Agonistic behaviour

Behavioural categories

Agonistic behaviour of the blackbuck is most commonly seen as a head up display. The other behaviours in this category are: chasing at a gallop, head down, vegetation thrashing, and lastly, there is fight. Amongst blackbuck does, aggressive behaviour seems to be restricted to butting of flanks and rearing up on hind legs and striking out with the forefeet (as mentioned earlier, because females could not be individually identified and observed, agonistic interactions among females are not described further).

Head up

This display consists of the neck and head held high, the horns thrown back, accompanied by a stiff-legged walk while the raised head is bobbed sideways. The ears are turned back and down, the tail is curled up and forward along the back exposing the rump patch. The horns are laid back flat along its back in the case of intense excitement or they may be just held high in the case of lesser intensity. Direction of approach is another indication of its intensity of aggression. A direct or straight approach clearly means high intensity.

Chasing at a gallop

Here the intention is clear: the blackbuck chases both males and females. Though chasing of females must not be confused with chasing of does which forms part of the rutting season manoeuvres. These chases however do not last for more than a hundred yards or so.

Head down

This display consists of lowering the head and pointing the horns forward at the addressee. This can take the form of an incipient movement of flicking the head downwards while walking in an agonistic fashion towards the other animal or a regular movement ending in a lunge at the opponent. Sometimes there is actual contact, though injury drawing blood has never been seen.

Vegetation thrashing

In blackbuck, this display consists of a vigorous thrashing or beating of vegetation with their horns. Redirected aggression in blackbuck takes the form of vegetation thrashing.

Fights

Fights are of three types. There are play fights between fawns and sub-adults, and immatures of a year or a little more, where they learn to fight. An experience very valuable to them when they grow up and become territorial males. There are fights between males of up to 2 years of age, and lastly, territorial or home range fights between adults of three years or more.

Behavioural context

The head-up position is used by males when herding does. When a female blackbuck enters the territory of a male, he approaches her in a head-up display and circles in front, cutting her off from her intended path. He keeps her moving but in the direction indicated; that is, her intended path is cut off and directed towards the interior of his territory. In the case of a male he intends to drive away, the same head-up display is used but this time it is a straight-on walk, moving the targeted individual from the position held by it. Clearly, this is a case of higher intensity than that with a female. This display in even higher inetsnity can be seen when the head is bobbed sideways.

Chasing of males and females is another form of showing aggression. This movement is usually instigated by a dominant male towards a sub-adult male or one in a lower hierarchical position and also by peer males if they are territorial neighbours. If a neighbouring male enters the territory of another during the rutting season, he will be chased. Sub-adults who enter the territory of a male are never tolerated. Such sub-adults are sometimes chased by 2 or 3 territorial males sequentially as they pass through their territories on their way to safety. Chasing is resorted to by territorial males or females. Sometimes does who are not in oestrus are chased by males when they approach and feed along with the does who are presently on the territory keeping company with its master. It is not clear why they do so but it has been observed.

The head down comprises of lowering the head and pointing the horns forward at the addressee. This is done at a walk and may take the form of only a downward flick of the head or a full-scale lunge. The head down is done to move a recalcitrant sub-adult or female or at the end of a fight. It is of a higher intensity than that of a head-up in the agonistic behaviour scale.

Redirected aggression in blackbuck takes the form of vegetation thrashing or beating of foliage or vegetation with their horns. In some cases, when a territorial buck drives away a trespassing male, he will mark pre-orbitally on a shrub. This action may be followed by thrashing of vegetation. Such redirected aggression may also be seen after a territorial fight.

Play fights between fawns and immatures of around one year in age are usually of long duration. In such fights, there is usually a lot of pushing though clashing of horns is not usual. They break off after a short session of about half a minute, to resume again. Displacement feeding has never been noticed in such a fight, though rest or intervals are in order. Displacement feeding usually occurs when two opposing drives are at clash such as attack and escape. In play fights there are no such different drives at play, it being only a play-fight. In these pushing sessions, they learn the various holds which they will require in their territorial fights when they mature into territorial masters. One of the holds they learn is one in which one of the animals tries to get one of its horns under one of the forelegs of the adversary and the other on the far side of the neck. With his horns in this position, the attacking animal raises its head. This action tends to lift the opponent and unseats him as it were. In most cases, this leads to a break off. In this type of fight, a great amount of tail wagging is done. When a fight such as this has been in progress for a long time, mature males with a full black coat have been seen to come from afar and break up a fight. The approach of such a male is usually enough to send the sub-adults scurrying. If they don’t, the bigger male closes in with his head down and horns presented forward. The one to get away last may receive a lunge in his haunches. There have been instances where a threesome has been seen to play-fight.

Just before the rut, immature males congregate on peripheral lands that may abut the territorial mosaic. Here, sub-adults and bachelor males are seen to graze and fight. These fights are of a more intense character. The clash audibly. The opponents face one another at a distance of a few feet, lower their heads and rush at one another. They clinch and strain, pushing and twisting their horns. The one that is gaining ground can be seen wagging its tail. These fights do not last even a minute. Here, displacement feeding of grass can be seen. After a short while, they resume fighting again. Fights of this nature between a particular pair may last even half a day.

