Honess 2006

transcript

8/3/2019 Honess 2006

http://slidepdf.com/reader/full/honess-2006 1/14

Anita. Behav., 199 1,41 , 121 134

Ag gression in interaction s of imm ature rhesus monkeys: components, con tex t

and relation to affiliation lev els

M A G D A L E N A J A N U S *

S u b - d e p a r t m e n t o f A n i m a l B e h a vi o u r, C a m b r i d g e U n i ve rs it y, M a d i n g l e y , C a m b r id g e C B 3 8 A A , U . K .

(Received 16 Februa ry 1990; initial acceptance 30 M arch 1990;

final acceptance 28 June 1990; M S. number 3535)

Abs t rac t . A g o n i s t i c i n t er a c t io n s o f i m m a t u r e r h e s u s m o n k e y s , M a c a c a m u l a t t a , were s t u d i ed o v e r two

seaso n s . Th e h y p o th es i s t e s t ed co n ce rn ed t h e l ev e l s an d t y p e o f ag g re ss io n b e tween mo n k ey s sh o win g

vario us degrees o f a ff i lia t ion : s t rong ly affi l ia ted par tne rs w ere expected to sh ow h igh er overa l l l eve ls , and

d i f fe ren t t y p es , o f ag g re ss io n t h an t h e wea k ly a f f il ia t ed p a r tn e rs . Pa i r s o f mo n k ey s w ere d iv id ed i n to s i b li n g s

( t h o se wi th t h e sam e mo th e r ) an d n o n -s ib l i n g s ( t h o se wi th d if fe ren t mo th e rs ) . Th e l a t t e r g ro u p was fu r t h e rd iv id ed i n to p ee rs ( same-ag e p a r tn e rs ) an d n o n -p ee rs (d i f fe ren t -ag e p a r tn e rs ) . I t i s k n o wn th a t y o u n g

s ib li n g s sh o w h ig h e r d eg rees o f a f f il i at i o n t h an n o n -s ib l i n g s an d t h a t p ee rs a re m o re a ff ili at ed t h an n o n -p ee rs .

F i r s t , t h e l ev e ls o f ag g re ss io n ex p re ssed b y m o n k ey s were e s t ab li sh ed . D y ad s o f s i b li n g s an d p ee rs sh o w ed

m o r e a g g r e s s io n t h a n d y a d s o f n o n - p e e r s. T h e n , a g g r e s s io n c o m p o n e n t s i n t e r m s o f s tr e n g t h a n d r e s p o n s iv e -

n ess , an d t h e co n t ex t o fag o n i s t i c ep i so d es b e tween m o n k ey s a f f i li a ted t o d i f fe ren t d egrees , we re in v es t i g at ed .

S t ro n g ly a ff il ia ted d y ad s sh o wed l es s o f t h e sev e re ty p es o f ag g re ss io n t h an weak ly a f fi li a ted o n es . B o th

s ib l i n g s an d p ee rs sh o wed mo re rec ip ro ca l ag g re ss io n t h an n o n -p ee rs . S ib l i n g s h ad mo re co n f l i c t s t h an

n o n -s ib l i n g s i n t h e co n t ex t s o f g ro o m in g an d p u n i sh m en t , b u t a h ig h e r p ro p o r t i o n o f sev e re co n f l i c ts o f

n o n -s ib l i n g s t h an o f s i bl in g s h ap p en ed i n a feed in g co n t ex t . Th u s a f f i l ia t io n seems t o h av e im p o r t an t l in k s

wi th the levels and c harac ter i s t ics o f agonis t ic in terac t ions . I t i s sugge sted tha t su ch d i fferences are a d i rec t

co n seq u e n ce o f d if fe ren t q u a l it ie s o f re l a ti o n sh ip b e tween s t ro n g ly an d weak ly a f fi li a ted d y ad s .

L iv in g c lo se t o g e th e r i n so c i a l g ro u p s , p r ima te s

s u c h a s m a c a q u e s a n d b a b o o n s a r e c o n s t a n t ly i n te r -

ac t i n g wi th t h e i r f e l lo w g ro u p -m em b ers . So c i a l l if e

i s u su a l l y co n s id e red t o b e ad v an t ag eo u s fo r

m o n k e y s , f o r e x a m p l e b y r e d u c i n g t h e r i s k o f p r e d -

a t i o n ( C h e n e y & W r a n g h a m 1 98 7) , o r b y p r o v i d i n g

p a r tn e rs f o r g ro o m in g (e .g . Sau n d e rs 1 9 87 ). Ho w -

ev e r , wh en re so u rces v i t a l fo r su ccess fu l r ep ro -

d u c t i o n a re sca rce , t h e an ima l s h av e t o co m p e te fo r

t h em wi th t h e i r c l o se n e ig h b o u rs (Cro o k 1 9 7 0 ) .

Th u s , t h e sam e in d iv id u a l s m ay a t t imes b e f r i en d ly

to each o th e r , an d a t o th e rs , ag g re ss iv e .

Th e re a re co n f l i c t i n g rep o r t s a s t o t h e d i s t r i -

b u t i o n o f a g g re s s io n i n p r im a t e g r o u p s . W h i le s o m e

s tu d i e s h av e sh o wn th a t t h e re i s l e s s ag g re ss io n

a m o n g r e l a t i v e s t h a n a m o n g u n r e l a t e d a n i m a l s

(e.g. vervets, Cercopithecus ae thiops: Lee 1987),

o t h e r s h a v e d e m o n s t r a t e d m o r e a g g r e s s i o n a m o n g

re la t ives ( rhesus , M a c a c a m u l a t t a : Bern s t e in &

*Present address: The Psychiatric Research Unit, TheHospital for Sic k Children , 555 U niversi ty A venue,Toro nto, Ontario M5G 1X8, Canada.

E h a r d t 1 98 6; J a p a n e s e m o n k e y s , M a c a c a f u s c a t a :

Gl ick e t a l . 1 9 8 6 ) . On t h e o th e r h an d , a l t h o u g h

fac to rs t h a t i n fl u en ce ag g re ss io n su ch a s ag e an d sex

(D i t tus 1977; E ato n e t a l. 1981; Y ou ng e t a l . 1982) ,

sea so n (Wi l so n & B o e lk in s 1 9 7 0; Dr i ck am er 1 9 75 ;

Eaton e t a l . 1981; Teas e t a l . 1982) or hormonal

s t a t e (Mich ae l & Zu mp e 1 9 7 0 ; Lo y 1 9 7 1 ; Dix so n

1980) have of ten been s tud ied , the k insh ip effec t

has of ten bee n neglec ted . Ei ther re la t ives have been

reg a rd ed sep a ra t e ly f ro m n o n - re l a ti v e s (e.g . Da t t a

1 9 83 a , b ) o r k in re l a t i o n s h av e n o t b een k n o w n

sufficiently (e.g. D it tu s 1977; E at on e t al . 1981; Te as

et al. 1982).

Ev en w i th in o n e sp ec ie s, t h e rh esu s mo n k ey , t h e re

a r e r e p o r t s o f b o t h m o r e a n d le ss a g g r e s s io n b e tw e e n

s t ro n g ly a f fi li a ted p a r tn e rs t h an b e tween t h o se w i th

weak aff i l ia t ive bonds . Bernste in & Ehard t (1986)

h a v e s h o w n t h a t y o u n g r h es u s m o n k e y s d i r e c t sig -

n i f i can t l y mo re ag g re ss io n t o ward s , an d rece iv e

m o r e a g g r e s s i o n f r o m , k i n t h a n n o n - k i n . C o l v i n& Ti s s i e r (1 9 8 5 ) , h o wev e r , fo u n d t h a t immatu re

rh esu s ma le s were l e s s ag g re ss iv e b o th t o ward s

s ib l i n g s an d u n re l a t ed ma le p ee rs wi th wh o m th ey

0003-3472/91/010121 + 14 $03.00/0 9 1991 The A ssociation for the Study of Animal Behaviour

8/3/2019 Honess 2006

h a d s t r o n g a f f i li a t iv e r e l a t i o n s h i p s t h a n t o w a r d s

l e ss a f f i l i a ted m a le p ee r s .

T h e e v i d e n c e f o r s e x d if f e re n c e s i n t h e a m o u n t o f

a g g r e s s i o n i n m a n y p r i m a t e s p e c i e s i s a l s o c o n f li c t -

i n g ( r e v i ew e d i n S m u t s 1 98 7) . I t h a s b e e n h y p o t h e -

s i zed th a t t h e sp ec ie s d i f f e r en ces in ag g r ess io n

d e p e n d o n w h i c h s e x e m i g r a t e s f r o m t h e n a t a l g r o u p .

