Expression and relevance of dominance in farmed Rusa deer (Cervus rusa timorensis)

Applied Animal Behaviour Science, 14 (1985) 275--287

275

Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands

EXPRESSION AND RELEVANCE OF DOMINANCE IN FARMED RUSA DEER (CER VUS RUSA TIMORENSIS)

SIMONE VAN MOURIK

University of Melbourne, School of Agriculture and Forestry, Parkville, Vic. 3052 (Australia) (Accepted for publication 7 November 1984)

ABSTRACT Van Mourik, S., 1985. Expression and relevance of dominance in farmed Rusa deer (Cervus rusa timorensis). Appl. Anim. Behav. Sci., 14: 275--287. A group of 50 hinds and four Rusa stags (Cervus rusa timorensis) were observed over a 2-year period under farming conditions. The aim of the study was to investigate the expression and relevance of dominance. A dominance order was calculated for the hinds. No significant influence of dominance value in relation to calving time, presence or absence of calf, mating time for the following season or the age of the hinds was found. The number of victories in comparison to the total number of interactions between stags was influenced by possession of a full set of antlers for young as well as old stags. However, the antler size or shape did not affect successful participation in the rutting activities of the stags. Hinds did not show a preference for stags based on antler appearance. It is recommended that stags should be velveted so as to minimize differences in antler shape and consequently to reduce dominance interactions between them.

INTRODUCTION D o m i n a n c e (social o r d e r , r a n k o r d e r , p e c k o r d e r or h i e r a r c h y ) p h e n o m e n a have b e e n s t u d i e d in m a n y species, e.g. c a t t l e (Beilharz a n d Z e e b , 1 9 8 2 ) , p r i m a t e s ( W e l k e r a n d L u h r m a n n , 1 9 8 2 ) , s w i n e (Beilharz a n d C o x , 1 9 6 7 ) , p o u l t r y ( B r a t e t al., 1 9 6 7 ) a n d c e r v i d s ( L i n c o l n e t al., 1 9 7 0 ) . L i k e m a n y o t h e r a n i m a l s , d e e r e x h i b i t e l a b o r a t e f o r m s o f t h r e a t a n d r i t u a l i z e d agg r e s s i o n ( S y m e a n d S y m e , 1 9 7 9 ) f r o m w h i c h a d o m i n a n c e h i e r a r c h y develops. E s p m a r k ( 1 9 6 4 ) u s e d t h e q u o t e by S c o t t ( 1 9 5 6 ) in d e f i n i n g a d o m i n a n c e - s u b o r d i n a t e r e l a t i o n s h i p as " a n a n t a g o n i s t i c b e h a v i o u r w h e r e t h e b e h a v i o u r o f o n e i n d i v i d u a l c o n s i s t s of t h r e a t or a c t u a l f i g h t i n g while t h e o t h e r i n d i v i d u a l r e m a i n s passive or tries t o e s c a p e " . In his s t u d y on r e i n d e e r (Rangifer tarandus), he f o u n d t h a t t h e m o s t usual f o r m o f c h a s i n g a w a y o r c h a l l e n g i n g was by h e a d b u t t i n g , e s p e c i a l l y by t h e a n t l e r e d a n i m a l s , b u t k i c k i n g w i t h t h e f o r e l e g s was also o b s e r v e d . O t h e r w o r k e r s f o u n d s i m i l a r r e s u l t s (e.g. G i l b e r t , 1 9 6 8 ) .