At Guindy Polo Field, there has never been more than 6 territorial males in occupation during the 3 years’ study. Territorial fights as the term implies are fights between two territorial males or between one owner and an outsider trying to stake a claim. These fights are almost always of a short duration and need not be conclusive. They are fierce, but short, the weaker animal giving way gracefully. Home range fights are of this category. The opposing animals may confront one another directly in an agonistic walk, or stand parallel (both facing the same way) or reverse parallel (tail to face) position. They may now slowly turn through 360° till they face one another again. In the parallel position, the animals turn back slowly till they face one another. During this action, the heads are lowered to the fighting stance. The turn about is slow. This display seems to have been evolved as there is at this moment strong conflict in motivation, that is between fight and flee. A territorial fight need not result in the defeated animal giving up his territory immediately. These fights may last for days. Off and on, till one day we notice that one of the animals seems to have more territory than before. It is a question of continual pressure till one gives way.

Observations and inference

In the overall activity scale of a blackbuck, agonistic behaviour is the third most important activity after feeding and resting, and is followed by social behaviour and vocalization in that order. Of the five agonistic categories of this animal that was studied, agonistic walk or head-up claimed 56.9% of its agonistic repertoire, chasing 24.6%, vegetation thrashing comes third at 7.6%, while fight and head down are 4.6% each (see Figure 1). The major part of the blackbuck male’s agonistic behaviour thus consists of agonistic walk or head-up and chasing.

agonfig1

Figure 1: Agonistic behaviour by category

The head-up display in its agonistic form was evident when blackbuck male named ‘Light Brown buck’ approached an animal named ‘B’ while it was foraging south of Park House in Guindy Park Reserve Forest.

At Light Brown’s approach, B leaves the area. After moving off, B starts to graze at another spot. Light Brown again approaches agonistically or head-up. B moves off again with Light Brown following. Finally, B leaves the area totally.

In this case, there has been no fight. The display meant ‘keep moving’. In these cases, it is normal for the attacker to follow its opponent to make sure that it leaves the ground. The approach in this display is direct, straight on of high intensity.

Here is another example of head-up being used as an aggressive display. The Tamil Nadu Forest Department have grass feeding spots in Guindy Park Reserve Forest durin the height of summer when green grass is hard to come by.

On 30-5-1978, male buck ‘A’ chased a sub-adult away from the females feeding along with him by rushing at him with head-up. Head-up display is directed towards does.

Here, they may have two meanings. One, to keep moving, or as a herding movement to get together and move in a certain direction. During the rut, these herding movements are accompanied by grunts. These grunts are not much heard during the rest of the year.

On 25-9-1977 in Guindy Park Reserve Forest Polo Field, animal ‘D’ makes short spurts of runs with head-up at a female that was straying out of his territory. These runs are accompanied by grunts.

By this means, D succeeded in steering the female back within his territory—indicates a herding display. On another occasion while I was observing blackbuck:

One doe comes close to my post and is looking at me in alarm position. Male ‘B’ walks agonistically with head up at a tangent towards the doe so that she moves towards his territory.

In this context, the aggressive walk is used as a means to drive the female.

Chasing at a gallop of both males and females is indulged in by blackbuck males. Chasing of males by territorial masters takes place when a strange male or sub-adult male enters its territory. This is greatly in evidence during the rut. Sub-adults are not tolerated.

On 23-11-1977 sub-adult males are chased by E from his territory into that of B, whose territory is next to his. Immediately, B energetically chases the sub-adults at a gallop till they reach C’s territory.

This is also a case of sub-adults being chased from one territory to another and the chase being taken up by its respective owners. During these chases the head is held in the high position (head up) though not necessarily in the full high position.

Chasing of does by male blackbuck:

On 22-04-1978, on the K. K. tank shores at the Guindy Park Reserve Forest, the territorial master buck is grazing near the tank’s edge. A young male who is feeding along with females suddenly approaches the master buck, stops some 10 – 15 yards away, turns around and walks back towards the females and stops. The master buck stops cropping and notices the sub-adult facing the females. He walks past the sub-adult towards the does. He goes amongst them and vigorously chases off one female off his territory.

The male chased a particular female from amongst a group of does. Since the male did not follow beyond his territory it is assumed that she was not in oestrus and hence the chase had no sexual connotation.

The head down display is not a commonly used one. At Guindy Park Reserve Forest where the density of blackbuck is high, the male buck attempts to move the does by means of head-up display. But at Point Calimere, where the density is considerably less, this result is obtained by a mild head-down. Though the full head-up is also performed here, it is less frequent.

Redirected aggression in blackbuck in the form of vegetation thrashing with their horns is seen sometimes after a trespassing male is chased away or after a territorial fight.

At the Indian Institute of Technology (IIT) field, a male is courting a doe. Their courtship is at an advanced stage, when some boys come and disturb them. The does leave the spot, one behind the other, followed by the male toward the scrub jungle. The male vigorously thrashes the vegetation with his horns on two occasions while following the females.