T h e m e m b e r s o f t h e n o n - e m i g r a t i n g s e x d e v e l o p

m u c h s t r o n g e r so c i a l b o n d s w i t h e a c h o t h e r t h a n t h e

m e m b e r s o f th e e m i g r a t in g s ex . A s a n i m a l s h a v i n g

s t r o n g a f f il i a ti v e b o n d s a r e q u i t e o f t e n a l s o m o r e

a g g r e s s i v e t o e a c h o t h e r t h a n l e s s a f f il i a te d d y a d s

( e .g . W a l t e r s 1 98 6), t h e r e m a y a l s o b e m o r e a g g r e s -

s i o n b e t w e e n m e m b e r s o f t h e n o n - e m i g r a t i n g s ex .

A l t e r n a t i v e ly , in f e m a l e - b o n d e d p r i m a t e s o c ie t ie s

l i k e t h o s e o f m a c a q u e s , a n i n f a n t f e m a l e i s a p o t e n -

t i a l f u t u r e c o m p e t i t o r f o r a d u l t f e m a l e s , w h e r e a s

i n f a n t m a l e s w i ll l e a v e t h e i r n a t a l g r o u p w h e n t h e y

m a t u r e . T h i s h a s b e e n u s e d t o e x p l a i n w h y a d u l t

f e m a l es d i r e c t m o r e a g g r e s si o n t o w a r d s f e m a l e t h a n

t o w a r d s m a l e i n f a n t s ( S i l k et a l . 1 9 81 )

I n v i e w o f t h e a b o v e e v i d e n c e , i t i s p o s s i b l e t h a t

l o o k i n g a t t h e a g o n i s t i c i n t e r a c t io n s i n m o r e d e t a i l,

t h a t i s, c o n s i d e r i n g t h e k i n d o f a g g r e s s i o n e x p r e s s e d

( e . g . B e r n s t e i n & E h a r d t 1 9 8 5 ) a n d t h e c i r c u m -

s t a n c e s a n d c o n t e x t i n v o l v e d ( e .g . P e r e i r a 1 98 8a ),

m a y t h r o w f u r th e r l i g h t o n q u e s t io n s a b o u t t h e d i f -

f e r e n ce s i n a g o n i s t i c i n t e r a c t i o n s b e t w e e n s t r o n g l y

a n d w e a k l y a f fi l ia t e d p a r t n e r s . I n p a r t i c u l a r , i t

m a y b e i m p o r t a n t t o f i n d o u t w h e t h e r c l o s e a f f i l i -

a t i o n l e a d s t o a h i g h e r i n c i d e n c e o f a g g r e s s i o n , b u t

t h a t e i t h e r s u c h a g g r e s s i o n i s n o t s e v e r e , o r t h a t

p o t e n t i a l l y c o m p e t i t i v e s i t u a t i o n s i n f e e d i n g t im e ,

f o r e x a m p l e , a r e r e s o l v e d w i t h o u t u s i n g m u c h

a g g r e s s i o n .

A m o n g i m m a t u r e r h es u s m o n k e y s p a i r s o f s ib -

l i n g s a r e t h e m o s t a f f il i a te d d y a d s , w i t h p e e r s

( n o n - s ib l i n g m o n k e y s b o r n i n t h e s a m e y e a r ) t a k i n gs e c o n d p l a c e, a n d n o n - s i b l in g n o n - p e e r d y a d s b e i n g

t h e l e a s t a f f il i a te d o f th e t h r e e g r o u p s ( J a n u s 1 9 89 a ,

b ) . I n t h i s p a p e r , I c o n s i d e r i n d e t a i l a g o n i s t i c i n t e r -

a c t i o n s b e t w e e n s i b l in g , p e e r a n d n o n - s i b l i n g n o n -

p e e r d y a d s o f y o u n g r h e s u s m o n k e y s . A s i n d i c a t e d

a b o v e , t h e q u e s t i o n s i n v e s t i g a t e d c o n c e r n d i f f e r-

e n c e s i n t h e le v e ls , c o m p o n e n t s a n d c o n t e x t o f

a g g r e s s i o n b e t w e e n d y a d s a f f i l ia t e d t o d i f f e ri n g

d e g r e e s . T h e r e f o r e , f i r st , I e x a m i n e t h e a m o u n t o f

a g g r e s s i o n in s i b l in g , p e e r a n d n o n - p e e r d y a d s a n d

e s t a b l i s h t h e r e l a t i o n s b e t w e e n t h e a f f i li a t io n a n da g g r e s s i o n l e ve l s i n d y a d s . S e c o n d , I e x a m i n e t h e

c o m p o n e n t s o f a g g r e s si o n , w i th t h e h y p o t h e s i s

t h a t t h e r e i s l e s s s t r o n g a g g r e s s i o n i n a f f i l i a t e d

Animal Behaviour, 41, 1

Table I . The composition of the study sample

1986-1987 1987-1988

N 20 20Males 7 8Fem ales 13 12Sibling dya ds 13 11All non-sibling dyad s 30 36Peer dyads 9 10No n-peer dyad s 21 26Nu mb er of focal hours

of observat ion perdya d 35 38.5

d y a d s . T h i r d , I te s t t h e h y p o t h e s i s t h a t c o n t e x t s o fa g g r e s s i o n d i f f e r b e t w e e n s i b l i n g a n d n o n - s i b l i n g

d y a d s . S e x a n d a g e d i ff e r e n ce s a r e r e p o r t e d , w h e r e

a p p r o p r i a t e .

M E T H O D S

The Monkeys

I s t u d i e d a c a p t i v e c o l o n y o f r h es u s m a c a q u e s i n

M a d i n g l e y a t C a m b r i d g e U n i v e r s i ty . T h e c o l o n y

h o u s e s s i x s o c i a l g r o u p s , e a c h c o n s i s t i n g o f o n e

a d u l t m a l e , t w o t o s i x a d u l t f e m a l e s a n d t h e i r s u b -

a d u l t , j u v e n i l e a n d i n f a n t o f f s p r i n g . E a c h g r o u p

h a d a n o u t d o o r w i re m e s h e n c l o su r e , l ea d i n g i n t o

a s m a l l e r h e a t e d i n d o o r r o o m . T h e o u t d o o r p e n s

wer e 7 - 8 m lo n g , 2 "5 m wid e an d 2 .2 m h ig h a t t h e

i n d o o r r o o m e n d , r i s i n g t o 3 . 9 m a t t h e o t h e r e n d .

T h e f l o o r a r e a o f e a c h o u t d o o r p e n w a s 1 8.2 m 2 .

T h e s t u d y p e r i o d l a s t e d f r o m N o v e m b e r 1 9 8 6 t o

S e p t e m b e r 1 9 88 , d i v i d e d i n t o t w o s e a s o n s . E a c h

s e a s o n s t a r t e d a t , o r j u s t b e f o r e , t h e o n s e t o f

t h e b r e e d i n g s e a s o n , a n d f i n i sh e d w i t h t h e e n d o f

t h e b i r t h s e a s o n . R h e s u s m o n k e y s a r e s e a s o n a lb r e e d e r s , w i t h c l e a r -c u t m a t i n g a n d b i r t h s e a s o n s

( e .g . A n d e r s o n & S i m p s o n 1 97 9) . F o r t h e p u r p o s e

o f m y o b s e r v a t i o n s , t h e f i rs t s e a s o n l a s t e d f r o m

18 N o v e m b e r 1 98 6 u n ti l 3 S e p t e m b e r 1 9 87 ( ' 1 9 8 6 -

1 9 8 7 ' ) . T h e s e c o n d o n e l a s t e d f r o m 4 S e p t e m b e r

1 98 7 u n t i l 2 9 Sep tem b er 1 98 8 ( ' 1 9 8 7 - 1 9 8 8 ' ) .

M y s u b j e c t s w e r e 28 y o u n g m o n k e y s , l i v in g i n

f o u r g r o u p s . I n e a c h s e a s o n I o b s e r v e d 2 0 m o n k e y s

( T a b l e I ) . O u t o f t h e 2 8 s u b j e c t s, 12 w e r e s t u d i e d

t h r o u g h o u t b o t h s e a s o ns , a n d 16 f o r o n l y o n e.

E i g h t o f t h e l a t t e r g r o u p w e r e d r o p p e d a f t e r t h e f ir s ts e a s o n b e c a u s e a t t h e a g e o f a b o u t 3"5 y e a r s t h e y

a p p r o a c h e d s e x u a l m a t u r i t y ( se e D r i c k a m e r 1 97 4;

M e l n i c k & P e a r l 1 98 7). I n t h e s e c o n d s e a s o n e i g h t

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Janus: Aggression in young rhesus monkeys 123

n e w i n fa n t s w e r e o b s e r v e d f r o m t h e a g e o f a b o u t 4

m o n t h s . B e c a u se o f t h i s d i s c re p a n c y in t h e n u m b e r

o f s ea s o n s m o n k e y s w e r e o b s e rv e d , d a t a f r o m e a c h

s e a s on w e r e n o t c o m b i n e d b u t a n a l y s e d s e p a r a te l y .

