a comparative analysis of subgroup structure and spatial

7/27/2019 A Comparative Analysis of Subgroup Structure and Spatial

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PRIMATES, 17(3) : 291-3 00, Ju ly 1976 291

A Compara t ive Ana lys is o f Subgroup S t ruc tu re and Spa t ia lRelat ionships in Capt ive Baboons and Squirrel MonkeysLYNN FAIRBANKSUniversity of Washington

AB STR AC T. Subgroup s tructure , spacing pat terns , a nd the re la t ionship between spat ia l andbehavioral in tera t ions were com pared for capt ive babo ons a nd squirre l m onkeys. Analysis ofthe s t ruc tu re , in tens ity , and pe rmanence o f subgroups revea led tha t the baboo ns fo rmed lowintensity, overlap ping subgro ups wh ich were relatively flexible while the squirrel m onk eyssegregated in to perma nent , h igh in tensi ty , m utua l ly exclusive c l iques. Clique associa t ions an dsocia l proxim ity re la t ionships were foun d to be bet ter predic tors th an dom inance ran k of thenature and frequency of behavioral in teract ions in the tw o colonies .I N T R O D U C T I O N

D i f f e r e n c e s b e t w e e n p r i m a t e s p e c i e s i n t y p i c a l s p a c i n g p a t t e r n s a n d s u b g r o u p i n gt e n d en c i e s h a v e b e e n n o t e d s in c e th e e a r l y d a y s o f p r i m a t o l o g y . T o m e n t i o n j u s t af e w o f t h es e v a r i at i o n s , h a m a d r y a s b a b o o n (Papio ham adryas) t r o o p s s u b d i v i d e i n t oh a r e m s c o n t a i n i n g o n e m a l e a n d s e v e r al f e m a l e s ( KU M M ER, 1 96 8) ; g i b b o n s (Hylobateslar) t y p i c a l l y l iv e i n f a m i l y g r o u p s w i t h o n e m a l e , o n e f e m a l e , a n d t h e i r y o u n g(CARPENTER, 1940); an d rh esu s m ac aq ue s (Macaca m ulatta) a r e u s u a l l y f o u n d i nm u l t i - m a l e t r o o p s w i t h s u b d i v i s i o n s a l o n g m a t r i l i n e a l k i n s h i p l i n e s ( S h o E , 1 9 6 5 ) .V a r i a t i o n s h a v e a l s o b e e n n o t e d w i t h i n s p e ci e s s tu d i e d i n d i f f e r e n t h a b i t a t s , w i t hl a n g u r s (Presbytis entellus) b e i n g f o u n d i n o n e - m a l e , m u l t i- m a l e , a n d a l l m a l e t r o o p s(JAY, 1965; SUGIYAMA, 1964).

W h i l e t h e se d i f f e r e n ce s i n s o c i o - s p a t i a l r e l a t i o n s h i p s h a v e l o n g b e e n r e c o g n i z e d a sa n i m p o r t a n t d i m e n s i o n i n u n d e r s t a n d i n g p r i m a t e s o c i a l o r g a n i z a t i o n , t h e re h a s b e e ns u r p r i s i n g ly l i t tl e q u a n t i t a t i v e d a t a o n d e t a i l s o f s u b g r o u p s t r u c t u r e a n d t h e r e l a t i o n -s h i p o f s o c ia l s p a c in g t o b e h a v i o r a l p r o c es s es . M o s t o f t h e i n f o r m a t i o n p r e s e n t lya v a i l a b l e o n p r i m a t e s p a t i a l p a t t e r n s c o m e s f r o m f i e l d s t u d i e s a n d i s p r i m a r i l yq u a l i t a t i v e i n n a t u r e w i t h a f e w n o t a b l e e x c e p t i o n s . K CM M ZR 19 68 ) c o l l e c t e d d a t a o nb o t h s p a t i a l d i s t a n c e a n d s o c i a l i n t e r a c t i o n s t o p r e c i s e ly d e f in e th e o n e - m a l e s u b u n i t so f t h e h a m a d r y a s b a b o o n . S A D E ( 19 72 ) a d a p t e d s e v e r al s o c i o m e t r i c t e c h n i q u e s t oi d e n t i fy g r o o m i n g n e t w o r k s a n d t h e i r r e l a ti o n s h i p t o d o m i n a n c e r a n k i n f r e e- r a n g in gr h e s u s m a c a q u e s o n C a y o S a n t i a g o .