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276 Antlers can be considered to be an i m p o r t a n t indicator of an animal's position in the social hierarchy, especially during the rut. Since males have n o t inherited visual discrimination of antlers either for species-specific constructions or for the antler rank, they must re-learn the shape, size and rank o f their own antlers each year (Bubenik, 1982b). T he di fferent stages of antler growth, i.e. sexual maturation, are well synchronized over the year among temperate cervids. In contrast, tropical cervids show individual annual patterns, resulting in males in different stages of antler m at urat i on at any particular time. Access to hinds in oestrus can be considered as a motivation for dominance display by the stags. It might well be that possession of hard antlers is n o t the definitive det erm i nant for dominance, but other clues, e.g. velvet antler shape, p h e r o m o n e s and bodyweight, may play a more i m p o r t a n t role in Rusa deer (Cervus rusa timorensis). Although research has been done on dominance in male cervids, relatively little attention has been paid to female dominance hierarchies in cervids. Dasmann and Taber (1956) described dominance hierarchies for black-tailed deer (Odocoileus hernionus columbianus), with the adult doe in a family group being dominant. Altmann (1952) n o t e d that elk cows (Cervus canadensis nelsoni) were d o m i nant in the herd as a whole. Brownman and Hudson (1957) described aggression and dominance relationships among females in a group of p en n e d male deer (Odocoileus hernionus). Hall (1983) studied the social organization in an enclosed group of red deer (Cervus elaphus) and f o u n d a well-defined hierarchy, with dominance rank related to age. The domestication of deer raises questions a b o u t the e f f e c t it will have on their social life after a long adaptation to a natural environment. Espmark (1964) stated that observations made on wild animals in a domestic situation should be interpreted with caution, and supplementary studies on the species in the wild should be consulted to determine the influence of domestication on social behaviour. However, no such studies have been undertaken with Rusa deer under domestic conditions. The aim of this study was to investigate the existence and expression of dominance in a group of 50 Rusa hinds of similar age and four Rusa stags with different stages of antler growth. Possible applications of these findings will be discussed in reference to management practices for farmed Rusa deer. MATERIALS AND METHODS

Study area Rusa deer (Cervus rusa timorensis) were one of the m any tropical deer species in tr o d u ced into Australia during the last 100 years. They were released in G e m b r o o k , Victoria (1890), the Royal National Park, New South Wales (1907) and Torres Strait Island (1912). Apart from N.S.W., where they flourish in the wild, they seem to have disappeared from Victoria

277 and Torres Strait Islands. An extensive culling program in the Royal National Park in 1970 resulted in Rusa deer being available for farming on "Bimb a d e e n " , a 320-ha p r o p e r t y of the pastoral division of Willow Ware Australia Pty. Ltd. The farm is located near Fish Creek in southern Victoria (38°42'S, 146 ° 6'E) on slightly undulating terrain with a b o u t 120 ha of improved pasture (rye grass and white clover) and teatree (Leptospermum laevigatum). The major enterprise is farming Rusa, fallow and red deer for velvet and venison p r o d u c t i o n as well as breeding. The deer are k e p t in separate paddocks ranging in size from 0.2 to 24 ha, with deer-proof fencing 2.4 m high. An 11-ha p a d d o c k with a slight fall from north to south and a minim u m o f natural shelter was chosen for behaviour observations. Observations were made f r o m a tower with an enclosed viewing platform. Bordering the p a d d o c k were other enclosures with deer. Nasal and visual c o n t a c t between animals from different paddocks was possible.

Study group Hinds and stags are normally kept separate over the year e x c e p t for the main rutting period (July--November). Calving is over an e x t e n d e d period from March to August, with a peak in April, and all calves are weaned at the end of October. The 50 hinds were all born in the 1980 season and were presumably pregnant at the beginning of the study in February 1982. All hinds had previously been living together, apart from Hind 23 which was i n t r o d u c e d at the start of the observations. Over the observation period, two hinds died from malignant catharral fever (MCF), one died due to a liver abscess, one was culled due to fat necrosis and one was shot because of severe lameness. Ten hinds were temporarily removed in June 1983 for an oestrus synchronization program, together with 10 maiden hinds (born 1982), and re-introduced in August 1983. In February 1982, f our stags were i n t r o d u c e d to the hind group. Two stags (W203, 4 years old, and Or76, over 4 years old) were n o t velveted and c o n s e q u e n t l y p r o d u c e d a full set of antlers. The other two stags (W206 and Or44) were velveted in February and did n o t show any aftermath 1 (Bubenik, 1982a). The antlered stags cast their antlers in December 1982, with an immediate start in antler growth after healing of the pedicles. In 1983, the antlered stags from the 1982 season were velveted and the other stags were allowed to grow a full set of antlers. Unfortunately, stag W206 died of MCF i n M a r c h 1983 with antlers still in velvet. The resulting situation was as follows: Or44, full set of antlers, Or76, aftermath in the form of approximately 20-cm long spikes, and W203, w i t h o u t aftermath. A stag used in the oestrus s ync hr oni zat i on program was i n t r o d u c e d in August 1983 together with the 20 hinds. 1Antlers g r o w i n g after the first cut, i.e. after the s o f t velvet antlers are a m p u t a t e d another small antler s o m e t i m e s develops f r o m the living beam.