T h e m o n k e y s w e r e c l a s s if i e d b y a g e a s I n f a n t s ,

Y o u n g J u v e n i l e s a n d O l d J u v e n i l e s , u s i n g a m o d i -

f ie d v e r s i o n o f E h a r d t & B e r n s t e i n ' s ( 1 98 7 ) c r i t e ri a :

I n f a n t s , u n t i l 1 . 5 y e a r s o f a g e ; Y o u n g J u v e n i le s ,

b e tween 1 .5 an d 2 " 5 y ea r s ; an d Old Ju v en i l e s ,

b e tw een 2 .5 an d 3 -5 y ea r s .

P a i r s o f m o n k e y s ( d y a d s ) w e re d i v i d e d i n t o

t h r e e c a t e g o r i e s : s i b l in g s , t h o s e w h o h a d t h e s a m e

m o t h e r ; p e e r s , th o s e w h o h a d d i f f e r e n t m o t h e r s b u t

w e r e b o r n i n t h e s a m e y e a r ; a n d n o n - p e e r s , t h o s e

w h o h a d d i ff e re n t m o t h e r s a n d w e r e b o r n i n d if -

f e r e n t y e a r s . T h e t w o l a t t e r g r o u p s ( p e e r s a n d

n o n - p e e rs ) a r e s o m e t i m e s j o i n t l y d e s c r ib e d a s n o n -

s i b l i n g s . T h e m a x i m u m a g e d i f f e r e n c e b e t w e e n

s t u d y s u b j e c t s w a s 2 y e a r s . T h e 2 0 s u b j e c t s o f t h e

f i r s t seas o n f o r m ed 1 3 s ib l in g , 9 p ee r an d 2 1 n o n -

p e e r d y a d s , t h e 2 0 s u b j e c t s o f t h e s e c o n d s e a s o n

f o r m e d 11 s i b li n g , 10 p e e r a n d 2 6 n o n - p e e r d y a d s .

T w o a d d i t i o n a l c a t e g o ri e s o f ' r e c i p r o c a l ' a n d ' n o n -

r e c i p r o c a l ' p a r t n e r s w e r e d i s t i n g u is h e d a m o n g a l l

d y a d s . D y a d s o f m o n k e y s w h o w e r e e ac h o t h e r ' s

m o s t o r s e c o n d m o s t f r e q u e n t p a r t n e r s i n p l a y ,

g r o o m i n g o r p r o x i m i t y , w e r e c l a s s if i e d a s ' r e c i p r o -

c a l p a r t n e r s ' i n o n e o r m o r e o f t h o s e t h r e e a f f il i a ti v e

b e h a v i o u r p a t t e r n s ( s e e J a n u s 1 98 9b f o r d e t a il s ) .

T h e f a m i l y r a n k o f a m o n k e y w a s i d e n t i fi e d a s l o w

i f i t s m o t h e r ' s r a n k i n t h e a d u l t - f e m a l e s ' h i e r a r c h y

w a s t h i r d o r l o w e r , a n d a s h i g h i f i ts m o t h e r w a s t h e

a - f e m a l e . F o r c l a r i t y , o f f s p r i n g o f s e c o n d - r a n k i n g

m o t h e r s w e r e o m i t t e d f r o m t h e c l a s s if i ca t io n .

Sampling and Behaviour

I s a m p l e d t h e 2 0 s u b j e c t s i n e a c h s e a s o n o n a f o c a la n i m a l b a s i s ( A l t m a n n 1 97 4). I n e a c h s e a s o n I o b -

s e r v e d a f o c a l m o n k e y f o r a t l e a s t 7 0 1 5 - m i n o b s e r -

v a t i o n s w h i c h w e r e g r o u p e d i n t o 2 - m o n t h b l o c k s.

D u r i n g a f o c a l o b s e r v a t i o n , a l l s o c i a l i n t e r a c t i o n s

i n v o l v i n g t h e s a m p l e d m o n k e y w e r e r e c o r d e d ,

t o g e t h e r w i t h t h e i d e n t i t y o f t h e i n t e r a c t a n t s ( f o r

d e ta i l s see Jan u s 1 9 89 b ).

A g g r e s s i o n w a s r e c o r d e d i f a m o n k e y a t t a c k e d ,

t h r e a t e n e d , h i t , g r a b b e d , c h a s e d o r d i s p l a c e d

a n o t h e r m o n k e y ( a g gr e s si v e b e h a v i o u r ) o r a v o i d e d ,

f e a r - g ri n n e d ( b a r e -t e e t h d i s p l a y , d e W a a l & L u t t r e t l1 98 5), s c r e a m e d o r j e r k e d a t a n o t h e r m o n k e y ( s u b -

m i s s i v e b e h a v i o u r ) . F o r e a c h a g o n i s t i c i n t e r a c t i o n

i n v o l v i n g a f o c a l m o n k e y , I r e c o r d e d t h e k i n d s o f

a g o n i s ti c b e h a v i o u r b y t h e f o c a l i n d iv i d u a l a n d i ts

p a r t n e r o r p a r t n e r s , a n d t h e i r i d e n t it i e s . I f k n o w n ,

t h e c o n t e x t a n d / o r t h e r e a s o n f o r t h e c o n f l i c t , a s

w e l l a s t h e n a m e s o f m o n k e y s w h o j o i n e d i n , w e r e

r e c o r d e d . I f 1 5 s o r m o r e e l a p s e d b e t w e e n a g o n i s t i c

e p i s o d e s , t h e y w e r e s c o r e d a s t w o i n t e r a c t i o n s .

A g o n i s t i c i n t e ra c t i o n s w e r e p o s t h o c d i v i d e d i n to

S t r o n g A g g r e s s i o n , M i l d A g g r e s s i o n a n d R e c i p r o -

c a l A g g r e s s i o n u s i n g t h e f o l l o w i n g d e f i n i t i o n s .

S t r o n g A g g r e s s io n : a n y o f t h e b e h a v i o u r d e f i n e d

p r e v i o u s l y a s ' a g g r e s s i v e ' a c c o m p a n i e d b y a b i te

a n d / o r f o l lo w e d b y a n e v a s iv e a c t io n b y t h e t a r -

g e t m o n k e y . M i l d A g g r e s s i o n : a n y a g g r e s s i o n o r

s u b m i s s i v e b e h a v i o u r w i t h o u t b o d y c o n t a c t a n d /

o r l a c k i n g a r e s p o ns e f r o m t h e t a r g e t m o n k e y .

R e c i p r o c a l A g g r e s s i o n : a n y k i n d o f a g g r e s s i v e

b e h a v i o u r t o w h i c h t h e t a r g e t m o n k e y r e s p o n d e d

w i t h a g g r e s s i o n .

I n a d l i b i tu m r e c o r d s o f a g o n i s t i c in t e r a c t io n s

I a l w a y s r e c o r d e d t h e i d e n t i t y o f th e m o n k e y s i n-

v o l v e d , a n y t h i r d p a r t i e s a n d t h e k i n d o f a g g r e s s i o n .

W h e n k n o w n , t h e c o n t e x t w a s a l so r e c o rd e d . I n t h i s

p a p e r I i n c l u d e o n l y t h e a d l i b i t u m d a t a r e c o r d e d

d u r i n g f o c a l o b s e r v a t io n s o n o t h e r m o n k e y s i n t h e

s a m e p e n . T h e r e f o r e , t h e t o t a l n u m b e r o f h o u r s i n

w h i c h t h e s e e p i s o d e s w e r e o b s e r v e d w e r e b e t w e e n

5 2 .5 an d 1 0 5 in 1 9 8 6 - 1 9 8 7 , an d b e tween 3 8 .5 an d

134.75 in 1987 -1988.

Derived Measure s

A s m e n t i o n e d a b o v e I c o n s i d e r h e r e o n l y a g o n -

i s t ic i n t e r a c t i o n s t h a t i n v o l v e d i m m a t u r e a n i m a l s .

T h e m e a s u r e s o f a g g r e s s i o n I u s e d a r e a s f o l l o w s .