T h e s e m e t h o d s o f q u a n t i t a t iv e l y e v a lu a t i n g s u b g r o u p i n g p a t t e r n s h a v e o n l y r e c e n tl ybeen app l ie d to lab ora to ry s tud ies o f p r im a te beh av io r (FAIRBANI(S, 1974a). Com -p l e x a n a ly s i s o f s p a t i a l r e l a t i o n s h i p s i n c a p t i v e p r i m a t e g r o u p s c a n n o t o n l y b e u s e f u lin desc r ib ing spec ies - typ ica l soc ia l o rg an iza t ion (MASON, 1971 ; ROSENBLUM, KAUF-MAN, & Sa 'VNES, 1964), bu t c an a l so be used to m on i to r be hav io ra l p rocesses oc -c u r r i n g w i t h i n th e g r o u p . S p a t i a l s t r u c t u r e o f a c a p ti v e g r o u p i s b o t h a c o n s e q u e n c ea n d a c a u s e o f so c ia l i nt e r a c ti o n s , a c o n s e q u e n c e i n t h a t s u b g r o u p i n g p a t t e r n s m a y


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29 2 L. FAIRBANKSb e d e t e r m i n e d b y p a s t a f fi li a ti v e o r h o s t i le i n t e r a c t i o n s b e t w e e n i n d iv i d u a ls , a n d ac a u s e i n t h a t n o n r a n d o m s p a t i a l d i s tr i b u t i o n i n f lu e n c es t h e p r o b a b i l i t y o f f u t u r eb e h a v i o r a l e v e n ts . D i f f e r e n c e s b e t w e e n s p e ci e s i n s p a c i n g p a t t e r n s a n d t h e i r c o n -c o m m i t a n t s o c i a l b e h a v i o r s c a n p r o v i d e in s i g h t i n t o t h e r e l a t io n s h i p s a n d i n t er -a c t i o n s b e t w e e n d i f f e r e n t s t y l e s o f s o c i a l a n d s p a t i a l b e h a v i o r .

T h e p r e s e n t s t u d y w a s d e s i g n e d t o d e s c r i b e s o c i o - s p a t i a l r e l a t i o n s h i p s i n t w op r i m a t e s p e c i e s , s a v a n n a b a b o o n s ( Pap i o cynocepha lus ) a n d s q u i r r e l m o n k e y s(Saimiri sciureus) . P r i o r i n f o r m a t i o n o n s p a t i a l p a t t e r n s i n t h e s e t w o s p e c i e s i n t h ef ie l d i n d i ca t e s t h a t b o t h l iv e in m u l t i- m a l e g r o u p s o f c o m p a r a b l e s i ze r an g e , b u t t h a tt h e s u b g r o u p s t r u c t u r e o f t h e t w o s p ec ie s i s q u it e d i f fe r e n t. B a b o o n s t e n d t o a g g r e g a t ei n r e la t i v e ly l a rg e g r o u p s w i t h n o d i s ti n c t s u b s t r u c t u r e t h r o u g h o u t m o s t o f t h e i r r a n g e( HA L L & D E V O R E , 1 9 6 5 ; R O W E L L , 1 9 6 6 a) w h i l e s q u i r r e l m o n k e y t r o o p s h a v e b e e nr e p o r t e d t o d i v id e i n t o s m a l le r u n i ts , u s u a l l y c o n t a i n i n g i n d i v i d u a ls o f th e s a m e a g e -sex c l a ss , t o fo r ag e o r soc i a l i ze (TnoRINGTON, 1968 ; BALDWIN, 1971).

T W O m e t h o d s o f a n a ly s i s h a v e b e e n c h o s e n t o d e s c r ib e a n d c o m p a r e s p a c i n gp a t t e r n s a n d s o c ia l r e l a ti o n s h i p s o f th e s e t w o s p e ci es u n d e r c a p t i v e c o n d i t io n s . F i r st ,a C l i q u e a n a l y s i s w a s d e s i g n e d t o i d e n t i f y s u b g r o u p s i n a m a t r i x o f s it ti n g a s s o c i a t i o n s ,t o a s s es s t h e i n t e n s i t y a n d s t a b i li t y o f t h e s e s u b g r o u p s , a n d t o e v a l u a t e t h e b e h a v i o r a lp r o c e s s e s r e s p o n s i b l e f o r m a i n t a i n i n g t h e m . A n d s e c o n d , a S o c i a l P r o x i m i t y m e a s u r ew a s d e v e l o p e d t o r e l a t e in d i v i d u a l d if f e re n c e s i n t h e a m o u n t o f t im e s p e n t i n s o c i alp r o x i m i t y t o f r e q u e n c y a n d q u a l it y o f b e h a v i o r a l i n t e ra c t io n s a n d d o m i n a n c e -s u b o r d i n a t e r e l a ti o n s h ip s .P ROC EDUR ESUBJECTS