278 All animals had eartags, and two of the stags (Or76, W206) were equipped with a collar to facilitate individual recognition. Supplementary feeding, in the form of hay and oats distributed at random in the paddocks, was mainly restricted to the winter months and the end of summer.

Data coIlection All the animals were observed from February 1982 onwards, at a regular interval of 1--2 weeks, from sunrise to sunset with the aid of binoculars and a telescope. Data collection was supplemented with two 1-week observation periods in May 1982 and 1983. Activities within the broad categories lying, standing and social behaviour, as well as position in the paddock, were recorded at 5-min intervals. Special attention was paid to any individual showing solitary activities or explicit behaviour in relation to reproduction, i.e. chasing hinds, mating, calving, nursing, sparring, fighting and threatening.

Analysis of data All interactions between hinds were tabulated for each individual in order to assess dominance. Aggressive interactions involving defence of newly born calves were excluded from Dominance Value (DV) calculations. Dominance values (DV) were calculated using the m e t h o d of Beilharz and Zeeb (1982) where the DV of an animal is the arcsine transformation of the square root of the proportion of animals to which it is dominant, compared against all animals with which it has recorded relationships. The DV for hinds was correlated with calving date, which was divided into early (March), middle (April), late (May, June, July and August) or no calf present. Analysis of variance was performed on these data. The DV was also correlated to the number of interactions with the stags and the presence of a calf. In all tests, apart from calculation of DV, only deer with five or more interactions were used. In view of the different stages of antler maturation, it was considered to be unrealistic to calculate a straightforward DV for the stags in the 2 years. RESULTS H/nds Dominance interactions have been defined as one animal inhibiting the behaviour of another (Beilharz and Zeeb, 1982), with no real distinction between dominance and aggression. Although rare, interactions t o o k m a n y forms, ranging from Hind A actually attacking Hind B to Hind A casually walking up to Hind B, which was lying down, and just by its presence

279 c a u s i n g H i n d B t o g e t u p a n d m o v e , o f t e n r e s u l t i n g in H i n d A t a k i n g B ' s place. On several occasions, interactions were induced by the feeding of h a y a n d c o n c e n t r a t i o n s . H o w e v e r , e v e n in t h e s e s i t u a t i o n s , i n t e r a c t i o n s between animals were rare. Hinds with newborn calves were noticed to use their frontlegs for kicking and occasionally they delivered a bite, but only during the main calving time. Hinds were not observed rising on their hindlegs a n d d r u m m i n g w i t h t h e f r o n t l e g s t o w a r d s a n o p p o n e n t ' s h e a d , as in other deer species. Dominance values (DV's) of hinds having interactions with 5 or more other hinds have been tabulated (Table I) for 1982. The DV's range between 0 and 90, and the majority of hinds had DV's below 55, the exception b e i n g t h e a n i m a l w h i c h w a s n o t o b s e r v e d as s u b o r d i n a t e i n a n y i n t e r a c t i o n TABLE I Dominance values of hinds having interactions with 5 or more hinds Tag

Dominant interactions

Total interactions

DV

53 73 10 34 56 70 85 94 97 20 80 83 21 38 91 32 63 86 1 4 76 2 54 88 23 29 92 27 198 33 77

