were no more than 20 m

of each other.

The first criterion can be used only to define

two-species associations, while the other two criteria can be used to define associations involving

two or more species.

RESULTS

GROUP SIZE AND COMPOSITION.—Table 2 presents

the size and composition of five blue monkey

groups on the first day complete counts were obtained from them. Since immature individuals were

extremely difficult to sex, I have distinguished

them only on the basis of age classes. Four of the

groups contained a single adult male each, while

the fifth group included two adult males. Thus

the "one-male group" was the most predominant

social structure of these blue monkey groups. The

sizes of these groups, however, were highly variable (range 13-27; X = 20.8), because each group

contained between 4 and 12 adult females and 7

to 16 immature animals.

The mean ratio of adult males to adult females

in these bisexual groups (i.e., the socionomic sex

ratio) was 1 :6.8. The large disparity in adult sex

ratio was at least partly caused by emigration of

young males from bisexual groups and also by the

slower rate of maturity of males. Due to the difficulty in sexing immature animals, I was unable to

ascertain whether an unequal sex ratio at birth

contributed to the disparity in adult sex ratio but

there was no evidence to suggest that differential

mortality among the sexes could have caused this

situation.

CHANGES IN GROUP COMPOSITION.—Changes in

the composition of blue monkey groups were usually minor and were caused by (1) births, (2)

recruitment of young animals into older age classes

and, (3) the "disappearance" of individuals, which

in most cases may have been due to deaths. One

of my study groups (i.e., Group II) also underwent

an important social change when an adult male

joined this group and took its leadership from the

resident adult male (Rudran, in prep.). The details

of the changes in composition of the two groups

that I studied most intensively (Groups I and II)

are given in Table 3.

MORTALITY FACTORS.—The reason for the disappearance of the two adult females from Group

I (Table 3) was unknown. In Group II, RLT's

infant died after being abandoned by its mother

when she was attacked by other group members.

Intragroup aggression may also have been the

cause of the disappearance of Bulb (and her infant), who was frequently harassed by other group

members just before she disappeared. Adult female

M may have succumbed to the wounds she had

TABLE 2.—Composition of five bisexual groups on the first day that

complete group counts were obtained

Group

I

II

Ill

IV

V

Total

Percent..

Date

Adult Adult Submales females adults Juveniles Infants Total

h Feb 73

25 Jan 73

22 Jan 73

19 Apr 73

25 Dec 73

1

1

1

1

2

6

5.8

11

5

12

U

9

Ul

39.8

3

2

3

1

U

13

12.6

30

29.1

1*

1

3

1

U

13

12.6

2k

13

27

13

27

101+
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

TABLE 3.—Changes in group composition in Groups I and II (AM = adult male,

AF = adult female, SA = subadult, J = juvenile, I = infant)

Group

and date

GROUP I

Feb 73

.Tun 73

Nov 73

Feb 7h....

GROUP II

Jan 73

Jun 73

Sep 73

Jan 7k

Jan 7k

Feb 7k

Feb Ik

Aug 7k

Sep 7k,...

AM

1

1

1

1

1

1

1

1

1

1

1

1

2

Age/sex

AF

11

9

9

9

5

k

k

k

3

3

3

3

3

SA

3

3

3

3

2

2

2

2

2

2

2

2

2

class

J

5

9

10

11

1+

5

1+

U

U

U

k

5

5

I

U

2

1

1*

1

-

-

2

1

2

1

-

-

Total

P.k

2k

2k

28

13

12

11

13

11

12

11

11

12

Comments

Recruitment of k infants into juvenile age

class; birth of 2 infants; loss of ? adult

females

Recruitment of 1 infant into juvenile age

class

Recruitment of 1 infant into juvenile age

class; birth of k infants; composition

unchanged in May 7k

Loss of adult female M; recruitment of M's

infant into juvenile age class

Loss of M's offspring (a small juvenile)

Birth of 2 infants (to females LLT and Bulb)

Loss of Bulb and her infant

Birth of infant (to RLT)

Loss of RLT's infant

Recruitment of LLT's infant into juvenile

age class

Addition of 1 adult male; composition

unchanged in October 7**

just prior to her disappearance. She may have sustained these wounds either during intragroup or

intergroup aggressive encounters. Female M's offspring disappeared due to unknown causes. During

the study, I did not find any evidence to suggest

that disease or predation was an important mortality factor. Aerial predation of young blue monkeys by large raptors may have been an infrequent

cause of mortality. Occasionally, I saw crowned

hawkeagles (Staphaeonatus coronatus) attempt to

catch these monkeys.

PERIODICITY OF BIRTHS.—Just prior to the beginning of and during the study, 14 infants were born

into Groups I and II. Their estimated birth dates

showed that in two successive years there were a

total of six births in December, four births in

January, two births in February, one birth in

March, and another in May. This shows that blue

monkey births occurred seasonally, and the above

data suggests that there was either a long birth

season between December and May or two shorter

seasons separated by the month of April. None of

the identifiable adult females carried infants during successive December-May periods, which indicates that interbirth interval was longer than one

year.

SOLITARY MONKEYS.—Solitary blue monkeys were

infrequently seen, which may have been partly because they were less conspicuous than social groups.

Throughout the entire study, I saw no more than

eight solitary animals. Six of these were adult

males and two were unsexed subadults. Adult

females or juveniles were not seen as solitary individuals. Solitary animals seemed to be transients

and did not appear to stay for more than three

weeks in any particular area. They were usually

evicted from the home ranges of bisexual groups

by the adult males of these groups.

Just before my study began an easily identifiable

subadult male that disappeared from Group III

was located as a lone individual within the home

range of Group I (M. S. and P. Waser, pers.

comm.). This suggests that males nearing adulthood emigrate from their parental groups and live

as solitary animals. The social change that took

place in Group II tends to show that these males

may reenter bisexual groups as adults.

INTRAGROUP SOCIAL STRUCTURE.—Intragroup social

structure may be elucidated by considering spatial

relationships within the group. The social structure

of blue monkey groups was relatively stable but,

in order to illustrate variations in spatial relation-
NUMBER 249

ships due to changes in group composition, I have

considered data collected from Group I during

April 1973 as well as October 1973.

In April 1973, the proportion of sightings of

adult females with neighbors was nearly twice as

large as in October 1973 (Table 4). This was beTABLE 4.—Group I, percent of sightings of different age/sex

classes with neighbors within 10 m, April 1973 and October

1973

Age/sex class

Adult male

Adult female

Subadult

Large juvenile...

Snail juvenile...

Infant

Percent

Group Frequency of sightings

composition of sightings with neighbors

Apr 73 Oct 73 Apr 73 Oct 73 Apr 73 Oct 73

1*8

l*oU

156

109

152

133

177

160

112

31

27. 1

59.2

27.6

30.1*

55.U

100.0

27.0

30.7

33-1*

36.2

7>*.1

96.8

cause Group I contained a greater number of

young infants in April 1973 than in October 1973

and these infants were always neighbors to their

mothers. Also, in October 1973, small juveniles

spent proportionately greater amounts of time with

neighbors than in April 1973, which was probably

related to the age difference between individuals

that belonged to the small juvenile class during

these two months. The small juveniles of October 1973 were between 6-10 months of age (born

during the 1972-1973 birth season), while the small

juveniles of April 1973 were 11 months or older

(probably born during the 1971-1972 birth season).

Therefore, it appeared that as infants matured

they progressively spent less time in the company

of neighbors. Large juveniles and older age classes

(except adult females with infants) spent a greater

proportion of time without neighbors than with

them, but these proportions were relatively constant between the two months. Thus, it would

seem that spatial relationships were affected by

births of infants and their early development.

Other factors, such as the estrous condition of females, may also have affected the social structure,

but in the field I was unable to assess the sexual

state of blue monkey females.

For any pair combination of age/sex class, a set

of two interindividual distances were obtained because an animal was considered as a focal animal

as well as a neighbor to other focal animals. Due

to changes in the spatial relationships between animals, these two distances were not necessarily the

same but they did not differ greatly. For example,

the mean interindividual distance between the

adult male and adult females was 2.0 m when the

adult male was considered as the focal animal, and

2.2 m when the adult females were considered as

focal animals. Thus, I obtained the mean of these

two distances in order to simplify the presentation

of results (Table 5). I have also combined the data

TABLE 5.—Group I, mean interindividual distances

(m) between different age/sex classes computed from

data collected in April 1973 and October 1973

(N = 1329 observations; small juveniles and adult

males were not recorded as neighbors within 10 m

of each other)

Age/sex class

Adult female....

Subadult

Large juvenile..

Small juvenile..

Infant

AM AF

2.1

2.6

SA

3.6

2.U

1.6

LJ

U.6

2.3

1.9

1.6

SJ

1.3

1.5

1.5

1.0

I

2.5

0.5

1.8

2.6

l.U

1.2

from April 1973 and October 1973 since interindividual distances did not vary appreciably between these two months.

Spatial relationships between different age/sex

classes show the following:

1. The adult male was in closer proximity to

adult females than to other age classes.

2. Adult females were nearest to infants, and

adult female to adult male distance was shorter

than adult female to adult female distance.

3. Subadults were in closest proximity to each

other or to small juveniles and farthest away from

the adult male. The spatial relations of large

juveniles were similar to those of subadults.

4. Small juveniles were closest to each other, and

of all age/sex classes were farthest from the adult

male.

5. Infants were closest to their mothers and they

were closer to each other than would be predicted

by distances between adult females. This suggests

that adult females with infants were in closer proximity to each other than to adult females who did

not carry infants.

Intragroup social structure can be further clarified by considering the frequencies with which
10

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

each age/sex class was nearest neighbor to other

classes. As indicated earlier, for each pair combination of age/sex class, a set of two nearest neighbor

values was obtained since each animal was considered as a focal animal as well as a neighbor

(Table 6). Observed frequencies of nearest neighbors were compared to frequencies expected from

a random model, which were computed in the following manner. Since the mean group count for

April 1973 and October 1973 was 24 each, a focal

animal could have 23 pair combinations of nearest

neighbors. Therefore, all 24 animals (each considered as a focal animal) could have (23 X 24) 552

pair combinations of nearest neighbors and the

probability of observing any particular pair combination was 1/552 (= 0.0018). Considering the

adult male and adult females, the probability of

the adult male having one of the 10 adult females

as nearest neighbor was 10/552 (= 0.018). Therefore, of 983 nearest neighbor records, the frequency

of adult females as nearest neighbors to adult male

would be 17.8 (0.18 X 938). The frequency of the

adult male as nearest neighbor to adult females

would also be the same. Similarly, the frequency

of 10 focal adult females having one of the other

nine adult females as nearest neighbors in 983

records would be (1/552 X 9 X 10 X 983) 160.3.

The frequencies with which different age/sex

classes had nearest neighbors differed significantly

from expected (x- = 59.95, df = 5, p< 0.005).

Large juveniles and older age classes had less than

the expected number of nearest neighbors while

small juveniles and infants had greater than the

expected number of nearest neighbors (Table 6).

Indices of association between different age/sex

classes can be obtained by computing the ratio of

observed frequency of nearest neighbors to the expected frequency (Table 7). The magnitude of

this ratio indicates the degree of association between age/sex classes and a ratio of one shows that

the association was as expected from the random

model. The indices of association between age/sex

classes substantiate the points made earlier using

interindividual distances. They also show that associations between two age/sex classes were not

always equally strong in both directions. For example, the indices of association between the adult

male and adult females were 0.8 and 1.2 depending on which sex class was considered as focal

(Table 7). This was because while the adult male

had adult females as his nearest neighbors, the

adult females sometimes had other age/sex classes

as their nearest neighbors (Table 6).

In order to understand the effect of the strong

association between adult females and infants on

the social structure of the group, adult females

TABLE 6.—Group I, observed and expected frequencies of nearest neighbors

of each age/sex class (mean number of animals in each age/sex class is given

within parentheses; focal animals in left vertical column, nearest neighbors

in top horizontal row)

Age/sex class AM(1) AF(1O) SA(3) LJ(3.5) SJ(U) 1(2.5) Total

Adult male

observed

expected

Adult female

observed

expected

Subadult

observed

expected

Large juvenile

observed

expected

Small juvenile

observed

expected

Infant

observed

expected

Total

observed

expected

ll*.O

17.8

k.O

3-0

6.2

o

7.1

1.0

i*.5

22.0

1*1.0

22.0

17.8

80.0

160.3

33.0

33-0

62.3

86.0

71.2

11*2.0

W*.5

396.0

5-0

5.1*

31.0

22.0

10.6

15.0

18.7

17.0

21.1*

1.0

13.1*

91.0

122.9

1.0

6.2

21.0

62.3

13.0

18.7

26.0

15.6

17.0

2l*.9

2.0

15.6

80.0

11*3-3

0

7.1

79.0

71.2

23.0

21.1*

23.0

6i+.o

21.1+

5.0

17.8

19>+.O

163.8

1*.O

156.0

1+1+.5

9.0

13.U

5.0

15.6

ll+.O

17.8

12.0

6.7

200.0

102.5

32.0

1*1.0

381.0

1+09.5

10l*.0

122.9

105.0

11*3.3

198.0

163.8

I63.O

102.5

983.0

983.0
NUMBER 249 11

with infants and those without infants were considered separately. The mean interindividual distances and indices of association of these two adult

female classes with other age classes indicate the

following:

1. Adult females without infants were in closer

proximity to the adult male than adult females

with infants (Table 8).

2. The closest association among adult females

was between those that had infants, and associations within each adult female class were greater

than associations between them (Table 9).

TABLE 7.—Group I, indices of association between age/sex

classes computed on the basis of observed and expected frequencies of nearest neighbors (focal animals in left vertical

column, nearest neighbors in top horizontal row)

Age/sex class

Adult- mftlfl

Adult female

Subadult

Large juvenile..

Small juvenile..

Infant

AM

0

0.8

0.7

0.5

0

0.2

AF

1.2

0.5

0.6

0.5

1.2

3.2

SA

0.9

0.6

2.1

0.8

0.8

0.1

LJ

0.2

0.3

0.7

1.7

0.7

0.1

SJ

0

1.1

1.1

0.9

3.0

0.3

I

0.9

3.5

0.7

0.3

0.8

1.8

Total

0.78

0.93

O.85

0.73

1.20

1.60

TABLE 8.—Group I, mean distances between adult females

(with and without infants) and other age classes

Age/sex class

Adult- feTWlp , ,. . ,

Adult female

plus Infant

AM

1.9

2.9

AF

2.6

3-1

AF+I

3.1*

1.7

SA

2.U

2.1*

LJ

2.3

2.7

SJ

1 ,k

1.5

3. Adult females without infants associated more

closely with subadults and juveniles than adult

females with infants.

4. Adult females without infants most closely

associated with small juveniles, while the closest

association of adult females with infants was with

other females with infants.

From the above it can be seen that, within the

group, adult females with infants formed subgroups, and, unlike the other adult females, they

had less than the expected number of nearest

neighbors tf = 4.36, df = 1, p<0.05).

An understanding of intragroup social structure

may also be gained by considering the directionality and frequencies of aggressive encounters. In

Group I, I observed only 99 aggressive interactions

in over 1100 hours of group contact (Table 10),

which may have been partly because my observations were hampered by poor visibility within the

forest. The observed and expected frequencies (computed in the same manner as before) of aggressive interactions show that the adult male and subadults

were the only animals that aggressed more frequently than expected. Also these two classes and

large juveniles were aggressees more often than

expected. The adult male who had the highest

overall index of aggression (Table 11) aggressed

far more frequently than expected against subadults and large juveniles. These age classes also

aggressed against the adult male more frequently

than expected. Moreover, the indices of aggression

within and between subadult and large juvenile

TABLE 9.—Group I, observed and expected frequencies of

nearest neighbors of adult females (with and without infants)

and the indices of association with other age/sex classes (focal

animals in left vertical column, nearest neighbors in top

horizontal row)

Age'sex class

Adult female

observed.•••

expected....

Adult female

plus Infant

observed....

expected....

Total

observed .

expected....

Adult female

Adult female

plus Infant

15.0 7U.0

11.1 72.1

33.0 21.0 86.0 2U3.O

33-3 38.8 W*.3 227.2

6.0

3.7

l.U

1.6

lU.o

27.7

88.0

99.8

9-0

5.5

23.0

33.2

7.0

U.I

5.0 19.0

12.9 1U.8

UO.O 26.0 105.0

1*4.1* 51.7 59.1

Indices of association

1.0 0.5 1.0 0.5 1.9

0.5 1.6 0.6 0.U 1.3

60.0

75.7

303.0

303.0

1.1

0.8

TABLE 10.—Group I, observed and expected frequencies of

aggressive interactions between different age/sex classes (mean

number of individuals within each age/sex class in parentheses; aggressee in top horizontal row)

Aggressor

Adult aale

observed

expected

Adult f eml i

observed

expected

Subadult

observed

expected

Large juvenile

observed

expected

Snail juvenile

observed

expected

Infant

observed

expected

Total

observed

expected

AM(1)

0

0

3.0

1.8

3 . 0

0.5

2.0

0.6

0

0.7

0

o.u

8.0

U.o

AF(10)

2.0

1.8

1.3

16.1

13.0

5.U

1.0

6.3

1.0

7.2

0

U.5

30.0

H.3

SA(3)

6.0

0.5

13.0

5.U

U.O

1.1

2.0

1-9

0

2.2

0

1.3

25.0

12.U

LJ(3.5)

9.0

0.6

5.0

6.3

10.0

1.9

5.0

1.6

0

2.5

0

1.6

29.0

1U.5

SJ(U)

1.0

0

2

7

3

2

7

0

2

0

2

0

2.5

0

2.2

0

1.8

6.0

16.6

1(2.5)

0

o.u

1.0

U.5

0

1.3

0

1.6

0

1.8

0

0.7

1.0

10.3

Total

18.0

U.O

37.0

U..3

33-0

12.U

10.0

1U.5

1.0

16.6

0

10.3

99.0

99.0
12 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

TABLE 11.—Indices of aggression between age/sex classes (mean number of

individuals in each age/sex class in parentheses; aggressee in top horizontal

row)

Aggressor

Adult male

Adult female....

Subadult

Large juvenile..

Small juvenile..

Infant

Total

AM(1)

1.6

6.0

3-3

0

0

2.0

AF(1O)

1.1

0.8

2.U

0.2

0.1

0

0.7

SA(3)

12.0

2.U

3-6

l.l

0

0

2.0

LJ(3.5)

15.0

0.8

5.3

3.1

0

0

2.0

SJ(«O

X.h

0.3

i.k

0

0

0

o.u

1(2.5)

0

0.2

0

0

0

0

0.1

Total

•* 5

0.9

2.7

0.7

0.1

0

age classes were high. Unfortunately, the sex of

immature individuals was not known, but the data

indicate that aggression, particularly by the adult

male, may have been the cause of the emigration

or eviction of young males from bisexual groups.

The contexts of nearly 60% of the aggressive

encounters were known and in these encounters

61% were conflicts over food (Table 12). About

67% of the interactions at feeding sites were considered to be high intensity aggressive encounters.

High intensity aggression included prolonged

chases and physical contact, such as biting, while

low intensity aggression was those interactions

without body contact. High intensity aggressive

interactions were greater in a feeding context than

in other contexts, which suggests that group members fought most frequently and most violently

over food.

INTERGROUP RELATIONS.—Aggressive interactions

between groups were infrequent and I observed

only 13 of these interactions during my entire

study. This was probably due to the fact that blue

monkey groups lived in home ranges that did not

overlap greatly with those of their neighbors. Intergroup interactions normally took the form of prolonged chases and counter chases accompanied by

threat vocalizations. Although I did not observe

TABLE 12.—Group I, contexts and frequencies of low

and high intensity aggressive encounters (March 1973

to February 1974, all sample periods)

Context

Feeding

Sitting, play,

grooming, etc.. .

Uncertain

Total

Low High

intensity intensity

aggression aggression Total

12

13

lU

39

10

26

60

36

23

Uo

99

physical contact between animals, I suspected that

the high incidence of injuries in Group II during

April 1974 was due to the unusually high frequency of intergroup conflicts (four in five days

of observations) that this group was involved in

during this period. Adults of both sexes as well as

subadults and juveniles took part in intergroup

interactions, and each group seemed to have priority of access to different parts of the areas of

range overlaps. For example, the area of overlap

between the home range of Groups II and III lay

to north and south of a track that ran through the

study area. Group II always evicted Group III

from areas to the north of this track, while Group

III displaced Group II every time these two groups

interacted in areas to the south of this track. Thus,

blue monkey groups appeared to hold territories

although they sometimes ranged outside these

areas. Seven of 10 encounters between Groups II

and III were at fruiting Ficus trees, which were

important food sources of these monkeys. This suggests that (as in the case of intragroup conflicts)

food was the major cause of intergroup conflicts.

Blue monkey groups reacted to loud calls such

as the "Ka" train and "Pyow" (terminology from

Marler, 1973) of their neighbors. The "Ka" train

was an alarm vocalization most frequently given

by the adult male, but I also heard other group

members emitting this call. Analysis of 531 hours

of observation of Groups I and II showed that these

groups responded immediately to 6 of 10 extragroup "Ka" train sequences. Their responses were

either "Ka" trains or chirps, which were also alarm

vocalizations. During the same time period 7 of

14 extra-group "Pyows" also evoked calls in Groups

I and II. The immediate responses to extra-group

"Pyows" were usually chirps and sometimes phrased
NUMBER 249 13

grunts (that were intragroup contact calls) or trills

(that usually served a submissive function), but

never calls in kind. In fact, of a total of 141

"Pyows" emitted by the adult males of Groups I

and II (during 531 hours of group contact), none

were immediately followed or preceded by similar

calls from neighboring groups. Thus, there was no

evidence for counter calling between adult males,

although Aldrich-Blake (1970a) found this to be

the case in the blue monkeys of the Budongo forest.

INTERSPECIFIC RELATIONS.—Blue monkeys interacted with all five resident monkey species, but

seemed to avoid chimpanzees, which have been

reported to prey on blue monkeys (Sugiyama, 1968;

Teleki, 1973). On one occasion, a group of blue

monkeys chirped and hastily evacuated a fruitladen Ficus tree as soon as a solitary and transient

adult male baboon (Papio anubis) climbed into it.

Throughout the study I observed a total of 201

interspecific encounters, of which nearly 88% were

aggressive encounters. In comparing the frequency

of interactions between blue monkeys and other

species, the density of these species within the study

area was taken into account. These comparisons

showed that blue monkeys interacted more frequently than expected with redtails (Cercopithecus

ascanius) and mangabeys (Cercocebus albigena) and

less frequently than expected with the red colobus

(Colobus badius), black and white colobus (Colobus

guereza), and Cercopithecus Ihoesti (Table 13). It

may be noted that mangabeys and redtails were

arboreal and had much in common in terms of diet

with blue monkeys while the two colobines were

folivorous and C. Ihoesti was a predominantly terrestrial species.

In about 92% of the aggressive interactions with

the smaller redtails, blue monkeys were aggressors.

Sometimes these aggressive encounters were bidirectional with redtails retaliating to harassment by

blue monkeys. Normally, aggressive interactions

between these two species were bipartite, but blue

monkeys sometimes formed temporary coalitions of

two or three animals against redtails. Blue monkeys

were also more frequently the aggressors than aggressees against the larger mangabeys and black

and white colobus, but, against the larger red colobus, they were more frequently the aggressees (Table

13). In aggressive encounters against these species,

blue monkeys normally formed coalitions of up to

four animals and against mangabeys the adult male

blue monkey was frequently involved in these

coalitions. In general, however, subadults and large

juveniles aggressed much more frequently than expected against other species (Table 14).

The contexts of 67 aggressive encounters were

known and 79% of these were conflicts over food.

About 80% of the conflicts over food were with redtails, whose diet had the greatest similarity to that

of blue monkeys (Struhsaker and Rudran, in prep.).

Interspecific affiliative encounters included play

and grooming. Participants of play were always

young animals and the duration of play was less

than 15 minutes. Grooming also usually involved

young animals and was unidirectional. On one occasion, however, a solitary adult male blue monkey

was groomed by a subadult red colobus. Adult female blue monkeys ignored interspecific solicitation for grooming on four occasions.

In addition to the above types of encounters, the

primates of the Kibale Forest interacted with each

TABLE 13.—Groups I and II, total frequency of interspecific aggressive and affiliative interactions

during all 5-day periods of observation (expected frequencies of interactions between blue monkeys and other species were computed on the basis of species densities from Struhsaker, 1975, and

Oates, 1974)

Interactions with—

C. ascanius

C. badius

C. guereza

C. Ihoesti

Total

Percent of

aggressive interactions

With Mitis as

aggressor

121

2

lU

5

With other species

as aggressor

10

16

5

U

Percent of

affiliative interactions

Play

9

6

2

17

Solicit

Grooming grooming

1* 3

2*"

1

3 h

Total interactions

Observed

Ihk

26

21

9

1

201

Expected

'1-9

1U8.0

U.I

15.1

1.9

201.0

C. mitis was groomer

C. mitis were groomees
14 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

TABLE 14.—Observed and expected frequencies of each age/sex class of blue

monkeys as aggressor against other species (data from Groups I and II combined)

Age/sex class

Adult male

Adult female

Subadult

Large juvenile..

Small juvenile..

Total

Observed

7

29

50

38

3

127

Expected

7.U

50.7

18.3

28.2

22. k

127.0

other through calls given during alarm situations.

Of 32 blue monkey "Ka" trains recorded during

531 hours of observation of Groups I and II, 22

(i.e., 69%) were either immediately followed or

preceded by the calls of one or several of the other

primate species. Blue monkeys also frequently reacted to the alarm calls of other mammals, such as

the sun squirrel (Heliosciurus rufobrachium), the

red duiker (Cephalophus harveyi), and the bushbuck (Tragelaphus scriptus), and to the calls of

birds like the great blue touraco (Corythaeola

cristata) and the hornbill (Bycanistes subcylindricus). These calls usually evoked loud chirps from

blue monkeys and sometimes also "Pyows" from

the adult male. Distant calls of aerial predators,

such as the crowned hawk eagle (Staphaeonatus

coronatus), were accompanied by geckers and chirps.

When these predators flew overhead, blue monkeys

emitted the "Ka" train and frequently sought cover

in the shrub vegetation. Perhaps the most remarkable interspecific vocal interaction was that between

adult male blue monkeys and adult male redtails.

About 50% of the "Pyow" sequence given by the

adult males of Groups I and II (N = 141 sequences)

evoked hack calls from adult male redtails. The

hack calls of redtails, however, were never followed

by "Pyow" sequences of blue monkeys.

POLYSPECIFIC ASSOCIATIONS.—An interesting aspect of the interspecific relations of blue monkeys

was their involvement in mixed groupings consisting of two or more primate species. Blue monkey associations with the black and white colobus,

the mangabey, and C. Ihoesti were usually transitory in nature but their associations with redtails

and red colobus sometimes lasted for six to seven

hours of a day.

Blue monkeys simultaneously associated with a

maximum of three other species, but these types

of associations were extremely infrequent. Most frequently blue monkeys associated with one other

species. Of a total of 815 associations recorded

during 20 sample periods of observations of Group

I about 85% were associations with one other species. About 64% of the two-species associations and

68% of all associations included the redtails. The

frequencies with which different monkey species

associated with blue monkeys did not appear to be

solely related to their population density (Table

15). Redtails and mangabeys associated with blue

monkeys proportionately more frequently than the

two colobines and C. Ihoesti. Considering this and

diets of blue monkeys, redtails and mangabeys, it

would appear that polyspecific associations were

biologically significant rather than random groupings.

Group I formed polyspecific associations during

all sample periods they were observed and spent an

average of 19% of the scan periods in mixed groupings (Table 16). Most consistently blue monkeys

were associated in either two- or three-species associations with redtails and red colobus; however,

the frequency with which Group I associated with

other species varied between sample periods. In

order to assess the significance of these variations,

Spearman rank correlation values (rs) were computed considering the percentage frequencies of associations during sample periods and various

aspects of blue monkey time budget, diet, and ranging patterns (Table 17). Since blue monkeys associated with mangabeys, black and white colobus,

and C. Ihoesti rather infrequently, these associations were not considered separately in these tests.

The above tests showed that there were significant

negative correlations between the percentage of time

Group I apportioned to feeding on plant material

during sample periods, and the percentage frequency with which they formed (1) polyspecific

associations with all species, (2) three-species associations including redtails and red colobus, and

(3) two-species associations with red colobus. On

the other hand, the percentage of time blue monkeys spent in searching and feeding on probable

invertebrate foods was positively and significantly

correlated with the percentage frequency with

which they formed two-species associations with
NUMBER 249 15

TABLE 15.—Group I, frequency of different types of polyspecific associations

recorded between February 1973 and February 1974, inclusive

Associations with—

Redtail

Red Colobus

Mangabey

Black-and-white Colobus

L'hoest's monkey

Total

Polyspecific associations Total

2-species 3-species U-species Observed Expected

445

229

18

3

2

110

108

6

5

3

557

337

2k

9

6

933

157.1

716.6

22.0

25.3

12.0

933.0

TABLE 16.—Group I, percent of frequency of polyspecific associations

during different sample periods

Sample

Feb 74

Mar 74

Mar 74

Apr 74

Apr 74

May 74

May 74

Jun 74

Jun 74

Jul 74

Jul 74

Aug 74

Aug 74

Sep 74

Oct 74

Nov 74

Nov 74

Dec 74

Jan 74

Feb 74

Mean

period

(I)....