A g g r e s s i o n r a te : t h e n u m b e r o f a g o n i s t i c i n t e ra c -

t i on s p e r h o f o b s e r v a t i o n ( f r o m f o ca l o b s e r v a t i o n s

o n l y ) . A l l a g g r e s s i o n : th e s u m o f a l l a g o n i s t i c i n t e r -

a c t i o n s in w h i c h a m o n k e y w a s i n v o l v ed ( fo c a l a n da d l i b i t u m c o m b i n e d ) . S t r o n g A g g r e s i o n : a g o n is t i c

i n t e r a c t i o n s c l a s s i fi e d a s ' s t r o n g ' a c c o r d i n g t o

t h e d e f i n i t io n s a b o v e . M i l d A g g r e s s i o n : a g o n i s t i c

i n t e r a c t i o n s c l a s s if i e d a s ' m i l d ' a c c o r d i n g t o t h e

d e f i n i t io n s a b o v e . R e c i p r o c a l A g g r e s s i o n : a g o n i s t i c

i n t e r a c t i o n s c l a s s i fi e d a s ' r e c i p r o c a l ' a c c o r d i n g t o

t h e d e fi n i ti o n s a b o v e . S t r o n g , M i l d a n d R e c i p r o c a l

A g g r e s s i o n al w a y s a d d e d u p t o t h e ' A l l a g g r e s s io n '

m e a s u r e .

I n c o m p a r i s o n s b e t w e e n i n d i v i d u a l s t h e d a t a

f r o m b o t h f o c a l a n d a d l i b i t u m o b s e r v a t i o n s w e reu s e d . T h e a g o n i s t i c i n t e r a c t i o n s i n w h i c h a p a r -

t i c u l a r m o n k e y w a s i n v o l v e d w e r e d i v i d e d i n t o

a g g r e s s i o n g i v e n a n d a g g r e s s i o n r e c e i v e d . F o r

8/3/2019 Honess 2006

J a n u s : A g g r e s s i o n i n y o u n g r h e s u s m o n k e y s

However, when the analysis was done separately

for siblings and non-siblings, he correlations were

weaker (siblings: 1986-1987, rs=0'242, P=0.2;

1987-1988, r s = 0"2t4, P = 0'2; non-s ibl ings: 1986-

1987, rs=0,184, P=0-16; 1987-1988, rs=0"305,

P=0"03). One possible explanation is that the

sample size of either siblings and non-sibl ingsalone

was not large enough to allow correlations to be

statistically significant. On the other hand, a more

plausible explanation for the significant (and

higher) correlation on the combined sample might

be that in siblings as a group b oth aggression and

proximity values were high and in non-sibl ingsas a

group both these values were low, which may have

enhanced the correlation when the two groups were

considered together.

Indiv idual Di fferenc es

Individuals directed more aggression to their

siblings than to non-siblings in both seasons

(Wilcoxon matched-pair signed-ranks test, one-

tailed probabi lities , 1986-1987: Z = - 1-89, N = 17,

P<0 .02 ; 1987-1988: Z= -l . 73 , N = 14, P<0.0 4).

This was tested by matching average scores of

aggressive behaviour towards siblings with those

towards non-siblings for each individual (seeMethods).

A g e a n d s e x d i ff e r en c e s

The levels of aggression in which individual

monkeys were involved differed according to their

age only in the second season (one-way ANOVA,

Infants versus Young Juveniles versus Old Juv-

eniles; 1986-1987, F=0.097, df =2 , NS; 1987-1988,

F=3-73, d f = 2 , P=0"045), but even then the

Stud ent- Newma n-Ke ul est did not show a differ-

ence between any two groups at et = 0'05: However,in both seasons the differences between the three

ages in propor tions of aggression given and received

were significant, with the youngest animals giving

the least but receiving the most aggression

(Kruska l-Wall is ANOVA, 1986-1987, N x (In-

fants) = 6, N z (Young Juveniles) = 6, N 3 (Old Juven-

iles)=8, aggression given ~2=8.41, P<0-01,

aggression received ~2 = 8.41, P<0 .0 1; 1987-1988,

N 1 (Infants) = 8, N 2 (Young Juveniles) = 6, N 3 (Old

Juveni les) = 6, aggression given Z2 = 8' 79, P < 0.01,

aggression received ~z = 8-79, P < 0.01).Aggression given versus aggress ion received were

tested separately for Infants, Youn g and Old Juv-

eniles. Among Infan ts, the percentage of aggression

2 "~ 0-8

?'//,,g ' - V//,,

2 ~ . I / / / /'4 " / / "

0 , 2 ! ; " "

0"0Infant Young Juvenile Old Juvenile

Figure 2. Median proportions of aggression given([]) andreceived ([]) out of all agonistic interactions in whichmonkeys of various ages were involved. N Infants = 14, NYoung Juveniles= 12, N Old Juveniles= 14. Sample com-

bined from both seasons, as no monkey could be in thesame age category over both seasons. Bars representinterquartile intervals.

received was significantly higher th an that given

(Wilcoxon matched-pai r test, Z= - 3.23, N= 14,

P<0.01). Among Young Juveniles there was

no difference between the two percentages (Z=

- 0.16, N = 12, P = 0'8). Among Old Juveniles per-

centage of aggression given was higher t han that

received (Z = -2 .1, N= 14, P < 0.05; Fig. 2).

There were no differences in the involvem ent inagonistic interaction between immature males and

females (1986 1987: t= -0 .7 8, d f = 18, NS; 1987-

1988, t = -- 1"46, NS). Nor were there any significant

sex differences in the amo unt of aggression given or

received.

F a m i l y r a n k

In both seasons, young monkeys coming from

low-ranking families received more aggression

than those coming from high-ranking families

(Ma nn- Whi tne y U-test, 1986-1987: U= 3, N I =11, N2= 5, P <0. 01; 1987-1988: U = I, N~=8 ,

N z = 5, P<0- 01). The monkeys from low-ranking

families also received more aggression than they

gave to other young monkeys (Wilcoxon test, one-

tailed probabilities, 1986-1987: Z = - 1.75, N=5 ,

P<0. 04; 1987-1988: Z--- -2- 02, N= 5, P<0.0 2).

The monkeys from high-ranking families, in con-

trast, gave more aggression than they received

(Wilcoxon test, one-tailed probabilities, 1986-

1987: Z= -1 .9 6 , N= l l, P<0.03 ; 1987-1988:

Z = -- 1-82, N= 8, P < 0.03).Interestingly, there was a sex difference in the

rates of aggression received by low-rank ingInfants.

Low-ranking females were more likely to receive

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12 6 Animal Behaviour, 41, 1

Table I I . Co mp onen ts o f aggression in s ib l ing , peer and non-pe er dyads

1986-1987

A g g res si o n M ed i an N u m b er o f M ed i anDya ds type propo r t ion in terac t ions P propo r t ion

1987-1988

N u m b e r o fin terac t ions

Siblings

N o n -p ee r s

Strong 0.25 160 0.21M ild 0.72 435 0.72Reciprocal 0-04 36 0.06

<0.001Strong 0.18 87 0.29M ild 0.69 328 0.69Reciprocal 0.09 29 0-05

<0.001Stro ng 0-32 192 0-29M ild 0.61 405 0.66

Reciprocal 0.04 28 0.00< 0 '0 0 1

12136 6

11028 4

25 349 5

<0.001

Prob abi l i t ies represent the resul ts of ch i-squared tests , df= 2 in a ll cases.

Table I I I . Com par i son of p ropor t ions o f St rong and Reciprocal Aggress ion between dyads

1986-1987

T y p e o f D y ad s D i r ec t io n o faggression com pared P difference P

1987-1988

D i rec t io n o fdifference

Stron g Sibl ing versus peer NS NSSibl ing versus non -pe er NS 0-03Peer versus non-pe er 0 .03 Peer < non-pe er NS

Reciprocal Siblin g versus pee r NS NSSibl ing versus non -pee r NS 0"02Peer versus non-pe er NS 0 '05

Sib l ing < non-pe er

Sib l ing > non-pe erPeer > non-p eer

Probabi l i t ies are der ived f rom M an n-W hi tn ey U-tes ts .

h i g h e r r a te s o f a g g r e s s i o n t h a n l o w - r a n k i n g m a l e s

( m e d i a n t e s t: m e d i a n = 0 . 46 , N m a l e s a b o v e = 0 , N

m a l e s b e l o w = 5 , N f e m a l e s a b o v e = 6 , N f e m a l e s

bel ow --- 3, P < 0"03).