His aggression against the disturbance or the aggressive component of the courtship was sublimated by this redirected aggression. This is an overflow of thwarted aggressive drive which is sublimated by attacking an inanimate object.

Fights can be divided into three classes: 1) Sub-adult and/or fawn fights, 2) Fights between non-territorial males, and 3) territorial or home range fights between adult bucks.

Play fights between those of the first category. These fights are not fierce, but with much pushing and leaning, muzzle rubbing and tail wagging. Displacement feeding is absent. On a rare occasion a play fight between a grown male and a sub-adult has been seen. For instance, on 15-03-1977 in the Polo Field, a play fight between a territorial male ‘E’ and a sub-adult was observed. E was very gentle, he did not butt, but merely pushed slowly. There was a great amount of tail wagging by the sub-adult. This fight was timed: bout 1 – 45 seconds, bout 2 – 25 seconds, bout 3 – 30 seconds. At the end of this, E walked away from the place.

Fights between animals of 1½ years and more. At this stage, these animls move about in all-male groups. During the rut, they congregate, on the peripheral lands outside the territorial mosaic. Here, during this period, continual fights can be seen. The same pair may fight for a while, break off and resume fighting again and again. These are more serious in nature and have all the features of an adult territorial fight, but are much longer in duration. Three-way fights also take place. When these fights are abnormally long, adult blackbuck have been known to approach the fighters in an agonistic walk. This will normally break up the fight. If this does not happen, the approaching male lowers his horns and charges head down. The last to leave may get a lunge in his rump.

Territorial fights are the serious fights of the blackbuck world. They are between two territorial owners or between one owner and an interloper. Here is the case history of an animal who took up a territory near another and won a piece of it to enlarge his own territory. The new territory was next to that of animal ‘A’.

15-08-1977. A blackbuck male is seen (later named ‘D’) trying to set up territory near A. The newcomer is always there and is seen frequently marking by means of pre-orbital glands and urination-defecation.

29-09-1977. D approaches A’s territory. A charges up and chases D off his territory, but stops abruptly at the end of his territory.

30-10-1977. A goes into D’s territory (now under dispute). They fight. A is pushed back. Both A and D mark by urinating and defecating and also using pre-orbital glands. They then crop near each other a few feet apart, as if they were on either side of a line (this behaviour was seen for a few days after this event).

Thereafter, D was seen occupying this territory, although there were a few more fights. In this case, it took about two months before D was able to establish himself. In the years of this study after these incidents, it was noticed that D slowly became a territory holder of good standing and on two occasions was seen to mate there. Till the end of this study, D was in possession of his territory with no interference from A.

Home range fights are naturally outside the territory. A blackbuck male walks a regular beat, especially when he does not have a ready doe on his territory.

On 07-05-1978, B was walking at the Rear Brick Field which is across the metalled road from his territory, when Light Brown who has already had a fight with B comes along. They both walk a parallel course a few feet apart. B is walking head-up, nodding his head. They stop parallel. Then turn slowly towards one another by backing a few steps, meanwhile lowering their heads. They clash, pushing and twisting, bracing their hind feet for better purchase. This lasts for about two minutes with intervals where the mouth is lowered to the ground level, though no cropping is done as no grass grows there. Two such intervals are noticed. At the end of two minutes, Light Brown breaks off and runs away towards the Polo Field, hotly pursued by B who lunges at Light Brown’s rump. No blood is seen to have been drawn.

During agonistic actions, as also during courtship activities, the male blackbuck’s coat gets darker in colour. This is due to pilo-erection. Raising of the body hair may make the animal look bigger, emphasising its aggressive overtures.

Among the three types of fights, play fights can be considered a sort of training programme while the second type involving  bachelors and non-territorial males tends to fix their position in relation to individual strength. But territorial fights are the ones which have survival value to the species, as these are the fights that lead to the establishment of territories and hence to mating and reproduction.

Of the major fights recorded during the study, 71.4% were territorial, 21.4% were between non-territorial males, and 7.1% were recorded as stray fights. Territorial fights predominate. Of the territorial fights, 35.7% terminated in grass cropping by one or both contestants. This seems to be a ritualized form of signal for the end of the fight. Taking its cue from displacement feeding where two opposite drives of fight and flee are at conflict, it manifests itself in the form of grass cropping. When this cropping is extended, the drive for flight having overruled that for fight, a cessation of hostilities result. The parties now slowly turn away from one another while cropping, increasing individual distance. Moynihan (1955) postulates:

The majority of animal displays are derived from intention movements, displacement activities and redirected aggression.

A cross-sectional view of the agonistic behaviour of blackbuck seen through the year shows that the month of October has the highest aggression. The winter rut, which is around this period, is also the most productive of the two ruts within the year.

agonfig2

Figure 2: Occurrence of agonistic behaviour across the year

[Note: Figures are redrawn based on RKG Menon’s hand-drawn figures on graph paper.]

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