(I)....

(ID...

(I)....

(ID...

(I)....

(ID...

(I)....

(ID...

(I)....

(II)...

(I)....

(ID...

(I)....

(I)....

(I)....

(ID...

(I)....

(I)....

(I)....

2-species associations

With C.

ascanius

2.1

8.9

11.1

22.2

8.2

22.6

16.3

9.5

5.7

14.0

7.0

9.9

16.7

13.4

11.2

6.2

10.1

3-1

10.6

10.4

With C.

badius

2.1

0.5

7.1

6.5

7.0

7.1

3.6

9.0

5.6

3-3

3.4

5.2

5.4

7.6

9.4

5.4

6.6

5.3

4.4

2.5

5.4

With

other species

0.9

(C. albigena)

-

0.5

(C. guereza)

_

-

0.6

(0. albigena)

0.4

(C. guereza)

0.4

(C. lhoesti)

-

-

0.5

(C. lhoesti)

0.5

(C. guereza)

1.3

(C. albigena)

0.9

(C. albigena)

2.0

(C. albigena)

-

1.3

(C. albigena)

-

0.5

3-species associations

With

C. ascanius

and

C. badius

_

5.4

3.2

4.1

l.l

6.7

6.4

2.2

-

1.7

1.3

0.8

5.2

2.2

2.2

1.2

3.6

-

1.3

2.4

With

C. ascanius

and one

other species

0.6

(C. guereza)

(C. albigena)

1.1

(C. lhoesti)

-

0.6

(C. guereza)

-

_

-

-

0.5

(C. albigena)

0.5

(C. albigena)

-

-

0.4

(C. albigena)

-

-

0.2

C.

With

badius

and one

other species

(C.

(c

(c.

(c.

(c.

(c.

_

-

-

0.5

guereza)

0.5

lhoesti)

-

-

-

0.4

guereza)

-

-

0.5

albigena)

-

0.5

guereza)

0.5

albigena)

-

-

-

-

0.1

Number of

scans with

association

8

1

36

49

59

33

65*

74

34

25*»

46

31

39

66

60

46

39

48

20

34

813+2

Total

number

of scans

recorded

187

223

168

216

171

184

195

233

179

245

235

229

242

210

224

224

244

247

229

236

4321

Percent of

scans with

association;

4.2

0.5

21.4

22.7

34.5

17.9

33-3

31.8

19.0

10.2

19.6

13.5

16.1

31.4

26.8

20.5

16.0

19.4

8.7

14.4

19.0

•One four-species association (i.e .

**0ne four-species association (i.e .

recorded.

0.4$ frequency) between blues, redtails,

0.4$ frequency) between blues, redtails,

red colobus, and C. lhoesti was recorded,

red colobus, and black and white colobus was

the extremely folivorous red colobus monkey. There

were also significant positive correlations between

the mean distance moved by Group I during a sample period and the percentage frequency of all four

types of associations considered in these tests (Table

17).
16 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

TABLE 17.—The rs values of Spearman rank correlation tests between percent of frequency of

polyspecific associations during different sample periods and aspects of time budget, diet, and

ranging patterns of Group I

Correlation with--

r

s values

for polyspecific association with--

Degrees -•

 ascaniu s

 £• Radius

o f only only

freedom 2-species association 3-species association

C. ascanius

and C. badius All

species

Percent of time plant feeding.

Percent of time invertebrate

feeding

Percent of time moving

Percent of time resting

Percent of fruits in diet

Percent of foliar food

Percent of invertebrates

Food diversity

Ranging diversity

(Mar 73-Jun 73)

Ranging diversity

(Jul 73-Feb 7h)

Mean distance moved

17

17

17

17

18

18

18

18

-0.253

0.126

0.1*19

-0.337

-0.091

0.2M+

0.3I+0

-0.01+1

-0.298

0.1+72

0.571*

-0.1*56

0.1*57*

0.1*38

-0.1+OU

0.091

0.01+1+

0.1*01

-0.079

0.673

0.389

0.791*

-0.565*

0.288

0.212

-O.I69

0.190

-0.013

0.1*09

-0.270

0.070

0.277

0.529*

-0.U8U

0.325

0.1*33

-O.368

0.101

0.050

0.1+35

-0.229

-0.02U

0.527,

0.672

•Indicates r s values significant at the 0.05 level

**Indicates r values significant at the 0.01 level

DISCUSSION

Blue monkeys of the Kibale Forest normally lived

in one-male social groupings and thus exhibited

the typical social structure of many rain forest

cercopithecines (Struhsaker, 1969). One-male groups

of blue monkeys were also the most common in the

Budongo Forest, although some two-male groups

were to be found (Aldrich-Blake, 1970a). In the

Budongo Forest, however, group sizes were somewhat smaller and less variable than in the Kibale

Forest. Two of my study groups that contained the

smallest number of animals (Groups II and IV) occupied home ranges in the selectively felled area,

while the other three lived in the undisturbed part

of the study area. Felling operations, which undoubtedly led to a decrease in blue monkey foods,

may have caused the apparent reduction in size of

the groups living in selectively felled areas. Thus,

the normal variation in blue monkey group sizes

may have been exaggerated within the Kibale study

area.

The emigration of young males from their parental groups provides a means by which the integrity of the one-male gioup structure could be

maintained in this species. Peripheralization of

young males was probably caused by the high frequency of adult male aggression directed against

subadults and large juveniles (Table 11). This

mechanism, however, does not prevent the possibility of inbreeding inherent in a one-male social

structure. The social change that occurred in

Group II through the addition of an adult male

(Table 3) suggests a means by which outbreeding

may be enhanced in these social groupings. Shortly

after an extra-group adult male took over the leadership of the Group II, all adult females of this

group became sexually receptive and copulated

only with the new leader (Rudran, in prep.). This

type of social change was in some ways similar to

those seen in the Asiatic langurs (Sugiyama, 1965;

Mohnot, 1971; Rudran, 1973; Hrdy, 1975).

The low frequency with which several age classes

were seen with neighbors (Table 4) may be partially

attributable to the poor conditions of visibility

within the forest, but it was also due to relatively

large intragroup dispersion. The median value of

the spread of Group I was 50 m, while the maximum was about 120 m. Dispersion over large areas

was probably necessary for the efficient exploitation

of the largely frugivorous diet of blue monkeys

(see Eisenberg et al., 1972). Nevertheless, blue

monkeys of the Kibale Forest lived in cohesive

social groupings. In this respect these social groupings may have differed greatly from those of the

Budongo Forest, which apparently broke up into

"parties" (Aldrich-Blake, 1970a). The term "party"
NUMBER 249 17

as defined by Aldrich-Blake was an aggregation of

animals of uncertain social status; for example, a

party might be a small portion of a group or two

groups combined. My own observations of the

Budongo Forest blue monkeys, however, indicated

that the social structure of both populations was

quite similar. Interinvestigator variability in the

ability to maintain group contact was probably one

factor that was responsible for our different views

on the social structure of blue monkeys. Even in

the absence of these biases, however, the social

organizations of different primate populations have

been found to be variable (Rowell, 1969; Gartlan

and Brain, 1968).

During relaxed movements phrased grunts emitted by juveniles and older age classes (except the

adult male) probably served to maintain group

cohesion (Marler, 1973; Rudran, unpubl.). When

the group was widely dispersed the loud "Pyow"

call (given only by the adult male) also probably

served the same function. "Pyows" of different

males were quite distinctive and therefore revealed

the location as well as the identity of the caller.

Furthermore, nearly 65% of "Ka" trains and other

alarm calls discussed in this paper were followed

by "Pyows." This suggests that the "Pyow" functions as a rally call that restores group cohesion

after a period of disruption. Struhsaker (1970) and

Gautier (1969) stress the rallying function of the

loud calls of west African cerecopithecines closely

related to the blue monkey, but Aldrich-Blake

(1970a) suggests that the "Pyow" of the blue

monkey serves in intergroup spacing.

In a relatively dense and compact population,

such as the one studied by Aldrich-Blake, "Pyow"

counter calls may function in intergroup spacing,

but at the same time they can serve to rally widely

dispersed members of neighboring groups in order

to maintain each group's integrity. On the other

hand, in the Kibale Forest where the population

was less dense and groups occupied home ranges

that were nearly 7 to 14 times larger than in the

Budongo Forest the lack of counter calling suggests

that the "Pyow" was ineffective in its possible intergroup spacing function. Using sonographic analyses

of blue monkey vocalizations, Waser and Waser (in

press) argue that the characteristics of the "boom"

call of the adult male makes it a mure effective

intergroup spacing call than the "Pyow."

Intragroup, intergroup, and interspecific aggressive interactions of the blue monkeys frequently

took place in a feeding context. Some important

plant foods of blue monkeys were also important in

the diet of one or more sympatric primate species

(see Struhsaker, 1975; Waser, 1975); however, interspecific conflicts for plant foods appeared to be reduced by avoiding polyspecific associations when

these foods were being eaten (Table 17). Intragroup

conflicts for food were probably minimized by different age/sex classes concentrating on different

aspects of the dietary spectrum of the species, and

intergroup conflicts for food may have been largely

averted through territoriality.

While avoidance of polyspecific associations

seemed beneficial in acquiring plant foods, the formation of these associations with red colobus appeared to enhance the acquisition of invertebrates

by blue monkeys. The exact nature of how this

may occur was unclear, but two explanations may

be offered. While moving in large mixed groupings

with the red colobus, a larger number of invertebrates may have been flushed (due to the greater

disturbance to invertebrate microhabitats) than

when moving in smaller monospecific groups. This

may happen in other types of mixed groupings as

well, but in these associations blue monkeys may

have had to share invertebrate foods with other

species (such as redtails and mangabeys) in whose

diets these foods were important (Struhsaker, 1975;

Waser, 1975). Thus, in associations with red colobus, blue monkeys may have accrued the same advantages that some birds were suggested to derive

from mixed flocks (Neave, 1910). The increased

exploitation of invertebrates by blue monkeys when

in the company of red colobus may have been due

to the reduction in the dangers of predator attacks

in these associations (see below). The red colobus

rarely indulged in invertebrate feeding (which was

an intent activity) and were, therefore, probably

more alert to the dangers of predators than blue

monkeys. As such, blue monkeys may have been

most efficient in acquiring invertebrates when in

the company of the red colobus (see also Willis,

1972). Thus, as in the case of mixed-species bird

flocks studied by Morse (1970), blue monkey-red

colobus associations may have served a multipurpose function (i.e., predator avoidance and invertebrate food acquisition).
18 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

Other types of associations of the blue monkeys

did not appear to enhance significantly their exploitation of invertebrate food. Among birds, Moynihan (1962) pointed out that the functions of

different flocks could be quite variable; however,

the fact that member species of all types of associations responded to each other's alarm calls strongly

suggests that predator avoidance was an important

function of these mixed groupings. Gartlan and

Struhsaker (1972) suggest that avoidance of predapators was one of the functions of the associations

of cercopithecines in the Cameroon.

The direct relation between blue monkey movements and frequency of associations suggests another advantage that blue monkeys may have derived from polyspecific associations, particularly

with redtails with whom they shared many dietary

similarities (Struhsaker and Rudran, in prep.). The

home ranges of blue monkeys were relatively large

and encompassed several home ranges of redtails.

Unlike blue monkeys, the redtails moved through

almost their entire range within a few days (Struhsaker, pers. coram.). Therefore, they were probably

more attuned to local abundances of food than

were blue monkeys. Thus, by moving with the

redtails, blue monkeys probably used the redtails

as "information centers" (Ward and Zahavi, 1973;

Krebs, 1974) to efficiently locate areas of food abundance. Once food resources were located, however,

interspecific conflict was probably avoided by temporal separation of feeding activities. For example,

the redtails usually began feeding earlier in the

morning and continued this activity until later in

the evening than blue monkeys (Struhsaker, pers.

comm.). It has been suggested that associations of

other primate species also function in food location and efficient exploitation of the environment

(Gartlan and Struhsaker, 1972; Gautier-Hion and

Gautier, 1975).

Food Habits of Blue Monkeys

METHODS AND DEFINITIONS

During the 5-day periods of contact with each

group, I used a systematic method of scoring feeding observations. These observations were operationally distinguished by using the following

criteria. Thirty minutes must elapse before an individual monkey M1 scored for feeding on a particular

food item lt from a particular food plant species

S! was scored again for the same specific food item.

During this 30-minute period, however, other feeding scores may be obtained if (1) individual Ma

utilized any other food item L, to Ix from the same

plant species S1( or (2) individual Mx utilized any

food item It to lx from food plants S2 to Sx, or (3)

another individual M2 utilized food items Ij to Ix

from food plants Si to Sx.

A change in the plant species, food item, or feeding individual would lead to a score but 30 minutes

must elapse before the same combination was

scored again.

I also recorded the frequency of exploitation of

probable invertebrate food using the same criteria.

Observations of invertebrate feeding were scored taking into account the 30-minute interval criterion, the

tree species, and the substrate from which the item

was taken, and the motor pattern employed in the

capture and ingestion of the food item. In most

cases, I was unable to distinguish these food items,

which were small, but the type of motor patterns

employed in exploitation of these food items and

the substrate (such as moss-covered branches) from

which they were taken did suggest that these were

invertebrate food items. Due to my inability to

distinguish the type of invertebrate foods used, I

restricted the dietary analyses that required species

distinction to plant foods. Invertebrate foods were

included only in the analyses of nonspecific food

items.

I analyzed all feeding data collected from Group

I (during 23 sample periods) and from Group II

(during 20 sample periods), but in order to avoid

unnecessary duplication of results, I have reviewed

only the diet of Group I in detail. The feeding

data for Group II are presented mainly by way of

intergroup comparison and to illustrate intragroup

food niche separation.

I computed intergroup overlaps in diet between

comparable sample periods on the basis of the percentage of use of specific food items exploited by

both groups (Holmes and Pitelka, 1968). The sum

of the shared percentages of mutually exploited specific food items yielded the total overlap in diet. In

other words, if during a sample period, the diet of

Group I consisted of 40% of a specific food item,

30% of another, 20% of a third, and 10% of a fourth,

and the extents of exploitation of the same specific
NUMBER 249 19

food items by Group II during the most comparable sample period were 20%, 20%, 30%, and

30% respectively, the total overlap in diet would

be 70%. Using this method, I also computed the

intermonthly overlaps in the diet of Group I. Indices of monthly diet diversity were calculated

using the Shannon-Wiener diversity equation H' =

- 2 Pi loge pj (Pielou, 1966) where FT was the measure of diversity and pt

 was the proportion of the

frequency of use of the ith specific food item.

In the initial analyses of the diet of Group I,

I have considered only one (the first) sample period

of each month through an annual cycle from February 1973 to January 1974. This was done in order

to overcome the biases introduced by unequal

number of days of monthly observations and by

the seasonal use of certain food plants. In the later

analyses, I have considered feeding data through

all sample periods.

RESULTS

Blue monkeys exploited a relatively wide variety

of plant species and food items. In addition, they

actively searched and preyed upon invertebrates

that constituted an appreciable proportion of their

diet.

PLANT DIET OF GROUP I DURING AN ANNUAL

CYCLE.—During the sample periods considered for

the annual cycle, 2068 feeding observations were

scored from the use of 59 plant species and 101

specific food items (Appendix Table A). Fifty-five

of these food plants were identified. Three of the

four unidentified species were mushrooms and the

other was a liana. Although Group I exploited a

wide variety of food plants, they concentrated their

feeding activity on a small number of food plants.

About 66% of the feeding observations were recorded from the top 10 food plants and nearly 87%

were from the top 20 food plants. Diospyros abyssinica was the most frequently used food plant with

a 10.7% frequency of use. This species occupied

top rank because Group I used it for as many as

three important food items (i.e., its young leaves,

fruits, and blossoms), while it usually exploited

other food plants intensively for single food items.

Thus, when specific food items were considered, the

fruits of Celtis africana were the most important

in the diet of Group I while the food items of D.

abyssinica occupied 7th, 9th, and 12th rank orders

(Table 18). The top 10 rank orders of specific food

items constituted 55.3% and the top 20 made up

75.2% of their diet. When the use of plant fovJ

items regardless of species was considered, fruits

were the most important food items and constituted 52.6% of the total plant diet used by Group

I (Appendix Table A).

TABLE 18.—Group I, rank order and percent of frequency of

use of top 20 specific food items exploited during first 5-day

periods of observations from February 1973 to January 1974,

inclusive

Rank order of specific food item

1. Celtis africana, fruits

2. Pancovia turbinata, fruits

3. Teclea nobilis, fruits

Uvariopsis congensis, fruits

h. Prenna anftolensis, blossoms

5- Celtis durandii, fruits

6. Diospyros abyssinica, young leaves

7. Ficus exasperata, fruits

8. Diospyros abyssinica, fruits

9. Mimisops bagshawei, fruits

10. Funtunia latifolia , seeds

11. Diospyros abyssinica, blossoms

12. Mnrfchnmin piatycniyir, petioles

13. Parinari excelsa, fruits

1U. Vangueria apiculata, nature leaves

15. Illigera pentaphylla, mature leaves

16. Monodora nyristica, leaf buds

Neoboutonia macrocalyx, mature leaves..

17. Teclea nobilis, mature leaves

Dombeya mukole, young leaves

Frequency

of use

170

169

135

135

UO

105

95

93

68

63

57

55

50

1*1*

39

37

33

33

32

32

Percent of

frequency

of use

8.22

8.17

6.53

6.53

5.32

5.07

J+.59

l*.l*9

3.29

3.05

2.76

2.65

2.1*2

2.13

1.89

1.79

1.60

1.60

1.55

1.55

SELECTION RATIOS.—The variable frequencies of

use of food plants suggest that blue monkeys were

selective feeders. The use of food plants, however,

may have been affected by differences in their densities and also possibly their canopy sizes (i.e., their

potential food-producing areas). Thus, the frequency of use of a food plant was divided by the

product of its density and canopy size (called the

cover index*) in order to obtain a standardized

measure of its use. This ratio, termed the selection

ratio, was computed for certain food plants used

by Group I (Table 19). Estimates of canopy sizes

(except those of U. congensis and P. turbinata) and

• Since tree canopies assume irregular shapes, the size of a

canopy cannot be easily measured in terms of its volume or

surface area. Therefore, Struhsaker (1975) obtained an index

of mean canopy size of a species by summing the mean depth

and the mean spread of several individuals. He has also

shown that the sum of these parameters was significantly correlated to their product (rg — 0.98; p <0.01), which may be

considered a better measure of canopy size.
20 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

TABLE 19.—Selection ratios of some food plants exploited by Group I during first

sample periods of months from February 1973 to January 1974, inclusive

Species

D. abyssinica..

C. africana..

P. turbinata.

T. nobilis...

U. congensis.

C. durandii..

M. bagshawei.

M. platycalyx

B. phoberos..

F. latifolia.

P. excelsa...

A. altissima.

Percent of

frequency

of use

10.7

9.0

8.1*

8.2

6.7

5.2

3.8

3 . 1

3.0

2.8

2.2

1.1

Density

/ h a

65.7

2 . 1

6.3

21.0

25.2

22.8

2 . 1

5.8

2.8

11+.7

10.5

0.7

Canopy

size

19.3

26. h

19.1

19-1

19.1

3U.3

31.7

19.2

18.6

13.9

Ul.3

29.7

Cover

index

1268.0

55. k

120.3

Uoi.i

U81.3

782.0

66.6

1113.6

52.1

2A.3

1*33.6

20.8

Selection

ratio X 100

0.9

16.3

7.0

2 . 1

l.U

0.7

5.7

0.3

5.7

l.U

0.5

5.3

Visibility

class

I II

I I *

IV

IV

IV

I *

II

II

II

I II

I

I I *

•Average of visibility in the least foliated and completely foliated stages

species densities were obtained from Struhsaker

(1975). Canopy sizes of U. congensis and P. turbinata were assumed to be similar to that of T.

nobilis (whose canopy size was estimated in the

field) to which they bear a close physiognomic resemblance.

Selection ratios indicate that the frequency of

use of food plants was affected by their density and

canopy size. For example, the use of D. abyssinica

(which was the most frequently exploited food

plant) was apparently due to its very high density

of occurrence. In terms of selection ratios, eight

species listed in Table 19 were more preferred than

D. abyssinica. C. africana was the most preferred

food plant and M. bagshawei, B. phoberos, and A.

altissima were more preferred than indicated by

their frequency of use.

The frequency of use of food plants may also

have been affected by how visible monkeys were to

the observer when they were within the canopies

of different species, although a half-hour interval

between feeding observations was used to minimize the effect of this variable. Since selection

ratios were computed without taking this possible

source of bias into account, comparisons are most

meaningful between species whose canopies afford

similar visibility. Struhsaker (1975) classified visibility conditions within the canopies of different

species on a I (excellent) to IV (poor) scale (Table

19). Some semideciduous species (e.g., C. africana,

C. durandii, and A. altissima), which afforded a

variety of visibility conditions depending on their

physiological state, were assigned an average of the

conditions of visibility within their canopies in their

completely foliated and least foliated stages.

IMPORTANT COMPONENTS OF TOTAL DIET DURING

AN ANNUAL CYCLE.—Four hundred and ninety-eight

scores of invertebrate feeding were recorded between

February 1973 and January 1974 inclusive. Thus

during an annual cycle, invertebrate feeding constituted nearly 20% of the total of 2566 feeding observations on plant and invertebrate matter (Table

20). The frequency of use of invertebrates was

second only to the use of fruits, which constituted

42.7% of the total feeding observations; however,

the sum of the frequencies of use of foliar food (i.e.,

leaf buds, young leaves, mature leaves, dry leaves,

and petioles) was greater than the frequency of use

of invertebrates.

The importance of foliar food was also indicated

by the fact that Group I used 9 food plants among

the top 20 (namely P. angolensis, M. platycalyx, D.

mukole, M. myristica, V. apiculata, N. macrocalyx,

Clausena anistata, I. pentnphylla, and M. dura) solely

for foliar food or more frequently for these than for

fruits (see Appendix Table A). Moreover, as indicated in Figure 7, foliar foods occupied top rank for

three successive months (from March 1974 to May

1974), when they comprised 41% to 64% of the

monthly feeding scores. This suggests that foliar

foods were periodically important food resources,

perhaps when fruits were scarce. Floral items were

also periodically important and occupied top rank

in July 1973 and February 1974.

FOOD PLANTS USED BY BLUE MONKEYS DURING THE

ENTIRE STUDY PERIOD.—During the sample periods

that were not included in the annual cycle, a total

of 1841 feeding observations were recorded from

Group I. Of these observations 1752 were distributed among the 59 species used during the sample
NUMBER 249 21

periods considered for the annual cycle, and 89

were scored from use of 18 other species (Table 21).

Thus the total number of food plants exploited

by Group I was 77 (70 identified and 7 unidentified). The food plant list of blue monkeys increased

further when the diet of Group II was considered.

During the 20 sample periods of observations of

this group, 3127 feeding scores were recorded from

the use of 60 plant species. Forty-four (41 identified

and 3 unidentified) of these were used by Group I

also, and 16 were used exclusively by Group II

(Table 22). The total number of food plants used

by both groups was therefore 93 (Appendix Table

B). Species acquisition curves (Figure 3) for the

two groups suggest that in both groups some infrequently used food plants may have been discovered

with further observations.

PATTERNS OF USE OF FOOD RESOURCES: INTERMONTHLY VARIATIONS.—Intermonthly variations in

the diet o£ Group I are indicated by the high

coefficients of variation computed for the top 10

food plants (Table 23). Diospyros abyssinica, which

was the top-ranking food plant of Group I, had

the lowest coefficient of variation, indicating that

it was the least variable in its monthly use, while

P. turbinata had the greatest coefficient of variation

and was the most variable in its monthly use. The

relatively large range of monthly frequency of use

of these food plants also indicates appreciable

intermonthly variations in diet.

Intermonthly variations in the diet of Group I

can also be shown by comparing the monthly rank

orders and frequencies of use of food plants and

specific food items. Usually there were striking

changes in the frequency of use of food plants (and

specific food items), with almost a monthly change

in the occupancy of top rank (Appendix Table C).

In March 1973, Group I used P. turbinata at a very

TABLE 20.—Group I, mean percent of frequency of use of plant and invertebrate

food items during first 5-day periods of observations from February 1973 to

January 1974, inclusive (N = 2566 observations)

Food item

Leaf buds

Young leaves

Mature leaves

Dry leaves

Petioles

Stems

Flower buds

Mean Mean

percent of percent of

frequency frequency

of use Food item of use

2.79 Blossoms 10. Uh

9.U5 Fruits U2.70

6.77 Seeds 2.1*3

0.11 Nectar 0.7U

1.91 Galls 0.58

0.26 Unidentified plant items.. 0.68

1.31 Invertebrates 19.83

TABLE 21.—Group I, frequency of use of specific food items exploited only outside the

first 5-day periods of observations from February 1973 to January 1974, inclusive

Species

Ficus dawei*

Tarenna pavettoides*

Apodytes dimidiata*

Pleiocarpa pycnantha*

Scniqpia rhnmniphylla*

Acalypha bipatita*

Carapa grandiflora*

Cassipourea ruvensorensis*..

Cissus oliveriana*

Doyyalis macrocalyx*

Euclinia longiflara»

Glyphaea lateriflora

Pyrenacantha sp.*

Ritchia albersii

Unidentified species (3)

Total

Leaf Young Mature Unidenti- Total

buds leaves leaves Petioles Blossoms Fruits fied items frequency

k6 U6

10 - - 10

6 2 - - - - 8

2 2

2 ---- - 2

1 1 - 2

1 1

1 .. . 1

1 1

1 1

1 1

1-- - - - . 1

1 ---- - x

1 1

1 1

1 - - 6 1 8

89

•Food plants not used by Group II
22 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

TABLE 22.—Frequency of use of specific food items exploited only by Group II

between February 1973 and October 1974, inclusive

Species

Angraecum distichum

Brachystephanus africanus

Basella alba

Brin«ntasia nitens

Chlorodendrum schweinfurthii..

Cahthium sp

Drypetes battiscooibei

Ficus stipulifera

Ficus congensis

Fagara mildbraedii

Lepisanthes senegalensis

M1niilnps1s solmsH

Paulinia pinnata

Strychnos mitis

Tabernaemontana usariberensis..

Tabernaemontana odoratissima..

Total

Leaf Young Mature Flower Total

buds leaves leaves buds Blossoms Fruits frequency

2 - - - 2

1 - - - 1

1 - 1

1 - 1

2 - - - 2

5 - - 5

2 - - - 2

18 18

1 1

1 - - - - 1

3 3

1 .. . . i 1 - - - - 1

6 3 - 9

1 - 1

11- 2

51

high frequency (85.6%), but during the next month

they did not use it at all when C. africana constituted 53.3% of their diet. In May 1973, the frequency of use of C. africana dropped to about 3.0%,

while C. gorungosanum occupied top rank with a

16.1% frequency of use; C. gorungosanum and

Clausena anistata were used only during the periods

that they occupied top rank. Thus their use not

only caused relatively large intermonthly variations

in diet, but also showed the periodic importance of

uncommon food plants.

When the rank orders of important food items

(regardless of species) were considered, intermonthly

variability in diet was less apparent than in the

case of food plants and specific food items (Table

24). This was largely due to the fact that fruits

often occupied top rank. Even when fruits were

top-ranking food items, however, the range of their

frequency of use was quite large (23.8%-75.5% in

January 1974 and March 1973, respectively). Group

I concentrated on fruits during certain months but

used several food items more equitably during other

months.

Intermonthly variations in the diet of Group I

can also be demonstrated by considering temporal

changes in the frequency of use of a selection of

food plants and specific food items. These are

illustrated in Figures 4, 5, and 6 for the food items

that Group I used from its top 10 food plants

and P. excelsa and A. altissima.

During each month, Group I usually concentrated its feeding activity on one or two specific

food items which were not used during many of

the other months. For example, the fruits of P.

turbinata, T. nobilis, and U. congensis constituted

over 40% of the feeding scores collected during

some months; but the fruits of the first two species

were used during five months and the fruits of the

third were used only for four of the 16 months

of observations (Figures 4, 5). Thus, intermonthly

differences in diet were caused by variability in the

frequency of use as well as restricted periods of use

of specific food items. This pattern of exploitation

holds true for species also except that the periods

of use were extended for some food plants that

were used for more than one food item, e.g.,

D. abyssinica and P. angolensis. The pattern of use

of food items shows that the intermonthly variations in diet were largely due to differences in their

frequency of use (Figure 7).