S u b j e c ts w e r e o n e s o c ia l g r o u p o f s a v a n n a b a b o o n s (Papio cynocephalus) c o n t a i n i n ge i g h t a d u l t f e m a l e s a n d o n e a d u l t m a l e , a n d o n e g r o u p o f s q u i r r e l m o n k e y s (Saimirisciureus) w i t h s ix a d u l t f e m a l e s a n d t w o a d u l t m a l e s. I n a d d i t i o n t o t h e a d u l t s o b s e r v e da s f o c a l s u bj e ct s , t h e b a b o o n c o l o n y c o n t a i n e d o n e j u v e n il e f e m a l e , o n e j u v e n i le m a l e ,o n e b r o w n i n f a n t , a n d f o u r b l a c k i n f a n t s . T w o a d d i t i o n a l i n f a n t s w e r e b o r n i n t o t h eg r o u p d u r i n g t h e c o u r s e o f th e p r e s e n t s t ud y . T h e s q u ir r e l m o n k e y c o l o n y c o n t a in e do n e ju v e n i l e m a l e a n d o n e i n f a n t a t t h e o n s e t o f t h e s t u d y , w i t h a n o t h e r i n f a n t b e i n gb o r n d u r i n g t h e c o u r s e o f d a t a c o l l ec t io n . A l l a d u l ts o f b o t h s p ec ie s w e r e f e r a l b o r na n d a ll i n f a n ts a n d j u v e n i le s w e r e b o r n i n c a p t iv i ty .HOUSING

T h e b a b o o n c o l o n y w a s m a i n t a in e d a t th e U n i v e rs i ty o f W a s h i n g t o n P r i m a t eF i e l d S t a t i o n a t M e d i c a l L a k e , W a s h i n g t o n . T h e g r o u p w a s h o u s e d i n a la r g e r o o m ,1 1' 2 2 ' 8 ' , w i t h b e n c h e s a l o n g t h e w a l l s a n d p i p e s i n th e c e i li n g f o r s i t ti n g p e r c h e s .O b s e r v a t i o n s w e r e m a d e t h r o u g h a p l e x i g l a s s w i n d o w f r o m a n a d j a c e n t r o o m .

T h e s q u ir r el m o n k e y c o l o n y w a s m a i n t a in e d a t t h e U n i v e r s it y o f W a s h i n g t o nP s y c h o l o g y D e p a r t m e n t i n a w i r e - m e s h c a g e, 8 ' 6 ' 4 ' , w i t h s e v e r a l b r a n c h e s a n dd o w e l s f o r s i t t i n g p e r c h e s . T h i s g r o u p w a s o b s e r v e d f r o m a n a d j a c e n t r o o m t h r o u g ha o n e - w a y g l a s s .


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Subgroup Structure and Spatial Relationships in Baboons and Squirrel Monkeys 293

OBSERVATION SCHEDU LE

Data from the squirrel monkey colony were taken during 45 days of observationbetween September 1 and December 1, 1972. During an observation day, continuousdata were recorded for each adult member of the colony, in random order, for 5minutes. Data on the baboon colony were collected for 45 days between January 15and April 15, 1973, according to the same observation schedule.COD ING SYSTEM

During a 5-minute observation period, data on spacing and behavioral interactionswere recorded on a data sheet in sixty 5-second intervals. Spatial relationships werecoded as:

S o l i t a r y : No other animals within arm's reach.N e a r : Within arm's reach of another individual.H u d d l e : In gross body contact with another individual.

In addition to a continuous record of spatial relationships, the following socialbehaviors were recorded when they occurred:Af f i l ia t i ve b ehav ior s : including touch, lip smack, social groom, present, and affilia-

tive behavior directed toward infants by non-mothers.Sexual behav ior s : including genital inspection, mounting, and copulation.Agonis t ic behaviors: including threat, fear grimace, manipulation, and physicalattack.D o m i n a n c e b e h a v i o r s: including displacement (a sequence where one individual

leaves as the result of the approach of another individual) and genital display (abduct-ing the thigh and exposing the genital region to another individual).DATA ANALYSIS

In order to identify subgrouping patterns within each of the two colonies, thespacing data were analyzed by a method developed by FESTINGER (1949) and LUCE(1950) and used by SADE (1972) to identify grooming cliques in rhesus monkeys.