Com ponents of Aggression

T h e t o ta l n u m b e r s o f i n t e r a c ti o n s o f e a c h c o m -

p o n e n t o f a g g r e s s io n ( S t r o n g , M i l d , R e c i p r o c a l )

w e r e t e s t e d f o r e a c h c a t e g o r y o f d y a d s ( s i b l in g s ,

p e e r s, n o n - p e e r s ) a g a i n s t t h e n u l l h y p o t h e s is t h a t

t h er e w o u l d b e a n e q u a l a m o u n t o f e a ch o f t h e c o m -

p o n e n t s i n t h e m o n k e y s ' a g g r e s s i v e e n c o u n t e r s .M i l d A g g r e s s io n w a s t he m o s t f r e q u e n t c o m p o n e n t

w i th S t r o n g A g g r e s s io n b e i n g s e c o nd a n d R e c i p r o -

c a l A g g r e s s i o n t h e l e a s t f r e q u e n t ( T a b l e I I ) . T h e

p r o p o r t i o n s o f S t ro n g a n d R e c i p ro c a l A g g r e s s io n

w e r e t h e n c o m p a r e d b e t w e e n e ac h p a i r o f g r o u p s

( T a b l e I I I ) . W h e r e d i f f e re n c e s w e r e s i g n i f ic a n t , t h e r e

w a s m o r e S t r o n g A g g r e s s i o n a m o n g n o n - p e e r s

t h a n e i t h e r s i b l i n g s o r p e e r s , a n d l e ss R e c i p r o c a l

A g g r e s s io n a m o n g n o n - p e e r s t h a n e i th e r s i b li n gs

o r p e e r s .

Reciprocal a nd non-reciprocal partne rs

T o f i n d o u t w h e t h e r m o r e a f f i l i a t e d n o n - s i b l i n g

d y a d s a r e l e s s l i k e ly t o h a v e s e r i o u s c o n f l i c t s t h a n

o t h e rs , t h e p r o p o r t i o n s o f S t r o n g A g g r e s s i o n w e r ec o m p a r e d b e t w e e n r e c i p r o c a l a n d n o n - r e c i p r o c a l

p a r t n e r s ( F i g . 3 ). I n f a c t, a g g r e s s io n b e t w e e n n o n -

s i b l in g r e c i p r o c a l g r o o m i n g d y a d s w a s u s u a l l y

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Janus." Aggression in young rhesus monkeys 12 7

.~ 0 .2

~ 0 , 1

0 .4-g

Grooming

Proximity

0 2 I t.1

N 9 27

Grooming Proximity

7 29 5 31

Figure 3. Median proportions of Strong Aggression inconflicts of non-sibling reciprocal ([ ]) and non-reciproc al

([] ) play, groom ing and prox imity partners. Bars rep-resent interquartile intervals. (a) 1986-1987; (b) 198%1988.

c h a r a c t e r iz e d b y s l ig h t ly lo w e r p r o p o r t i o n s o f

S t r o n g A g g r e s s i o n ( s e e F i g . 3 ), b u t t h e s e d i f fe r e n c e s

d i d n o t r e a c h s t a t i s t i c a l s i g n if i ca n c e . I n t e r e s t i n g l y ,

h o w e v e r , t h e r e w a s a l s o , a n d m o r e c l e a r l y , l e ss

S t r o n g A g g r e s s i o n a n a o n g n o n - s i b l i n g r e c i p r o c a l

p l a y p a r t n e r s. I n g e n e r a l , a m o n g n o n - s i b li n g s ,

p a r t n e r s r e c i p r o c a l i n o n e o f th e t h r e e a f f i li a t iv e

b e h a v i o u r p a t t e r n s t e n d e d t o h a v e l e s s s e r i o u s

c o n f l ic t s t h a n t h e n o n - r e c i p r o c a l o n e s.

Individual compar&ons

I n t h e l i g h t o f t h e f a c t t h a t t h e r e w a s m o r e

a g g r e s s i o n a m o n g s i b l in g s , t e s t i n g p e r c e n t a g e s

r e v e a le d r e la t i v e c o n t r i b u t i o n s o f e a c h c o m p o n e n t

t o t h e t o t a l a m o u n t o f a g o n i s t i c i n t e r a c ti o n s . A s

w i t h t h e t o t a l a m o u n t o f a g g r e s s i o n (s e e a b o v e ) ,

o n l y i n d i v i d u a ls t h a t h a d b o t h a s i b l in g a n d a

n o n - s i b l in g w e re c o n s i d e r e d , a n d t h e p r o p o r t i o n so f e a c h t y p e o f a g g r e s s i o n d i r e c t e d t o a n d f r o m

s i b li n g s a n d n o n - s i b li n g s w e r e c o m p a r e d . M i l d

A g g r e s s i o n w a s t h e m o s t f r e q u e n t t y p e o f a g -

g r e s s i o n a m o n g i m m a t u r e i n d i v i d u a l s ( F i g . 4 ) ,

b o t h a m o n g s i b li n g s a n d n o n - s ib l in g s . N o n e o f t h e

d i f fe r e n c e s b e t w e e n t h e t w o g r o u p s w a s s i g n i f i c a n t

i n t h e f i rs t s e a s o n . I n t h e s e c o n d , h o w e v e r , t h e p e r -

c e n t a g e o f S t r o n g A g g r e s s i o n g i v e n w a s h i g h e r

a m o n g n o n - s i b l i n g s t h a n a m o n g s i b l in g s ( Z =

- 2 " 2 3 , N = 14 , P < 0 - 0 1 ) , b u t t h e p e r c e n t a g e o f

R e c i p r o c a l A g g r e s s i o n gi v e n w a s h i g h e r a m o n g s i b-

l i n g s t h a n a m o n g n o n - s i b l i n g s ( Z = - 1 .7 0, N = 1 4,

P < 0 . 0 5 ) .

C o n t e x t o f A g g r e ss io n

O u t o f 1 70 0 c o n f l ic t s b e t w e e n i m m a t u r e i n d i v i d -

u a l s i n t h e f i r s t s e a s o n , t h e c o n t e x t o f 8 13 ( 4 7 . 8 % )

w a s r e c o r d e d . O u t o f 1 7 10 c o n f l ic t s i n t h e s e c o n d

s e a s o n , t h e c o n t e x t w a s k n o w n i n 8 1 7 c a s e s

( 4 7 - 8 % ) .

T h e d i s t r i b u t i o n o f a g o n i s ti c in t e r a c t io n s a m o n g

c o n t e x t s i n e a c h s e a s o n a m o n g s i b l in g s a n d n o n -

s i b l in g s s e p a r a t e l y i s s h o w n i n T a b l e I V . I n n o n -

s i b l i n g d y a d s t h e o b s e r v e d f r e q u e n c i e s o f b o t h

s t r o n g l y a n d m i l d l y a g g r e s s i v e i n t e r a c t i o n s a r e s i g -

n i f i c a n t ly d i f f e re n t f r o m e x p e c t e d . O n e o f t h e c o n -

t e x t s m a i n l y r e s p o n s i b l e f o r t h is r e s u l t is p r o x i m i t y :

i n b o t h s e a s o n s t h e re w a s m o r e S t r o n g A g g r e s s i o n

i n t h is c o n t e x t t h a n e x p e c t e d , b u t l e s s M i l d

A g g r e s s i o n t h a n e x p e c t e d . A l s o i n b o t h s e a s o n s , i n

t h e p l a y c o n t e x t t h e r e w a s l es s S t ro n g A g g r e s s i o n

b u t m o r e M i l d t h a n e x p e c t e d . O t h e r d i f f e r e n c e s

w e r e n o t a s u n i f o r m . F o r e x a m p l e , i n t h e f i r s t

s e a s o n th e r e w a s m o r e S t r o n g a n d M i l d A g g r e s s i o n

t h a n e x p e c t e d i n t h e f o o d c o n t e x t , b u t i n t h e s e c o n d

s e a s o n t h e r e v e r s e w a s t r u e i n t h e s a m e c o n t e x t .

A m o n g t h e f o u r m o s t f r e q u e n t c o n t e x t s o f

a g g r e s s i o n ( p l a y , p r o x i m i t y / c o n t a c t , f o o d / w a t e r

a n d o b j e c t ) p r o x i m i t y w a s t h e m o s t f r e q u e n t , t h e n

p l a y , t h e n f o o d / w a t e r a n d l a s t l y o b j e c t ( T a b l e IV ) .

T h e o n l y r e v e r s a l f r o m t h i s p a t t e r n o c c u r r e d i nM i l d A g g r e s s i o n c o n te x t s w h e r e p l a y w a s u s u a l l y a

m o r e f r e q u e n t c o n te x t t h a n p r o x i m i t y / c o n t a c t .