PATTERNS OF USE OF FOOD RESOURCES: INTERMONTHLY SIMILARITIES.—The patterns of use of food

resources also showed certain similarities in monthly

diet. For example, Group I exploited the fruits

of F. exasperata, the mature leaves of T. nobilis,

and the petioles of M. platycalyx more or less continuously throughout the study, although they used

these resources at variable frequencies (Figures 5, 6).

Hence, their use produced some similarities in the

diet during different months. Similarly, fruits, foliar

food, and invertebrates were regularly exploited

food resources of Group I (Figure 7).

Dietary similarities were sometimes produced by

seasonal use of specific food items. Since feeding
NUMBER 249 23

100-

90-

80-

u

&

I/)

i?

U.

"5

70

60

50

40

30

3

3 2O

10

(N=60 species)

GroupH

=77 species)

100 200 300 4 0 0 5 0 0 600 700 800 9 0 0 1000 1100 1200

Cumulative Hours of Observations

FIGURE 3.—Cumulative percentage increase of food plant list of

Groups I and II during study period.

TABLE 23.—Group I, mean and range (in percent) of monthly

use of top 10 food plants during first 5-day period of observations from February 1973 to May 1974, inclusive

Species

D. abyssinica...

C. africana

P. turblnata....

T. nobilis

U. congensis....

P. angolensls...

C. durandii

F. exasperata. • •

M. bagshawei....

Mean use

/month

8.95

8.66

6.6U

8.16

4.08

5.35

U.78

U.5U

5.62

2.01

Standard

deviation

10.07

13.16

21.33

14.68

10.99

7.1*3

9.07

5.85

9.38

3.63

Coefficient

of variation

112.51

151.96

321.23

179.90

269.36

138.88

189.75

128.85

166.90

180.60

Monthly

range

of use

0-29.13

0-53.33

O-85.56

0-57.89

0-1*3.51*

0-23.62

0-28.15

0-21.1*8

0-3U.00

0-13.71

data from Group I were collected for an annual

period plus four months, seasonal periodicity of

use cannot be described with much certainty but

the data do show some trends. The blossoms of

M. bagshawei and leaf buds of P. angolensis were

the only specific food items that were used with

a truly annual periodicity, being used in April and

May of 1973 and 1974 (Figure 6). If one or two

months leeway in use is assumed to be within the

normal range of variation of use of specific food

items, then a few more can be considered to be

used seasonally on an annual basis, e.g., the fruits
24

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

of P. turbinata and the fruits and blossoms of D.

abyssinica.

Some of the other specific food items showed

annual peaks of use that brought about greater

dietary similarity during these periods than others.

The major peaks of use of F. exasperata fruits occurred nearly one year apart. When data from

Groups I and II were considered, the fruits of

C. durandii also showed a similar pattern of use.

Consideration of the diets of both groups also indicated that the use of U. congensis fruits may bring

about intermonthly similarities on a biannual basis.

The use of the blossoms of A. altissima produced

dietary similarities on a triannual basis, but the

greatest similarities resulting from their use occurred on an annual basis.

Dietary similarities brought about by the patterns

of use of food plants, such as U. congensis, C.

durandii, P. excelsa, F. exasperata, and A. altissima,

remain much the same as described for food items

used from them. For some of the other species,

the patterns of use changed from those described

for each of their food items. P. angolensis showed

a less than annual periodicity of use and the use

of D. abyssinica suggests an extended period of use

from December to August (Figure 6). The exploitation of P. turbinata and M. bagshawei indicates that

they may bring about dietary similarities on a biannual basis.

Some food items (regardless of species) also

showed regular peaks of use (Figure 7). The peak

frequency of use of blossoms occurred in February

1973, May 1973, July 1973, and February 1974;

in May 1974 flower buds were used at high frequency. This suggests a triannual periodicity of

intensive use of floral items. The frequency of

use of leaf buds suggests a biannual periodicity of

intensive use in April-May and December. Thus,

certain aspects of the diet of Group I may be said

to show intermonthly similarities. Dietary similarities, however, are to be found mainly in respect to

the periods of use rather than the frequency of

use of food resources. In fact, intermonthly variations in the diet of Group I appear to be more

conspicuous than similarities.

FACTORS AFFECTING THE PATTERNS OF USE OF FOOD

RESOURCES.—The patterns of use of food resources

were intimately related to the phenological activity

of food plants. For instance, the patterns of use and

availability of P. turbinata fruits were the same.

However, the patterns of use of specific food items

do not always follow their patterns of availability

(Figures 4-6). For example, C. africana fruits were

used at a low frequency in March 1973 when their

availability had reached a peak (Figure 5). During

the same month the availability of P. turbinata

fruits had also peaked, and they were extensively

exploited (Figure 4). This suggests that the freTABLE 24.—Group I, rank order <I-V) and percent of frequency of use of top five food items

during the first 5-day period of observations from February 1973 to May 1974, inclusive

Sample

Feb 73

Mar 73

Apr 73

May 73

Jun 73

Jul 73

Aug 73

Sep 73

Oct 73

Nov 73

Dec 73

Jan 71*

Feb 7k

Mar 7U

Apr 7U

May 7k

perio d

(I)... .

(I). .

(I). .

(I). .

(I). .

(I). .

(I). .

(I). .

(I). .

(I)... .

(I)... .

(I)... .

(I)... .

(I)... -

(I)... .

(I)... .

I

Food ite m

Fruits

Fruits

Fruits

Invertebrates

Fruits

Blossoms

Fruits

Invertebrates

Fruits

Fruits

Fruits

Fruits

Blossoms

Invertebrates

Young leaves

Flower buds

Percent

57.23

75.52

66.93

28.32

1*1.67

36.72

22.03

33.70

50.00

71.50

1*2.17

23.81

27.99

30.71

30.12

23.1*8

II

Food item

Blossoms

Invertebrates

Invertebrates

Fruits

Invertebrates

Fruits

Young leaves

Young leaves

Invertebrates

Invertebrates

Invertebrates

Mature leaves

Fruits

Petioles

Mature leaves

Petioles

Percent

27.01*

18.11+

15.32

17.31+

20.83

21.31

21.15

25.00

21.51

2l*.O0

25.30

22.08

25.75

15.75

16.87

17.39

I I I

Food item

Invertebrates

Young leaves

Petioles

Blossoms,

mature leaves

Young leaves

Invertebrates

Blossoms

Fruits

Young leaves

Young leaves

Seeds

Young leaves

Mature leaves

Young leaves,

fruits

Flower buds

Young leaves

Percent

6.29

2.95

6.1*5

15.61

12.88

16.72

20.26

22.83

15.70

1.50

12.65

15.15

13.06

1I+.96

12.05

16.52

IV

Food item

Young leaves

Mature leaves

Blossoms

-

Blossoms

Mature leaves

Invertebrates

Petioles

Blossoms,

nectar

Mature leaves

Leaf buds

Seeds

Young leaves

-

Leaf buds

Invertebrates

Percent

l*.l*O

2.53

5.21+

.

8.33

12.13

18.50

U.89

3.1*9

1.00

10.21*

11.69

10.82

_

10.81*

13.oU

V

Food item

Unidentified

Blossoms,

unidentified

Young leaves

Leaf buds

Mature leaves

Young leaves

Mature leaves

Mature leaves

.

Leaf buds,

petioles,

flower buds,

unidentified

Mature leaves

Invertebrates

Invertebrates

Mature leaves

Fruits,

invertebrates

Fruits

Percent

3.11*

0.1*2

2.02

9.25

6.1*1*

9.18

13.22

3.26

0.50

3.01

9.09

10.07

lU.17

8.U3

11.30
Key-- • Fruits Other items

4-,

3-

2-

1 -

4 0 -

Fruits

J FMAMJJASOND J FM A

3 0 -

"o 20-

I 10-1

P. turbinata

M

1

 A1M

1

 J1 J1 ^ S1 °1 N1 D1 J1 ^ ^1 A1 M1

4 -.

3 -

1 - \

Fruits

J FMAMJJASOND J FM A

3 0 -

73

3 0 -

20-

10-

4

1

 n

3-

2 -

1 -

3 0 ^

N

Fruit s

J FMAMJ J ASOND J FM A

2 0 J P- excelsa

Sample Period

FIGURE 4.—Patterns of use of food plants and specific food items by Group I and

availability indices (AI) of selected specific food items.
Key: HFruits E l Blossoms ^Matur e leaves I I Petioles [HID Other items

4-1

3 -

< 2 -

1 -

40-

30-

Fruits

J FMAM J J ASOND J FM A

4

1

3-

2-

1 -

3 0 -

20-

10-

Young leaves (= Petioles)

J FMAM J J ASOND J FM A

M. platycalyx

= ^ 20-

= = 10-

Fruits

40-

30-

20-

10-

J FMAM J JASOND J FM A

T. nobilis

3-

2-

1-

30-

\

Blossoms

J FMAM J JASO N D J FM A

A. altissima

i

73

Sample Period

74

FIGURE 5.—Patterns of use of food plants and specific food items by Group I and

availability indices (AI) of selected specific food items.
NUMBER 249 27

.,Key: • Fruits Blossoms CH Young leaves Other items

30-

F, M A^M J., J, A,S.

4

.3-

< 2-

1-

30-

\

Fruits

J FMAM J J ASOND J FM A

£. exasperata

F

1

- Ml"

73

J, A, S, Q, N, D, J, F^ M, ^ M f^ ^ ^M^^ " J,1 A, S, O, N, D, J,

Sample Period

FIGURE 6.—Patterns of use of food plants and specific food items by Group I and

availability indices (AI) of selected specific food items.

quency of use of specific food items was dependent

on factors such as relative abundance and food

preference as well as their availability.

INTRAMONTHLY VARIATIONS IN DIET.—The relatively large intermonthly differences in diet suggest

that these variations may even occur over a time

span shorter than a month. Data collected during

seven months (from March 1973 to August 1973

inclusive, and November 1973) when two 5-day

periods of observations were made each month

tend to support this view. The diet during the two

5-day periods of each month was never identical

although the intervals between observation periods

were relatively short. In May and June the 5-day

periods of observations were conducted over a 10-

day period without a break in data collection. In
28

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

30-

20-

• Young Leaves

° Mature Leaves

A Petioles

+ Leaf Buds

73

80-

70-

Monthly Sample Periods

• Blossoms

° Invertebrates

* Flower Buds

+ Fruits

73

M, A, J

1

A . SL Q R D.

Monthly Sample Periods 74

FIGURE 7.—Patterns of use of food items (regardless of species) by Group I.

M1

April, July, and November there were 2-day intervals between sample periods and in March and August there were 7- and 3-day intervals respectively.

Of the seven months considered above, intramonthly differences in diet were greatest between

the two sample periods of March and M?y (Table

25). In March, only two among the top fi.e specific

food items (i.e., fruits of P. turbinata and C. africana) were used during both sample periods and

these were used at extremely variable frequencies.

In May, the leaf buds of P. angolensis were the

only specific food item among the top five that

were used during both 5-day periods. Both in

March and in May, the top-ranking specific food
NUMBER 249 29

TABLE 25.—Group I, rank order (I-V) and percent of frequency of use of top five specific food

items of both 5-day periods of observations conducted from March 1973 to August 1973 and

in November 1973

Sample

Mar 73

Mar 73

Apr 73

Apr 73

May 73

May 73

Jun 73

Jun 73

Jul 73

Jul 73

Aug 73

Aug 73

Ncrv 73

Nov 73

period

(I)

(ID.. .

(I)... .

(ID.. .

(I)... .

(ID.. .

(I) ... .

(II).. .

(1)... .

(ID.. .

(I)... .

(ID.. .

(I)... .

(ID.. .

I

Food item

F. turbinata,

fruits

£. africana,

fruits

C. africana,

fruits

C. africana,

fruits

C. gorungosanum

blossoms

F. dawe i,

fruits

U. congensis,

fruits

U. congensis,

fruits

P. angolensis,

blossoms

P. angolensis,

blossoms

D. abyssinica,

young leaves

D. abyssinica,

young leaves

T. nobilis,

fruits

T. nobilis,

fruits

'ercent

85.57

30.00

53.33

1+3.89

16.13

31*. 65

1+3-06

69. U9

23.62

26.95

23.21*

15.1+2

57.89

56.(A

II

Food item

P. excelsa,

fruits

P. turb inata,

fruits

D. abyssinica,

fruits

D. abyssinica,

fruits

P. angolensis,

leaf buds

P. angolensis,

leaf buds

D. abyssinica,

young leaves

F. exasperata,

fruits

D. abyssinica,

blossoms

D. abyssinica,

young leaves

P. angolensis,

blossoms

T. nobilis,

fruits

C. durandii,

fruits

M. bagshawei,

fruits

Percent

1+.6U

20.67

lU.76

11.11

12.90

19.69

13. Uo

9.01+

20.U7

15.65

17.83

9.35

2U.3**

8.79

I II

Food item

D. mukole,

young leaves

D. abyssinica,

fruits

P. excelsa,

fruits

M. platycalyx,

petioles

N. macrocalyx,

mature leaves

F. exasperata,

fruits

F. exasperata,

fruits

F. angolensis,

fruits

U. congensis,

fruits

D. abyssinica,

blossoms

M. bagshawei,

fruits

I. pentaphylla,

mature leaves

F. latifolia,

seeds

M. bagshawei,

fruits

C. durandii,

fruits

F. latifolia,

seeds

Percent

1.55

lit.67

8.10

7-78

6.1+5

11.81

7.66

U.52

13.38

6.52

8.65

8.76

7.89

6.59

IV

Food item

A. gummifera,

young leaves

B_. unijugata,

young leaves

T. nobilis,

mature leaves

C. africana,

fruits

C. durandii,

fruits

M. platycalyx,

petioles

P. angolensis,

leaf buds

0. welwitschii,

flower buds

D. abyssinica,

young leaves

P. angolensis,

blossoms

M. platycalyx,

petioles

D. abyssinica,

young leaves

P. microcarpa,

fruits

C. durandii,

fruits

F. angolensis,

fruits

C. africana,

fruits

I. pentaphylla,

mature leaves

Percent

1.03

10.00

7.62

7.22

U.81*

11.02

7.17

3-39

8.66

8.11

8.1*1

1.32

V

Food item

M. platycalyx,

petioles

M. bagshawei,

blossoms

0. welwitschii

flower buds

T. nobilis,

mature leaves

M. platycalyx,

petioles

T. nobilis,

mature leaves

P. angolensis,

blossoms

M. bagshawei,

fruits

F. latifolia,

seeds

M. platycalyx,

petioles

T. nobilis,

fruits

V. apiculata,

mature leaves

D. mukole,

young leaves

Percent

_

6.67

1*.29

U.W+

I+.03

7.09

U.78

2.26

6.69

1+.78

it.86

6.07

6.0U

N

19!+

150

210

180

121+

127

2 09

177

25l+

230

185

211+

152

182

items of the two sample periods of each month

were different, indicating that at least some of the

important specific food items had very short periods

of use. The fruits of F. dawei, which occupied top

rank in May II 1973, are another example of an

important resource that was exploited only during

one sample period.

DIET OVERLAP.—Intramonthly as well as intermonthly variations in diet can also be shown by

computing the total overlap in diet between the

relevant pair combinations of the 23 sample periods

recorded from Group I (Table 26). The mean overlap in diet between the 15 pair combinations of

the first sample periods of adjacent months was

26.88% and the range was from 7.14% (between

March 1973 and April 1973) to 55.88% (between

October 1973 and November 1973). The mean

overlap in diet between pair combinations of sample periods recorded during the same months was

52.83% (range 25.5%-73.8O% in March 1973 and

April 1973, respectively). Although intermonthly

variations in diet were usually greater than intramonthly variations, this analysis shows the relatively rapid temporal changes in the diet of

Group I.

DIET DIVERSITY.—Diet diversity indices, calculated using the Shannon-Wiener equation, also indicate variations in intermonthly and intramonthly

diet of Group I (Figure 8). When the first sample

periods of each month were considered, diet diversity indices range from 0.73 in March 1973 to

3.13 in May 1973. Between sample periods of the
30 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

TABLE 26.—Group I, total percent of overlap of specific food items in diet between different pair

combinations of all 5-day periods of observations from February 1973 to May 1974, inclusive

(N = 253, X = 15.96, standard deviation = ±12.61, range = 0.52-73.80)

Sample period

Feb 73

Mar 73

Mar 73

Apr 73

Apr 73

May 73

May 73

Jun 73

Jun 73

Jul 73

Jul 73

Aug 73

Aug 73

Sep 73

Oct 73

HOT 73

Nov 73

Dec 73

Feb 74

Apr 74

(I)... .

(I)... .

(ID...

(I)... .

(ID...

(I)....

(ID...

(I)....

(ID...

(I)....

(ID...

(I)....

(ID...

(I)....

(I)....

(I)....

(II)...

( I)

( I)

( I)

( I)

(I)....

1973

Mar Mar

(I) (ID

7.88 23.44

25.58

-

-

_

-

-

-

-

-

-

-

_

-

Apr Apr

(I) (ID

26.09 17.99

7.14 7.02

57.63 55.11

73.80

-

_

-

-

-

-

-

-

-

_

-

May

( I)

12.64

5.72

19.08

17.38

32.87

-

-

-

-

-

-

-

-

-

May

(II)

1 3 .

2 .

1 4 .

I P .

1 8 .

PH.

_

-

_

-

-

-

-

39

11

52

PI

47

17

Jun

( I)

8.62

1.55

4.98

7.17

17.65

17.10

28.22

-

-

-

-

-

_

-

Jun

(II)

9.04

0.52

3.95

5.29

7.32

11.14

16.92

6O.58

_

-

-

-

-

-

J u l

( I )

2.12

3.34

1.84

3.41

6.26

17.04

16.14

35.45

21.62

-

_

_

-

J u l

(II)

1.77

1.76

5.87

6.07

8.79

14.40

18.26

35.34

12.04

60.72

-

-

-

-

-

Aug

( I)

7.82

2.58

6.60

6.31

10.32

15.59

11.81

25.85

5.05

36.65

45-55

-

-

_

-

Aug

(ID

9.82

4.58

17.49

9.87

13.60

22.90

19.01

28.12

8.74

30.40

44.71

47.37

-

-

_

Sep

( I)

12.06

3.90

33.77

23.77

24.87

16.30

8.14

5.46

4.21

7.70

10.54

15.08

23.39

-

_

-

Oct

( I)

4.74

3.10

19.18

6.68

5.78

9.44

5.37

2.68

2.08

4.93

6.27

14.66

27.18

33-42

_

Nov

( I)

5.38

2.73

11.38

2.04

2.64

5.10

1.51

1.92

3.15

9.12

9.73

10.20

24.19

16.79

55.88

Nov

(ID

6.08

3.65

10.39

4.35

4.95

10.78

3.18

2.61

1.70

11.89

14.68

11.91

30.22

16.75

1*6.63

73.56

Dec

( I)

9.94

2.88

13.71

14.00

18.78

20.92

n.96

17.58

16.02

21.50

16.61

11.39

21.68

17.84

11.18

13.05

24 60

1974

Jan

( I)

14.87

4.00

4.76

6.68

9.70

14.31

16.91

21.05

16.63

12.19

19.37

15.00

34.69

8.37

5.86

7.12

11 22

24 89

Feb

( I)

19.19

16.28

20.60

8.52

8.73

12.50

16.56

20.15

15.78

10.90

18.34

11.15

25.91

10.31

5.52

6.20

8 44

43.68

Mar

( I)

13.84

5.65

27.78

27.59

25.94

24.70

28.70

24.24

10.76

16.07

20.27

23.88

30.77

22.16

12.63

3.84

8.90

17 83

18 71

Apr

( I)

3.29

6.15

16.56

12.58

19.69

29.60

25.86

17.58

7.23

10.63

18.25

13.86

20.77

20.35

18.59

4.74

ft

2.34

2.58

21.33

?4.Hn

28.1U

21.67

25.68

20.68

6.08

14.19

21.61*

19.48

24.42

10.88

8,68

? . *

5 45

45.88

45.45

3-

1 1 1 1

1974

Sample Period

FIGURE 8.—Diversity indices of the diet of Group I.
NUMBER 249 31

same months, the greatest variation in diet diversity

was found in March 1973 (0.73 to 2.04). During

this month Group I used the same number of

specific food items during both sample periods,

but during the first sample period P. turbinata

fruits formed an extremely high proportion (85.5%)

of its diet. During the second sample period, the

frequency of use of this resource decreased greatly

(to 20.67%) and several specific food items were

used more equitably.

Spearman rank correlation tests (Snedecor and

Cochran, 1969) showed significant negative correlations between the frequency of use of fruits during

a sample period and (1) the number of food plants

exploited (r, = -0.570, p <0.01) and (2) diet

diversity (rg = -0.860, p <0.01). There was also

a significant positive correlation between the frequency of use of foliar foods and specific food items

diversity (r. = 0.809, p <0.01).

INVERTEBRATE COMPONENT OF THE DIET OF BLUE

MONKEYS.—As mentioned earlier invertebrate food

items were usually indistinguishable even at relatively close quarters. The rare observations when

these food items were clearly seen include feeding

on a butterfly, a grasshopper, and some ants (two

observations). On three occasions cocoons that probably contained immobile insect pupae were also

eaten. Invertebrate food constituted nearly 20% of

the feeding scores recorded from Group I (Table

20). They were eaten during all months of the

study and were the most frequently used food item

in May 1973, September 1973, and March 1974

(Table 24). About 81% of the total scores of ingestion of probable invertebrate food items were

recorded from 29 identified plant species and 11

different microhabitats and 19% of the scores were

recorded from several unidentified plants (Appendix Table D).

Considering microhabitats alone, invertebrate

prey was taken most frequently from the surfaces

of leaves, which accounted for 38.75% of the total

scores of invertebrate feeding (Appendix Table D).

Nearly 74% of the scores of ingestion of invertebrates were recorded from leaf surfaces, mosscovered branches and lichen-covered branches.

Considering plant species, invertebrates were most

commonly captured and eaten from P. excelsa

(17.6%) and S. scheffleri (11.45%). Considering

specific microhabitats, invertebrates were most frequently taken from the moss-covered branches of

TABLE 27.—Group I, percent of frequency of ingestion of

probable invertebrates from 15 specific microhabitats most

commonly used for this purpose during first 5-day periods

of observations from February 1973 to January 1974, inclusive (N = 498 observations)

Specific microhabitat

P. excelsa, moss-covered branches

S. scheffleri, foliage

D. abyssinica, foliage

P. excelsa, foliage

S. scheffleri, moss-covered branches

P. excelsa, lichen-covered branches

D. abyssinica, lichen-covered branches...

C. durandii, foliage

B. vilsoniana, lichen-covered branches...

T. nobilis, foliage

M. platycalyx, dry leaves

P. turbinata, foliage

0. welwitschii, lichen-covered branches..

U. congensis, foliage

P. excelsa, epiphyte-covered branches

Total

Percent of

frequency

of ingestion

7.1*3

6.02

5.62

l*.6l

2.61

2.U1

2.21

1.81

1.61

1.1*1

1.20

36.91*

P. excelsa (7.43%) and the leaf surfaces of S. scheffleri (6.02%) (Table 27).

MONTHLY IMPORTANCE OF PLANT SPECIES AND

MICROHABITATS IN PROVIDING INVERTEBRATE FOOD

ITEMS.—Table 28 presents the five plants most

frequently used for the acquisition of invertebrates

during each month. Almost every month, either

P. excelsa or S. scheffleri provided the greatest

amount of invertebrate prey, although neither of

these species was exploited frequently for plant

foods (see Appendix Table C). It is therefore possible that the distribution of P. excelsa and S.

scheffleri within the home range of Group I affected

the ranging patterns of this group, especially during

those months when they exploited invertebrate

food items at relatively high frequencies.

When the monthly frequency of ingestion of

invertebrates from different microhabitats was considered, it was found that during a majority of the

months of study, Group I took invertebrate prey

most often from the surfaces of leaves (Table

29). Lichen-covered branches provided the greatest

amount of invertebrate prey in one month (October 1973), and moss-covered branches provided the

greatest amount of the same in three months (May

1973, September 1973 and March 1974). Peak frequencies of invertebrate feeding from moss-covered

branches usually coincided with peaks in monthly

rainfall (Figure 9). This may have been due to an
32

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

TABLE 28.—Group I, monthly percent of frequency of ingestion of invertebrates from five species

most commonly used for this purpose during first sample periods between February 1973 to

May 1974, inclusive

Xonth/year

Feb 73

Mar 73

Apr 73

May 73

Jun 73

Jul 73

Aug 73

Sep 73

Oct 73

Nov 73

Dec 73

Jan 7k

Feb 7k

Mar 7U

Apr 7U

May 7k

I

Species

S .

S .

P .

P .

P .

D.

S .

P .

P .

P .

s.

s.

s.

T.

c.

p.

s.

c.

scheffleri

scheffleri

excelsa

excelsa

excelsa

abyssinica

scheffleri

excelsa

excelsa

excelsa

scheffleri

scheffleri

scheffleri

nobilis

durandii

excelsa

scheffleri

africana

Percent

20.0

11.6

15.7

36.7

20.0

13.7

21. k

33.8

18.9

20.8

33-3

23-8

11.1

1*6.1

21.1*

26.6

I I

Species

F .

D.

P.

S .

M.

M.

D.

S .

P .

D.

D.

D.

D.

P .

M.

D.

D.

P .

latifolia

abyssinica

excelsa

scheffleri

bagshawei

abyssinica

scheffleri

excelsa

abyssinica

abyssinica

abyssinica

abyssinica

turbinata

platycalyx

abyssinica

abyssinica

excelsa

Percent

9.3

12.2

18.1

11.7

ll*.2

12.9

16.2

18.7

ll*.2

9.5

30.7

ll*.2

20.0

I l l

Species

S .

c.

s.

s.

0 .

M.

c.

B.

D.

C.

U .

T.

N.

P .

C.

D.

M.

B.

T.

C.

F.

globulifera

durandii

scheffleri

scheffleri

-

welwitschii

platycalyx

africana

wilsoniana

abyssinica

aristata

congensis

splendida

buchanani

excelsa

aristata

mukole

phoberos

nobilis

durandii

latifolia

Percent

1* 6

_

6 . 1

10.9

-

9.5

8.0

10.8

8-3

9.5

U.7

7.6

7.1

13.3

IV

Specie s

C.

U.

A.

M.

T.

C.

c.

N.

P .

M.

T.

P .

P .

D .

P.

C.

D.

U .

D.

C.

F .

gorungosanum

congensis

altissima

platycalyx

nobilis

durandii

durandii

buchanani

excelsa

dura

nobilis

_

excelsa

turbinata

abyssinica

angolens is

durandii

mukole

congensis

mukole

durandii

kisantuensis

Percent

7.2

9.8

7 . 1

6.U

8.1

6.2

7 . 1

7.1*

2.5

-

6.6

V

Specie s

N.

F .

N.

B.

B.

C.

B.

C.

P .

B.

P.

P.

T.

A .

T.

B.

C.

C.

U.

s.

F .

T.

-

buchanani

dawei

-

buchanani

phoberos

wilsoniana

durandii

wilsoniana

durandii

excelsa

wilsoniana

angolensis

turbinata

nobilis

altissima

nobilis

wilsoniana

africana

durandii

congensis

scheffleri

brachylepis

nobilis

-

-

Percent

-

2.3

-

U.o

5.U

7.8

U.7

U 8

5.U

U.I

-

-

N

10

38

U9

55

51

U2

62

37

1*8

U2

31

27

39

11*

15

increase in abundance of this substrate and/or its

invertebrate inhabitants during the rainy season.

FEEDING MOTOR PATTERNS EMPLOYED IN THE CAPTURE AND INGESTION OF PROBABLE INVERTEBRATE

FOOD ITEMS.—In this section, I have included feeding motor patterns (employed in the capture and

ingestion of probable invertebrate food) recorded

from both groups through all 5-day periods of

observations because some motor patterns that occurred at low frequency in Group I were not recorded in Group II and vice versa. The complete

catalog of motor patterns employed in the capture

of probable invertebrates by both groups is given

in Appendix Table E. In both groups, a very high

percentage (over 90%) of the motor patterns employed in the capture and ingestion of probable

invertebrate food items was slow motor patterns.

This suggests that both groups concentrated their

invertebrate feeding activity on slow-moving or

immobile forms rather than on fast-moving forms,

such as winged insects.

INVESTIGATIVE ACTIVITIES RELATED TO THE INGESTION OF PROBABLE INVERTEBRATE FOOD.—Invertebrate feeding was usually preceded by a considerable
NUMBER 249 33

Invertebrate Feeding

Rainfall

FMAM J J ASOND J FMA M

FIGURE 9.—Relation between monthly rainfall and the percentage frequency of use of

moss-covered branches for the acquisition of probable invertebrate food.