0 0 1 2 2 2 2 2 2 3 3 3 4 4 4 5 3 3 6 5 4 3 3 3 10 5 5 4 6 4 6

9 5 5 7 5 5 5 5 5 7 7 7 9 9 9 10 6 6 11 9 7 5 5 5 16 8 8 6 9 5 6

0 0 27 32 39 39 39 39 39 41 41 41 42 42 42 45 45 45 48 48 49 51 51 51 52 52 52 55 55 63 90

280 and so had a DV of 90. The average n u m b e r of interactions between hinds was 8, with the except i on of the later-introduced No. 23, with 16 interactions. Analysis of variance, t-tests or correlation coefficients revealed no significant influence of DV in relation to calving time, presence or absence of calf, mating time for the following season or the age of the hinds (P> 0.05).

Stags T h e following activities of the stags relevant to this paper were observed over the two seasons: (1) " F r i e n d l y " grooming of t h e antlers during the velvet stage. Stag A could be standing or lying down while Stag B was standing. For extensive periods (up to 1 h), Stag A would rub its antlers along the neck of Stag B. When both stags were standing, the role of "rubbing-pole" was often reversed. Apart fom three observations in which the two antlered stags participated, this was only recorded between stags of the same age. (2) Rubbing of the velvet antlers or aftermath against the tree t r u n k or wo o d en poles. This was p e r f o r m e d before or after wallowing in a mudpool, if present, and was consistently followed by roaring. (3) Sparring with tussocks, during the velvet stage and after hardening of the antlers. At the same time, the stag would squirt urine forward between the legs, wetting the full length of the t hroat mane. Urination was n o t observed in rubbing or sparring activities with other objects. (4) Thrashing of hard antlers in tussocks or hay which resulted in decoration of the antlers or head of the stag. The cautious way in which the stag moved afterwards indicated an awareness of the plant debris on its head. Hinds seemed n o t to be impressed by the covered antlers and mo v ed away from approaching stags. (5) Moving stiff-legged with a head-high position and producing a "hissing" noise. Shortly bef or e and during the rut stags approached each ot her in this way, resulting in active avoidance by one stag or parallel walking for approximately 10-~-15 m with their heads turned outwards. Depending on an undefined signal, the stags could turn sideways and continue their own way w i t h o u t f ur t her interactions, or turn abruptly towards each other, clanging their antlers together and starting a pushing combat. If one or both of the stags was velveted no grip was possible, and the stags turned away from each other w i t hout serious chasing. Instead, the sparring action was re-directed towards tussocks, or an imaginary stag on the other side of the fence. (6) No fighting with the frontlegs while standing on the hind legs was recorded. Dominance in stags has been assessed by distinguishing betweeen "friendl y " and "fighting" interactions for each m o n t h in 1982 (Table II). Wins

281 were scored for a stag if the opponent moved away after a threat or actual combat. From the total number of wins, Stag W203 (antlers) showed clear domin a n c e 6ver all other stags. From July onwards, Or76 seemed dominant to W203. Between the velveted stags, the older stag, Or44, seemed to show dominance over Stag W206. Friendly interactions were mainly restricted to the velvet period, and a clear increase in fighting activities occurred during the main rutting period (June--August). In absolute terms, the oldest stags showed more friendly interactions than the younger ones. TABLE

n

Interactions

and sexual activities; stags, 1982 ~

Animal

Antlers

Age

Or76

Antlers

Old

Or76

W203

W206

Or44

3

1

10

12 4 W203

Antlers

10 2

1 W206

Velvet

Win % wins

9 chased

9 mated

14

28

72

17

5

7

35

69

14

3

7

2

8

15

2

14

S

26

13

--

6 1

Young 10

Friend

9 2

16 2

Young 2 8

Or44

Velvet

2

4

Old '1

1Figures underlined

3

4

indicate wins; others indicate friends.