A matrix was constructed of the percent of the tota l observat ion intervals tha t eachadult in the group spent near or huddled with each other adult. This matrix was thenanalyzed to identify subgroups, or cliques, which included individuals who eachreciprocally spent more than a specified amount of time near or huddled with eachother individual in the clique. The intensity of clique relationships is determined bysetting a discriminative value ( D V ) , below which interactions are set at 0 and abovewhich they are considered to be 1. (In SADE'S(Ioc. cir.) analysis the minimum numberallowed in a clique was three individuals, but in the present study cliques of twomembers were also considered.)

In addition to the subgroup analysis, the Social Proximity score was computed foreach individual as a second measure of spatial association in the two colonies. SocialProximity was defined as the percent of the total timed intervals that each individualwas recorded near or huddled with at least one other adult colony member.

In order to relate spatial interactions with dominance-subordinate relationships, ameasure of dominance was defined for each o f the two species. The dominance rank


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294 L. FAIRBANKSfor baboons was constructed according to the ability of each individual to displaceeach other individual. This method of ranking was found by ROWELL (1966b) toprovide the clearest index of rank in a similar captive group of baboons. The squirrelmonkeys were ranked according to the relative frequency of giving vs. receiving genitaldisplays between individuals, a method used by several investigators (PLOOG, BLITZ,& PLOO6, 1963; CANDLANDe t a l . , 1970) as an index of rank in this species.RESULTSCLIQUE STRUCTURE

Figure 1 shows the subgroup structure for the baboon and squirrel monkeycolonies. A clique analysis with a discriminative value (D V) of 10 % of the total timespent together in the baboon colony revealed four overlapping subgroups with twofemales remaining solitary. A similar analysis in the squirrel monkey colony detected

BABOONS SQURRELMONKEYS

B? F? 2c~

DV = 25% NOCLIQUES

@| l%DV : 50% NOCLIOUES %

Fig. 1. Clique structure of the baboon and squirrel monkey colonies at three levels of intensity.


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Subgro up S t ruc tu r e and Spa t ia l Re la t ionsh ips i n Baboon s and Squ i r re l M onkeys 295Table 1 . Instances per individual per ho ur of aff il ia t ive , agonist ic , and sexu al b ehav ior wi th inand be tween subgroups fo r t he babo on an d squ i r r e l mo nkey co lon ies .

Affiliative Agonistic SexualBaboonsWithin 5.49 0.94 0.50subgroups

Between 3.14 0.90 0.50subgroups **Squirrel monkeysWithin 10.17 0.17 0.50subgroups

Between 0.49 0.07 0.22subgroups **** p


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29 6 L. FAIRBANKS

B A B O O N S

O - 10- 20- 30- 40- 50- 60- 70- 80- 90 -10 20 30 40 50 60 70 80 90 100

MALE N

FEMALE ~' ~

4

f 3

2

1

S Q U I R R E L M O N K E Y S

, N |0 - 10- 20 - 30- 40- 50- 60 - 70 - BO 90 -1 o 2 0 3 0 4 0 so 6 0 7 0 8 0 90 ~ 0 o

F i g . 2 . F r e q u e n c y h i s t o g r a m o f S o c i a l P r o x i m i t y s c o r e s f o r b a b o o n s a n d s qu i r r e l m o n k e y s .(Socia l Proxim i ty score is the percent of 5 second in tervals that each individual sp ent ne ar o rhudd led w i th a t l eas t one o the r adu lt g roup mem ber . )SOO AL PROXIMITY SCORE

A f r e q u e n c y d i s t ri b u t i o n o f t h e S o c i a l P r o x i m i t y s c o r es ( p e r c e n t o f t i m e d i n t e r v a lss p e n t n e a r o r h u d d l e d w i t h a t l e a s t o n e o t h e r i n d i v i d u a l) is s h o w n i n F i g u r e 2 . A d u l tf e m a l e s in t h e b a b o o n c o l o n y v a r ie d a l o n g a c o n t i n u u m o n t h is m e a s u r e , f r o m 2 9t o 8 0 ~ . I n c o n t r a s t , t h e s q u i rr e l m o n k e y f e m a l e s w e r e u n i f o r m l y h i g h in t h e p e r c e n to f t im e s p e n t i n S o c i al P r o x i m i t y w i t h a r a n g e f r o m 6 2 ~ t o 8 6 ~ . I n b o t h s p e c ie s ,m a l e s w e r e r e la t i v e ly l o w i n th e a m o u n t o f t i m e s p e n t n e a r o t h e r g r o u p m e m b e r s .DOMINANCE RANK