I n a l l c a s e s w h e r e d i f f e r e n c e s b e t w e e n s i b l i n g s

a n d n o n - s i b l i n g s i n t h e n u m b e r o f c o n f li c t s i n a p a r -

t i c u l a r c o n t e x t w e r e s i g n i f i c a n t ( M a n n - W h i t n e y ,

P < 0" 05 , T a b l e V ) , t h e r e w e r e m o r e o f t h e s e c o n -

f li c ts a m o n g s i b l in g s t h a n n o n - s i b l i n g s . T h e m o s t

c o n s i s t e n t w a s t h e c a s e o f p r o x i m i t y / c o n t a c t ,

w h e r e i n b o t h s e a s o n s s ib l in g s h a d m o r e M i l d a n d

R e c i p r o c a l A g g r e s s i o n c o n fl i c ts t h a n n o n - s i b l i n g s .

I t m u s t b e n o t e d , h o w e v e r , t h a t o n l y f o u r o f a l lt h e s e r e s u l t s ( u n d e r l i n e d i n T a b l e V ) w e r e u p h e l d

a f t e r t e s t i n g t h e d i f f e r e n c es in r e l a t i v e p r o p o r t i o n s

o f c o n f l i c ts i n p a r t i c u l a r c o n t e x t s .

8/3/2019 Honess 2006

. > " o $o~ 0 e #g"~ g

< I 0 0

Sibl ing N0n-sibl ing

12 8 Animal Behaviour, 41, l

iSibling Non-sibl ing

Figure 4. The com ponents of aggression among siblings and no n-siblings: Strong A ggression (U]), M ild Aggression (~ )and Reciprocal Aggression ( 1) . The values represent percentages o f the total number of agonistic episodes ofindividuals that included both a sibling an d a non-sibling. (a) 1986 1987,N= 17; (b) 1987-1988, N = 14.

D I S C U S S I O N

T h e a g o n i s t ic i n t e ra c t i o n s o f i m m a t u r e r h e su s

m o n k e y s a s s h o w n i n t h i s p a p e r w e r e m o r e f r e q u e n t

a m o n g s i bl in g s a n d p e e r s t h a n a m o n g n o n - p e e r s .

H o w e v e r , t h e r e w a s l e ss S t r o n g A g g r e s s i o n a m o n g

s i b l in g s a n d p e e r s t h a n a m o n g n o n - p e e r s , a n d a l s oa m o n g n o n - s i b l in g r e c i p r o c al s o c i al p a r t n e r s t h a n

a m o n g n o n - r e c i p r o c a l p a r t n e r s. T h u s a l t h o u g h

h i g h l e v e l s o f a f f i l i a ti o n d o n o t p r e c l u d e h i g h l e v e l s

o f a g g r e s s i o n , t h e y d o m i t i g a t e i t s f o rc e .

I n a s t u d y o f t h e f u n c ti o n o f a g g re s s iv e b e h a v i o u r

i n r h e s u s m o n k e y s , B e r n s t e i n & E h a r d t ( 1 9 8 6 )

a r g u e d t h a t a g g r e s s i o n c o u l d h a v e a p o s i t i v e fu n c -

t i o n i n t h e s o c i a l i z a t i o n p r o c e s s . I n t h e i r v i ew , m o s t

a g g r e s s i o n a m o n g k i n , e s p e c i a l ly t h a t d i r e c t e d f r o m

o l d e r t o y o u n g e r a n i m a l s , s e r v e s a s a p u n i s h m e n t

f o r u n a c c e p t a b l e b e h a v i o u r . N e g a y a m a ' s ( 1 9 8 1 )f i nd i n g t h a t J a p a n e s e m o n k e y m o t h e r s b e h a v e

a g g r e s s i v e l y t o w a r d s t h e i r i n f a n t s a s a r e a c t i o n t o

t h e i n f a n t s ' b e h a v i o u r , a n d B e r n s t e i n & E h a r d t ' s

o w n r e s ul ts s h o w i n g t h a t r h es u s m o t h e r s a n d o l d e r

s i b l i n g s d i r e c t m o r e a g g r e s s i o n t o w a r d s y o u n g

m o n k e y s t h a n o t h e r g r o u p s m e m b e r s , s u p p o r t t h e ir

h y p o t h e s i s . H i g h e r l e v e l s o f a g g r e s s i o n a m o n g

i m m a t u r e s i b li n g s t h a n n o n - s i b li n g s i n m y s t u d y

s e e m t o a g r e e w i t h B e r n s t e i n & E h a r d t ' s ( 1 9 8 6 )

h y p o t h e s i s a s w e l l . T h e l o w e r a g g r e s s i o n a m o n gn o n - s i b l i n g s m i g h t h a v e b e e n d u e t o a f e a r o f r e t a l i -

a t i o n b y a m o t h e r . H o w e v e r , a m o n g i m m a t u r e

i n d i v i d u a l s in m y s t u d y , s a m e - a g e n o n - s i b l i n g s ,

i . e . p ee r s , h a d l ev e l s o f ag g r e ss io n a s h ig h a s s ib -

l i n gs , a n d h i g h e r t h a n n o n - p e e r s . T h i s c a n n o t b e

a c c o u n t e d f o r b y B e r n st e in & E h a r d t ' s h y p o t h e s i s ,

a s th e t h e o r y o f ' p u n i s h m e n t ' d o e s n o t w o r k w i t h

m o n k e y s o f t h e s a m e a g e . N e i t h e r c o u l d i t b e

e x p l a i n ed e n t i re l y b y t h e f e a r o f r e t a l i a ti o n h y p o t h -

e s is , b e c a u s e t h e n a g g r e s s i o n b e t w e e n p e e r s w o u l d

h a v e t o b e l e ss f r e q u e n t t h a n a m o n g s i b l in g s , w h i c hw a s n o t t h e c a se . I n a d d i t i o n , m o t h e r s i n t e r f e r e d in

m o r e s i b l i n g ( 7 % ) t h a n n o n - s i b l i n g c o n fl i c ts ( 5 % ,

Jan u s 1 9 8 9 b ) .

8/3/2019 Honess 2006

Janus. 9Aggression in young rhesus monkey s

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Janus: Aggression in youn g rhesus m onk eys 131

W h a t t h e n c o u l d b e th e r e a s o n f o r su c h a m a r k e d

d i f fe r e n c e b e t w e e n a f f il i a te d a n d n o n - a f f i l i a t e d

p a r t n e r s ? O n e o f t h e p o s s i b i l i t ie s i s o p p o r t u n i t y : i f

t w o m o n k e y s s h o w a h i g h d e g r e e o f a f f i li a t io n , t h e y

s p e n d a l o t o f t i m e t o g e t h e r , p l a y i n g , g r o o m i n g o r

j u s t s i t t i n g c l o s e t o e a c h o t h e r a n d t h u s t h e y h a v e

f a r m o r e c h a n c e o f g e t t i n g i n v o l v e d in a c o n f l i c t

t h a n m o n k e y s w h o a r e n o t t o g e t h e r s o f re q u e n tl y .

I n d e e d , i n t h e s a m p l e a s a w h o l e ( t h a t i s , s i b l i n g s

a n d n o n - s i b l i n g s c o m b i n e d ) , t h e r e i s a s i g n i fi c a n t

c o r r e l a t i o n b e t w e e n t i m e s p e n t i n p r o x i m i t y a n d

a g g r e s s i o n r a t e s . T h i s , h o w e v e r , p r o b a b l y r e s u l t s

f r o m t h e f a c t t h a t s i b l in g s s p e n d m o r e t i m e t o g e t h e r

t h a n n o n - s i b l i n g s ( J a n u s 1 9 8 9a ) a n d a r e a l s o m o r e

a g g r e s s i v e t o e a c h o t h e r t h a n n o n - s i b l i n g s , a s th i s

c o r r e l a t i o n i s w e a k e r w h e n t h e y a r e c o n s i d e r e d

s e p a r a t el y . A s t h e m a i n d i ff e re n c e i n t h e n u m b e r

o f c o n f l i c t s b e t w e e n s i b l i n g s a n d n o n - s i b l i n g s o c -

c u r r e d i n t h e p r o x i m i t y / c o n t a c t c o n t e x t , i t se e m s

l ik e l y t h a t p r o x i m i t y t o a t h i r d p a r t y o r c o m i n g t o o

c l o s e w h e n a s i b l in g d o e s n o t w a n t s u c h p r o x i m i t y

a r e m o r e c o n f l i c t -p r o v o k i n g s it u a t io n s t h a n o t h e rs .

