Territorial behaviour

Blackbuck are gregarious antelopes that congregate in open plains and form territories. They defend these territories against conspecific male intrusion. These animals are territorial through most of the year in southern India, but around the two ruts of the year their territorial defense is more emphasised. Territorial behaviour is an aspect of social behaviour and as such territories are formed by social animals like blackbuck. Territorial mosaics are part of the social network and is expressed in relationship and social conventions between neighbours. This has survival value. In a mosaic of territories, the limitations or boundaries of territories are strongly enforced and neighbours live in what would be described as a ‘dear enemy’ situation (ref).

Blackbuck territories have reproductive connotations and are held by mature adult males only. The immature males and sub-adults are excluded and driven away. Thus we have the twin effect of the territorial mechanism. The mature male is attracted towards the forming of territories, while the adolescent male is expelled. This expulsion effects in forming pioneer colonies.

Although territorial behaviour confers a certain amount of protection against predators, the greater benefit that this behaviour confers is that it serves to introduce potential mates and thus guarantee a continuity of reproduction by providing a meeting ground for both the sexes.

The size of territory in blackbuck varies with habitat. In Guindy Park Reserve Forest (GPRF) where most of the study was conducted, it is about 100 yards [91 metres] across in diameter [0.65 ha area]. At  Point Calimere Reserve Forest it is about 3 or 4 acres in area [1.2 to 1.6 ha]. At Kanha, the territories were about 100 feet in diameter (Schaller 1967). In the waterbuck (Kobus defassa) living and breeding territories are one-fourth to one square mile (Kiley-Worthington 1965), while Grants Gazelle (Gazella grantii) in Ngorongoro, Tanzania uses some 900 feet × 900 feet for the same purpose (Walther 1965).

At the Polo Field, the largest meadow in GPRF, there were never more than 6 territories, the usual number being 5 through the 3 years of this study. Only the western half of the field, away from disturbance was utilized. Freedom from disturbance is of prime value for territories in these antelopes here. In both habitats (GPRF and Point Calimere) studies, man’s interference and presence was felt and responded to by establishing the territories as far away as possible. The quality of the territory is not related to its resource value but to its privacy.

The alpha buck at the GPRG help a plot of land that had little grass on it, but it was situated far away at the north-western end of the field. This territory attracted a large number of does. At Point Calimere also, the high ranking males formed territories away from paths used by people. In the waterbuck (Kiley-Worthington 1965), the length of the river bank and density of thicket appears to be related to the social rank of the male. At the GPRF, the sub-optimal territories are near the road.

Territory holding is a prerequisite to mating in blackbuck. The does select the territory, usually those of high ranking males. In blackbuck, there are no harems. The does do not belong to any territory or male. Females form herds of their own with juveniles of both sexes. A harem may be defined as a stable group of females that consort with a given male for a length of time such as a rut. Blackbuck does visit the males in the territory only temporarily for short periods of a few hours to maybe a day or two. The male is alone a considerable part of the time in his territory. Both Estes (1967) and Walther (1964, 1968, 1969) hesitate to speak of harem herds in the Thomson’s Gazelle though Brook (1961) Hvidberg Hansen and De Vore (1971) did.

Female blackbuck herds move about and feed outside the territories. They move into the territorial mosaic en masse (they move out similarly). The territorial bucks try to herd and hold as many as each can. The females may not stop at the first territory, but move sequentially through one territory to another, till she grazes at the territory of her choice. When a doe in oestrus happens to be amongst those that are passing through the territory, the male is excited and intense herding displays follow. If the receptive doe chooses to stay, mating may take place. But if the doe passes through his territory to another, the male will not follow her beyond his boundary. As the does pass through, the territories provide a meeting place for both the sexes.

In comparison, the Uganda kob (Adenota kob) has a highly specialized form of territorial behaviour. The kob’s territorial mosaic consists of 30/40 territories of 15/30 metres in diameter. All matings take place in the centre of the mosaic occupied by high ranking males. From this area there is a gradient of intensity of mating towards the periphery. Mating activities are most intense in the 3 or 4 central territories (Buechner & Schloeth 1965). Mating goes on throughout the year and these stamping grounds are traditional. As with the blackbuck, the females show their choice of territory by cropping grass of the chosen territory. The blackbuck, like the kob, displays fidelity to the site and not to the female of the species. In the Uganda kob only females in oestrus visit the stamping grounds while in the blackbuck, all females pass through the territories. The male tries to retain the maximum number he can. He will mate with those that are in season.