A n a l y s i s o f r e l at i v e d is p l a c e m e n t s y i e ld e d a n a l m o s t p e r f e c t l i n e a r d o m i n a n c eh i e r a r c h y i n t h e b a b o o n c o l o n y ( F i g . 3 ). A l l d y a d s f o l l o w e d t h e m o s t r i g id d e f i n i ti o no f a d o m i n a n c e h i e r a r c h y w h e r e e a c h i n d i v id u a l w a s o b s e r v e d t o d i s p l a c e e a c h lo w e ri n d i v i d u a l a n d b e d i s p la c e d b y e a c h h i g h e r in d i v i d u a l in t h e d o m i n a n c e r a n k i n g , w i t ho n e e x c e p t i o n . N o i n s t a n c e s o f d i s p l a c e m e n t s o f ~ ~ b y ~ c o r ~ r) w e r e r e c o r d e dd u r i n g t h e o b s e r v a t i o n s e s s io n s , s o t h e d i r e c t i o n o f o t h e r a g o n i s t i c b e h a v i o r s w a su s e d t o d e t e r m i n e ~ E 'S r a n k .N o s y s t e m a t ic r a n k i n g o f t h e s q u i r r e l m o n k e y s w a s p o s si b le b a s e d o n d i r e c t i o n o f


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Subgroup Structure and Spatial Rela t ionships in Baboo ns and Squirrel M onkey s 297O'~A

?,1, z ? E?,t.~ J?+v ~"~,v G~4,n F ig . 3 . Dom inance h ie ra rchy o f baboon g roup as de te rmined by? ~ direction of spatial displacements.

g e n i t a l d i s p l a y s. O n ly o n e g e n i t a l d i s p l a y w a s r e c o r d e d b e tw e e n t h e tw o a d u l t m a l e s ,a n d t h i s w a s b y t h e a p p a r e n t l y l e ss a s se r t iv e m a le t o w a r d t h e m o r e a s s e r t iv e . Be tw e e na d u l t f e m a le s , g e n i t a l d is p l a y s w e r e r e l a ti v e ly f r e q u e n t i n o n e s u b g r o u p b u t w e r er e c ip r o c a l w i th n o c l e a r - c u t l i n e a r o r d e r i n g . N o g e n i t a l d i s p l a y s w e r e r e c o r d e d b e -tw e e n f e m a le s o f t h e s e c o n d s u b g r o u p .B E HAVIOR AL INT ER AC T IONS , S OC IAL P R OXIM IT Y R AN K, AND DOM INANC E R AN K

T h e c o r r e l a t io n b e t w e e n S o ci a l P r o x i m i t y r a n k , D o m i n a n c e r a n k , a n d f r e q u e n c yo f a ff i li a ti v e a n d a g o n i s t i c i n t e r a c t i o n s f o r t h e b a b o o n c o lo n y is s h o w n in Ta b l e 2 .Th e r e w a s a r e la t i v e ly h ig h p o s i t iv e c o r r e l a t i o n b e tw e e n S o c i a l P r o x im i ty r a n k a n din v o lv e m e n t i n b o th a f f i li a ti v e a n d a g o n i s t i c b e h a v io r . I n c o n t r a s t , t h e r e w a s n o l i n e a rr e l a t i o n s h i p b e t w e e n D o m i n a n c e r a n k a n d e i t h e r b e h a v i o r a l c a t e g o r y .

A s im i l a r a n a ly s i s w a s n o t p e r f o r m e d f o r t h e s q u i r r e l m o n k e y d a t a a s t h e S o c i a lP r o x im i ty s c o r e s w e r e r e l a t i v e ly i n v a r i a n t , e s p e c i a l l y a m o n g a d u l t f e m a le s , a n d aD o m i n a n c e r a n k c o u l d n o t b e r e l i a b l y d e t e r m i n e d f o r t h e r e a s o n s e x p l a i n e d a b o v e .Table 2 . Spearm an 's rank order corre la t ion between Socia l Proximity rank, Do m inanc erank, and affi lia tive and agonist ic behavior in the b abo on colony.

Social ProximityrankDominance rank

Affiliative Agonisticbehavior behaviorrho=.68 rho=.59r h o = . 0 0 r h o - - - - . 0 7

D I S C U S S I O NA n a l y s i s o f t h e c l iq u e a s s o ci a ti o n s o f t h e c a p t i v e b a b o o n a n d s q u ir r el m o n k e y

g r o u p s s t u d i e d h e r e r e v e a l e d d i f f e r e n c e s b e tw e e n t h e s e tw o s p e c i e s i n s u b g r o u pin tens i ty , s tab i l i ty , and s t ruc tu re .