T w o s i b li n g s h a v e o n l y o n e m o t h e r t o b e i n c o n t a c t

w i t h d u r i n g r e s t i n g t i m e s ; tw o n o n - s i b l i n g s w o u l d

b e s e e k in g p r o x i m i t y o f t h e i r o w n m o t h e r s . E v e n i f

w e a s s u m e t h a t a l l o t h e r g r o u p m e m b e r s , e x c e p t

m o t h e r s , a r e e q u a l l y a t t ra c t i v e a s p r o x i m i t y p a r t -

n e r s f o r t w o y o u n g m o n k e y s , a n d t h u s e q u a l l y

l i k e l y t o b e c o n t e s t e d a s a r e s o u r c e , t h e t w o s i b l in g s

w o u l d h a v e t o c o m p e t e o v e r a c ce s s t o t h e m o t h e r ,

w h e r e a s n o n - s i b li n g s w o u l d n o t , w h i c h p r o b a b l y

m a k e s t h e d i ff e r e n c e i n t h i s c a s e . A d d i t i o n a l c o m -

p e t i t i o n m i g h t o c c u r o v e r a c c e ss to o l d e r / y o u n g e r

s i b l i n g s a n d m a t e r n a l r e l a t i v e s , w h i c h a r e d i f f e r e n t

f o r t w o n o n - s i b l i n g s , b u t t h e s a m e f o r s i b l in g s .

C o n f l ic t s o v e r p r o x i m i t y t o a t h i r d p a r t n e r a r e

m o r e f r e q u e n t a m o n g s t r o n g l y a ff il i at e d p a r t n e r s

t h a n a m o n g l e s s - a ff i li a t e d o n e s i n r h e s u s m a c a q u e s( C o l v i n 1 9 8 2 ) a n d h a m a d r y a s b a b o o n s , Papio

hamadryas ( K u m m e r e t a l . 1 97 8) .

A g e c l e a rl y i n fl u e nc e d t h e p r o p o r t i o n o f a g -

g r e s s i o n g i v e n b y a n d r e c e i v e d f r o m i m m a t u r e

m o n k e y s : I n f a n t s r e c e iv e d m o s t a g g r e s s i o n f r o m

o t h e r i m m a t u r e i n d i v id u a l s , a n d g a v e l e a st . T h e y

w e r e t h u s m o r e o f t e n t a r g e ts o f a g g r e s s i o n t h a n

a g g r e s s o r s , w h e r e a s O l d J u v e n i l e s w e r e m o r e o f t e n

a g g r e s s o r s t h a n t a r g e t s i n i m m a t u r e a g g r e s s i o n .

T h e a g e d i f f e re n c e s i n t h e i n v o l v e m e n t i n a g o n i s t i c

i n t e r a c t i o n s a r e w e l l d o c u m e n t e d ( D i t t u s 1 97 7;d e W a a l 1 97 7; B e r m a n 1 98 0; W a l t e r s 1 98 0; H a y a k i

1 9 8 3 ; B e r n s t e i n e t a l . 1 9 8 3 ; B e r n s t e i n & E h a r d t

1 98 5) a n d g e n e r a l l y a g r e e w i t h r e s u l t s f r o m m y

s t u d y w h i c h i n d i c a t e t h a t t h e r a t e o f a g g r e s s iv e

e n c o u n t e r s i n w h i c h a m o n k e y i s i n v o l v e d i n c r e a s e s

w i t h a g e . T h e m o s t l i k e l y e x p l a n a t i o n s o f t hi s

d e v e l o p m e n t a l c h a n g e a r e t w o f o ld . F i r s t , g r o w i n g

i n d i v i d u a ls b e c o m e m o r e s e r io u s c o m p e t i t o r s f o r

r e so u r ces , b e th ey f o o d so u r ces ( e .g. Pe r e i r a 1 9 88 b )

o r so c ia l p a r tn e r s ( e .g . C o lv in 1 9 85 ). I n f ema le -

b o n d e d p r i m a t e s p e c ie s ( c f. W r a n g h a m 1 98 0)

m o t h e r s o f f e m a l e i n f a n ts r e c ei v e m o r e a g g r e s si o n

t h a n m o t h e r s o f m a l e i n fa n t s ( rh e s u s: S i m p s o n

1 98 3) a n d y o u n g f e m a l e s r e ce i v e m o r e a g g r e s s i o n

t h a n y o u n g m a l e s ( r h e s u s : o f f s p r in g o f l o w - r a n k i n g

f e m a l e s , t h i s s t u d y ; b o n n e t , Macaca radiata: Si lk

e t a l . 1 98 1 ). Th e ab o v e f ac t s su p p o r t t h i s f i rs t p o ss i -

b i l i ty : f e m a l e s w i l l s t a y i n t h e i r n a t a l g r o u p a n d

c o m p e t e w i t h a d u l t f e m a l e s , w h i l e m a l e s w i l l

e m i g r a t e ; t h e r e f o r e t h e e s t a b l i s h m e n t o f a c l e a r

d o m i n a n c e r e l a t i o n s h i p w i th a y o u n g f e m a l e is

m o r e i m p o r t a n t t h a n w i t h a y o u n g m a l e . S e c o n d , a s

t h e y g r o w u p , y o u n g a n i m a l s b e c o m e m o r e s o c i a l ly

c o m p e t e n t a n d m o r e a c t iv e l y i n v o l v e d in t h e s o c i a l

d y n a m i c s i n t h e i r g r o u p ( W a l t e r s 1 98 7; K u e s t e r &

Pau l 1 9 8 8 ; Pe r e i r a 1 9 8 8 b ) , an d th e r e f o r e th ey a l so

p a r t i c i p a t e m o r e f u l l y i n a g o n i s t i c i n t e r a c t i o n s

(Cheney 1978; Colv in 1985; Pere i ra 1988a, 1989) .

T h e e f fe c t o f a g e o n t h e b a l a n c e o f a g g r e s s i o n g iv e n

a n d r e c e i v e d ( I n f a n t s r e c e i v e m o r e t h a n t h e y g i v e,

n o d i f fe r e n c e i n Y o u n g J u v e n i l e s , O l d J u v e n i l e s g iv e

m o r e a g g r e s s i o n t h a n t h e y r e c e i v e ) r e f l e c t s t h i s

d e v e l o p m e n t a l i n c r e a s e .

T h e r e a r e r e p o r t s o f b o t h p o s s i b l e se x in f l ue n c e s

o n a g g r e s s i o n : t h a t m a l e s a r e m o r e a g g r e s s i v e

t h a n f e m a l e s (e . g. t o q u e m a c a q u e s , M aeaea s in ica:

D i t t u s 1 97 7; i n f a n t b a b o o n s , Papio s p . : Y o u n g e t a l.

1 98 2), o r t h a t f e m a l e s a r e m o r e a g g r e s s i v e t h a n

ma les ( e .g . r h esu s : Lo y e t a l . 19 8 4) . Of t en , t h o u g h ,

t h e d i r e c t i o n o f re s u l t s d e p e n d s o n t h e m e a s u r e u s e d .

B e r n s t e i n ( 19 7 2 ) f o u n d t h a t a l l a g o n i s t i c i n t e r a c -t i o n s w e r e m o r e f r e q u e n t a m o n g f e m a l e t h a n m a l e

p i g t a i l m a c a q u e s , Ma eaea nemestr ina , b u t d a m a g -

i n g a g g r e s s i o n w a s m o r e f r e q u e n t a m o n g m a l e s .

A m o n g s t u m p t a i l m a c a q u e s , Maeaea aretoides,

f e m a le s t h r e a t e n e d a n d b i t m o r e o f t e n t h a n m a l e s,

b u t t h e r e w a s n o d i f fe r e n c e i n o t h e r t y p e s o f a g -

g r e ss io n ( B er n s t e in 1 9 80 ). S imi l a r ly , t h e r e wer e

m o r e a p p r o a c h - a v o i d i n t e r a c t i o n s a m o n g a d u l t

f e m a le b a b o o n s , Papio eynoeephalus ursinus, t h a n

a m o n g a d u l t m a l e s, b u t o t h e r a g g r e s s iv e i n t e r-

a c t i o n s w e r e m o r e f r e q u en t a m o n g m a l e s ( S e y f a r th1 9 7 6 ) . C a p t i v e f e m a l e J a p a n e s e m a c a q u e s w e r e

l e ss a g g re s s i v e t h a n m a l e s , w h e n m e a n f r e q u e n c i e s

p e r h o u r w e r e c o n s id e r e d , b u t t h e y d i r e c t e d m o r e

8/3/2019 Honess 2006

132 A nim al B e hav iour , 41 , 1

a g g r e s s i o n t o w a r d s a d u l t g r o u p m e m b e r s t h a n

m a l e s ( E a t o n e t a l . 1 98 1). F r e e - r a n g i n g r h e s u s

m a c a q u e f e m a l e s i n i t i a t e d m o r e a g g r e s s iv e i n c i-

d e n t s t h a n m a l e s , b u t t h e m e a n r a t e s o f a g g r e ss i o n

p e r m o n k e y w e r e h i g h er a m o n g m a l e s (T e a s e t al .

1982).