Despite the increase in fighting during the rut, the stags showed a remarkable tolerance towards each other. No fatalities or serious injuries occurred. All stags were involved in chasing hinds until the stage where she would stand for the stag and mating was attempted. A velveted stag would be chased away by an antlered stag unless the latter was already engaged in chasing a particular hind. Usually the defeated stag started checking other hinds for signs of heat, or moved away and vigorously rubbed his head in tussocks. On one occasion the antlered stags were involved in fighting over access to a hind to such an extent that the previously defeated velveted stag was able to mate the hind successfully. After mating, the stag remained with the hind for more than 3 h unless other hinds showed signs of heat and his attention was diverted to those. In this case, the already mated hind might be courted by a velveted stag. Double mating was only recorded for the antlered stags. Reproductive activity for all the stags, i.e. chasing hinds and actual matings observed, have been included in Tables II and III. In regard to the changed antler appearance, a notable event, after hardly any occurrences of social interactions, took place in March during feeding of hay. Stag W203 (no aftermath) chased away Stag Or76 (aftermath approxi-

282 mately 10 cm in velvet). The latter rushed towards Stag Or44 (antlers in velvet) and only Hind No. 23 was allowed to eat with Stag W203. In contrast to 1982, hardly any further interactions, friendly or fighting, took place up to August. Stag W203 was positively engaged in chasing hinds over those months, accompanied by Stag Or44 in July. Cleaning of the velvet was extremely slow, and in October pieces of dried velvet were still attached to the antlers. The aftermath spikes of Stag Or76 were clean by the end of July and reached a length of approximately 20 cm. Stag " I n t r o " (3 years old) had been together with five hinds of the group and five malden hinds for 3 weeks before introduction back to the herd in August together with 10 other hinds (five of the group, five maiden). No fighting occurred among the hinds, but all the "resident" stags challenged the newcomer. The only victories for " I n t r o " were scored against Stag Or76 (aftermath) and Stag W203 (no aftermath) (Table III). TABLE

III

Interactions and sexual activities; stags, 19831

Animal

Antlers

Age

Or76

After M.

Old

Velvet

Young

Or76

W203

Intro.

Or44

0

1

2

6

11

Friend

Win

% wins

~ chased

~ mated

3

24

80

10

3

1

9

32

13

1

2

8

26

4

1

2

15

9

3

7 1

W203

1 1 Intro.

Velvet

Young

Or44

Antlers

Old

7

1

1

--2

6

3

7

2 5

~Figures underlined indicate wins; others indicate friends.

Contrary to the predictable, ritualized combats of the previous year, Stag Or76 showed surprise attacks in 1983. Without warning he rushed towards other stags and pushed his spikes into the rear end of the unaware animal. This resulted in a minor injury for Stag Or44 (antlers). All stags avoided Stag Or76 with more or less success. The number of wins for Or76 indicates dominance over all others, including the equally old antlered stag. Both old stags were d o m i n a n t over the younger velveted animals. In 1982, the presence of a full set of antlers increased the percentage of victories of the total number of interactions for the old stag Or76 as well as the younger stag W203 in comparison to the velveted stags. After Stag Or44 was allowed to grow a full set of antlers in 1983, he showed a substantial increase in victories. However, Stag Or76, with aftermath in the form of spikes, was the most successful of all the stags.