TABLE 29.—Croup I, monthly percent of frequency of ingestion of invertebrates from different categories of microhabitats (I-XI) during first sample periods of months from

February 1973 to May 1974, inclusive (for key to categories of microhabitats, see Appendix

Table D)

Month/ye VII

Feb 73...

Mar 73-.-

Apr 73-..

May 73-..

Jun 73-..

Jul 73-..

Aug 73...

Sep 73-..

Oct 73-..

Nov 75. • •

Dec 73...

Jan 7k...

Feb 74...

Mar 74...

Apr 7k...

May 7k...

Total..

50.00*

48.84*

36.84*

28.57

36.36*

31.37*

35.71*

30.65

32.43*

39.58*

76.19*

52.38*

74.07*

25.64

57.Ik*

60.00*

2.33

10.53

18.37

14.55

27. 45

11.90

12.90

32.k3*

12.50

2.38

7.4l

17.95

21.43

6.67

11.63

34.21

32.65*

21.82

19.61

23-81

32.26*

18.92

25.00

2.38

3.70

30.77*

7.1k

20.00

2.33

2.63

3.64

3.92

1.61

2.70

2.08

2.38

5-13

5.26

2.04

3.64

5.88

9-52

6.45

5.41

2.08

7.14

33-33

3.70

7.69

2.33

8.16

3.64

1.96

2.38

1.61

2.70

10.42

2.38

4.76

2.56

20.00

11.63

2.63

2.04

10.91

5.88

16.67

11.29

2.70

6.25

7.14

4.76

11.11

10.26

14.29

6.67

30.00

16.28

5.26

8.16

5-45

1.96

1.61

4.76

6.67

4.65

2.63

1.61

2.70

1.96

10

43

38

49

55

51

42

62

37

48

42

21

27

39

14

15

593

•Indicates microhabitat with tbe highest frequency of invertebrate ingestion score
34

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

amount of visual scanning and/or manual examination of microhabitats, and followed by mastication of the invertebrate prey. Since a considerable

proportion of the time budget of blue monkeys

was apportioned to visual scanning and manual

examination of microhabitats, I scored these as

separate activity categories. A score for one of these

investigative activities indicates that the activity

was sustained for a period of five seconds, but that

the search for invertebrates was unsuccessful during

this period. However, if the search resulted in the

capture and ingestion of an invertebrate food item,

then I scored it as a separate category of activity,

termed ingestion. Thus, the monthly frequency of

ingestion scores divided by the sum of the frequencies of investigations and ingestions yields a relative

measure of success in seeking out invertebrate prey

during that month. Group I showed considerable

intermonthly variation in their success in capture

of invertebrate food items (Table 30). Usually they

captured invertebrates in less than half the investigations in different microhabitats.

A relative measure of invertebrate capture success can also be obtained by comparing the rate

of investigations and ingestions to the rate of ingestions of invertebrate food items. The rates of

investigations and ingestions were generally higher

during peak rainfall periods (April 1973 to May

1973 and September 1973 to November 1973) and

one month after the peaks than during other periods, but the rates of capture (and ingestion) during many of these months were less than average.

This suggests that Group I searched more intensively

for invertebrates during peak rainfall periods (and

immediately after them) than during other times,

either because invertebrate populations reached low

levels or because they remained less active and

hence less conspicuous during these months. It is

also possible that during the rains more of the

insects were present as winged adults and, therefore,

more mobile and relatively unavailable to blue

monkeys.

The percentage success of capture of invertebrates from different microhabitats is given in

Table 31. The greatest success in the capture of

invertebrates occurred in unidentified microhabitats. Among the identified microhabitats, Group I

was most successful in prey capture on bare trunks

and branches, presumably because invertebrates

were most easily detectable on these surfaces.

FRUITS AS A SOURCE OF INVERTEBRATE FOOD.—In

addition to searching actively and ingesting invertebrates, blue monkeys also took them along with

the fruits of certain species. Of special interest

were the fruits of several species of Ficus, which

were eaten by both groups. The fruits of these

plants usually contained heavy infestations of the

developmental stages of the wasps that aid in pollination, as well as chalcid and braconid wasps,

which were parasitic on the pollinators (Table 32).

TABLE 30.—Group I, monthly percent of frequency of success in the capture of probable

invertebrate food items during the first sample periods from February 1973 to May 1974, inclusive

Sample period

Feb 73 (I)

Mar 73 (I)

Apr 73 (I)

May 73 (I)

• 'un 73 (T)

•'ul 73 (I)

Aug 73 (I)

Sep 73 (I)

Oct 73 (I)

Nov 73 (I)

r ec 73 ' 11

• Ian 7U (I)

Feb 7U (I)

Mar 7k (I)

Apr 7k (I)

May 74 (I)

Mean

Frequency of

successful and

unsuccessful

investigations

Frequency

of successful

inve s t igat ion

(i.e., capture)

for invertebrates of invertebrates

Percent

of success

in capture of

invertebrates

Total

hours

of

group

contact

Rate of al l

inve st igat ions

for invertebrates

(per hour)

Rate of

capture of

invertebrates

(per hour)

76

91

99

110

7k

9k

159

126

1?6

127

k?

kk

56

33

18

55

1+6

k?

6o

35

1+1

38

16

20

27

11

1+7.6

56.6

1+1.8

^9-5

50.0

62.2

kk.7

37.7

27.3

32.5

29-9

38.1

U5.5

U8.2

33.3

50.0

1*6.25

5U.00

52.75

1+1+.25

57.00

60.00

56.00

51.25

5U.75

5U.75

60.50

56.00

56.50

20.75

25.50

18.00

0.1+5

1.U1

1.73

2.21+

1.93

1.23

1.68

3.10

2.30

2.30

2.10

0.75

0.78

2.70

1.29

1.00

1.69

0.22

0.80

0.72

1.13

0.96

0.77

0.75

1.17

0.6U

0.75

0.63

0.29

0.35

1.30

0.1+3

0.50

0.71
NUMBER 249 35

TABLE 31.—Group I, percent of success of capture of probable invertebrates in different micro

habitats (I-XI) during first sample periods from February 1973 to May 1974, inclusive {for key to

categories of microhabitats, see Appendix Table D)

Capture

Frequency of investigation

and capture of invertebrates..

Frequency of capture

Percent of success in capture..

528.

223.

1+2.

0

0

2

167

72

>*3

.0

.0

.1

311

112

36

.0

.0

.0

55

10

18

.0

.0

.2

66

30

k5

.0

.0

.5

51

19

37

.0

.0

.3

72

U6

63

.0

.0

.9

28.

23.

82.

0

0

1

10

5

50

.0

.0

.0

3

0

0

.0 3

0

0

.0

TABLE 32.—Percent of insect infestation of certain fruits

eaten by Groups I and II

Species

F. exasperata.

F. brachylepis...

F. dawel

F. natalensis.

F. stipulifera

M. bagshawei

P. turblnata

Number Percent

Number of fruits of fruits

of fruits with insect with insect

examined infestation infestation

35

30

39

Uo

16

13U

32

30

28

35

33

16

15

30

85.71

93-33

89. Th

82.50

100.00

11.19

93.75

Some Ficus spp. also carried infestations of other

insects; the fruits of F. brachylepis sometimes contained the large larvae of the weevil, Omophorus

stomachosus (P. Waser, pers. coram.); a small black

unidentified species of ant was frequently found

on the surfaces of the fruits of F. stipulifera. Other

fruits that were found to be infected with insects

were those of P. turbinata and M. bagshawei. During

certain months, the fruits of these two species and

those of F. exasperata and F. dawei were very important in the diet of Group I (Appendix Table C).

Similarly, during certain months the diet of Group

II contained large amounts of the fruits of F.

exasperata and F. brachylepis (see section on intergroup dietary differences).

WATER REQUIREMENTS OF THE BLUE MONKEYS.—

Water requirements of the blue monkeys were

probably largely satisfied by the succulent fruits

that they ate. By comparing wet and dry weights

of fruits, I estimated that the fruits of F. exasperata,

F. brachylepis, F. natalensis, C. durandii, and T.

nobilis contained over 70% water, while those of

M. bagshawei and U. congensis contained about

55% and 67%, respectively. Occasionally, after

a shower of rain blue monkeys also drank water

from holes in trees. This they did either by applying their mouths directly to the surface of the

water or dipping one hand into it and lapping

up the moisture from the fur.

VERTEBRATE FOOD EATEN BY BLUE MONKEYS.—I

once observed a subadult male of Group II eating

an African wood owl (Ciccaba woodfordii bohndorffi). The bird vocalizations heard at the beginning of this observation and freshness of the small

quantity of meat that remained after the meal

indicated that the bird was captured alive rather

than taken as carrion. The subadult male did not

share any of the meat with other members of his

group, most of whom watched him from within

five m. During the time he fed on the bird, he once

chased a juvenile who approached him. This behavior is in contrast to the meat-sharing behavior

reported in the chimpanzees (Van Lawick-Goodall,

1971; Teleki, 1973), and, unlike chimps, the subadult male blue monkey did not eat leaves along

with the meat. The wings of the bird that were

recovered after the meal spanned 33 cm. This

indicated that the bird was an adult, and adults

of this species weigh about 450 gms (MackworthPraed and Grant, 1952). This observation was recorded after nearly 2070 hours of contact with blue

monkeys and, hence, predation on adult birds

must be considered a rare occurrence.

INTRASPECIFIC FOOD NICHE SEPARATION.—In this

analysis, I compared the relative frequency of feeding and the composition of diet of four age/sex

classes. In order to do this, it was important that

(1) the exact age/sex composition from which the

feeding observations were derived be known and

(2) each age /sex class was equally likely to be

scored for feeding. Feeding data collected from

Group II during the December 1973 to September

1974 period (when each group member was individually identifiable) best satisfied these two criteria. All members of this group were completely

habituated to my presence, but one of the four

adult females (female RLT) remained peripheral

to the group and was less likely to be scored for

feeding than the others. Therefore, feeding data
36

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

recorded from this female were discarded; adjustments were also made for the disappearance of

another adult female in January 1974.

During the period of observations mentioned

above, excluding infants, Group II comprised of

a mean of one adult male, 2.175 females (excluding

RLT), two subadults, and four juveniles (Table 33).

Feeding observations recorded from these age/sex

classes showed that their relative frequencies of

feeding differed significantly from expected {x

2

 —

47.94, df=3, p <0.005). The adult females and subadults fed more frequently than expected, while the

adult male and the juveniles fed less frequently than

expected. Pairwise comparisons of feeding frequency suggested that (1) the adult male apportioned less time to feeding activity than the other

three age/sex classes, (2) juveniles spent less time

feeding than adult females and subadults, and (3)

adult females and subadults spent similar amounts

of time attending to their dietary needs (Table 34).

The proportion of different food items constituting the diet of each of these four classes also

differed significantly (x2=36.94, df=12, p <0.01).

The composition of the diet of the adult male was

different from that of the other three classes; the

variations in the diet of these three classes were

not statistically significant (Table 34). Evidently

the adult male concentrated more on fruits and

far less on invertebrates than the others. Invertebrates were most important in the diet of immature

individuals (i.e., subadults and juveniles).

INTERGROUP DIETARY DIFFERENCES.—Dietary comparisons between Groups I and II were restricted

to the period when monthly observations were

made on both groups (i.e., between February 1973

and January 1974). Also these comparisons were

made only between those sample periods of observations of both groups with the shortest time

interval between them, regardless of whether these

periods occurred within the same month or in

adjacent months. This reduced the possibility of

intergroup differences in diet being affected by the

time interval between sample periods. When a

period of observations of a group was comparable

to two sample periods of the other group, I compared both pair combinations.

TABLE 33.—Group II, proportion of different food items eaten by four classes of individuals

during sample periods from December 1973 to September 1974, inclusive

Age/sex class

Adult »i »

Adult female

Subadult

Mean

number of

individuals

1.0

2.175

2.0

U.O

Nuntoer

of feeding

observations

97

369

3U7

U99

Percent of

different food item

Foliar

items

22.7

23.0

25.U

23.1

Floral

Items

10.3

ll.U

11.5

11.2

Fruits

59-9

U3.6

33.7

36.3

in diet

Other

plant items

2.1

3.8

U.9

U.2

Invertebrates

5.2

18.2

2U.5

25.3

TABLE 34.—Group II, x

2

 statistic for comparisons between different

pair combinations of age/sex classes

Pair

X

2

df

Level of

X

2

df

Level of

combination

significance...

significance...

Adult

-ale/

adult fenale

2U.620

1.0

0.005

13.U3

u.o

0.01

Adult

male/

subadult

Adult

-ale/

juvenile

Adult

female/

subadult

Feeding Frequency

26.350

1.0

0.005

5.160

1.0

0.025

Composition

28.81

U.O

0.01

27.16

U.O

0.01

0.07

1.0

0.05

of Diet

8.82

U.O

0.05

Adult

female/

juvenile

2O.lUo

1.0

0.005

7.81

U.O

0.05

Subadult/

juvenile

22.U70

1.0

0.005

1.12

U.O

0.05
NUMBER 249 37

TABLE 35.—Time interval between comparable sample periods

of observations on Groups I and II

Month/year

Feb 73...

Mar 73...

Apr 73...

May 73...

Jun 73-••

Jul 73...

Aug 73...

Sep 73-..

Oct 73-.-

Nov 73...

Dec 73...

Jan 7k...

FebMay 7k..

JunSep 7k..

Total..

Mean...

Number of

sample periods

of obs

Group I

1

2

2

2

2

2

2

1

1

2

1

1

k

-

23

ervation

Group II

1

1

1

1

1

0

1

1

1

1

1

1

3

k

18

-

Comparable

sample periods

Group I

Feb 73 (I)

Mar 73 (II)

Apr 73 (I)

May 73 (I)

Jun 73 (I)

Jul 73 (I)

Sep 73 (I)

Sep 73 (I)

Nov 73 (I)

Nov 73 (II)

Dec 73 (I)

Jan 7k (I)

-

-

-

Group

Feb 73

Mar 73

Mar 73

Apr 73

May 73

Jun 73

Aug 73

Sep 73

Oct 73

Nov 73

Dec 73

Jan 7k

.

-

-

II

(I)

(I)

(I)

(I)

(I)

(I)

(I)

(I)

(I)

(I)

(I)

(I)

Interval

between

sample

periods

(days)

2

1*

1*

5

3

1*

2

10

3

7

7

k

-

U.58

Eleven periods of observations of each group

between February 1973 and January 1974 inclusive

provided 12 pair combinations of sample periods

for comparison (Table 35). The mean time interval between comparable sample periods was 4.58

days (range 2-10 days). During these sample periods,

I observed Group I for 584 hours and recorded a

total of 2329 plant and invertebrate feeding scores

at the rate of 4.0 feeding scores per hour of group

contact. Of these feeding scores, 1977 were recorded

from the use of 60 food plants and 102 specific

food items (Appendix Table G). Group II was observed for 558 hours, and 2268 feeding scores were

collected at the rate of 4.1 feeding scores per hour

of contact. Feeding on plant food accounted for

1856 scores from this group and were recorded

from the use of 47 plant species and 86 specific

food items (Appendix Table G). In view of the

small differences in duration of group contact and

similar rates of feeding data collection, it appears

that Group II utilized a less diverse plant diet than

Group I. The less diverse nature of the diet of

Group II was also indicated by the fact that this

group exploited its top 13 food plants to the same

extent that Group I used its top 21 food plants.

Both groups exploited a total of 74 food plants,

but only 33 (44.6%) of these were shared by them;

27 were used exclusively by Group I and 14 were

used only by Group II. In general, mutually exploited food plants were used at different frequencies, these differences being most appreciable in the

use of F. exasperata and T. nobilis, which were top

ranking food plants of Groups I and II. Intergroup

differences in the frequency of use of U. congensis,

M. platycalyx, and M. bagshawei were also relatively large. Due to intergroup variability in the

frequency of use of food plants, only 13 mutually

exploited species occur among the top 20 food

plants of each group. The top 20 food plants

account for as much as 89.65% and 95.80% of the

vegetable diet of Groups I and II respectively, and

therefore, must be considered as an important component of their diet. Included among the top 20

ranks were P. turbinata, which was exclusively

used by Group I, and F. stipulifera, which was

used only by Group II. There were also several

species, such as M. bagshawei and L. johnsonii, that

occur only among the top 20 food plants of one

group and occupy lower ranks in the diet of the

other group.

In order to assess intergroup differences in food

preferences, I computed selection ratios. These

ratios were computed only on the basis of the densities of food plants, because it was reasonable to

assume that canopy size was more or less constant

for a particular plant species. Estimates of food

plant densities within the home ranges of Groups

I and II were obtained from Struhsaker (1975) and

Waser (pers. corara.), respectively, and from personal investigations.

Selection ratios indicate that intergroup differences in the frequency of use of some species (C

durandii and D. abyssinica) were probably due to

differences in their densities within the two home

ranges (Table 36). In terms of selection ratios,

however, certain species were more preferred by

Group I than by Group II (e.g., C. africana, P.

angolensis, F. exasperata, and M. bagshawei), while

some others were more preferred by Group II than

Group I {e.g., F. brachylepis and C. gorungosanum).

Since the frequency of use of food plants may also

have been affected by the size of their canopies,

selection ratios given in Table 36 do not reflect

intragroup preference of food plants.

Comparisons of the proportions of food items

constituting the vegetable diet of the two groups
38 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

show that Group I used 25.1% of foliar foods,

while Group II used about 17.0% of these food

items (Appendix Tables F, G). Group I also used

relatively higher proportions of blossoms and lower

proportions of fruits in its vegetable diet than

Group II. Intergroup dietary differences can also be

shown by considering the use of plant as well as

invertebrate food items exploited by both groups

during comparable sample periods (Figure 10).

During the February 1973 sample periods recorded

from Groups I and II, their diets varied appreciably

in the frequency of use of fruits (by 18.3%),

blossoms (by 27.0%), and invertebrates (by 10.7%).

Similarly in the May 1973-April 1973 pair combination intergroup variability in diet was largely

due to a 13.7% difference in the use of foliar items

and a 12.1% difference in the use of blossoms. In

the July 1973-June 1973 pair combination, the two

groups showed large differences in the frequency

of use of fruits (28.5%) and blossoms (25.4%). Considerable intergroup variability in the use of food

items can also be found in the September 1973-

August 1973, September 1973-September 1973,

December 1973-December 1973, and January 1974—

January 1974 pair combinations of sample periods.

Intergroup variability in diet was also apparent

in the relative importance and the frequency of use

of specific food items used by the two groups.

Among the top 20 ranks of specific food items exploited by each group, only 11 were mutually exploited, and the top-ranking specific food item of

each group occupied a much lower rank in the diet

Jan, 74

Jan,

0°/. 50

Cumulative Frequency of use

FIGURE 10.—Cumulative percentage frequency of use of different food items by Groups I and II during comparable

sample periods.

of the other group (Table 37). Usually, both groups

used a food plant for the same food items, but the

frequencies of use of these food items by the two

groups were quite variable. Thus, in the diet of

Group I, M. myristica was included within the top

TABLE 36.—Selection ratios of important food plants exploited

by Groups I and II

Species

Percent of

frequency of use

Group I Group II

Density/hectare

Group I Group II

hone home

range range

Selection ratio

Group I Group II

T. nobilis. • •

C. africana..

D. abys8inlca

U. congensiB.

C. durandll..

P. angolensis

F. exasperata

M. bagshawei.

M. platycalyx

F. latlfolla.

F. brachylepis

C. gorungosanum

13.06

11.39

10.02

6.98

6.52

5.11

4.76

4.61

3.90

2.88

0.05

1.06

4.47

11.48

7.70

11.53

7-17

1.94

19.61

0.48

7.U9

4.04

6.63

1.78

20.0

2.1

65.7

25.2

34.3

1.4

0.2

2.1

58.0

14.7

0.1

2.1

12.3

7.4

35.7

14.8

31.4

1-9

1.6

0.6

45.5

9.9

0.4

0.6

0.62

5.42

0.15

0.28

0.19

3.65

23.80

2.20

0.07

0.20

0.40

0.60

0.36

1.55

0.22

O.78

0.23

1.05

12.30

0.77

0.16

0.4l

16.60

2.97
NUMBER 249 39

TABLE 37.—Groups I and II, percent of frequency of use of top 20 specific food items

Group I

Rank order and specific food item

1. Teclea nobilis, fruits

2. Celtis africana, fruits

3. Uvariopsis congensis, fruits

It. Celtis durandii, fruits

5. Ficus exasperata, fruits

6. Diospyros abyssinica, fruits

7. Mimusops bagshawei, fruits

8. Premna angolensis, blossoms

9. Markhamia platycalyx, petioles....

10. Funtumia latifolia , seeds

11. Diospyros abyssinica, blossoms....

12. Diospyros abyssinica, young leaves

13. Dombeya mukole, young leaves

Ik. Parinari excelsa, fruits

15. Vangueria apiculata, mature leaves

16. Pancovia turbinata, fruits

17. Monodora myristica, leaf buds

18. Teclea nobilis, mature leaves

Neoboutonia macrocalyx,

mature leaves

Chaetachmo aristata , fruits

Total

Percent of

frequency

of use

11.53

10.52

6.83

6.52

it.66

U.55

3.85

3.80

2!88

2.78

2.68

2.07

2.02

1.82

1.72

1.62

1.37

77.10

Group II

Rank order and specific food item

1. Ficus exasperata, fruits

2. Uvariopsis congensis, fruits

3. Celtis africana, fruits

h. Celtis durandii, fruits

5. Ficus brachylepis, fruits

6. Teclea nobilis, fruits

7. Funtumia latifolia , seeds

8. Ficus exasperata, leaf buds

9. Markhamia platycalyx, nectar

10. Markhamia platycalyx, petioles... .

11. Diospyros abyssinica, blossoms....

12. Diospyros abyssinica, young leaves

13. Konodora myristica, fruits

lit. Linociera johnsonii, fruits

15. Diospyros abyssinica, fruits

16. Chrysophyllum gorungosanum, blossoms

17. Premna angolensis, blossoms

18. Ficus exasperata, young leaves....

19. Monodora myristica, blossoms

Olea welwitschii, mature leaves...

Total

Percent of

frequency

of use

15.09

11.53

9.16

7.00

6.63

U. 36

4.0lt

3.50

3.18

?.96

2.69

2.37

2.21

2.10

1.78

l.ltO

1.2U

0.97

0.86

83.93

20 ranks because of the use of its leaf buds, and in

the diet of Group II it was included among these

ranks due to the use of its fruits and blossoms.

Group II used the nectar of M. platycalyx more frequently than its petioles, but Group I used the

petioles more frequently than the nectar of this

species. The frequencies of use of food items from

D. abyssinica were also reversed in the diet of the

two groups.

Most of the high-ranging specific food items exploited by both groups showed restricted periods of

use (and importance), but their patterns of use

were somewhat variable. For example, M. bagshawei

fruits were important (i.e., included within the

top five ranks) in the diet of Group I during four

sample periods, but were never important in the

diet of Group II (Figure 11). The fruits of U. congensis were important in the diet of Group II during the mid and late 1973 sample periods, but

their importance in the diet of Group I was restricted to the midyear sample periods. The use of

P. angolensis blossoms showed a pattern where a

specific food item was exploited during similar

sample periods, but assumed importance in the

diet of the two groups during different sample

periods. The fruit of F. brachylepis, which was the

fifth ranking specific food item in the diet of Group

II, was important to this group in two sample

periods, but was not used at all by Group I during

the comparable sample periods between February

1973 and January 1974.

Perhaps the most striking intergroup variation in

the pattern of use of specific food items was found

in the use of the fruits of F. exasperata (Figure 12).

There were periods when Group I used little or

none of these fruits, but Group II used them more

or less continually from February 1973 to January

1974 and always at a higher frequency than Group

I. In addition to the fruits of F. exasperata, Group

II also used its leaf buds and young leaves, both of

which were available to, but not exploited by,

Group I. When the use of these fruits decreased,

Group II took appreciable amounts of leaf buds

from F. exasperata. Therefore, this species remained important in the diet of Group II through

all sample periods except June 1973, but its importance in the diet of Group I was restricted to three

sample periods.

Usually Group II exploited fewer specific food

items than Group I (Table 38). The ShannonWiener indices of diet diversity showed that in 9

of the 12 pair combinations of sample periods,

Group II utilized a less diverse diet than Group I.

During comparable sample periods the number of

mutually exploited specific plant food items was

generally low when compared to the total number
40 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

Groupl • Groupl

P. anaotensis blossoms

A

| GroupT D Group?

F. brachylepis fruits

Group!

Groupl

n

Groupl

Groupl

Comparable sample periods

FICURE 11.—Percentage frequency of use of selected specific food items and their rank order of

importance in the diets of Groups I and II during comparable sample periods.

of specific plant foods used by each group. Intergroup diet overlaps due to mutual use of specific

plant foods range from 22.6% to 65.2% (mean =

40.1%), which, in view of all the variables of sampling methods, vegetation, and phenology of tree

species, may be considered to be usually low or

moderate.

DISCUSSION

BLUE MONKEY FEEDING PATTERNS AND ADAPTIVE

SIGNIFICANCE OF DIET.—Although blue monkeys

exploited a relatively diverse diet, they appeared

to be fairly selective feeders. Their use of food resources seemed to be affected by their selectivity as

well as the relative abundance and availability of

food items.

Fruits were the most important component of the

diet of blue monkeys but foliar foods were also

periodically important. The folivorous aspect of

the diet was perhaps adaptive in the context of

the life-style of this species and the periodic fluctuations in the abundance of various food resources

(see "Introduction"; also Ellefson, 1964). During
NUMBER 249 41

GrpI

Grpfl

Feb - Mar^r^- Apr;- M«ay- Jun ( - Jul,-

Feb) Mdr( Mar; Apr M«3y| Jun(

Comparable sample

Nov. Dec.

Sep - Sep— Nov - Ncv - Dec -

Auq Sep Oct.

periods

2

jan

FIGURE 12.—Percentage frequency of use of food items exploited from F. exasperata and the rank

order of importance of this species in the diet of Groups I and II.

TABLE 38.—Indices of diet diversity and percent of overlaps in diet of Groups I and II

Comparable

sample period

Group I

Feb 73 (I)

Group

Feb 73

Mar 73 (II) Mar 73

Apr 73 (I)

May 73 (I)

Jun 73 (I)

Jul 73 (I)

Sep 73 (I)

Sep 73 (I)

Nov 73 (I)

Mar 73

Apr 73

May 73

Jun 73

Aug 73

Sep 73

Oct 73

Nov 73 (II) Nov 73

Dec 73 (I)

Jan lh (I)

Dec 73

Jan 7^

II

( I)

( I)

( I)

( I)

( I)

( I)

( I)

( I)

( I)

( I)

( I)

( I)

Number

of

food

Group

20

Ik

22

38

22

25

2k

2k

15

20

23

30

specific

items used

I Group II

8

12

12

27

25

20

15

16

15

20

19

Indices

of diet diversity

Group I

2.2996

2.OU3U

1.7U51

3.129^

2.1272

2.U139

2.5U12

2.51*12

1.3U27

1.73V+

2.1*613

2.9105

Group II

1.3U55

1-7319

1.7319

2.53^0

2.6369

1.921U

2.1733

2.2159

1.6993

2.0931*

2.0501

2.3891+

Number

of specific

items shared

3

1*

1*

11

10

11

7

8

6

6

9

13

Percent

of overlap

in diet

38.2

Ul.8

56.1*

3^.7

53.5

39.0

35.1*

38.7

65.2

22.6

26.U

29.3

1*0.1

22.6-65.2
42 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

periods of fruit shortage, blue monkeys were left

with two possible options. One was to range over

extensive areas in search of fruits like the mangabeys do in the Kibale Forest, and the other was to

switch to more readily available foods, such as foliar

foods. In view of the relatively small size of blue

monkeys, energetic considerations may make movements over extensive areas unfeasible (McNab,

1963). Thus when fruits were in short supply, the

only possible alternative appeared to be to switch

to foliar foods that were more readily available

than fruits. Since the diet of adult males contained

a large proportion of fruits, the one-male social

structure may also be viewed as an adaptation to

periods of fruit shortage. The use of foliar foods

also probably satisfied certain nutrient requirements of blue monkeys. Some young leaves contain

a very high percentage of crude protein (Struhsaker, 1975), and mature leaves have fairly high

concentrations of calcium (Biddulph, 1959).