A d u l t s i n th e c a p t i v e b a b o o n c o lo n y w e r e o r g a n i z e d i n a s e r ie s o f l o w in t e n s i t y ,o v e r l a p p in g a s s o c i a t i o n s w i th n o d i s t i n c t s u b u n i t s . O n e i n d iv id u a l w o u ld f r e q u e n t l ya s s o c i a t e w i th s e v e r a l o th e r s s e q u e n t i a l l y , r a t h e r t h a n s im u l t a n e o u s ly , s o t h a t m o s tm e m b e r s w e r e li n k e d t o m o s t o t h e rs i n d i r e c tl y t h r o u g h m u t u a l s i tt in g c o m p a n i o n s .P a t t e r n s o f s i t ti n g t o g e t h e r te n d e d t o b e c o n t i n u o u s l y g r a d e d s o t h a t t h e s u b g r o u p sr e v e a l e d b y a c l i q u e a n a ly s i s w e r e r e l a t i v e ly a r t i f i c i a l b r e a k s i n a c o n t i n u u m r a th e rt h a n r e p r e s e n t i n g t r u e s t r u c tu r a l u n i t s .


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298 L. FA1RBANKSThe subgroup relations in the squirrel monkey colony were distinctively different

from those found for the baboons. The squirrel monkeys segregated into clear-cut,mutually exclusive cliques with a high degree of association within and little or nointeraction between units. Each of the two squirrel monkey subgroups contained ahigh intensity core of two adult females who spent more than 50 ~ of their totalrecorded time in close proximity to one another, with a third adult female who spentmore than one-third of her time in close association with the other two.

In addition to these structural features, the baboon and squirrel monkey subgroupsalso differed in relative permanence. Baboon subgroups were relatively flexible andwere particularly influenced by the birth of an infant. In several cases in the babooncolony new subgroup relationships were formed when an adult female bore an infantand gradually broke up as the infant grew older or was removed from the group.

In contrast, the squirrel monkey subgroups appeared to be relatively permanentand impervious to change. The subgroups described here have been constant for atleast three years in spite of seasonal changes, births, deaths, and experimental manipu-lation following the termination of the observations reported here (FAIRBANKS,1974a,b).Data from the present study indicated that the loosely structured baboon sub-groups and the more intense, exclusive squirrel monkey cliques were maintainedprimarily by affiliative behavior within the group. In the baboon colony, there wastwice as much affiliative behavior directed toward other subgroups members as tooutsiders, while in the squirrel monkey colony there was 20 times as much affiliativebehavior within subgroups as between.

Behavior between subgroups was characterized by lack of interaction rather thanby any specific behaviors in both species. In the baboon colony, aggression wasobserved within subgroups as frequent ly as between, and there were no organizedattacks of subgroup members against outsiders. With descriptive data of this nature,it is impossible to determine whether the spatial separa tion of non-interacting in-dividuals was due simply to lack of positive attraction or to active avoidance basedon past history of agonistic encounters. Experimental manipulation of spatial re-lationships would be necessary to determine the causal mechanisms for subgroupsegregation in this species. For the squirrel monkeys, experimental analysis of sub-group processes in this same colony following the present study (FAIRBANKS,1974a)revealed tha t segregation of the females into separate groups was mainta ined bymutual avoidance rather than overt antagonistic behavior and that non-membermales were excluded from female subgroups by infrequent, but intense, instances ofaggression.

Social Proximity analysis revealed differences between baboons and squirrel mon-keys in the integration of each individual into the group spatial pattern. In the ba-boons there were marked individual differences in the amount of time spent in socialproximity, with some females spending practically all of their time near other groupmembers, and others remaining solitary. In contrast, squirrel monkey females wereuniformly high in social proximity with only one of the males spending most of histime alone.