283 Although the outcome of interactions might be influenced by antlers, the antler shape or size did not interfere with participation and success during rutting activities in both seasons. Contrary to other hinds, Hind No. 23 showed a distinct preference for Stag W203 without aftermath. During heat she avoided approach by the antlered stag Or44, and both Hind 23 and W203 were chased by Or44. The antlered stag succeeded in retrieving Hind No. 23 and mated. However, immediately after copulation, the hind went back to Stag W203 without intervention by Stag Or44. DISCUSSION Dominance hierarchies have been reported for red deer (Lincoln et al., 1970), moose, Alces alces (Dodd, 1958), white-tailed deer, Odocoileus virginianus (Taylor, 1956), roe deer, Capreolus capreolus (Espmark, 1974) and reindeer, Rangifer tarandus L. (Espmark, 1964). Males and females tend to develop almost completely independent hierarchies (Jackson, 1974), although there are some heterosexual groupings (Lowe, 1966). The observations of this study will therefore be discussed separately for hinds and stags. Apart from studies in the Bensbach Plains, Papua New Guinea (Fraser Stewart, 1981), Royal National Park, New South Wales, Australia (Hamilton, 1979) and Mauritius (P. Carosin, personal communication, 1983), no comparative data are available for the general biology of Rusa deer and observations of Rusa under farming conditions are non-existent. It is even doubtful whether the Rusa deer in Mauritius and Papua New Guinea belong to the same sub-species as the Rusa representatives in Australia (Mohr, 1918; Van Bemmel, 1949). Consequently, the results of this study will be compared with studies of all cervids. Hall (1983), in a study with red deer hinds, noted that rank was closely related to age, as is the case for stags. This might be an indirect relationship with size or weight (Hook et al., 1965). Age, size or weight differences between the Rusa hinds were minimal, but a difference in DV could be observed. In several other ungulate species, it has been found that there is a tendency for individuals close in rank to be threatened most (Brantas, 1968; Reinhardt and Reinhardt, 1975 {dairy cattle); Tyler, 1972 (New Forest ponies); McHugh, 1958 (American buffalo)). In respect to the number of hinds with equal or nearly the same DV, more interactions would have been expected. Despite the confined situation, this occurred neither for aggressive nor for friendly (e.g. mutual grooming) interactions. Hall {1983) found a significant increase in threats for confined feeding situations in red deer hinds. During feeding of supplements to a herd of the animals with stags present among the hinds, no increase in aggressive encounters was recorded. In roe deer (Capreolus capreolus), social rank also did not influence feeding (Espmark, 1974). Reindeer females have antlers, and they dominate the males during the winter when the males have lost their antlers.

284 Espmark (1964) postulated that this dominance allows females to c o m m a n d scarce grazing areas and so ensure the survival of their calves. The majority of dominance display among the hinds was settled w i t h o u t real conflict. Preference of a dominant hind for a particular position, e.g. for ruminating, was accomplished by causing the other hind to rise and to lie down a few metres further away. If part of the preferred spot was vacant, the approaching hind could squeeze in as well w i t h o u t seriously disrupting the existing situation. A c o m m o n behaviour of red deer hinds, i.e. rising on their hindlegs and drumming of the frontlegs towards the opponent's head, was never seen in Rusa hinds. The absence of injuries and the failure of DV to correlate with calving time, presence or absence of a calf, and mating time for the following season, suggests that dominance in hinds has no relevant consequences for farming purposes. Antlers are said to have a visual role in the behaviour of red deer stags during the rut, acting as a status symbol, influencing the outcome of encounters between unfamiliar animals (Beninde, 1937), and being used as a display symbol in attracting hinds (Bubenik, 1968). Outside the rutting season, antlers are said to have further functions, e.g. they are important in dictating social dominance within the bachelor herds (Bubenik, 1968; Gossow, 1969; Lincoln et al., 1970, 1972), the high-ranking animals having the advantage of priority of access to food or shelter. Velveting of stags does n o t interrupt the antler growth process. In some cases aftermath occurs and remnants of the antler shaft after velveting pass through the same stages of velvet shedding and eventual casting. The velvet stage of the Rusa stags coincided with the calving period and no aggressive movements were recorded towards females or calves. Stags even participated in play behaviour of the calves, i.e. running and jumping around. The secretion of velvet pheromone has an important function, since it is rubbed all over the body, gently deposited on vegetation and brought down to the ground by hooves scratching the velvet (Bubenik, 1982b). The rubbing of antlers around the neck of another stag of the same age is hard to understand with regard to this pheromone function. If the antlered stags had only been using the velveted stags for this purpose, it might have been a sign of subordinance, but with both stags participating and distributing pheromones of a possible competitor in the rut, this might well illustrate altruistic behaviour. No hinds were used as a "rubbing-pole" for antlered or velveted stags. Rubbing might give the stags up-to-date information concerning the shape and stage of their antlers. None of the stags had grown a full set of antlers before because of velveting procedures. Any dominance which exists in the stag groups must be based on features other than antlers, e.g. bodyweight, which is related to age. As has been shown for red deer (Lincoln, 1972), rank is related to age. The Rusa stag might be able to discriminate between different ages on subtle differences in general appearance. Rubbing of the