Morton (1973) has noted that among frugivorous birds there may be intense selection favoring

abilities to find other types of food even if periods

of fruit scarcity were relatively improbable. Primates like the blue monkey, which depend a great

deal on fruits, also probably experience the same

selection pressure. This affords an explanation for

the wide variety of food items used by blue monkeys. The wide variety of foods used by blue monkeys was the result of a diverse diet during periods

of fruit shortage as well as exploitation of small

quantities of different items when fruits were being

used extensively. Freeland and Janzen (1974) hypothesize that herbivores must continuously sample

a variety of foods available to them in order to

maintain enzymatic pathways for detoxifying secondary compounds. This allows them to ingest

large quantities of relatively toxic foods if necessary (i.e., when preferred foods were in short supply) without suffering any ill effects. It is possible

that blue monkeys used several foods, especially

foliar foods (that usually contain toxic substances),

in order to keep periodically important metabolic

pathways open. The use of a wide variety of foods

may also have been necessary (1) to maximize

nutrient intake and (2) to increase total food consumption (Smith, 1959).

INTRASPECIFIC FOOD NICHE SEPARATION.—Food

niche separation between the age/sex classes

occurred along at least two dimensions, and the

greatest similarity in diet was between subadults

and females. The adult male seemed to adopt a

"time minimizing" strategy (Schoener, 1971) and

maintained himself on a fairly bulky diet, primarily of fruits. Fruits normally contain relatively

large amounts of simple sugars, which are readily

utilizable sources of energy (Jenkins, 1969). On the

other hand, immature individuals concentrated

more on food resources rich in proteins (i.e., invertebrates), which were probably important during

the growth phase of individuals. The fact that adult

females also used invertebrates more frequently

than the adult male may be related to their reproductive cycle and nutrient requirements of infant

care. Compared to adult females and subadults,

the juveniles fed less frequently, which may be

because they were smaller and therefore required

lesser quantities of food than adult females and

subadults. Also a portion of the time budget of

juveniles was allotted to group socialization processes, such as play, in which the older age classes

rarely indulged. In the field, I sometimes observed

play between juveniles, while older individuals

were involved in a bout of feeding.

FOOD NICHE SEPARATION BETWEEN SYMPATRIC

CERCOPITHECINES.—The feeding motor patterns

employed in the acquisition of invertebrates suggested that blue monkeys most frequently used

slow-moving or immobile forms, such as insect

larvae and pupae. In contrast redtails used rapid

motor patterns more often than blue monkeys to

capture their invertebrate source of food, indicating that they concentrated more on fast-moving

forms, such as winged (adult) insects (Struhsaker,

pers. coram.). Apparently, these two species reduced

overlap along this niche dimension by focusing

their activity at different points on the spectrum

of invertebrates available to them. The redtails,

which were socially subordinate to blue monkeys,

exploited a wider range of invertebrates, showing

that there was an inverse relationship between

dominance rank and niche breadth (Morse, 1974)

along this resource dimension. The plant diets of

these two species were quite similar.

The mangabeys, which were larger than blue

monkeys, were able to use their heavy jaw musculature to bite through wood, bark, and lianas
NUMBER 249 43

with channeled piths to obtain invertebrates

(Waser, 1975) that neither the blue monkeys nor

the redtails were able to exploit. Also the mangabeys specialized in selecting and eating hard latexfilled (F. brachylepis) fruits, which contained the

relatively large larvae of a weevil, Omophorus

stomachosus Bah. This type of feeding behavior

was not seen in the blue monkeys. The greater

strength of the mangabeys also allowed them to

strip and eat bark that blue monkeys did not use

as food. The extensive home ranges of mangabeys

seemed to enable them to rely on abundant sources

of fruits and to maintain a highly frugivorous diet

throughout the year. Thus their diet consisted only

of 5.4% of foliar food, which strongly contrasted

with the folivorous component of the diet of blue

monkeys.

Very little is known of the food habits of C.

Ihoesti, but its dental structure indicates that it

may be the most folivorous of the four cercopithecines found within the study area (Kay and Hylander, in press). Moreover, being a largely terrestrial species, it probably exploited food plants

different from those used by the other three more

arboreal cercopithecines.

Cercopithecines have been variously classified as

opportunistic omnivores (Struhsaker, 1967, 1969),

arboreal frugivores, frugivore-omnivores (Eisenberg

et al., 1972), and frugivore-insectivores (Gartlan

and Brain, 1968; Jones and Sabater Pi, 1968;

Bourliere, Hunkeler, and Bertrand, 1970; Dittus,

1974). The broad ecological categories used to describe their diet sometimes obscure the varying

degrees of importance of different dietary components, which in the case of the cercopithecines of

the Kibale Forest probably led to a substantial separation of their feeding niches. Gautier and GautierHion (1975) also found similar dietary differences

between Cercopithecus pogonias, C. cephus, and

C. nictitans, which were sympatric in Gabon, west

Africa. Although these species were mainly frugivorous, C. pogonias was the most insectivorous,

while C. nictitans, which belongs to the same superspecies as C. mitis, was the most folivorous in food

habits.

Although the food niche of blue monkeys seemed

distinct enough to allow for their coexistence with

other species, they apparently met with intense

competition for certain food items. For example,

their use of unripe fruits of certain species (e.g.,

C. durandii, C. africana, and C. betacea), which

probably contained starch rather than sugars and

considerable amounts of acid (Winton and Winton,

1935), was probably due to interspecific competition

for these resources. Also the fact that many of the

interspecific conflicts of blue monkeys occurred in

a feeding context suggests that blue monkeys competed for certain food resources with other species.

INTERGROUP DIETARY DIFFERENCES.—Intergroup

variability in diet was expressed by the relatively

low percentage of mutually exploited food plants

and by differences in the total number of food

plants used by each group. Since the difference

between the total durations of contact with the

two groups was small (being less than 5% of the

duration of contact with either group), this alone

could not have caused the appreciable difference

in the total number of food plants used by the

two groups during comparable sample periods.

Differences in group size and visibility within the

two home ranges could affect the rate of collection

of feeding observations and, therefore, the rate of

discovery of the food plants of each group. The

fact that the rates of collection of feeding observations from both groups were similar suggests

that these factors were also probably not important

in causing food plant diversity differences found

between the two groups.

Selective felling operations for commercially valuable timber within the home range of Group II

involved the removal of certain large food plant

species (e.g., P. excelsa, O. welwitschii, A. altissima,

M. bagshawei, etc.). Felling of large trees invariably

resulted in the destruction of the lower story vegetation that included some of the important food

plants of blue monkeys. This destruction to habitat

provides an explanation for the less diverse nature

of the diet of Group II and the lowered frequency

of use of the above species as well as some of the

smaller species by Group II. Comparison of densities from the two home ranges, however, also showed

that some important food plants (F. exasperata,

F. brachylepis, C. africana) were found at higher densities within the felled area and some (C durandii,

P. angolensis) were found at more or less equal densities in both areas (Table 36). Thus selective felling

does not entirely explain the density differences between the two home ranges and suggests that, at
44 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

least in some respects, the study area was more

heterogeneous prior to selective felling.

Differences resulting from vegetational heterogeneity at least in part explain why Groups I and II

had exclusive access to certain species. For example,

F. dawei and P. microcarpa occurred only within

the home range of Group I, while F. congensis and

D. battiscombei were located only within the home

range of Group II. Ficus dawei occupied top rank

as a food plant and constituted nearly 35% of the

feeding scores of Group I during the second sample

period of May 1973, and it exemplified the profound intergroup dietary differences that can be

caused by the use of food plants available to only

one group.

In considering present density differences within

the two home ranges, it can be reasonably assumed

that the densities of tree species that did not produce commercially valuable timber and were also

large (e.g., F. exasperata, F. brachylepis, F. dawei,

P. microcarpa, etc.) would have been relatively unaffected by selective felling. Hence any intergroup

dietary variability caused by the exploitation of

these species must be a reflection of density differences due to vegetational heterogeneity rather than

due to selective felling. This is particularly true of

large species that are presently found at higher densities within the selectively felled area (F. exasperata

and F. brachylepis).

Ficus exasperata provided some of the greatest

intergroup dietary variations through its markedly

different patterns of use by both groups. Phenological study of this species showed that asynchronous

activity of individuals provided both groups with

one to three potential food items throughout all

months of observations (Rudran, unpubl.). During

any particular month, however, the relative abundance of these items was much greater within the

home range of Group II. Group I used only the

fruits of this species, while Group II used all three

food items. Ficus exasperata, which was used fairly

continuously and at relatively high frequencies by

Group II, provided at least some of the intergroup

dietary differences during every month. The manner

in which Group II used this food plant was also

probably responsible for its less diverse diet. Ficus

brachylepis was another species that was an important food plant to Group II that was hardly ever

used by Group I.

Local variations in the phenological activity of

a food plant also gave rise to dietary differences

between the two groups. In November 1973, when

Group II used Uvariopsis congensis at high frequency (Figure 11), much of its feeding activity

was centered around a grove of this species, whose

phenological activity was presumably out of phase

with the majority of its individuals found within

both home ranges. The variable patterns of use of

Premna angolensis by the two groups were also

probably due to differences in relative abundances

of these blossoms caused by local variations in the

activity of this species. The flowering activity of

Markhamia platycalyx, which was far more conspicuous within the home range of Group II, provided an important food source (nectar) to this

group during August 1973, whereas nectar was never

important in the diet of Group I. This may have

been due to local variations in the phenology of

this species, but Struhsaker (in press) also provides

evidence to suggest that the heavier predation of

these blossoms (particularly by the red colobus)

within the home range of Group I made them less

readily available to this group than to Group II.

The red colobus, being best adapted to old mature

forest, occurred at higher densities within the home

range of Group I than Group II (Struhsaker and

Oates, 1975). The extensive predation of M. platycalyx blossoms within the home range of Group I

and its effect on fruit crop size (Struhsaker, in press)

was probably responsible for the fact that only

Group II used the fruits of this species.

INTERPOPULATIONAL COMPARISONS OF BLUE MONKEY DIET.—In Kahuzi-Biega National Park, Zaire,

Schlichte (1975) found that a large proportion of

blue monkey diet was restricted to a small proportion of the total food plant list. This is consistent

with my findings in the Kibale Forest. Schlichte recorded a total of 36 food plants used by his groups,

while I noted more than twice that number in my

study groups. This may have been due to differences

in the durations of the two studies and /or to the

floristically depauperate nature of the Zaire study

area. Schlichte found group-specific food preference

for Kotyschya blossoms, which were available to

both his study groups but were used only by one.

Similar observations were also made by me in the

Kibale Forest. Due to methodological differences,

direct comparisons of the proportions of different
NUMBER 249 45

food items constituting the diet of the two populations cannot be made. In both populations, however, fruits formed a major part of the diet, while

foliar food was used more frequently than invertebrate food. The major component of the diet of

blue monkeys of Budongo Forest was also fruits

(Aldrich-Blake, 1970a).

The blue monkeys of the Kibale Forest did not

use 30 food plants exploited by the Zaire population, and 20 food plants of a total of 30 eaten by

the Budongo Forest population. Interpopulational

differences found in the diet of blue monkeys, as in

several other primate species (see Chalmers, 1968;

Gartlan and Brain, 1968; Oates, 1974; Dunbar and

Dunbar, 1974; Clutton-Brock, 1975; Struhsaker,

1975; Waser, 1975), were probably mainly due to

differences in floristic composition between widely

separated areas.

The Ranging Patterns of Blue Monkeys

METHODS

While observing a blue monkey group, I mapped

the locations of individuals soon after recording

their activity during 10-minute scan periods of systematic sampling (see "Introduction"). From March

1973 to June 1973, these plots consisted only of locations of the greatest concentration of individuals

during the scan periods centered at the hour and

at the half hour. From July 1973 onward I plotted

locations (1) during all four scan periods recorded

during the hour, and (2) of every individual whose

activity was noted. In the analysis I segregated these

location plots into quadrats, and for most of the

data analysis used a 50 m X 50 m (i/4 hectare) grid

system. Measurements of home range size were also

obtained by using two smaller grid systems, each

comprising yie to y64 hectare quadrats, respectively.

In the following sections, reference to the quarter

hectare quadrats used by Group I has been made

with respect to its location—first along numbered

rows and then along numbered columns.

Throughout each day I also recorded the paths of

movement of the group. When the group was widely

dispersed, I mainly relied on recognizable animals

to plot the movements of the group, and when it

was compact, I noted the path of movement of the

greatest number of individuals. Since these paths of

group progression do not take into account vertical

movements, they must be considered as minimal distances moved by the group. From September 1973

onward, daily movements were subdivided into

hourly movements.

During each hour of group contact, I collected

climatic data on a subjective basis by using a scale

from \-\ to denote sunny, hazy, cloudy and rainy

weather conditions respectively. When the weather

changed drastically within the hour, the weather

condition with the longest duration was assigned

to that particular hour.

In order to calculate range overlaps, I used

Holmes and Pitelka's (1968) method, which I had

used earlier in the computation of diet overlap.

Using this method, I computed two measures of

range overlap between sample periods and in both

cases considered the ]/4 hectare quadrat as the unit

of overlap. In one case, I measured overlaps considering only the number of overlapping quadrats

and in the other took into account the frequencies

of use of these quadrats also. The first measure is

related to spatial overlap between sample periods

while the second is related to temporal overlap in

areas of overlap. Range overlaps between different

days of a sample period were also computed, but

only as a measure of spatial overlap. Quadrat utilization diversity was computed using the ShannonWiener diversity equation (Pielou, 1966).

RESULTS

HOME RANGE SIZE.—From March 1973 until May

1974 inclusive (i.e., through 22 sample periods),

Group I entered a total of 290 14 hectare quadrats,

which amounted to a home range size of 72.5 hectares. Grassland abutted the northwestern and western periphery of their home range, and a small

stream that ran along the southeastern and eastern edge separated their home range from that of

Group III (Figure 13). The stream was not a barrier

to movements and could have been crossed at several points via arboreal pathways. Aldrich-Blake

(1970a) also noted that a road overhung by arboreal

pathways served as a boundary between the home

ranges of some of his study groups of blue monkeys.

This suggests that when easily recognizable physical

features of the habitat were available, blue monkeys

used them to demarcate range boundaries.
46

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

+14

•13

+12

•11

•10

• 9

• 8

• 7

• 6

+s

• 4

• 3

• 2

-1

- 2

- 3

- 4

- 5

- 6

- 7

- 8

- 9

-K)

-11

-12

-13

-14

-15

-16

-17

-18

-19

-20

-21

-22

-23

-24

-26

-25 i

5

?

CM

/

z <

/

J

-20

N

\\

-19

ID

-18

tt-

-17

Ml

\

-16

w

mm

1 r1

\

-15-14

-13

N

• • •

T

r—

-12

=

TP

•

s

r

2k.

T

\

i

•f

tm

f

LIf

f

rs

p

rn

T

)Fp:

V

1h

T

eg

1

10

,T

•n

•14

+13

•12

•11

•10

•9

•8

•7

•6

•5

•4

•3

•2

•1

-1

-2

-3

-4

-5

-6

-7

-«

-9

-10

-11

-12

-D

-H

-0

-16

-17

-18

-19

-20

-21

-22

-23

-24

FIGURE 13.—The home range of Group I. The 290 quarter-hectare quadrats used by Group I are

enclosed within the dark outline.

The cumulative area used by Group I increased

during the first 1008 hours of group contact but

remained stable over the last 64 hours of observations (Figure 14). This suggests that during my observations of Group I, I had discovered their entire

home range. The range estimate of 72.5 hectares,

however, may be considered an overestimation because group members were not mapped in every

part of each y4 hectare quadrat they entered.

In order to exclude small lacunae from the 14

hectare quadrats used by Group I, I used two grid

systems of smaller dimensions. A grid composed of

i/16 hectare quadrats yielded a home range size of

60.8 hectares, and a grid of %4 hectare quadrats

yielded an estimate of 48.5 hectares. The home

range estimate decreased by 33% of the original

value when quadrat size was reduced by y16.

AREAS USED DURING DIFFERENT SAMPLE PERIODS.—

In Figure 15 I have segregated the estimates of the

areas used by Group I during different sample

periods in accordance with the slightly different

methods used in plotting locations before and aftei
NUMBER 249 47

U 50

I

M, M 2 A, A2 M, M 2 J, J2 J, J2 A, A» S, O, Ni N, Di Ji F, M, Ai M,

54 95 148 189 234 281 338 382 442 499 555 614 666 720 775 835 895 951 1008 1029 1054 1072

Sample period and Cumulative hours of group contact

FIGURE 14.—Cumulative increase in the area used by Group I during group contact through all

sample periods from May 1973 to May 1974, inclusive.

June 1973. The fewer locations plotted by the

method used from March 1973 to June 1973 were

probably largely responsible for the smaller areas

used during this period. Nevertheless, even between

July 1973 and February 1974, Group I used only a

small proportion of the entire range during any

one sample period. The first sample period of

November 1973 was the only time that Group I

visited more than half its home range during a five

consecutive day period.

Within the segregated data, it can also be seen

that the total area used during different sample

periods showed considerable variation. Since these

variations may have been due to differences in the

durations of group contact, the areas used were

standardized to the least durations of group contact during sample periods. The least durations of

contact during March 1973 and June 1973 and

July 1973 to February 1974 sample periods were

41 hours and 51 hours, respectively. Since the
48

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

S 20-

J2 J,

Sample Period

FIGURE 15.—The total and standardized measures of the areas used during different sample

periods and the percentage of the home range used during each sample period.

methods used during these two time periods were

somewhat different, I felt it was unnecessary to

standardize the areas used during all sample periods

to one fixed time period. The standardized measures

of areas used between March 1973 and June 1973

showed little variation; however, the areas used between July 1973 and February 1974 varied significantly from the mean area used during this period

(x2 = 18.8, df = 10, p<0.05). The variability in the

areas used during different sample periods is depicted by movements during two sample periods in

Figure 16.

RANGE OVERLAP BETWEEN SAMPLE PERIODS.—As

mentioned before, I computed range overlaps between sample periods as a measure of area overlap

as well as a measure of time overlap in areas of

overlap. Overlap measures were computed only between sample periods during which similar methods

of data collection were used. Neither the areas used

during different sample periods {Tables 39 and 40)

nor the proportions of time spent in areas of overlap (Tables 41 and 42) were high, and three pair

combinations of sample periods—March (I) 1973

and May (II) 1973, March (I) 1973 and June (II)

1973, September (I) 1973 and January (I) 1974—

showed the extreme case of zero overlap (see Figure

17). This suggests that usually Group I not only

used relatively small areas, but also somewhat different parts of their range during different sample

periods.
NUMBER 249 49

-26 -25 -24 -23 -22 -21 -20 -19 -18 -17 -16 -15 -14 -13 -12 -11 -10 -9 -8 -7 -6 -5 -A

•14

•13

•12

•11

•10

+9

•8

•7

•6

•5

+4

• 3

•2

• 1

-1

-2

-3

-4

-5

-6

-7

-8

-9

-10

-11

-12

-13

-14

-15

-16

-17

-18

-19

-20

-21

-22

-23

-24

Extrapolated

i day 2 March I 1973

! Novemderl 1973

movements

xi day 2

•14

• 13

•12

• 11

• 10

•9

• 8

•7

•6

• 5

•4

•3

•2

•1

-1

-2

-3

-4

-5

-6

-7

-8

-9

-10

-11

-12

-13

-14

-15

-16

-17

-18

-19

-20

-21

-22

-23

-24

-26 -25 -24 -23 -22 -21 -20 -19 -18 -17 -16 -15 -14 -13 -12 -11 -10 -9 -8 -7 -6 -5 -4

FIGURE 16.—Group movements on different days of the first sample periods of March 1973 and

November 1973 depicting variability in the areas used during different sample periods.
50

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

- 2 6 -2 5 -24 -2 3 -2 2 -21 -2 0 -19 -18 -17 -16 -15 -14 -13 -12 -11 -10 -9-8-7- 6 - 5 - 4

-1 1 r

——2 -•— Movements on dsy 2

*

2

 Night resting tree on day 2

•2

• 1

-1

-2

-3

-4

„ c

-6

-7

-8

-9

-10

-11

-12

-13

-14

-15

-16

-17

-18

-19

-20

-21

-22

-23

-24

- 2 6 -2 5 -24 -2 3 -22 -21 -2 0 -19 -18 -17 -16 -15 -14 -13 -12 -11 -10 ^9 -8- 7 - 6 - 5 - 4

FIGURE 17.—Group movements during the first sample periods of September 1973 and

January 1974 showing nonoverlap in the areas used.
NUMBER 249 51

TABLE 39.—Group I, percent of overlap in home range use

based on the area of quadrats used in common during sample

periods from March 1973 to June 1973, inclusive {all pair

combinations of sample periods: N = 28, X = 21.1%, range

= 0%-43.9%; successive combinations of sample periods:

N = 7, X = 24.5%, range = 3.4%-43.9%)

Sample

Mar 73

Mar 73

Apr 73

Apr 73

May 73

May 73

Jun 73

period

(I)... .

(ID.. .

(I)... .

(ID.. .

(I)... .

(ID...

(I)....

Mar

(II)

21.0

-

-

-

-

-

-

Apr

( I)

21.3

35.0

-

-

-

-

-

Apr

(II)

13.7

38.5

27.1+

-

-

-

May

( I)

37.8

27-5

31.9

20.6

-

-

-

May

(ID

0

15.8

1.5

19.6

3.1+

Jun

( I)

1+.0

22.6

37.2

26.6

16.0

20.0

-

Jun

(II)

0

27.1+

21.9

16. h

2.7

37.0

1+3-9

The low values of time overlap indicate that during different sample periods the proportion of time

Group I spent in overlapping quadrats was greatly

variable. From this it can be inferred that during

each sample period Group I used different quadrats

at proportionately high frequencies. This can also

be shown by comparing the overlap between sample

periods due to area of use (Tables 39 and 40) with

those weighted with the frequency of use of overlapping quadrats (Tables 41 and 42), where the latter measures of overlap were consistently lower than

the former.

DAILY RANGE.—Since duration of group contact

affected the records of areas used, I limited the computations of daily ranges to 67 days with 11 or more

hours of group contact. The mean and the range of

areas used on these days are presented in Figure 18.

Frequently the areas used on different days of a

sample period as well as mean daily ranges of different sample periods varied considerably. Comparison of Figures 15 and 18 shows that usually day

ranges also constituted a small proportion of the

total area used during a sample period. On any

particular day of a sample period, Group I infrequently used over half the total area used during

that sample period, which suggests that daily ranges

of Group I must have frequently included areas that

were previously not used during the same sample

period. This can be illustrated by considering the

cumulative increase in the number of quadrats used

through days of each sample period. In 16 of 19

sample periods there were continuous increases in

the area used through five days of group contact

(Figure 19). Only in three sample periods (March (I)

1973, August (I) 1973, and January (I) 1974) did the

increase in cumulative area of use reach a plateau

prior to the end of five days of observations.

A restricted analysis for 19 days (between March

and June 1973) with 11 or more hours of observations per day showed that the daily distances moved

were positively correlated with the sizes of the areas

used on these days (P = 0.004 two-tailed Kendall's

correlation test; Sokal and Rohlf, 1969). Thus,

revisits to quadrats or back-and-forth movements

within a limited number of quadrats must have

been infrequent.

In order to find out if the area used by Group I

would stabilize over a 10-day period, I combined

the ranging data from two sample periods conducted

during the same month in six months of the study.

I excluded the data from the sample periods in

March 1973 from this analysis since there was a

relatively long (seven days) interval between sample

periods. During the months of April to August 1973

and November 1973 intervals between sample peTABLE 40.—Group I, percent of overlap in home range use based on the area of

quadrats used in common during sample periods from July 1973 to February

1974, inclusive (all pair combinations of sample periods: N = 55, X = 36.6%,

range = 0%-66.8%; successive combinations of sample periods: N = 10, X =

42.8%, range = 19.8%-66.8%)

Sample

J u l

J u l

Aug

Aug

Sep

Oct

Nov

Nov

Dec

Jan

73

73

73

73

73

73

73

73

73

71+

period

(I). .

(II).

(I). .

(II).

(I). .

(I). .

(I). .

(II).

(I). .

(I). .

Jul Aug

(II) (I)

1+8.2 1+2.1+

- 19.8

-

-

-

-

-

_

-

-

Aug

(II)

1+5.8

1+7-3

2U.0

-

-

-

-

-

-

-

Sep

(I)

3^-7

1+3.0

0.9

39.8

-

-

-

-

-

-

Oct

( I)

36.

38.

1+.

1+3.

66.

-

-

-

-

-

1+

7

6

5

8

Nov

( I)

39-5

1+2.9

20.8

55.6

1+7.6

1+6.9

-

-

-

-

Nov

(II)

5U.2

1+1.3

1+3.9

1+9-5

18.9

26.7

50.3

-

-

-

Dec

( I)

1+7.5

33.5

1+7-6

1+0.5

19-6

23.7

38.2

1+7.3

-

-

Jan 71+

( I)

29.3

16.3

56.0

21.8

0

9 . 1

19.1+

37.8

1+5.2

-

Feb

( I)

1+1+.1+

35.3

33-3

1+5.0

2U.9

35.5

1+1.5

1+9-9

51+.5

39.1+
52 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

TABLE 41.—Group I, percent of overlap in home range use

based on the frequency of use of quadrats during sample

periods from March 1973 to June 1973, inclusive (all pair

combinations of sample periods: N = 28, X = 13.6%, range

= O%-32.1%; successive pair combinations of sample periods: N = 7,X - 16.9%, range = 4.2%-32.1%)

Sample

Mar

Mar

Apr

Apr

May

May

Jun

73

73

73

73

73

73

73

period

(I)....

(II)..

(D...

(ID..

(D... (II)..

(I)...

Mar

(II)

12.2

-

-

-

-

-

-

Apr

(I)

15.6

17.6

-

-

-

-

-

Apr

(II)

9-3

20.5

21.9

-

-

-

-

May

(I)

24.3

UM

16.8

12.9

-

-

May

(II)

9.0

10.2

2.1

7.5

4.2

-

-

Jun

(I)

1.6

10.5

21.3

15.6

12.5

17.2

-

Jun

(II)

0

18.5

18.5

10.6

4.8

?7.8

32.1

riods were 2, 0, 0, 2, 3, and 2 days, respectively. The

combined data for the above months show that the

cumulative area of use increased even over 10-day

periods of observations (Figure 20), although during

some months the rate of increase declined somewhat

toward the latter stages of observations.

RANGE OVERLAP BETWEEN DAYS OF THE SAME SAMPLE PERIOD.—The use of somewhat different areas

on days of a sample period can also be shown by

computing area overlaps between days of the same

sample period. With two exceptions I restricted this

analysis to those sample periods with either four or

five days of 11 or more hours of group contact. The

exceptions included in this analysis were one day in

July (II) 1973 and another in February (I) 1974

when group contact was maintained for 10.5 hours.

Thus, the time bias was minimized in this analysis,

which is summarized in Table 43. The relatively

low mean and maximal overlaps indicate that repeated use of quadrats was infrequent. Generally

the greatest overlaps occurred between successive

days, and the mean overlaps between successive days

were normally greater than the mean overlaps between all pair combinations of days. During successive days as well as during other pair combinations

of days, however, Group I sometimes used mutually

exclusive areas of their range.

Since daily ranges were relatively small and at

least partially different, large proportions of the

areas used during a sample period were used only

on one day of a sample period. This is illustrated

for the sample periods considered in the above analysis in Figure 21. On the average nearly two-thirds

of the area used during a sample period was not

revisited during the same sample period, and in

most sample periods more than half the area used

was visited only on one day. Group I, however,

repeatedly used small areas for four and five days

of a sample period. This shows that Group I used

their home range rather unevenly.

Given the area used during a sample period, the

ranging patterns during 5 of the 11 sample periods

considered in Table 43—i.e., March (I) 1973, July (II)

1973, August (I and II) 1973, and December (I) 1973

sample periods—differed significantly from that expected from the mean ranging patterns (using x

2

test, df=4, p<0.025 in all cases). The ranging patterns of the other six sample periods did not differ

significantly from the mean ranging patterns (xz test

df=4, p>0.05). As mentioned earlier, however, the

areas used during sample periods between July 1973

to February 1974 differed significantly from the

mean area used during these sample periods.

TABLE 42.—Group I, percent of overlap in home range use based on the frequency of use of quadrats during sample periods from July 1973 to February

1974, inclusive {all pair combinations of sample periods: N = 55, X = 23.3%,

range — 0%-42.4%; successive pair combinations of sample periods: N = 10,

X - 29.1%, range - 21.3% -42.4%)

Saiqple

Jul

Jul

Aug

Aug

Sep

Oct

Nov

Nov

Dec

Jan

73

73

73

73

73

73

73

73

73

74

period

(I)..

(II).

(I)..

(II).

(I)..

(I)..

(I)..

(II).

(I)..

(I)..