An analysis of the relationship between Social Proximity rank and behavior


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S ubg roup S t ruc tu re and S pa t i a l Re la t ions h ips in Bab oons and S qu i r re l M o nkeys 299p r o d u c e d r e m a r k a b l y h ig h c o r re l a t i o n s w i t h i n t h e b a b o o n c o l o n y . T h e i n d i v i du a l sw h o w e r e t h e m o s t s o c i al f r o m a s p a t i al s t a n d p o i n t w e r e a l so i n v o l v e d in t h e m o s tb e h a v i o r a l i n t e r a c t i o n s , b o t h p o s i t i v e a n d n e g a t i v e . T h e f a i l u r e t o f i n d a r e l a t i o n s h i pb e t w e e n d o m i n a n c e r a n k a n d t h e f re q u e n c y o f a g o n is t i c b e h a v i o r i s n o t a s s u r p r is i n ga s it m a y s e e m a t fi rs t g l an c e . D o m i n a n c e r a n k i s b a s e d o n d y a d i c r e l a ti o n s h ip s a n dn o t o n b e h a v i o r a l f r e q u e n c ie s . S t u d i e s o f t h is a n d o t h e r s p e c ie s (R O W E L L , 1 9 6 6 b ;K AU FM A NN , 1 96 7) h a v e o f t e n n o t e d t h a t m i d - r a n k i n g a n i m a l s a r e m o r e a g g r e s s i v e o nt h e b a s is o f fr e q u e n c y o f a g g r e ss i o n, b u t n o t i n t e r m s o f t h e n u m b e r o f o t h e r i n d i v id u -a ls t h a t t h e y c a n d o m i n a t e . W h i le d o m i n a n c e r a n k m a y b e a u s ef u l m e a s u r e i n u n d e r -s t a n d in g s o m e f e a t u re s o f b a b o o n s o c ia l o r g a n i z a t i o n , i n t h e p r e s e n t s i t u a ti o n S o c i alP r o x i m i t y r a n k p r o v e d t o b e a b e t t e r p r e d i c t o r o f d a y - t o - d a y a c t i v i ty a n d e v e n t s int h e c o l o n y .

I n t h e s q u i rr e l m o n k e y c o l o n y , a n a n a l y s i s o f t h e d i r e c t i o n o f g e n i ta l d i s p l a y s w a sn o t a u s e f ul m e a s u r e o f g r o u p s t r u c t u re a n d f a i l e d t o p r o d u c e a l in e a r r a n k i n g b e -t w e e n i n d i v i d u a l s. T h e s i g n a l f u n c t i o n o f t h e g e n i t a l d i s p l a y i s c o m p l e x a n d i t i s o n l yp a r t i a l l y u s e d a s a n a s s e r t io n o f r a n k ( P L o o a , 1 9 67 ). I n t h e p r e s e n t s i t u a t i o n , d i s p l a y sb e t w e e n a d u l t f e m a l e s w e r e t y p ic a l l y o b s e r v e d w h e n o n e m e m b e r r e t u r n e d t o h e rh a b i t u a l h u d d l e g r o u p a f t e r a b r i e f a b s e n c e a n d a p p e a r e d t o f u n c t i o n a s a g r e e t i n g -r e c o g n i ti o n c e r e m o n y b e t w e e n in d i v id u a l s. S u b g r o u p s t ru c t u r e p r o v e d t o b e t h em o s t u s e f u l i n d i c a t o r o f t h e q u a l i t y a n d d i r e c t i o n o f i n t e ra c t i o n s f o r s q u i r r e l m o n k e y s ,w i t h 8 8 % o f a ll r e c o r d e d b e h a v i o r s b e t w e e n a d u l t s o c c u r r i n g w i t h i n s u b g r o u pb o u n d a r i e s .

S u b g r o u p s t ru c t u re a n d m e a s u r e s l ik e th e S o c i a l P r o x i m i t y r a n k u s e d i n th ep r e s e n t s tu d y m a y p r o v i d e a u se f ul f r a m e w o r k f o r o r g an i z i n g i n f o r m a t i o n o n p r i m a t es o c i a l s y s te m s . D i m e n s i o n s s u c h a s in t e n s i ty , c o m p o s i t i o n , f le x i bi li ty , a n d p e r m a n e n c eo f s u b g r o u p s a r e r e la t iv e l y e a si ly m e a s u r e d a n d c o m p a r e d a c r o ss s p e ci es , a n d c a ns e r ve a s s e n s it i v e m e a s u r e s o f i n d i v i d u a l i n t e g r a t i o n i n t o a g r o u p . T h e p r e s e n t s t u d yh a s d e m o n s t r a t e d t h e c l o s e t i e b e t w e e n s u b g r o u p s t r u c t u r e , s o c i a l p r o x i m i t y , a n d t h es o c i a l d y n a m i c s o f a c a p t i v e g r o u p , a n d t h e u s e f u l n e s s o f s p a c i n g c o n c e p t s i n p r e -d i c t in g s p e ci fi c d e t a il s o f i n t r a - g r o u p i n t e r a c t i o n s i n t w o p r i m a t e s p e ci e s.

Acknowledgement. T h i s w o r k w a s s u p p o r t e d b y a N a t i o n a l S c i e n ce F o u n d a t i o n G r a d u a t eFel lowship .