285 antlers between equally old stags is therefore more likely than between stags of different age. Rising testosterone levels result in a stimulation of male behaviour, expressed in display and sparring of antlers. This was shown with the increase of total interactions during the main rutting period (May--August) and the larger proportion of fights. However, the fights were n o t too serious, because each stag had an exact knowledge of antler shape and related rank. Useless sparring and fights in the rut would thus have been reduced. Red deer are quick to realize the predicament of an animal which has lost antlers, Animals rear up and thrash at each other with the forelegs. Only on rare occasions did the animals in "hard h o r n " take advantage of the cast stag's vulnerability in these encounters and attack with antlers (Lincoln, 1972; Lincoln et al., 1972). All aggressive encounters between the Rusa were settled with head-to-head pushing combats, despite the possible lack of antlers in one or both competitors. The fully grown hard antlers were not different in appearance between stags, in relation to size or shape. Although Or76 was older than W203, the W203 stag had a stockier body composition, which might have influenced his position in the herd. The higher number of aggressive encounters, however, did not enhance the number of hinds chased and mated, observed during the day. The observation in red deer (Lincoln et al., 1970) that rank is related to age in a positive way holds for the velveted stags with respect to the number of combats, but does not express itself in sexual activity. Beilharz and Zeeb (1982) stated that "once B has learnt to submit to A this relationship will become fixed by learning and will presumably remain unchanged unless there is a reason which causes the learning of a new relationship". Also, males have to re-learn the shape, size and rank of their own antlers each year (Bubenik, 1982b). The display of dominance by W203 early in 1983 towards two subordinates of the previous season illustrates the fixing of rank. Until antlers reached their final shape, it was n o t necessary to dispute the existing hierarchy. Gradually, the stags learnt their new antler size and shape and new relationships were established. The m e m o r y of body size may have been responsible for the reduction in total number of interactions in 1983. Teen-age antlers are offensive in construction and architecture, and are thus less suitable weapons for defence in comparison with prime-age antlers, which have a protective shield for the eyes and skull and the capacity to clinch with antlers of diverse spread (Bubenik, 1982b). The spike-shaped aftermath of Or76 clearly resembled teen-age antlers. The lack of a possible defence in combat might have influenced his fighting strategies; expressed in abolishment of ritualized patterns. However, after initial attempts to maintain his dominance, Or76 showed respect to the antlered Or44 and no serious disruptions were recorded. Other than for the newly introduced stag, antler shape and size did not affect participation in the rut.

286 The f o l l o w i n g features o f Rusa deer a p p e a r to m a k e t h e m m o r e suitable f o r f a r m i n g p u r p o s e s t h a n o t h e r cervids: (1) aggressive i n t e r a c t i o n s within and b e t w e e n the sexes are minimal; (2) there is n o evidence t h a t d o m i n a n c e relationships in b r e e d i n g units have an i n f l u e n c e on r e p r o d u c t i v e p e r f o r m a n c e ; (3) hinds s h o w no p r e f e r e n c e f o r stags based on antler size or shape; (4) d o m i n a n c e relationships are established in one season a n d are unlikely t o c h a n g e unless antler size and or shape are altered. Velveting reduces possible differences in a p p e a r a n c e and s u b s e q u e n t l y reduces aggressiveness in stags. ACKNOWLEDGEMENTS The a u t h o r is grateful to Willow Ware Australia Pty. L t d . f o r p r o v i d i n g animals a n d facilities. I w o u l d also like t o t h a n k Dr. P. T a y l o r , Mr. D. Piggin a n d Mr. M. Vella f o r care of the animals.

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