Jul Aug

(II) (I)

26.5 38.3

- 11.4

-

-

-

-

-

-

-

-

Aug

(II)

30.8

31.2

21.3

-

-

-

-

-

-

Sep

(I)

17.8

23-9

0.3

25-3

-

-

-

-

Oct

(I)

17.5

26.0

1.6

30.8

42.4

-

-

-

-

Nov

(I)

20.4

27.0

13.2

34.8

29.4

36.7

-

-

-

Nov

(II)

37.7

16.5

39-9

30.8

8.8

11.4

24.5

-

-

-

Dee

(I)

33.7

15.9

34.3

23.4

15.1

18.5

28.2

39.6

-

-

Jan 74

(I)

20.9

6.5

28.4

15-9

0

4.4

10.8

28.8

27.5

-

Feb

(I)

29.6

16.8

23.1

31.5

12.3

17.4

26.5

27.7

34.4

36.1
NUMBER 249 53

10

h

• Daily Range

• Mean

Sample Period

FIGURE 18.—Areas used on days with 11 or more hours of group contact segregated

according to sample periods.

TABLE 43.—Group I, mean and range of area overlap between pair combinations

of days of observations during sample periods with four or five days of 11 or more

hours of group contact

Sample

Mar 73

Jun 73

Jul 73

Jul 73

Aug 73

Aug 73

Oct 73

Nov 73

Nov 73

Dec 73

Feb 7h

period

(I). .

(I). .

(I). .

(II).

(I). .

(II).

(I). .

(I). .

(II).

(I). .

(I). .

Mean

percent

of overlap

between

a l l pair

combinations

36.6

15-3

19-3

10.8

36.3

U.5

23.8

1U.7

16.8

27.9

13.6

Range

of overlap

between

a ll pair

combinations

29.1+-1+6.7

0-35.7

0-1+8.5

0-3^.5

2U. 2-1*7.7

0-12.9

3.7-1*2.9

1*.3-29.I

0-35.3

3-3-51*.5

2.8-19.5

Pair combinatio n of days

with greatest

overlap

Day 1 & Day 2

Day 1 & Day 2

Day 2 & Day 3

Day 1 & Day 2

Day 1 & Day 1*

Day 2 & Day 1*

Day 3 & Day 1*

Day 1 & Day 1+

Day 2 & Day 3

Day 1 & Day 5

Day 1 & Day 1+

Mean

percent

of overlap

between

successive

days

36.5

19.6

2U.8

21.9

38.0

6.95

21.2

11.3

19-32

25.1+

12.7

Range of

overlap

between

successive

days

29.1+-1+6.7

0-35.7

0-1+8.5

5.9-3!+.5

31.1-1*5.0

U.6-12.0

3.7-1+2.9

U.3-17.O

0-35.3

9-1-39.0

6.7-19.3

DISTRIBUTION OF TIME IN SPACE.—The amount of

time that Group I spent in different parts of their

range can be considered in terms of frequency of

location plots in the different quadrats as well as

in terms of days, sample periods, and months each

quadrat was used. Figures 22 and 23 clearly show

that there was considerable variation in the distribution of these time-related elements among the

290 quadrats that comprised home range of Group I.

If the number of days of use and the number of
54

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

Cumulative hours of group contact

of group contact

sample periods of use of quadrats were considered

together, then each quadrat would occupy one of

four classes depending on whether or not it was used

above or below the mean number of days or sample

periods of use. The 290 quadrats that made up

the home range of Group I belonged to all four

classes, which again illustrates the differential use

of quadrats (Figure 24). The greatest number of

quadrats (141 = 48.6%) was used less than the mean

number of days of use (8.2 days) and mean number

of sample periods of use (6 sample periods). The

smallest number of quadrats (3 = 1.0%) belonged to

the class that consists of those that were used on

Cumulative hours of group contact

FIGURE 19.—Increase in the cumulative number of quarterhectare quadrats used through five successive days of group

contact during different sample periods.

less than average number of sample periods but on

greater than average number of days. These were

quadrats that Group I used very frequently during

a few sample periods. On the other hand, some

quadrats were used during less than average number

of days, but on greater than average number of

sample periods, showing that they were visited only

for one and sometimes two days each sample period

on more than the average number of sample periods. Figure 24 also shows that more than half the

home range (168 quadrats = 57.9%) was used on less

than the mean number of days of use and about

half the total number of quadrats was used more

than the mean number of sample periods.

Figure 25 considers the number of days of use of

the quadrats together with their frequency of use.

Here again there was an unequal distribution of
NUMBER 249

55

150-

P 120

b 90-

3 80H

30-

IMov.

May

-•Apr.

10 20 30 40 50 60 70 80 90 100 110 120

Number of Hours of Group Contact

FIGURE 20.—Increase in the cumulative number of quarter-hectare quadrats used through

10-day periods of observations during different months.
56 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

Man

Jun,

Jul,

JulAug,

Aug2

Oct1

Nov.

Nov.

Dec,

Feb,

Percent Area Used on: W&i 1 Day,

\y-, . ••:••••- -

{-1 . ,-' : ! • r, L. i 1 1

0 50 100

Cumulative Percent Range Use

FICURE 21.—Cumulative percentage of areas used for different numbers of days

of a sample period illustrated for a selection of sample periods.
NUMBER 249 57

4 0 i

30"

N=290 quadrats

CO

CO

l _

CO

13

CJ

10-

No. of months used

15

No. of sample periods used

FIGURE 22.—Quadrats comprising the home range of Group I segregated according

to number of months and sample periods of use.
58 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

quadrats among all four possible classes of quadrats.

Group I used more than half their home range

(150 quadrats = 51.7%) on less than average number of days and below average frequency. They used

17 quadrats (5.8%) below average number of days

but at greater than mean frequency, indicating that

these quadrats were intensively used at least on one

occasion they were visited. Conversely, 28 quadrats

(9.7%) were visited more often than the average

number of days but used at less than average frequency. Comparison of Figures 24 and 25 show that

the number of days of use, the number of sample

periods of use, and the frequency of use of a quadrat

were not always interdependent. In other words, the

quadrat with the highest frequency of location plots

was not the one with the greatest number of days of

use. Similarly the quadrat used on the greatest number of days was not the same as the one that was

used during the greatest number of sample periods.

Through all sample periods (i.e., from March

1973 to May 1974) a total of 15,094 location plots

was recorded from the 290 quadrats used by Group

I (Figure 26). The steady increase of the cumulative percent frequency of location plots in rank

ordered quadrats comprising the entire home range

(Figure 27) further illustrates the differential use of

the habitat. Just over 50% of the total number of

location plots belonged to quadrats occupying rank

orders 1 to 59, which amount to only 20.34% of the

total number of quadrats used (Table 44). Similarly,

quadrats that occupied the top 50% of the rank

orders included 84.12% of the total number of

location plots that were recorded.

Also, during each sample period, Group I used

different quadrats at variable frequencies. This is

shown in Table 45, which gives the percent fre10 Illlllilll ,•• ,, ,

15 20 25 29

No. of days used

1-10 51-60 101-110 51-60

Frequency of use

FIGURE 23.—Quadrats comprising the home range of Group I segregated according

to number of days of use and frequency of location plots.
NUMBER 249 59

quency of use of quadrats occupying top five ranks.

Quadrats occupying these ranks constituted a small

fraction of the areas used, but included relatively

large proportions of the locations plotted during

each sample period. Moreover, different quadrats

frequently occupied these high ranks during different sample periods.

DIFFERENTIAL USE OF QUADRATS AND FOOD ABUNDANCE.—Perhaps one of the more obvious reasons

for the differential use of quadrats is the fluctuations

in food availability within quadrats. Therefore, for

a phenological study, I selected individuals of three

important food plants of Group I that periodically

produced extensive amounts of fruits. My sample

consisted of five P. turbinata and all F. exasperata

and F. dawei trees found within the home range of

Group I. The two Ficus species, which were large

and sometimes had their canopies extending over

more than one quadrat, periodically produced such

extensive amounts of fruits that they were good indicators of the temporal variation in food abundance

in the quadrats they were located.

Since I collected phenological data at the end of

TABLE 44.—Group I, summary of the

cumulative percent of frequency of

use of 290 rank-ordered one-fourth

hectare quadrats constituting the area

used from March 1973 (I) to May

1974 (I), inclusive

Cunulative

percent of

frequency

of use

2.3U

10.12

2U.66

50.19

75.02

8U.12

89.83

100.0

Rank

order of

quadrats

1 (-2-13)

1-7

1-22

1-59

1-111 +

1-1U5

l-l£5

1-290

Percent

of

quadrats

0.3

2.U

7.6

20.34

39.31

50.0

56.9

100.0

each month, just prior to the observation of Group

I the following month, in the results presented below I have considered the phenological data from

February 1973 to January 1974 in relation to the

frequency of quadrat use between March 1973 and

February 1974.

Table 46 shows that during the fruiting period

of the five P. turbinata, all quadrats in which they

N=27

1 3 5

9» 9*

21» S» 1«

17*

 2* N-141

• ?• IB

e periods used No. Samph

. » •

7

6*

2 «

3 «

15

13

11

•9 1 .

7 7.

9

•5 1 *

3

•

1

3«

5»

4 «

2»

N=n9

i« 1*

3»

3« 7

3« 3

3 . 2

11

1 .

1 » 3»

, . 3. 4* 1 . 3«

1 . 1 . 4 . 2« 2« 1 '

4» 2*

» 1 . 1.1 .

> 1 .

13 15 17

Na Days used

)

2* 2» 1 .

1»

1« 1» l .

! • 1 • 3»

1»

1 . 1«

19 21

i •

23

2 •

25 2'/ ' 29

FIGURE 24.—Four-way classification of quadrats comprising the home range of Group I based on

mean number of days and mean number of sample periods of use of a quadrat. The number

beside each point represents the number of quadrats occupying identical intersects.
60

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

N=17

'353

220

210

190

170

150

130

no

9 0

70.,

= 95

:: :;

 1:,

.1 .1 .1

50-

15 17 19

No Days Used

23 25 27 29

30

10

N=150 N=28

FIGURE 25.—Four-way classification of quadrats comprising the home range of Group I based on

mean number of days and the mean frequency of use {i.e., location plots) of a quadrat. The

number beside each point represents the number of quadrats occupying identical intersects.
NUMBER 249

61

-25-24-23-22 -21 -20 -19 -18 -17 -16 -15 -14 -13 -12 -11 -10 -9 -8 -7 -6 -5 -4

1—i—i—i—i—i—r

-6

-7

-8

-9

-10

-11

-12

-13

-14

-15

-16

-17

-18

-19

-20

-21

-22

+14

7 :£

100m.

. V

'V. -

v' i \

•11

•10

•9

+8

+7

•6

•5

*4

+3

+2

+1

-1

-2

- 3

- 4

- 5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

2 0

21

22

-26 -25 -24 -23 -22 -21 -20 -19 -18 -17 -16 -15 -14 -13 -12 -11 -10 -9- 8 -7-6-5- 4

FIGURE 26.—Distribution of location plots and some paths of movements recorded within

home range of Group I between February 1973 and May 1974 (N = 15,094 location plots).

the
62 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

IOOT

90

80

70-

U

c

<D

ZJ

cr

i 50

C

<D

U

V 40

Q.

•^ 30

E

o

20

10

10 50 100 150

No. of quadrats

200 250 290

FIGURE 27.—Cumulative percent frequency of use {i.e., location plots) of 290 rank-ordered

quadrats comprising the home range of Group I.

were located were used more frequently than would

be expected if their frequency of use were equally

distributed through all months. In fact these five

trees formed part of a grove of this species in this

area that was extensively used for its fruits in

March (I) 1973 (see Figure 4). Nearly 49% of the

locations plotted during this sample period were

recorded from these five quadrats, which constituted

only 15% of total area used during this 5-day period.

Moreover, the locations plotted in these quadrats in

March (I) 1973 made up about 41% of the locations

recorded in them through all sample periods.

The quadrats in which F. exasperata Nos. 50, 51,

52, 53, 55, and 58 and F. dawei No. 2 were located
NUMBER 249 63

TABLE 45.—Group I, percent of frequency of use of top five rank-ordered quadrats during

all full-day sample periods March 1973 to February 1974

Sample

tor 73

Mar 73

Apr 73

Apr 73

May 73

May 73

Jun 73

Jun 73

Jul 73

Jul 73

Aug 73

Aug 73

Sep 73

Oct 73

Nov 73

Nov 73

Dec 73

Jan 74

Feb 74

period

( I )

(II)... .

(I)

(II)... .

( I )

(II)... .

( I )

(II)... .

(I)

(II)... .

(I)

(II)... .

( I )

(I)

( I )

(II)... .

(I)

(I)

(I)

Total

frequency of

location

plots

509

323

2 9 1

279

310

496

473

463

1077

900

943

1003

906

854

1004

1013

1077

911

1023

1

Quadr a t

number

-1-9

-16-18

-6-13

-12-22

-9-7

-16-17

-10-18

-10-18

-8-15

-14-17

-4-10

-9-19

-14-17

-14-20

-17-14

-1-12

-9-15

-2-13

-6-9

Percent of

frequency

of use

17.9

16.1

9.6

13.3

6.1

17.7

5.7

5.6

5.0

4.0

11.7

3.6

4 .1

6.7

3.9

6.5

5.2

22.1

8 . 0

I I

Quadr a t

number

-2-10

-15-21

-4-13

-18-16

+7-12

-15-16

-12-10

-14-20

+5-10

+11-9

+5-11

-15-23

-8-18

-14-22

-15-20

-9-15

-6-11

-7-13

-6-9

+6-12

Percent of

frequency

of use

13.8

6.2

4.8

6.1

5.2

11.7

5.1

4.8

4.7

3.2

5.6

3-3

3.5

4.8

2.9

6.3

4.2

7.1

6.8

i l l

Quad- Percent of

r a t

number

-1-10

-9-15

-6-11

-14-12

-9-19

-4-12

-19-15

-15-20

-13-22

+3-11

+9-9

-13-18

+4-9

+3-10

-11-15

-9-13

-15-13

-9-18

-9-15

-

-6-7

-5-7

frequency

of use

10.8

4.5

5.7

4 5

^. J

10.5

4 4

4.3

4.2

3.1

5.2

3 . 1

3-2

3.5

2.7

3.4

-

6.0

6.7

IV

Quadr a t

number

+1-8

+1-9

-17-15

-15-17

+1-10

-1O-Q

±.\j ~y

-10-18

-15-17

-16-19

-15-13

-15-20

-15-21

-16-19

-16-23

-9-15

+1-9

-8-15

-10-13

-18-19

+6-10

-1-9

-4-11

-2-12

-7-12

Percent of

frequency

of use

7 Q

f * y

3.4

_

5.4

-3 Q

j • y

7.3

3.4

3.0

4.0

.

4.8

3.0

3.1

3.3

_

3.2

4.0

5.7

5.2

V

Quadr a t

number

+2-8

-6-12

-14-15

-1-9

-15-19

-10-18

-5-11

+1-10

+8-10

+2-9

-2-14

-12-10

-14-20

-9-16

-10-15

-1-13

-

+5-12

-5-8

Percent of

frequency

of use

6.1

4 .1

4.7

4.2

3.0

3.6

3.0

4.5

2.5

3.0

2.9

2.4

3.0

-

5.1

4.8

Percent of

frequency

of use of

top 5 ranks

S6 S

37.1

27.5

39-9

23.6

55.6

21.6

29.7

21.5

16.4

31-8

18.0

16.9

21.2

14.6

22.4

21.6

46.0

31.5

Percent

of area of

top 5 ranks

15.1

10.5

7.8

11.7

8.8

13.0

6.7

11.0

5-1

8.9

4.5

4.5

4.6

3.3

4.3

6.0

8.8

5.1

were also used more frequently than expected during their fruiting period. This suggests that temporal variations in the frequency of use of quadrats

were related to the variations in food abundance in

them. Details of two examples may be given to further illustrate this point. During the sample period

of January 1974, F. exasperata No. 51 bore ripe

fruits and provided an abundant food resource to

Group I. Nearly 28% of all locations plotted during

this sample period were recorded from the quadrats

in which F. exasperata No. 51 was situated, although

this area comprised only 3.5% of the total area used

in January 1974. Also nearly 49% of the locations

plotted throughout study in this area were recorded

in January 1974.

Ficus dawei No. 2, which had ripe fruits from late

April 1973 through May 1973, provides a similar

example. Its fruits were not eaten by Group I during the first sample period of May 1973 (when

Group I used an area farther to the north of these

quadrats), but these fruits became the top-ranking

food resource during the second sample period.

Nearly 38% of all locations plotted in May (II) 1973

were recorded from the quadrats in which this tree

was situated, which composed only 8.7% of the area

used during this period. Moreover, 70.8% of all

locations plotted in these quadrats were recorded

in May (I) 1973.

Quadrats in which F. exasperata Nos. 54, 56, 57,

59, 60, and 61 and F. dawei No. 1 were located were

used less frequently than expected when food was

abundant. A possible explanation for this may be

the fact that the fruiting activity of these individuals

was more or less synchronized with that of the individuals in the previous category. For example, the

fruiting periods of F. exasperata Nos. 56, 57, 59, 60,

and 61 and F. dawei No. 1 coincided or overlapped

with those of F. exasperata Nos. 50-53, and the fruiting period of F. exasperata No. 54 coincided with

that of F. exasperata No. 55. When there are several

foci of abundant food resources, one or more of

these appeared to be overlooked or missed. Ficus

exasperata Nos. 54, 59, and 60 and F. dawei No. 1

were situated in relatively infrequently used quad-
64 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

TABLE 46.—Group I, fruiting periods of individual trees (between February

1973 and January 1974) and the frequency of use of their locations

Species

P. turbinata...

F. exasperata.•

F. dawei

Tree

number

1

2

3

1+

5

50

51

52

53

55

58*

51+

56*

57

59*

60

6 1 *

1

2

Location

-3-11

-2-10

-1-10

-2-9

-1-9

-3-12

-2-13

-2-lU

-U-13

-11-13

-10-17

-10-18

-17-21

-11-1U

-10-20

-12-19

-17-2U

-18-2U

-13-13

-13-10

-15-16

-15-16,

-15-17

-16-16,

-16-17

Total

Fruiting frequencyperiod

Feb

Feb, Jan

Feb, Jan

Feb

Feb, Jan

Feb, Oct-Jan

Sep-Jan

Sep-Jan

Jul-Nov

Feb-Jun,

Dec-Jan

Apr-May

Feb-May, Jan

Oct-Jan

Feb, Aug-Jan

Nov-Jan

Feb-Mar, Jan

Dec-Jan

Jul-Aug

Apr-May

of use

51

131

1U2

52

230

118

390

152

1+1+

202

51

26

26

72

56

26

30

58

26U

Observed

frequency

of use

during

fruiting

period

7

76

55

11+

95

97

286

75

35

157

18

0

5

37

0

0

6

0

199

Expected

frequency

of use

during

fruiting

period

h.3

21.8

23.7

h.3

38.3

1+9.1

162.5

63.3

18.3

117.8

10.2

IO.83

11.6

1+2.0

18.7

6.5

6.7

9-7

l+l+.o

••The phenology of these trees was monitored only for 9 months between

February 1973 and January 197U; hence, the frequency of use of the

quadrats they occupied was adjusted accordingly.

rats, which were not used throughout the sample

periods these individuals were in fruit (Table 46).

GROUP SPREAD.—In order to obtain a measure of

group spread, Struhsaker and I made simultaneous

plots of individuals belonging to Group I while

maximizing interobserver distance via the use of

walkie-talkies. This was done on four days, and the

maximum group spread in terms of linear distances

was about 120 m with a median value of 50 m.

Sometimes when working alone I was able to make

reasonably accurate estimates of maximum group

spread when the adult male moved away from the

group and emitted loud calls (termed "Pyows" by

Marler, 1973). In Group I these estimates of group

dispersal did not exceed 125 m. Considering the

poor visibility conditions within the forest canopy,

these group spreads appear to be large enough to

prevent continuous visual contact between group

members. Aldrich-Blake (1970a) found that blue

monkey groups in the Budongo Forest dispersed

over greater distances than in the Kibale Forest.

GROUP MOVEMENTS.—Group movements were coordinated and normally began with the directed

movements of a few individuals who were then followed by other members of the group. Initiators of

group movements did not appear to belong to any

particular age or sex class. Occasionally when the

adult male moved away from the main body of the

group and emitted loud calls, others then moved

in the direction of the call. Sometimes, however,

the adult male rejoined the group after emitting

"Pyows" and moved with the others in quite a

different direction.

In order to obtain unbiased estimates of total

daily distances moved, I confined the analysis of

group movements to 65 days of observations when

movements were monitored for 11 or more hours.

On these days Group I moved an average of 1298 m

per day (range 445-1961 m, std deviation = ±345).

The modal value of daily movements was between

1000 and 1100 m, but on over 50% of the days this

group moved greater than 1200 m (Figure 28).

Comparison of mean daily movements of different

sample periods shows considerable variation, with

peaks occurring in June (I) 1973 and October (I)

1973 (Figure 29); however, the variations in the
NUMBER 249

65

NU65days

Distance (kms)

FIGURE 28.—Group movements segregated according to daily

distances moved by the group on 65 days with 11 or more

hours of group contact.

daily distances traveled within each sample period

were also large, making interpretation of the variations of mean distances moved difficult. It is likely

that, during certain sample periods, daily movements were related to the pattern of distribution of

food resources. For example in March (I) 1973,

Group I moved very little when they repeatedly

used a grove of P. turbinata whose fruits served as

their primary food resource. During many other

sample periods also, they fed in areas where food

was concentrated, but distribution of these areas

was probably different to that in March (I) 1973.

As mentioned earlier, total daily distances were

subdivided into hourly movements during the sample

periods from September 1973 to February 1974. In

the analysis of hourly movements, I have treated

rainy and nonrainy hourly periods separately, since

rainfall was found to inhibit movements (see below).

Occasionally, movements for the half hour between

0630 hours and 0700 hours were also recorded.

When data of group movements during nonrainy

hourly periods from September 1973 to February

1974 were lumped, mean hourly movements showed

a clear bi modal pattern where peaks occurred between 0700 and 0800 hours and between 1700 and

1800 hours, and the period of least movements

occurred between 1300 and 1400 hours (Figure 30).

The upper limits of the range of hourly movements

also showed a similar pattern, but the range itself

was great, suggesting that some variable(s) other

than rainfall also affected hourly movements.

The pattern of hourly movements during each

sample period differed from the above pattern, but

belonged to two distinct classes. During the sample

periods from September 1973 to November 1973,

peaks of movements occurred during midday as well

as during early morning and late afternoon hours

(Figure 31). Also throughout the day hourly movements were usually greater than the mean distances

of travel computed for the September 1973 to February 1974 period. Hourly movements during the

sample periods from December 1973 to February

1974 better represent the bimodal pattern, but they

were usually less than for previously considered

sample periods and the mean hourly movements for

all sample periods considered together.

EFFECT OF CLIMATIC FACTORS ON GROUP MOVEMENTS.—Between September 1973 and February

1974, heavy rain affected 18 hourly periods of group

contact. These periods were distributed throughout

the day and because of the small sample size the

distances moved during these periods were pooled

regardless of the time of day of records. The mean

rate of movement was 63 m per hour (range

8-183 m, std. deviation ±39), which is less than the

least mean rate of movement during nonrainy periods (Figure 30). In general at the beginning of a

period of heavy rain, individuals sat hunched up

without regard to exposed and unexposed areas of

a tree. If heavy rain continued for more than 30-45

minutes, they usually left their sitting places and

moved relatively slowly while indulging in some activity such as feeding. Slight drizzles did not appear

to affect adversely the movements of the group.

Although rainfall appeared to inhibit movements,

Group I moved greater total distances during the

September 1973 to November 1973 sample periods

that were more affected by rain than the December

TABLE 47.—Group I, percent of number of hours of sunshine

and cloud cover on days with 11 or more hours of observations and mean of total daily distances moved during sample

periods from September 1973 to February 1974, inclusive

Sample

Sep 73

Oct 73

Nov 73

Nov 73

Deo 73

Jan 7k

Fet> 7U

period

(I). .

(I). .

(I). .

(II).

(I). .

(I). .

(I). .

Sunny

22.7

2U.U

16.3

15.5

6^.9

•jk.6

3>».9

Hazy

31.8

26.7

32.7

25.9

15.8

9.1

30.2

Cloudy

31.8

Uo.o

1*2.9

51.7

17.5

36.U

32.6

Rain

13.6

8.9

8.2

6.9

1.8

-

2.3

N

(hr)

22

U5

1*9

58

57

33

1*3

Mean total

movements

(•)

l>+97

1665

1625

137>»

11U8

1069

12U5
66 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

2 0 ,

15-

5 10

0 5-

3

A, A2 M, M2 J, J 2 J, J 2 A, A2 S, O, N, N2 D, J, F,

212353544534 4 553 4

Sample Period & No. Complete Days Observations

FIGURE 29.—Group movements on days with 11 or more hours of group contact {indicated by the

points on the vertical lines) segregated according to sample periods. Variations in the mean daily

distance moved is shown by the dashed line.
NUMBER 249

450-

350-

250-

.2 170

67

£

<D 150

<J

C

03

100-

70-

630-700 700 800 1200-1300

Time of

1800-1900

day

FIGURE 30.—Mean and range of group movements during nonrainy hourly periods

between September 1973 and February 1974.

1973 to February 1974 sample periods (Table 47).

This may be explained as the effect of cloudy

weather (which is usually associated with rainfall)

in enhancing group movements.

Considering only the data from days with less

than one hour of heavy rain, it was found that the

mean daily distances moved during nonrainy hours

(obtained from daily movements during nonrainy

hours standardized to a 12-hour period) were positively correlated with the corresponding mean cloud

cover indices during the September 1973-February

1974 period (Spearman Rank. Correlation Coefficient, rs=0.786, df=5, P<0.05). When days with

two or more hours of rain were included in the

analysis, however, the mean distances moved during nonrainy hours were not significantly correlated with the respective mean cloud cover indices

(rs=0.714, p>0.05). This suggests that long durations of rainfall inhibited movements during subsequent hours under different weather conditions.

This may have been due partly to the relatively

long bouts of grooming activity that usually followed heavy rainfall and the wetness of the substrate that may have retarded progression.

Hourly movements from September to November

1973 and December 1973 to February 1974 indicate
68 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

250-

200

12

•*->

0)

E

0)

u

c

In 100

5

5 0

700-800 900-1000 1100-1200 1300 " 1400 1500~1600 1700" 1 BOO

Time of day

200 I

50

Dec I

Febl

700-800 900-1000 1100 -1200 1300-1400 1500 -1600 1700 - 1800

Time of day

FIGURE 31.—Mean of hourly group movements during sample periods from September 1973 to

November 1973 and from December 1973 to February 1974 compared with mean of hourly group

movements between September 1973 and February 1974.
NUMBER 249

69

that one peak of movements always occurred before

1000 hours and after 1600 hours, and the greatest

variations between the two periods occurred during

the interim hours (Figure 31). Indices of hourly

weather conditions showed that movements during

early morning and late evening hours were more or

less independent of weather conditions, but they

were affected by weather conditions during the intervening period. Climatic factors were, however,

not the only variables that affected group movements. Movements during the same hour with similar weather conditions on different days varied

appreciably, and conversely, Group I sometimes

moved the same or equivalent distances during the

same hourly periods under different weather conditions. It must also be pointed out that although

movements, particularly during midday, were shown

to be influenced by cloud cover, it is possible that

they were actually affected by some related factor,

such as temperature.

AREAS AND TREES USED FOR NIGHT RESTING.—Late

in the evening I recorded the areas used for night

resting and usually reconfirmed the presence of

monkeys in these areas early next morning. Night

resting areas used by Group I were located on a

total of 83 evenings, on days just prior to and during sample periods from February 1973 to February

1974 inclusive (Table 48). On these days Group I

used a total of 50 quadrats for night resting. Since

the group moved until it was almost completely

dark, normally I was able to locate only one of possibly several quadrats that they used for resting each

night. Occasionally, however, I was able to locate

two or three adjacent quadrats used for night resting. On these occasions, I assigned each quadrat a

score of one for a night's use and therefore the total

of evenings on which Group I used the 50 quadrats

for night resting (i.e., 104 evenings) exceeded the

total of evenings that I located their night resting

areas.

TABLE 48.—Group I, location of quadrats used for night resting during and just

prior to sample periods from February 1973 to February 1974

Sample

Feb 73

Mar 73

Mar 73

Apr 73

Apr 73

May 73

May 73

Jun 73

Jun 73

Jul 73

Jul 73

Aug 73

Aug 73

Sep 73

Oct 73

Nov 73

Nov 73

Dec 73

Jan 7k

Feb 7U

period

(I)... .

(D.. .

(II). .

(D...

(II). .

(D...

(II). .

(D.. .

(ID.. .

(I)... .

(ID.. .

(i)... .

(ID...

(i)... .

(i)... .

(i)... .

(ID...

(i)... .

(i)... .

(i)... .

Two days One day

prior to prior to

sample sample

period period

-2-10

-10-13

-

-I*.-12

-

-

-

-13-19

-2-10

~5-y

-5-13 +U-9

_

-

-6-13

-15-20

-U-10

-2-13

+5-10

+6-10

Day 1

-6-13

-2-10

-

-5-11

-6-11

-5-11

-8-13

.