B e r n s t e i n & E h a r d t ( 1 9 8 5 ) r e p o r t e d t h a t i n f a n t

m a l e r h e s u s m a c a q u e s w e r e m o r e a g g re s s iv e t h a n

i n f a n t f e m a l e s b u t t h i s s ex d i f fe r e n c e r e v e r s e d w h e n

t h e y b e c a m e j u v e n i l e s . I t is a v e r y g o o d i l l u s t r a t i o n

o f t h e p o i n t t h a t a n y s e x d i f fe r e n c e s a r e n o t i n h e r e n t

p r o p e r t i e s o f a p a r t i c u l a r g e n d e r b u t r a t h e r a j o i n t

e f fe c t o f t h i s a n d m a n y o t h e r a d d i t i o n a l v a r i a b le s

( s e e D a t t a 1 98 3c ). R e c e n t l y , d e W a a l s u g g e s t e d t h a t

t h e s e x d i f f e re n c e s i n t h e e x p r e s s i o n o f a g g r e s s i o n

m a y b e m o r e q u a l i t a t iv e t h a n q u a n t i t a t i v e ( 19 8 9a ,

b ) , a s r e f l ec t ed in se l ec t iv i ty n r eco n c i l i a t io n e f f o r t s .

T h u s f e m a l es a p p e a r t o r e c o n c il e r e a d i ly w i t h a

l i m i t e d s et o f p a r t n e r s , u s u a l l y t h o s e w i t h w h o m

t h e y h a v e s t r o n g a f f il i a ti v e b o n d s ( e .g . c l o s e r e la -

t i v es , c l o s e f e m a l e a s s o c i a t e s) , b u t b e a r p e r s i s t e n t

' g r u d g e s ' t o o t h e r g r o u p m e m b e r s , w h i l e a m o n g

m a l e s t h e s e p a t t e r n s a r e m u c h l e ss e v i d e n t . E x c e p t

f o r t h e f a c t t h a t i n f a n t f e m a l e s a r e m o r e f r e q u e n t

t a r g e ts o f a g g re s s i o n b y o t h e r i m m a t u r e i n d i v i d u a ls

t h a n i n f a n t m a l e s , n o s e x d i ff e r e n ce s i n a n y a s p e c t

o f a g g r e s s i o n e m e r g e d i n m y s t u d y s a m p l e . T h i s

c o u l d r e f le c t t h e f a c t t h a t s e x u a l d i m o r p h i s m i n

s iz e a m o n g i m m a t u r e r h e s u s m o n k e y s i s o n l y sl ig h t .

I n m y s t u d y g r o u p , a n d p e r h a p s i n g e n e r a l , i t i s

p o s s i b l e t h a t t h e c o m b i n a t i o n o f f a c to r s l e a d i n g to

s e x d i ff e r e n ce s in a g g r e s s i v en e s s d o e s n o t o c c u r

u n t i l y o u n g m o n k e y s r e a c h p u b e r t y .

F o o d w a s t h e c o n t e x t o f t h e m o s t f r e q u e nt c o n -

f li ct s a m o n g u n r e l a t e d j u v e n il e v e r v e t m o n k e y s

( L e e 1 9 8 7 ) a n d s a v a n n a b a b o o n s ( P ap io c . c y no-

cephalus , Per e i r a 1 9 88 a) . Ju v en i l e v e r v e t s ib l in g s

a l s o h a d m o r e c o n fl ic t s i n a g r o o m i n g c o n t e x t t h a nu n r e l a t e d m o n k e y s ( L e e 1 98 7) . T h e s e f i n d i n g s h a v e

b e e n o n l y p a r t i a l l y c o n f i r m e d i n t h e p r e s e n t s t u d y .

C o n f li c ts d u r n g g r o o m i n g o c c u r r e d m o r e o f t e n

a m o n g s i b l in g s t h a n n o n - s i b l i n g s , a n d c o n f l ic t s

o v e r f o o d d i d c o n s t i t u t e s l i g ht l y l o w e r p r o p o r t i o n s

o f a ll c o n te x t s a m o n g s i b li n g s t h a n a m o n g n o n -

s ib l in g s . On ly th e f i r s t d i f f e r en ce , h o wev er , was

s i g n i f i c a n t . B o t h p o p u l a t i o n s o f v e r v e t s a n d o f

s a v a n n a b a b o o n s m e n t i o n e d a b o v e , ho w e v e r , w e r e

f r e e -l i v in g , w h e r e a s m y s u b j e c t s w e r e i n c a p t i v i t y

w h i c h m e a n t t h a t t h e y h a d f o o d a n d w a t e r a dl i b i t u m . F o r t h a t r e a s o n , i t is l i k e l y t h a t f o o d w a s

n o t a s i m p o r t a n t a r e s o u r c e a s i n n o n - c a p t i v e c o n -

d i t i o n s . C o n f l i c ts in a p r o x i m i t y c o n t e x t w e r e t h e

m o s t f r e q u e n t o f a l t c o n t e x ts , s u g g e s ti n g th a t p r o x -

i m i ty to a n o t h e r m o n k e y m a y b e a m o r e i m p o r t a n t

r e s o u rc e t h a n a n y o t h e r i n t h e p a r t i c u l a r c o n d i t io n s

i n o u r c o l o n y . T h e e v i d e n c e t h a t e s p e c i a l l y S t r o n g

A g g r e s s i o n o c cu r r e d b e t w e e n 32 a n d 4 2 % o f ti m e

i n t h i s c o n t e x t , s u p p o r t s t h e s e r i o u s n e s s o f t h i s

c o m p e t i t i o n . O n t h e o t h e r h a n d , p l a y w a s a l m o s t

u n i f o r m l y t h e m o s t f r e q u e n t c o n t e x t o f M i l d

A g g r e s s i o n , s u g ge s t in g t h a t p l a y i n g p r o v i d e s o p -

p o r t u n i t y f o r c o n fl i c t, b u t t h a t t h e s e c o n fl i c t s d o n o t

u s u a l l y c a r r y s o m u c h w e i g h t a s t h o s e i n v o l v i n g

p r o x i m i t y . I n t h e l i g h t o f t h e f a c t t h a t s i b l in g s

g r o o m e a c h o t h e r m u c h m o r e f r e q u e n t ly t h a n n o n -

s ib l in g s ( see Jan u s 1 9 89 a) , t h e tw ice o r m o r e f r e -

q u e n t c o n f l ic t s o c c u r r i n g i n t h e g r o o m i n g c o n t e x t

a m o n g s i b li n g s t h a n n o n - s i b li n g s a r e p r o b a b l y a

r e s u lt o f m o r e o p p o r t u n i t y .

t n c o n c l u s i o n , t h e d i f f e re n c e s i n t h e c h a r a c t e r o f

a g o n i s t i c i n t e r a c t i o n s b e t w e e n s i b l i n g s , p e e r s a n d

n o n - p e e r s w e r e n o t o n l y q u a n t i t a t i v e , b u t a l s o

q u a l i t a t i v e . T h e s e d i f f e r e n c e s , d e p e n d i n g o n t h e

s o c i a l r e l a t i o n s h i p b e t w e e n t w o p a r t n e r s , w e r e

m o r e e v i d e n t t h a n t h o s e d u e t o t h e i r i n h e r e n t i n d i -

v i d u a l c h a r a c t e r i s t i c s s u c h a s s e x o r a g e . T h i s s e r v e s

a s a n o t h e r i n d i c a t i o n t h a t b a s i c a l l y s o c i a l f a c t o r s

s u c h a s k i n s h i p o r a f f i l i a ti o n , w h i c h i n f l u e n c e t h e

l i v e s o f a d u l t p r i m a t e s s o s t r o n g l y , b e g i n t h e i r

in f lu en ce a t a v e r y ea r ly ag e .

A C K N O W L E D G M E N T S

I a m g r a t e f u l t o R o b e r t H i n d e a n d M i c h a e l

S i m p s o n f o r c r i ti c a l r e a d i n g o f t h e m a n u s c r i p t a n d

f o r t h e i r s u p p o r t a n d e n c o u r a g e m e n t w h i l e I w a s

c a r r y i n g o u t t h e r e s e a rc h . S a r o j D a t t a a n d S t e ve

H o l m a n p r o v i d e d h e lp f u l c o m m e n t s . I w a s s u p-

p o r t e d b y B e n e f a c t o r s ' R e s e a rc h S t u d e n t s h i p f r o m

t h e S t J o h n ' s C o l l e ge , C a m b r i d g e , U . K . T h e

m o n k e y c o l o n y w a s s u p p o r t e d b y t h e M e d i c a l

R e s e a r c h C o u n c i l , U . K .

R E F E R E N C E S

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