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30 0 L. FAIRI3ANKSs p ec i e s , Papio cynocephalus, Macaca nemestrina, and Saimiri sciureus, u n p u b l i s h e d P h .D . d i s s e r t a t i o n .F ES T IN 6E R , L . , 1 94 9. T h e a n a l y s i s o f s o c i o g r a m s u s i n g m a t r i x a l g e b r a . Human Relations, 2 :153-158 .H A L L , K . R . L . & I . D E V oR E , 1 9 65 . B ab o o n s o c i a l b eh av i o r . I n : Primate Behavior: FieldStudies of Monkeys and Apes, I . D EV oR E ( e d .) , H o l t R i n e h a r t & W i n s t o n , N e w Y o r k .JA Y , P . , 1 96 5. T h e c o m m o n l a n g u r o f N o r t h I n d i a . I n : Primate Behavior: Field Studies ofMonkeys and Apes, I . DE Vo RE ( ed . ), H o l t R i n e h a r t & W i n s t o n , N e w Y o r k .KAt~FMANN,J . H . , 1 96 7. S o c i a l r e l a t i o n s o f a d u l t m a l e s i n a f r e e - r a n g i n g b a n d o f r h e s u s m o n -k e y s . I n : Social Communication among Primates, S . A . A L TM A N N ( e d . ) , U n i v e r s i t y o fC h i c a g o P r e s s , C h i c a g o .KUMMER, H ., 1968. Social Organization of Hamadryas Baboons, A Field Study. U n i v e r s i t y o fC h i c a g o P r e s s , C h i c a g o .L u c E , R . D . , 1 95 0. C o n n e c t i v i t y a n d g e n e r a l i z e d c l i q u e s i n s o c i o m e t r i c g r o u p s t r u c t u r e . Psy-chometrika, 15 : 169-1 90 .

M A SO N W . , 1 97 1. F i e l d a n d l a b o r a t o r y s t u d i e s o f s o c i a l o r g a n i z a t i o n i n Saimiri a n d Cal-[ieebus. I n : Primate Behavior: Developments in Field and Laboratory Research, L. A.R OSE NB LU M (ed . ) . V o l . 2 . A ca d e m i c P re s s , N ew Y o rk .P L OO G , D . W . 1 96 7. T h e B e h a v i o r o f s q u i r r e l m o n k e y s a s r e v e a l e d b y s o c i o m e t r y , b i o a c o u s -t ic s , a n d b r a i n s t i m u l a t i o n . I n : Social Communication among Primates= S . A . A L T M A n N( e d .) , U n i v e r s i t y o f C h i c a g o P r e s s , C h i c a g o .~ , J . B LIT Z, & F . P LO OG , 19 63. S t u di e s o n so c ia l a n d se x u al b e h a v i o r o f t h e sq u ir r elm o n k e y (Saimiri sciureus). Folia Primat., 1 : 29 -66 .R O W E LL , T . E . , 1 9 6 6 a. F o r e s t l i v in g b a b o o n s i n U g a n d a . Jour. ZooI. Soe. Lond., 1 4 9 : 3 4 4 -364 .~ , 1966b . H i e ra r ch y in t he o rg a ni za t i on o f a c a pt iv e b a b o o n g ro up . Anim. Behav., 1 4 :4 3 0 - 4 4 3 .S AD E , D . S . , 1 9 65 . S o m e a s p e c t s o f p a r e n t - o f f s p r i n g a n d s i b l in g r e l a t i o n s i n a g r o u p o f r h e s u s

m o n k e y s , w i t h a d i s c u s s io n o f g r o o m i n g . Amer. Jour. Phys. Anthrop., 2 3 : 1 - 1 7 .~ , 1972. S o c io m et r i c s o f Maeaca mulatta. I . L i n k a g e s a n d c l iq u e s i n g r o o m i n g m a -t r i c e s . Folia Primat., 18 : 19 6-224 .S U 6I VA M A , Y . , 1 96 4. G r o u p c o m p o s i t i o n , p o p u l a t i o n d e n s i t y , a n d s o m e s o c i o l o g i c a l o b s e r v a -t io n s o f H a n u m a n l a n gu r s (Presbytis entellus). Primates, 5 : 7 -3 8 .T H OR IN ~T O N, R . W . , 1 9 68 . O b s e r v a t i o n s o f s q u i r r e l m o n k e y s i n a C o l u m b i a n f o r e s t . I n : TheSquirrel Monkey, L . A . R O SE NB LU M & R . W . C O OV ER (ed s . ) , A c ad em i c P re s s , N e w Y o rk .

- - R e c e i v e d March 1, 1975; A c c e p t e d May 24, 1975Au thor ' s Ad dress : LYNN FAmBANKS,Department of Psychiatry, University of Cal(fornia at LosAngeles, Los Angeles, California 90024, U.S.A.

a comparative analysis of subgroup structure and spatial

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