-lU-20

-13-20

-

-5-11

-U-ll

-U-io

+9-13

-5-10

-11-15

-9-19

-15-15

-16-15

-10-15

-5-H

-

-2-12

-5-8

Day 2

_

-5-12

-9-19

-

-U-12

-

-lU-22

-lU-22

-15-22

-15-21

-lU-22

-U-12

-I+-12

-5-13

-11-18

-lU-20

-9-19

-3-12

-2-12

-3-12

-2-12

+5-12

-k-12

Day 3

-2-13

-3-12

-2-13

-6ll3

-

+7-12

-

-

-10-19

+5-10

-9-18

+6-U

-9-19

-16-23

-17-2U

-lU-20

-15-20

-12-16

-2-13

-2-12

-1-12

+7-U

-2-11

-U-12

Day 1*

-

-2-10

-3-10

-

-5-12

-15-21

-U-12

-

-2-10

-

-U-10

-U-12

-lU-21

-lU-20

-lU-20

-

-2-13

-2-12

-U-12

-U-ll

-2-13

-12-10

Day 5

-5-12

-3-10

-U-12

-6-12

-6-13

-6-13

-

-13-22

-lU-21

-

-

-

-5-11

+7-12

-

-

-

-

-2-13

-
70 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

The distribution and the frequency of use of the

quadrats used for night resting showed that there

was probably some selectivity in the area used for

night resting (Figure 32). For example, Group I

most frequently slept in an area consisting of several

quadrats located at approximately the center of

their range and rarely slept in the eastern part

of their range. Nine of 11 quadrats rank ordered

according to the number of nights of use (i.e.,

quadrats used on 3 or more nights in Figure 32)

occurred at the center of their range while the other

two were located farther to the south. Group I spent

a total of 56 nights (i.e., 54%) in these 11 quadrats

that were distributed such that they formed a part

of three large discrete clusters of adjacent quadrats

used for night resting (Figure 32). These clusters

consisted of 33 quadrats, and the group spent a

total of 84 nights (i.e., 81%) in them.

The blue monkeys of Budongo did not appear to

sleep in particular areas of their home range, but

rather spent the night in the area in which they had

been feeding during the evening (Aldrich-Blake,

1970a). Similarly manga beys (Chalmers, 1968;

Waser, pers. comm.) and the vervet monkeys of

Lolui Island (Gartlan, 1966) also did not have regular sleeping areas. On the other hand, the vervets of

Masai-Amboseli Game Reserve (Struhsaker, 1967)

and the olive baboon of the same area (Altmann

and Altmann, 1970), the black and white colobus of

the Kibale Forest (Oates, 1974), and the primates

of Semliki Forest (Lumsden, 1951) used certain parts

of the range more frequently than others for night

resting.

Certain aspects of movement patterns of Group I

can be elucidated by considering the pattern of use

of the areas used for night resting. Group I spent all

or several successive nights of many sample periods

in the large cluster of quadrats located at the center

of the home range indicating that they began and

ended their diurnal movements in more or less the

same area (Table 48). Sometimes use of quadrats in

the central area alternated with the use of quadrats

in the two clusters to the south. Movements to the

north of the range were more frequent than would

be expected from the number of nights Group I

used this area for night resting, but these movements usually began and ended at the central cluster

of quadrats. During two sample periods (September (I) 1973 and October (I) 1973) areas used for

night resting alternated between the two clusters of

quadrats in the south of the range. This suggests

that the locations of preferred night resting areas

had some effect on the patterns of movements of

Group I.

On four pairs of successive nights, Group I used

the same quadrat for night resting, and on five pairs

of successive nights their movements began and

ended in adjacent quadrats (Table 48). On these

occasions, they described a loop using different

quadrats on their outward and return journey to

night resting areas. Circuitous rather than direct

movements from one night resting area to another

may also be shown by considering the straight line

distances between quadrats used for night resting

(i.e., "travel distance," Mason, 1968) on successive

nights and the actual distances traveled during the

intervening daytime periods (i.e., "path length").

Figure 33 relates both of these measures for 50 pairs

of successive nights. The path length was usually

much greater (X=1290 m, range 699-1900 m) than

the travel distance (X = 291 m, range = 0-675 m),

which shows the movement patterns were not entirely dependent on the locations of night resting

areas.

The use of a quadrat for night resting dpes not

necessarily mean that Group I used all trees in that

quadrat for this purpose. Group I seemed to prefer

large trees (frequently over 30 m tall) to small ones

for night resting. About two-thirds of 29 individual

trees that they used for night resting were large

trees belonging to one unidentified and seven identified species (Table 49). The large tree species

were also used on more nights and monkey-nights

than the smaller tree species. A monkey-night is

defined as a single night's use of a tree by an individual monkey (Struhsaker, 1967). Thus, if three

individuals used a sleeping tree on a single night,

the tree would be scored for three monkey-nights

of use. Parinari excelsa was the most commonly

used night resting tree. The 29 trees that Group I

used for night resting were located in 19 quadrats,

two of which contained a maximum of three individuals. On the few evenings that I was able to

locate two or more night resting trees, the distances

between sleeping subgroups using these trees ranged

from 10-90. Because of the difficulty in locating

sleeping trees, the maximum number of night resting trees per quadrat and dispersion between sleep-
NUMBER 249 71

+14

+13

+12

+11

+10

+9

+ 8

+7

+ 6

+ 5

+4

+3

+ 2

+ 1

- 1

- 2

- 3

- 4

- 5

- 6

- 7

- 8

- 9

-10

-11

-12

-13

-14

-15

-16

-17

-18

-19

-20

-21

- 2 2

- 2 3

-24

-26

<— -25 <

-24

-23

C?IRA

r

1

1

-22

/

c <

, |

1

2

1

-21

/

>\

2

2

-20

N

^^

1

5

2

-19

P

v+

1\

1

-18

-17

1

3m

-16

,1

„

HI 1

1

M\

1

IB

1

=

-15

••••i

**

1

1

.1

•1

\

-14

-13

1

i

1

IUII

_8

2

5

1

-12

2

1

1

5

3

IQ

3

1

-11

1

1

1

2

5

1

i

t

-10

en

f

1

21

h

5

2 1

?L

1

1

CO

1

.••

I

S

I

HI

in

r

/_

I

lr

HI

f

1

_

R

Gri

Str

Trf

T

DF

san

CM

frt

FC

[in

CM to

>T

in 00 en

+14

+13

+12

+11

+10

+9

+8

+7

+6

+5

+4

+3

+2

+1

-1

-3

-4

-5

1-6

-7

-8

-9

-10

-11

-12

-13

-14

-15

-16

-17

-18

-19

-20

-21

-22

-23

-24

m * io RI

(VI CO (VI M

i i i I

«o to m *fr ro CM

i i i

CM ro

M"- 1 .-« •-• *-• ~* •-• •-• »-•«-•«-.

I I t I I I I I II I

FIGURE 32.—Distribution of 50 quadrats used by Group I for night resting. The number of nights

spent in a quadrat is indicated by a number within that quadrat.

f»- CO

ing subgroups may be underestimations of the

actual values.

Group I spent only 6% of the nights when night

resting trees were located in trees laden with ripe

fruit. By selecting a tree that did not bear ripe

fruits, they probably avoided being disturbed by nocturnal visitors to fruiting trees (e.g., bats, viverrids,

etc.). Usually their last feeding bout for the evening
72

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

2 0

1-8

1-6

1-2

CO

1 0

0-8

0-1 0:2 0-3 CM

Distance between night resting areas

0"-5

(kms.)

0-6 0

:

7

FIGURE 33.—Comparison of distance between night resting areas on 50 pairs of successive nights

and distance moved during intervening daytime periods.

was at a fruit-laden tree, from which they moved out

to nearby night resting areas and returned early

next morning for their first bout of feeding.

QUADRAT UTILIZATION DIVERSITY.—I computed

measures of quadrat utilization diversity on the

basis of the proportionate frequency of use of quadrats entered during a sample period. Measures of

H' (in Shannon-Wiener equation, Pielou, 1966)

segregated according to differences in methodology

between March 1973 to June 1973 and July 1973

to February 1974 showed considerable variations

(Figure 34). In an attempt to explain these variations, Spearman rank correlation tests were done

comparing quadrat utilization diversity with various
NUMBER 249

TABLE 49.—Group I, tree species used for night resting

Species

P. excelsa*... .

M. bagshawei*..

B. wilsoniana*.

0. welwitschii*

A. altissima*..

D. abysslnica. .

S. scheffleri..

N. buchanani*..

C. durandii

T. splendida*..

C. africana....

Unidentified

(2 species)...

Total

Number of Number Number of

individual of nights monkey nights

trees used used of use

5 10 25

h 8 22

2 7 22

3 6 19

2 3 12

k k 10

3 3 9

1 1 k

1 1 2

1 1 2

1 1 1

2 2 5

29 ^7 133

*Large tree species.

aspects of diet and weather. The results of these

tests are given in Table 50.

Quadrat utilization diversity was not significantly

correlated with several measures of diet diversity,

proportion of fruits and foliar food in diet, density

of food plants, or their dispersion (Table 50). It

was significantly correlated, however, with the percentage concentration of plant feeding or food related activities (i.e., plant feeding considered together with search and ingestion of invertebrates

and chewing of food) in a few quadrats used at

relatively high frequencies. The concentration of

plant feeding (or food related) activities in a quadrat is a percentage measure of the plant feeding

scores recorded in that quadrat during a sample

period divided by the plant feeding scores recorded

from all quadrats used during the same period. The

percentage frequencies of plant feeding and foodrelated activities in the most frequently used quadrat, and in the top three and top five quadrats

of each sample period are given in Table 51.

Quadrat utilization diversity during March 1973

to June 1973 was negatively correlated with the

percentage concentration of plant feeding in the

three most frequently used quadrats (rs = -0.881

p<0.01), and with the concentration of food-related

activities in the top-ranking quadrat (rs = -0.881,

p<0.01) as well as in the top three quadrats (rs =

-0.857, p<0.01). Similarly ranging diversity during the July 1973-February 1974 period was negatively correlated to the concentration of plant

feeding in the top five quadrats (rs = -0.609,

p<0.05) and with the concentration of food-related

73

activities in the top three quadrats (r8 = —0.627,

p<0.05). The requirements of larger numbers of

quadrats in the July 1973 to February 1974 period

for significant correlation with ranging diversity

may be the result of methodological differences,

whereby greater number of locations were plotted

during this period than during March 1973 to

June 1973. From this analysis, however, it may be

inferred that during sample periods when food was

concentrated in a small area, Group I ranged less

diversely than during periods when food was widely

dispersed.

Significant negative correlations between quadrat

utilization diversity and percentage hours of rainfall

and insolation during sample periods suggest that

climatic factors also affected the ranging patterns

of blue monkeys.

INTERGROUP HOME RANGE OVERLAP.—At the

southern end the home range of Group I overlapped with that of Group V. Group V was first

seen (at 1000 hours on 25 December 1973) in quadrats -10-19 and -10-20, which were located well

within the home range of Group I (see Figure 13).

During three hours of observations that day they

used an area of 2y4 hectares (9 quadrats), and the

following day for two hours prior to leaving the

home range of Group I (at 1100 hours) they used

another 214 hectares. The areas used by Group V

on these two days were separated by a straight line

distance of about 200 m, some parts of which must

also have been traversed by this group between

observation periods. Therefore, the total time spent

(25 hours) and area used (4i/2 hectares) by Group V

within the range of Group I should be considered

minimal estimates of overlap. Group V left the

home range of Group I via quadrat —20-19, which

showed that their incursion had taken them about

475 m into the home range of Group I. On one

day (the evening of 7 May 1973) I suspected that

Group V used an area about 250 m within the

home range of Group I where a fruit-laden Ficus

dawei was located. Group V was not in the vicinity

of this tree when Group I used this area a few

hours earlier and when Group I returned to it early

the following morning. Therefore, if Group V had

used this area, their stay must have been relatively

short on this occasion.

At the northern end of the home range, Group I

used a \/A hectare quadrat (4-8-9), which was also
74 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

5 3H

(TJ

O

C

M2 A, M 4, A, Q

1973

Sample Period

FIGURE 34.—Indices of quadrat utilization diversity during different sample periods

from March 1973 to February 1974.

1974

used by their neighbors, Group III. Group I used

this quadrat only on one day (11 July 1973) and

during the short time they were there, they interacted with Group III and were evicted. Group III

did not pursue the retreat of Group I outside this

quadrat, which suggests that spatially as well as

temporally range overlaps between these two groups

were small. These interactions as well as those between Group II and Group III in areas of overlap

were always aggressive, with chases and threats being

extremely common. Thus each group appeared to

defend an area from the incursions of conspecific

groups, which according to Burt's (1943) definition

classifies this species as being territorial.

DISCUSSION

HOME RANGE SIZE.—The size estimates of the

home range of Group I decreased appreciably as

the size of the grid system used was reduced.

Although the smaller grids yielded more precise

measures of the physical presence of Group I in
NUMBER 249

75

TABLE 50.—Croup I, results of Spearman rank correlation tests comparing ranging

diversity with various aspects of diet and weather (for the two time intervals, left

column = rg values, right column — p values)

Correlation with — Mar 73 - Jun 73 Jul 73 - Feb 71*

1. Food plant diversity

2. Specific food item diversity

3. Food item diversity,

1*. Percent of fruits in diet

5. Percent of foliar items in diet

6. Density of top-ranking food plant

7. Mean density of top 3 food plants

8. Mean density of top 5 food plants

9. Mean density of top 10 food plants

10. Dispersion index of top food plant

11. Mean dispersion indices of top 3 food plants

12. Mean dispersion indices of top 5 food plants

13. Percent of concentration of plant feeding

in top ranking quadrats

Ik. Percent of concentration of plant feeding

in top 3 quadrats

15. Percent of concentration of plant feeding

in top 5 quadrats

16. Percent of concentration of food related

activities in top ranking quadrat

17. Percent of concentration of food related

activities in top 3 quadrats

18. Percent of concentration of food related

activities in top 5 quadrats

19. Percent of hours of rainy weather

20. Percent of hours of sunshine

0.310

0.310

0.381

-0.238

0.21U

0.630

0.21*0

-0.11*0

0.050

0.399

0.1*52

O.38O

-0.1+76

-0.881

-0.691

-0.881

-0.857

-0.71U

-0.821

0.1*39

0.05

0.05

0.05

0.05

0.05

0.05

0.05

0.05

0.05

0.05

0.05

0.05

0.05

0.01*

0.05

0.01*

0.01*

0.05

0.05*

0.05

-0.2l£

-0.291

-0.26U

0.318

-0.21*6

0.11*2

0.UO9

0.31*6

0.500

0.518

0.366

0.039

-0.21*6

-0.291

-O.6O9

-0.538

-0.627

-0.570

0.286

-0.6l8

0.05

0.05

0.05

0.05

0.05

0.05

0.05

0.05

0.05

0.05

0.05

0.05

0.05

0.05

0.05*

0.05

0.05*

0.05

0.05

0.05*

^Significant correlations with ranging diversity.

TABLE 51.—Group I, percent of frequency (i.e., concentration) of plant feeding and food-related activities in the top-ranking, top three, and top five

quadrats (ranked according to frequency of use) of each sample period

Sample period

Mar 73 (I)-.

Mar 73 (II).

Apr 73 (I)..

Apr 73 (II)-

May 73 (I)..

May 73 (II).

Jun 73 (I)--

Jun 73 (II)-

Jul 73 (I)--

Jul 73 (II).

Aug 73 (I)..

Aug 73 (II).

Sep 73 (I)--

Oct 73 (I).-

Nov 73 (I).-

Nov 73 (II).

Dec 73 (I)-.

Jan 7U (I)..

Feb 7*+ (I).-

Percent

of food-related

activities in quadrat

Rank 1 Ranks 1-3 Ranks 1-5 Rank 1 Ranks 1-3 Ranks 1-5

Percent

of plant-feeding

activities in quadrat

15.8

U.l

5.6

7.0

l.l*

1.5

3.7

3.6

6.0

6.6

16.1

3.8

h.G

15.7

2.0

17.1

1.9

12.5

3.7

3^-9

9.7

10.7

12.0

2.1

8.8

6.2

11.3

11.5

2U.2

9.6

15.6

20.0

9.8

26.1

2.9

25.9

10.6

1*0.7

13.8

12.6

13.5

5-5

30.2

12. h

14.9

18.1

18.0

37.9

15.0

22.0

20.7

10.5

35-2

10.5

36.5

29.0

11.6

2.9

3.2

5.3

2.6

3.3

2.7

2.1t

U.l

U.5

12.3

?.9

3-9

8.9

0.9

8.0

1.6

11-9

1+.5

26.3

7.7

6.1

10.6

1*.!+

11. h

6.8

U.2

9.0

11.5

22.1

7.8

8.6

16.5

5.5

ll+.O

6.3

2U.8

15.6

32.3

10.6

7.5

13-3

7.6

17.1

9.9

10.8

15.2

18.3

31.0

15-3

15.0

21.7

9.7

21.1

lfc.3

31*. 7

30.0

different parts of their range, the lacunae included

within the larger quadrats were not used by other

groups. Therefore, there was some justification for

using the larger quadrats; this analysis, however,

points out the importance of considering methods

of home range estimation before valid home range

size comparisons can be made between different

studies. Among primate studies particularly, several

methods have been used in the estimation of home

range size (see Aldrich-Blake, 1970a; Waser, 1974;

Struhsaker, 1975; Clutton-Brock, 1975b).

FACTORS AFFECTING RANGING PATTERNS.—The

factors that affect the ranging patterns of blue

monkeys are best understood by considering several
76 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

aspects of ranging patterns, such as areas used during different time periods, differential use of quadrats, group movements, group spread, ranging

diversity, and the pattern of use of night resting

trees. This is so because, for example, the relative

abundance of food may not affect movements as

much as it would the differential use of quadrats.

Considering the area used, Group I normally

exploited only a relatively small proportion of its

home range during each sample period. Figure 15

shows that the areas used during the sample periods

from March 1973 to June 1973 were usually smaller

than during the sample periods from July 1973 to

February 1974. This may have been partly due to

the difference in methodology used during these

two time periods. Group movements that were noted

using the same method throughout the study, however, also showed that blue monkeys used only a

small part of their home range during any one

sample period (see Figures 16 and 17), suggesting

that this type of ranging pattern was not a mere

artifact of the methodology employed in this study.

Also it was quite unlike the ranging behavior of

the mangabeys of Eastern Uganda, which used

almost their entire range within a single day

(Chalmers, 1968). Since blue monkeys are comparatively small in size, energetic considerations may

have precluded the possibility of exploiting the

entire range during a 5-day period. The question

then is why do they occupy relatively large home

ranges?

The direct relation betwen temporal variations

in the frequency of use of quadrats and food abundance in them (Table 46), and the inverse relation

between indices of quadrat utilization diversity and

concentration of feeding activity in a small part

of the area used during a sample period (Table 50)

suggest that (1) the relative abundance of food was

an important factor that led to the preferential

use of quadrats and (2) when food was concentrated

in a small area, Group I ranged less diversely than

when food was more widely distributed. In other

words, the ranging patterns of Group I were related

to the location and exploitation of concentrated

sources of food. Since fruits were the major food

resources of blue monkeys, their abundance probably had the greatest effect on the ranging patterns

of this species.

Also, it was pointed out earlier (see "Introduction") that many of the important food plants of

Group I exhibited a clumped distribution. Due to

the interplay of this pattern of plant distribution

and the phenological behavior of food plants, blue

monkey foods can be highly variable in their temporal as well as spatial abundance. Thus, since blue

monkeys relied on concentrated food resources, frequent temporal shifts in the area used, and the

occupancy of a relatively large home range are necessitated.

A large proportion of the area used during a

sample period was visited only on one day of that

sample period (Figure 21). These transitory movements probably enable blue monkeys to monitor

changes in the conditions of resource availability

in different parts of their range and to locate areas

of food abundance. The efficacy of locating areas

of food abundance was probably increased by blue

monkeys associating particularly with the redtails

during movement. Moreover, transitory movements

tend to maximize their use of the available resources

of invertebrates. In the previous section, it was

shown that blue monkeys depended largely on slowmoving or immobile forms of invertebrates. These

invertebrate types are likely to remain depleted

from an area for relatively long periods because,

unlike winged adults, they cannot move in quickly

from nearby areas. Thus blue monkeys have to continually exploit "new" areas of their range for this

particular type of invertebrate resource.

Another aspect of the ranging patterns of blue

monkeys that tends to maximize the use of invertebrate food is the relatively large spread of the group.

This reduces intragroup conflict over choice but

sparsely distributed food and thereby promotes the

efficient use of the home range. The large spread

within the group also probably enhanced the location of abundant food resources.

The ranging patterns of Group I were also affected by climatic factors. Similar observations were

made on the black and white colobus, the red colobus, and the mangabey of the Kibale Forest (Oates,

1974; Struhsaker, 1975; Waser, 1975). The fact that

the ranging patterns of all four species were affected

by climatic factors suggests that the ecological implications of this may have a common physiological basis. Extensive cloud cover probably produces

optimal conditions of ambient temperature under

which the net energy gained by the exploitation of
NUMBER 249 77

food resources may be greater than under conditions

of intense insolation or rainfall. Thus it is beneficial

for a group to range more diversely during periods

of cloudy weather than during other times.

Two other factors had limited effects on the

ranging patterns of Group I. One was the presence

of arboreal pathways across streams and swamps.

The lack of a continuous canopy in some areas

produced "bottle-necks" that had to be used frequently for movement from one part of the home

range to another (Rudran, unpubl.). Thus, these

predetermined crossing points probably affected the

direction of movement and quadrat use at least for

a short period before they were negotiated. The

second was the location of preferentially used

sleeping areas. Since path length was always greater

than travel distance (Figure 33), the locations of

sleeping areas probably did not affect movements

throughout the day. Unless they partially affected

group movements (probably during late evenings),

however, certain areas would not have been preferentially used for night resting purposes.

COMPARISON WITH OTHER STUDIES.—The home

range size of Group I far exceeded the range sizes

reported for the blue monkeys of the Budongo

Forest (mean 8.0 ha, range 5.1-11.7 ha, AldrichBlake, 1970a). These differences are all the more

appreciable considering the fact that I used a more

conservative method of range estimation. Had I

used the method that Aldrich-Blake used (encircling

of the most peripheral locations), the home range

of Group I would have been larger and included

a relatively large section of grassland that Group I

never used. The Sykes monkey (C. m. kolbi), which

is a related subspecies found in Kenya, occupied

home ranges varying in size from 13.2 to 16.0 ha

(DeVos and Omar 1971).

Interpopulational differences in home range size

have been reported for other primate species, such

as the gray langur (Jay, 1965; Ripley, 1967; Yoshiba,

1968), the purple-faced langur (Rudran, 1970), the

black and white colobus (Marler, 1969; Oates, 1974),

the red colobus (Clutton-Brock, 1975b; Struhsaker,

1975), the manga bey (Chalmers, 1968; Waser and

Floody, 1974), and many others. Variations in home

range size and optimal area defended have been

found to be related to group size (Dittus, 1974).

Also Sugiyama (1967) points out that differences

in vegetation and influences of adjacent troops

may also be important in regulating range sizes.

Gross habitat differences were not apparent between

the Kibale and the Budongo study areas (pers. observation); neither were group sizes significantly

different in these two forests. In the Kibale Forest,

however, the population density of blue monkeys

was about 35 individuals/km2 while in the Budongo

Forest it was about 185/km2 (Aldrich-Blake, 1970b).

It is possible that the greater density of blue monkeys in the Budongo Forest may have resulted in

the compression of the home ranges there. The

Indian gray langur that has also been studied in

several areas was found to occupy small home ranges

in places where they occurred at high densities

(Yoshiba, 1968).

Unfortunately Aldrich-Blake's data does not allow

further comparisons to be made between the ranging patterns of the two populations; however,

Aldrich-Blake also suggests that food was an important factor that influenced the ranging patterns of

blue monkeys. Although one may intuitively feel

that the ranging patterns of primates were related to

some aspect of the foods they eat, Struhsaker (1974)

has shown that this was not the case in the red

colobus of the Kibale Forest.

Summary and Conclusions

The blue monkeys of the Kibale Forest normally

lived in cohesive "one-male" social groups. Emigration of young males from their parental groups

partially served to maintain the integrity of this

social structure. Although these groups were relatively widely dispersed during their daily activities,

group cohesion was facilitated by the loud "Pyow"

calls of the adult male.

These monkeys exploited a diverse diet but they

were fairly selective feeders. Fruits were the most

frequently used food item although blue monkeys

periodically exploited invertebrates and foliar foods

at high frequencies. Blue monkeys concentrated

their invertebrate feeding on slow-moving and immobile forms, thereby reducing niche overlap with

the redtails and the mangabeys along this resource

dimension.

The patterns of use of food resources depended

on the phenological activity of food plants, relative

abundance of food, as well as the food preference

of blue monkeys.
78 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

Intragroup, intergroup, and interspecific conflicts

most frequently occurred in a feeding context. Intragroup conflicts for food were probably minimized by

different age/sex classes concentrating on different

aspects of the dietary spectrum of the species. The

diet of the adult male consisted of a higher proportion of fruits and a lower proportion of invertebrates than the diet of other age/sex classes.

Intergroup conflicts for food were largely averted

through the territorial nature of this species, while

interspecific conflicts appeared to be reduced by

avoidance of polyspecific associations during the

times when plant foods were being exploited.

The formation of polyspecific associations with

the folivorous red colobus seemed to enhance the

acquisition of invertebrates by blue monkeys. Also

blue monkeys may have been able to efficiently

locate areas of food abundance by associating with

other species (particularly with redtails) during

movement. In addition, predator avoidance was

probably an important function of the associations

between blue monkeys and other primate species.

Blue monkeys of the Kibale Forest occupied relatively large home ranges, but during 5-day periods

of observations they used only a small proportion

of their home range. Daily ranges also constituted

only a small fraction of the area used during a 5-day

period, and on different days of a 5-day period, blue

monkeys used somewhat different areas of their

home range. Thus they frequently revisited only a

small proportion of the area used during a 5-day

period, while using the remainder of the area for

transitory movements.

These ranging patterns of blue monkeys were

dependent on the location and exploitation of concentrated food resources. Blue monkeys ranged less

diversely when food was concentrated than when

food was more widely distributed. Climatic factors

and location of night-resting areas also had limited

effects on the ranging patterns of these monkeys.

Blue monkeys of the Kibale Forest occupied relatively large home ranges presumably because they

depended on the exploitation of concentrated food

resources in a habitat where food availability

showed a great deal of temporal and spatial fluctuations. Their transitory movements through parts

of their home range probably enabled them to monitor changes in food availability and to locate areas

of food abundance. Transitory movements could

have also maximized the use of slow-moving and

immobile invertebrates by blue monkeys. In addition, the exploitation of these invertebrate forms

may have been enhanced by the relatively large

spread within groups, which probably reduced intragroup conflicts for these sparsely distributed food

resources. Thus, this study tends to support the

hypothesis that space utilization patterns arising

from the peculiarities of diet and food dispersion

affected the social organization of primates.
Appendix

TABLE A.—Group I, percent of frequency of use of specific food items exploited during first 5-day

periods of observations from February 1973 to January 1974, inclusive (N «= 2039 observations;

• = food plants not used by Group II; other species were used by both groups)

Species

Diospyros abyssinica

Celtis africana

Pancovia turbinata*

Tec lea nobllis ,

Uvariopsis congensis ,

Premna angolensis

Celtis durandii

Fieus exasperata

Mimusops bagshawei ,

Markhamia platycalyx

Bosquiea phoberos ,

Funtumia latifolia

Parinari excelsa

Vangueria apiculata ,

Monodora myristica

Illigera pentaphylla ,

Dombeya mukole ,

Chaetachme aristata

Neoboutonia macrocalyx

Clausena anistata ,

Linociera Johnsonii

Aningeria altissima*

Plea welwitschii

Chrys ophyllum gorungosanum.,

Balanites wilsoniana

Pseudospondias microcarpa*.,

Milletia dura

Blighia unijugata

Symphonia globulifera

Newtonia buchanani

Coffea eugenoides*

Loeseueriella apiculata*...,

Trichilia splendida*

Dichapetalum ugandense*

Trema orientalis

Urera c«m<Toonensis

Albizia g'iTMTMifera*

Strombosia scheffleri

Spathodea campamilata*

Fie us natalensis ,

Fie us kisantuensis

Cyphomandria betaceae ,

Fagaropsis angolensis

Cardiospermum grandiflorum.,

Polystachya sp.* ,

Belonophora glomerata* ,

Erythrina sp.* ,

Vangueria aeutiloba*

Ficus brachylepis ,

Randia urcelliformis ,

Diaphananthe sp ,

Harungana madagascariensis*.

Landolphia sp.*

Platycerium elephantotis*..,

Saba florida*

Unidentified species (U)

Number of specific

food items ,

Percent of frequency of use.

v u

-

0.31+

-

-

-

0.92

0.05

0.05

1+.59

0.21+

0.2U

-

0.15

0.05

0.05

_

-

-

-

1.

-

0 .

-

_

55

05

1.60

0.50

0.19

7

3.20

0.15 2.65

0.15

0.15

2.1+2

3.29

8.22

8.17

6.53

6.53

5.32

5.07

1+.1+9

0.19 0.53 3.05

0.10 0.05

0.05 1.1+0 0.73

0.05

0.53

2.76

O.58 0.19

0.10

o.M*

0.19

1.55

0.05

1.21

0.73

0.19

0.53

0.68

1.89

0.05

1.71+

0.39

1.60

0.05

0.15

0.05

0.53

0.39

0.05

0.92

2.13

0.19

1.1+0

0.05

0.3U

0.39 0.10

0.97 0.05

0.1+1+

0.77

0.10 0.10

0.31+

0.05 - 0.31+

0.15 -

0.31+

0.15

0.05

0.19

0.05

0.05

0.31+

0.05 0.21+

0.15

0.29

0.10

0.19

0.15

0.15

0.10

0.05

0.05

0.05

0.05

0.05

0.05

0.05

0.05

0.05

23

11.92

0.31+

15

8.93

0.29 0.58

123 9 18 27 22 2

0.15 2.1+7 0.30 1.57 8.3U 57.89 2.91 0.87 0.68 0.92

222

187

171+

170

138

131

107

95

78

65

61

57

1+6

1+1+

1+1+

1+1

1+0

35

31+

26

23

23

21

21

17

16

15

11+

8

7

7

7

7

6

6

5

5

5

k

h

3

3

2

2

2

2

2

2

1

1

1

1

1

1

1

27

10.71+

9.01+

8.1+1

8.22

6.67

6.33

5.17

1+.59

3.77

3.11+

2.95

2.76

2.22

2.13

2.13

1.98

1.93

1.69

1.6U

1.26

1.11

1.11

1.02

1.02

0.82

0.77

0.73

0.68

0.39

0.3U

0.3!+

0.31+

0.3U

0.29

O.29

0.21+

0.2U

0.21+

0.19

0.19

0.15

0.15

0.10

0.10

0.10

0.10

0.10

0.10

0.05

0.05

0.05

0.05

0.05

0.05

0.05

0.31

2068

79
80

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

TABLE B.—List of food plants exploited by the blue monkeys

ACANTHACEAE

Brin»"itasia nitens Lindau

ANACARDIACEAE

Pseudospondias mlcrocarpa (A. Rich.) Engl.

ANNONACEAE

Monodora nyristic a (Gaertn.) Dunal

Uvariopsis congensis Robyns and Chesquier e

APOCYANACEAE

Funt'"^a latifolia (Stapf) Stapf ex Schltr.

Pleiocarpa pycnantha (K. Schum.) Stapf

Tabernaemontana odoratissima Stapf

Tabernaemontana usaniberensis Stapf

BASELIACEAE

Baselia alb a L.

BIGNONIACEAE

Markhamla platycaly x (Bak.) Sprague

Spathodea nilotic a Seem.

CAESALPINIACEAE

Loesenerle 1 1 " apiculat a R. Wilkzell

CAPPARIDACEAE

Ritchiea albersii Gilg

CHAILIETIACEAE

Diehapetalum ugandense M. B. Moss

EBENACEAE

Diospyros abysslnic a (Hiern) F. White

EUPHORBIACEAE

Acalypha bipatit a Muell. Arg.

Drypetes battiscombe i Hutch.

Neoboutonia macrocalyx Pax

FIACOURTIACEAE

Dovyalis TM»"*rocalyx (Oliv.) Warb.

Scolopia rhamniphylla Gilg

GUTTIFERAE

Syngihonia globulifer a L. f.

HERNANDIACEAE

Illiger a pentaphyi i« Welw.

HYPERICACEAE

Hariingana madagascarensis Lam,

ICACINACEAE

Apodytes dimidiat a E. Mey. ex Arn.

Pyrenacantha sp .

LOGANIACEAE

Strychnos mitis S. Moore

MELIACEAE

Carapa grandiflora Sprague

Trichilia splendida A. Chev.

MIMOSACEAE

Albizi a giTMn1fera (Gmel.) C. A. Sm.

Newtonia buc>""'""''i (Baker) Gilb . and Bout.

MORACEAE

Boaqueia phoberos Baill .

Ficus brachylepis Welw. ex Hiern

Ficus eongensis Engl.

Ficua dawei Hutch.

Ficua exasperat a Vahl

Ficus kisantuensia Warb.

Ficua natalenaisTMiq.) Hochst.

Ficus atipullfera Hutch.

OLACACEAE

Stronflao8ia scheffleri Engl.

OLEACEAE

Linociera .iohnsonii Baker

Plea welwitschii (Knobl.) Gilg and Schelleng

ORCHIDACEAE

Anagraecum distichum Lindl.

Diaphananthe sp .

Polystachya sp .

PAPILIOKACEAE

Erythrina sp.

Milletia dura Dunn

POLYPODIACEAE

Laxogramme lanceolata C. Presl.

Platycerium elephantotis Schweinf.

RHIZOPHORACEAE

Cassipourea ruvensorensis (Engl.) Alston

ROSACEAE

Parlnari excelsa Sabine

RUBIACEAE

Belonophora glomerata M. B. Moss

Canthium sp.

Coffea eugenoides S. Moore

Euclinia longiflora Salisb.

Randia urcelliformis Hiern.

Tarenna pavettoides (Harv.) Sim.

Vangueria acutiloba Robyns

Vangueria apiculata K. Schum.

RUTACEAE

Clausena anistata (Willd.) Hook f. ex Benth.

Fagara mildbraedli Engl.

Fagaropsis angolensia (Engl.) Dais

Teclea nobilis Del.

SAPINDACEAE

Blighia unijugata Bak.

Cardiospermum grandiflorum Sw.

Lepisanthes senegalensis (Poir.) Radlk.

Pancovia sp. nr P. turbinata Radlk.

Paulinia pinnata L.

SAPOTACEAE

Aningeria altissima (A. Chev.) Aubr. and Pellegr.

Chrysophyllum gorungosanum Engl.

Mi misops bagshawei S. Moore

SIMAROUBACEAE

Balanites vilsoniana Dawe and Sprague

SOIANACEAE

Cyphonw.ndrea betacea Sendtu.

STERCULIACEAE

Dombeya mukole Sprague

TILIACEAE

Glyphaea lateriflora (G. Don) Hutch and J. M. Dalz.

ULMACEAE

Celtis africana Bum. f.

Celtls durandii Engl.

Chaetac^TM" aristata Planch.

Trema orientalis (L.) Bl.

URTICACEAE

Urera caTn°roonensiB Wedd.

VERBANACEAE

Premna angolens is Guerke

VITACEAE

Cissus oliveriana Engl. j.

 r<ilg
NUMBER 249 81

TABLE C.—Group I, rank order (I-V) and percent of frequency of use of top five food plants and

specific food items during the first 5-day period of observations from February 1973 to May 1974,

inclusive

Sample

period Species Percent Species Percent Species Percent Species Percent Species Percent N

FOOD PIAHTS

Feb

Mar

Apr

May

• un

• lul

Aug

Sep

Oct

Nov

Dec

•Tan

Feb

Mar

Apr

May

73

Y3

73

73

73

Ti

73

73

73

73

73

71*

7U

7U

71*

71*

(I)..

ID..

(1)..

(1)..

(I)..

(D-.

(I)..

(I)..

(I)..

U)..

(1)..

(I)..

(I)..

(I)..

(I)..

(I)..

D.

P.

C.

c.

u.

D.

D.

C.

c.

T.

M.

V.

A.

M.

D.

M.

abyssinica

turbinata

africana

gorungosanum

congensis

abyssinica

abyssinica

anistata

durandii

nobilis

bagshawei

apiculata

altissima

platycalyx

mukole

bagshawei

22.1

85.6

53-3

16.1

1*3.5

29.1

2l*.8

21.3

28.1

57.B

21.7

13.3

21.9

22.7

17.7

31*.0

F.

P.

D.

P.

D.

P.

P.

C.

T

C.

V.

F.

P.

D.

T.

M.

exasperata

excelsa

abyssinica

angolensis

abyssinica

angolensis

angolensis

africana

nobilis

durandii

latifolia

exasperata

turbinata

abyssinica

nobilis

platycalyx

21.1*

k.6

11*. 7

12.9

1U.3

23.6

18.3

19.6

2U.1+

2l*.3

16.9

12.8

1U.1

1U.7

13.1

20.0

B.

D.

P.

M.

0.

F.

U.

I.

T.

C.

D.

M.

M.

F.

F.

C.

P.

D.

C.

phoberos

mukole

excelsa

welwitschii

exasperata

congensis

pentaphylla

nobilis

durandii

mukole

bagshawei

myristica

latifolia

exasperata

africana

angolensis

abyssinica

africana

lU.O

1.5

8.0

7.6

13.3

8.6

13.9

11.8

7.8

13.7

11.1+

9.1

11.3

11.1

13.0

A. altissima

P. excelsa

C. africana

0. welwitschii

B. unijugata

T. nobilis

-

N. macrocalyx

P. angolensis

M. bagshawei

B. phoberos

M. platycalyx

M. dura

I. pentaphylla

C. africana

C. axistata

V. apiculata

0. welwitschii

C. africana

-

6.1*

7.1

6.6

1 1 1*

8.8

2.6

10.1+

8.5

a.7

9.0

7.2

_

M. bagshawei

M. bagshawei

T. nobilis

N. macrocalyx

P. microcarpa

B. phoberos

M. platycalyx

C. africana

F. angolensis

D. mukole

C. afr icana

U. congensis

M. myristica

M. platycalyx

M. dura

M. platycalyx

T. nobilis

_

1*.2

l*.8

1+.7

5.9

8.1

7.!+

1.3

6.1+

7.6

5.8

6.8

6.5

5.0

1U9

19I+

210

l?l*

209

251+

185

1??

1V>

15?

1?1*

210

2l+l

88

is?

100

SPECIFIC FOOD ITEMS

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Jan

Feb

Mar

Apr

May

73

73

73

73

73

73

73

73

73

73

73

71*

7U

71*

71*

71*

(I)..

(I)..

(I)..

(I)..

(I)..

(I)..

(I)..

(I)..

(I)..

(I)..

(I)..

(I)..

(I)..

(I)..

(I)..

(I)..

D. abyssinica,

fruits

P. turbinata,

fruits

C. africana,

fruits

C. gorungosanum,

blossoms

U. congensis,

fruits

P. angolensis,

blossoms

D. abyssinica,

young leaves

C. anistata,

young leaves

C. durandii,

fruits

T. nobilis,

fruits

M. bagshawei,

fruits

V. apiculata,

mature leaves

A. altissima,

blossoms

petioles

D. mukole,

young leaves

M. bagshawei,

flower buds

22.1

85.5

53.3

16.1

1*3.0

23.6

23.2

20.1+

28.1

57.0

21.7

13.3

21.1

22.7

17.7

22.0

F. exasperata,

fruits

P. excelsa,

fruits

D. abyssinica,

fruits

P. angolensis,

leaf buds

D. abyssinica,

young leaves

D. abyssinica,

blossoms

P. angolensis,

blossoms

C. africana,

fruits

T. nobilis,

fruits

C. durandii,

fruits

F. latifolia,

seeds

F. exasperata

fruits

P. turbinata,

fruits

D. aby6sinica,

young leaves

C. africana,

fruits

P. angolensis,

leaf buds

M. platycalyx,

petioles

21.1*

k.6

1U.7

12.9

13.1*

20.1*

17.8

17.2

21*.1*

2U.3

16.9

12.8

ll+.l

10.2

10.5

20.0

B. phoberos,

blossoms

D. mukole,

young leaves

P. excelsa,

fruits

N. macrocalyx,

mature leaves

F. exasperata,

fruits

U. congensis,

fruits

I. pentaphylla,

mature leaves

C. durandii,

fruits

D. mukole,

young leaves

M. bagshawei,

fruits

M. myristica,

leaf buds

F. latifolia,

seeds

F. exasperata,

fruits

-

T. nobilis,

mature leaves

M. bagshawei,

blossoms

12.0

1.5

8.1

6.1*

7.6

13.3

8.6

13.9

11.1

7.8

13.7

11. k

9-1

-

9.8

12.0

P. excelsa,

fruits

A. gummifera,

young leaves

B. uni.jugata,

young leaves

T. nobilis,

mature leaves

C. africana,

fruits

petioles

0. welwitschii,

flower buds

P. angolensis.

blossoms

D. abyssinica,

young leaves

P. microcarpa,

fruits

D. mukole,

young leaves

M. dura,

young leaves

F. angolensis,

fruits

C. africana,

fruits

I. pentaphylla,

mature leaves

C. africana,

fruits

C. aristata,

fruits

V. apiculata,

nature leaves

0. welwitschii,

mature leaves

petioles

D. abyssinica,

young leaves

10

1

7.

1*.

7.

8.

8.

9.

6.

1.

10.

7.

8.

9-

6.

11.

7

0

6

8

1

6

1

0

6

3

I*

6

7

0

5

0

A. altissima,

blossoms

M. bagshawei,

blossoms

T. nobilis,

mature leaves

T. nobilis,

mature leaves

M. bagshawei,

"fruits

T. nobilis,

fruits

petioles

M. platycalyx,

nectar

-

U. congensis,

fruits

M. myristica,

leaf buds

petioles

B. wilsoniana,

mature leaves

F. exasperata,

fruits

M. bagshawei,

flower buds

C. africana,

fruits

8.0

U.2

U.O

lt.7

6.6

U.8

6.5

k.k

-

6.1+

6.1

5.8

5.6

5.9

9.0

ll+9

191*

210

12U

209

251*

185

122

135

152

121*

210

2l*l

fi8

152

100
82 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

TABLE D.—Group I, percent of frequency of ingestion of probable invertebrates from specific

microhabitats (I-XI) during first 5-day periods of observations from February 1973 to January

1974, inclusive ^N = 498 observations, I = foliage, II = lichen-covered branch, III = moss-covered

branch, IV = moss- and epiphyte-covered branch, V = dry leaf, VI = epiphyte-covered branch,

VII = trunk or branch (bare), VIII = unidentified microhabitat, IX = bark or twig, X =

lichen- and epiphyte-covered branch, XI = moss- and lichen-covered branch)

Species

S. scheffieri

D. abyssinica....

M. platycalyx....

C. durandii

B. wilsoniana....

T. nobilis

P. turbinata

C. africana

N. buchanani

0. welwitschii...

U. congensis

M. bagshawei

A. altissijna

F. brachylepis...

S. globulifera...

P. ansolensis....

B. phoberos

F. latifolia

C. Korungosanum. ,

D. mukole

Chaetachme

aristata

F. dawei

Fagaropsis

angolensis

M. m/ristica

M. macrocalyx....

T. splendida

V. apiculata

Unidentified

Total percent of

frequency

I

1+.61

6.02

5.62

o.8o

l.8l

1.00

1.8l

l.6i

o.8o

0.1+0

0.1+0

l.l+i

0.60

o.6o

0.20

0.80

o.6o

o.8o

0.1+0

0.1+0

_

o.6o

0.1+0

-

0.20

-

0.20

0.20

0.20

6.22

38.75

II

2.1+1

0.1+0

2.21

1.00

o.8o

1.81

0.20

.

0.60

0.60

1.1+1

-

0.20

0.20

-

_

0.20

-

0.20

0.20

_

-

-

-

-

-

-

-

1 20

13.65

I II

7.1+3

2.61

0.80

0.1+0

0.60

0.80

0.1+0

0.20

0.80

0.60

-

-

0.1+0

0.80

0.80

0.20

0.1+0

0.20

0.20

-

0.20

-

-

-

0.20

-

-

3 1+1

21.1+9

0

0

0

0

0

n

2

IV

an

. 2 0

-

. 2 0

_

_

_

_

_

. 2 0

-

_

-

-

. 2 0

_

-

-

_

1+0

. 0 1

V

0.1+0

0.20

0.60

1.61

0.1+0

0.20

0.^0

0.60

-

-

-

0.20

-

0.20

-

-

-

-

0.20

-

-

-

-

-

_

1 1+1

6.22

VI

1

0.

0.

0.

0.

.

0.

-

_

-

-

-

-

-

-

-

-

h.

9 0

60

20

20

1+0

1+0

00

02

VII

0.60

0.60

1.00

0.80

0.1+0

-

0.60

0.20

0.20

0.1+0

0.20

0.20

_

_

0.20

-

0.20

0.20

0.20

0.20

-

_

1 6 l

8.03

VIII

n

0.

0.

0.

n

-

-

0 .

_

-

_

1+.

2 0

80

20

1+0

20

20

22

IX X XI

-

. . .

-

_

. . .

-

-

-

-

-

-

-

-

0.20

. . .

-

-

-

_

-

. . .

. . .

-

_

1.20 0.20 0.20

Total

percent of

frequency

17.67

11.1+5

10.61+

5.02

1+.1+2

1+.22

3.21

2.61

2.58

2.1+1

2.01

1.61

1.61

1.6l

1.1+1

1.1+1

1.20

1.00

1.00

0.80

0.60

0 60

0.1+0

0.1+0

0.20

0.20

0.20

0.20

0.20

18 88
NUMBER 249

TABLE £.—Cercopithecus mitis, Groups I and II, frequency of use of different motor patterns in

the capture of probable invertebrate food from different microhabitats, I-XI (see Appendix

Table D; data collected from Group II given within parentheses)

Motor Patterns VI VII VIII IX X XI

Rapid Movements

Run first, grab with both hands into mouth

One-hand grab, placed with hand into mouth

Two-hand grab, placed with both hands

into mouth

Series of picks with mouth applied

to substrate

Repeated one-hand picks, placed with

hand into mouth

Quick grab

Quick slap

Total

Slow Movements

One-hand reach for food item:

Rub on branch, placed with hand

into mouth

No rub, placed with hand into mouth:

Not repeated

Repeated in succession

One-hand reach for substrate:

Mouth directly applied to substrate....

Food item picked, placed with hand

into mouth

Two-hand reach for substrate:

Mouth applied to substrate, licking

food item

Picking with lips

Uncurl or HWTHIHI ly examine..

Mouth applied to substrate

Repeated licking

Remove substrate, mouth applied to .

substrate

Lick without reaching for or holding

substrate

Mouth applied to substrate without reaching for or holding

vement not seen:

Rub on branch, placed with hand

into mouth

Rub between hands, placed with hand(s)

into mouth

Hold, place with hand(s) into mouth

Pluck foliage and mouth applied

to substrate*

Licking substrate

Picking with mouth or hands

Total

Total frequency of motor patterns.

2(9)

11(10)

21(23)

-(1) 3(2) -(1)

1(1*)

-(1)

8(3)

-(3)

1

2

-(1)

2(1)

2(1)

-(1)

1

3C0 8(5) 1(1) 1(5)

17(56) 11(31) 12(15) 2 1(3)

-(5) - -(1)

7(33) - - - -(1)

3 - - - 1

2(1) ... .

22(1*8) - 1 - 5(8)

1(1) - - - 2(15)

5(3)

2(1*) 2(3)

-(1)

2(7)

-(1)

-

9(6)

1(5)

1

13(20)

-

3

-(1)

-

1(2)

2(2)

-

6(5)

-

-

-

-

-

-(1) -

-

-(1) -

0(1)

11(20)

13(16)

1(0)

10(lU)

15(12)

5(1)

55(6U)

6.6*(9.9

1(1) 5(2U)

-(2)

1

KD

1(5)

-(2)

5(1)

-(2) -(2)

-(1)

-(1)

-(1) K2)

-(2)

7(1)

U9(137)

0(8)

8(3U)

Ml)

3(1)

29(58)

3(16)

1(0)

6(3)

1(0)

6(1U)

1(2)

-

-

-

1(1)

35(17)

1*7(1*5)

-

-

-

-

23C0

2M5)

-(1)

-

-

l*(3)

1*1(35)

56(7U)

-(1)

1

-

1(2)

15(12)

23(19)

-

-

-

1(1)

8(2)

9(8)

-

-

-

-

1(11

-(1) 1(3)

0(2)

1(0)

3(2)

3M29)

628(272)

781*(586)

93.W9O.lS)

3(2)

IM15) 7C*) 6(2) -(1)

255(128) 88(37) 1U3(33) 19(3)

331(297) 108(76) 16M5U) 21(1*)

352(320) 111(80) 172(59) 22(5) 1*8(50) 26(5) 69(9"*) 29(2"*) 9(8) -(2) 1(3) 839(650)

'incomplete descriptions that were used between February and December 1973, Inclusive, but were further subdivided later throuah fuller

descriptions of feeding motor patterns. Note also that after December 1973 Group II was observed for longer periods than 3roup I.
84

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

TABLE F.—Group I, percent of use of specific plant food items during 11 observation periods most

comparable to those of Group II between February 1973 and January 1974, inclusive

Specie s

6 - d

T e c le a nobili s ,

Celtl s afrlcan a ,

Dlospyro s abyssinic a

Uvariopsl s congensl s

Celtl s durandi i

Premn a angolensl s

Flcu s exasperat a

Mlmusop s bagshawe l

Markhami a platycaly x

Funtuml a latlfoli a ,

Dombey a mukol e ,

Bosquie a -phobero s ,

Monodor a nyristlc a

Parlnar l excels a ,

Vangueri a aplculat a ,

Pancovi a turblnat a

Chaetacha e aristat a ,

Neoboutoni a macrocalyx.... ,

Clausen a anlstat a ,

Illiger a pentaphyll a ,

Mllletl a dur a

Llnocier a .John s oni i

Chrysophyllu m gorungosanum ,

Ple a welvltschi l ,

Anlngerl a altissim a

j3alanlte s vilsonian a ,

Bllghl a unijugat a ,

Symphoni a globullfer a ,

New t onl a buchanan i

Coffe a eugenoide s ,

Loeseuerlell a aplculata... ,

Trlchlli a splendld a

Dichapetalu m ugandense .

Urer a earneroonensl a

Cyphamandrl a betacea e ,

Loxogramn e lanceolat a

Stromboal a scheffler l

Flcu s natalensl a ,

Polystachy a s p

Flcu a klsantuensl s ,

Pseudospondla s mlcrocarpa. .

F a g axopsI s angolensi s

Albizl a gunmifer a

Cardiospermu m grandlflorum .

Apodyte s dlmldiat a

Belanophor a glomerat a ,

Erythrln a s p

Vangueri a acutllob a

Spathode a campanulat a

Ficu s brachylepi s

Randl a urcelllforml s

Dlaphananth e s p

Harungan a aadagascarensls. ,

Landolphl a s p

Platycerlu m elephantotis.. ,

Sab a florld a ,

Unidentifie d specie s (4).. .

Tota l

0.05

0.35

0.0 5

0.10 1.;

0.25

2.68 -

0.15 -

1.2 7 0.0 5

0.0 5

1.6 2

2.0 7

0.U6

0.10

_

0.25

-

1.27

0.20

0.91

O.76

0.40

0.05

-

1.82

-

1.37

-

1.07

0.10

_

0.05

0.05

0.46

0.U0

0.05

0.61

0.35

0.15

0.20

0.10

0.05 0.05

0.05

0.05

3.59 n.01 7.34

0.25

0.05

-

0.05

_

-

-

-

0.20

0.10

0.10

0.05

-

-

-

-

0.15

-

-

o.4o-

- 0.15

2.78

-

-

3.80

_

0.56

0.05

1.21

0.05

-

-

*

0.10

-

1.01

0.10

0.71

0.U6

11.53

10.52

4.55

6.83

6.52

-

4.76

3.85

-

1.01

.

2.02

0.30

1.72

1.37

-

0.30

0.05

-

0.35

0.05

0.05

0.05

0.05

0.3 5

0.25

-

_

-

0.05

-

-

-

0.10

0.10

-

-

0.20

0.10

0.20

.

0.15

0.10

0.10

-

0.05

0.56

0.15

0.35

258

225

198

138

129

101

94

91

77

57

51

49 43

42

42

39

34

27

26

25

25

22

21

19

18

17

12 8

7

7

7

7

6

5

4

4

4

4

3

3

2

2

2

2

2

2

2

2

1

1

1

1

1

1

1i-i 4

13.06

11.39

10.02

6.98

6.52

5.11

4.76

4.61

3-90

2.88

2.58

2.48

2.18

2.13

2.13

1.97

1.72

1.37

1.32

1.27

1.27

1.11

1.06

0.96

0.91

0.86

0.6l

o.4o

0.35

0.35

0.35

0.35

0.30

0.25

0.20

0.20

0.20

0.20

0.15

0.15

0.10

0.10

0.10

0.10

0.10

0.10

0.10

0.10

0.05

0.05

0.05

0.05

0.05

0.05

0.05

0.05

0.20

3.19 o.4o i.4o 12.03 56.48 3.03 0.91 0.30 1977
NUMBER 249 85

TABLE G.—Group II, percent of use of specific plant food items during 11 observation periods

between February 1973 and January 1974, inclusive

Species

>• H EH

Flcu8 exasperata

Uvariopsls congensis

Celtis africana

Diospyros abysslnica

Markhamla platycalyx

Celtis durandii

FICUB brachylepls

Tec lea nob His

Funtumia latifolla

Monodora nyristica

Llnoclera Johnsonii

Premna angolensls

ChrysophyHum gorungosanum..

Cyphomandria betaceae

Plea velvltschii

Clauaena anlstata

Illigera pentaphylla

Ritchla albersli

Ficus stlpullfera

Bosquiea phoberos

Neoboutonia macrocalyx

Himusopa bagshawei

Urera earneroonensis

Strombosia scheffleri

Faj-.aropBJB angolensia

Ficus kisantuensis

Vangueria apiculata

Symphonia globulifera

Lepisanthes senegalensis•...

Dombeya nmkole

Angraecum dlstichum

Chlorodendrum schweinfurthii

Drypetes battiscombei

Newtonia buchanani

Parinari exeelsa

Chaetachme aristata

Trema orientalis

Basella alba

Brachystephanus africana....

Diaphananthe sp

Fagara angolensls

Ficus congensis

Glyphaea laterifolia

Tabernaemontana usamberensis

Unidentified species (3>

Total

3-50

0.65

-

-

-

-

0.32

-

0.65

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

5.12

0.97

0.32

2.37

-

0.05

-

0.1*3

0.27

-

-

0.16

-

0.75

0.22

0.05

-

-

-

-

-

-

-

-

-

0.05

0.11

-

-

-

-

0.05

-

o 05

5.85

-

0.05

0.05

0.05 0.05

0.11

-

-

0.05

-

-

0.86 -

-

0.5l*

-

-

-

0.5I* -

0.05

0.05

-

0.11 -

-

-

0.05

O i l

n i l

-

-

-

0 05

-

-

2.89 0.05

0.05

-

-

2.96 -

-

-

-

-

-

0.05

-

-

-

-

-

-

_

-

-

-

-

-

-

-

-

-

-

-

-

-

3.06 -

-

0.65

0.81

0.05

-

-

-

-

-

0.05

-

-

0.22

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

1.78

-

0.70

2.69

-

-

-

0.86

_

1.2U

1.1*0

0.37

0.11

-

0.05

-

-

-

-

0.38

0.05

-

-

-

-

-

-

-

-

0.05

-

-

-

-

8.05

15.09 -

9.16 -

1.78 -

0.59 - 3-18 -

7.00 - - -

U.36 -

U ol*

2.21 - - -

2.10 -

. _ . _

0.32 -

0.5l* -

- - - -

-

- - - -

0.65 - - -

0.59 -

O.59 -

- - _ -

- - - -

0.27 - - -

n 00

U.Jd

0.27 -

0.05 - - -

0.16

0.16 - - -

- - - -

- - - -

0.11 -

0 0*5

0.05 . . .

. . . _

0.05 . . .

. . . .

0.05 - . .

0.05 . . .

61*.1+2 U.oi* 3.31* -

36U

Ol li

213

139

133

123

83

O

71*11*

36

33

21

18

18

15

13

11

11

10

y

8

7

6

5

3

3

3

2

C

C

2

22

1

1

1

"1

-L

1

1

1

1

5

1856

19-61

11.53

11.1*8

7.70

7.1*9

7.17

6.63

1*.1*7

L n)i

3.83

2.37

1.9U

1.78

1.13

0.97

0.97

0.81

0.70

0.59

0.59

0.5I*

n lift

U . HO

0.U3

0.38

0.32

0.27

0.16

0.16

0.16

0.11

n i l

\J . XX

ni U l

. J.J.

A l U l

. XX

0.11

0.11

0.05

0.05

0.05

0 OS

0.05

0.05

0.05

0.05

0.05

(\ -\C Vs. XO
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