Blackbuck mating takes place throughout the year, but there are two peaks when more females are in oestrus. Of the two ruts, March and November, the second is more productive. Blackbuck go out into the scrub jungle in search of fodder during the months of May and June, the hottest months, when the grass of the meadows are burned off. The meadows are now left unattended. The sub-ordinate males occupy the sub-optimal territories for short periods in the hope of herding some does. Never has a sub-ordinate male been seen to occupy preferred or optimal territory. Matings at such territories have never been seen, though there is no doubt that there is some success as neonate fawns have been seen throughout the year.

Territorial males sometimes cross the territorial boundaries while chasing a doe. The owner will most certainly challenge him and the trespasser will move out. The establishment of a territory may take as long as two months. The newcomer frequents the area of his choice or a vacant plot, marking frequently with his pre-orbital glands and also urination/defecation. On his approaching the demarcating line of territory he will be challenged. This leads to fights. The persistent newcomer will keep on pressurising the owner till he gives way gracefully. The boundary is then marked by pre-orbital gland, urination – defecation, and also by pawing the ground by both parties. The newcomer now tries to herd does into his territory. Ownership of territory is a prerequisite for mating.

Pawing as a marking device has been observed by Daniel (1967) and Nair (1974) at Point Calimere. It is suggested here that pawing is a scent-marking device rather than a visual one. The inter-digital glands probably leave scent signals for the hoof marks are not deep enough to be visible for any length of time. During spronking (Pocock 1910) and also stamping of both hind and forefeet during alarm (Menon 1981a), scent marking has been suggested. At Point Calimere, where the littoral soil is soft and sandy a more permanent mark may be possible with a few scrapes of the forefeet. Pawing followed by excretion is accentuated territorial demarcation in African gazelle (Walther 1964). Blackbuck mark by means of pre-orbital glands and urination – defecation also.

Pre-orbital marking consists of rubbing the pre-orbital glands on twigs and shrubs usually inside the territory. This behavioural pattern has been noticed amongst sub-adults who do not own territories. Evidence of this marking behaviour long before the actual ownership of territory points to the fact that pre-orbital marking belongs to the ontogeny of territorial behaviour (Walther 1964).

Urination – defecation in its characteristic posture follows pre-orbital marking. Blackbuck urinate with both front and hind legs stretched outwards. It then squats on its hindlegs, pulls its forelegs straight and stiff, points its nose high up and defecates. This posture is ritualized and has marking significance. On occasions pawing with forefeet precedes the others.

The centre of most territories are covered by faecal pellets. They are so numerous that a large part of the ground is black in colour and it is unmistakable. Newly acquired territories are especially probe to such heavy marking. The tenure of a high ranking blackbuck male in his territory appears to be quite long and stable.

The alpha buck, animal ‘C’, at the Polo Field in GPRF has been in his territory since the beginning of this study. He is still the dominant male occupying the same territory to this day in 1980. ‘A’ another male is also there since 1977. ‘D’ who occupied his territory in October 1977 (see sketch) is now (1980) not frequently seen.

For a short period of the year, blackbuck are non-territorial. On 25-9-1977 there were 5 territorial males in occupation at the Polo Field. By January 1978, there was a break down of territoriality and mixed herds were noticed. By March – April 1978, they were territorial again. On October 1980, A, B, and C were present in their respective territories, but a new animal was noticed in E’s vacant territory. Untenanted D’s territory was also occupied by a new animal around the same time. High-ranking males like C and A hold their territories for over 3 years at a stretch. At Point Calimere also, the three animals studied were found to be in their territories in 1978 and 1979.

Summary

Blackbuck demarcate their territories by marking with pre-orbital gland, urination – defecation and pawing. Territories are a pre-requisite for mating. Female blackbuck form herds of their own along with juveniles of both sexes. They feed mostly outside the territorial mosaic and enter the territories in large numbers at a time, where the males try to retain as many as they can. The does have the choice of territory, which they indicate by cropping grass of the chosen territory. When a doe in oestrus enters a territory, the male displays intense herding behaviour and chasing. If the doe passes on to the next territory, the male will not cross the territorial boundary. Matings take place in the centre of the individual territory. Blackbuck are territorial most of the year except for short periods during the height of summer and during January – February. Acquisition of territory is a lengthy process sometimes taking 2 months. High-ranking males retain their territories for more than 2 or 3 years at a stretch. The arena behaviour of the Uganda kob in comparison is a ritualised form of territorial behaviour of Antilope cervicapra. Both species are territorial, the females visit the males in their territories, where mating occurs. In both species, the females show their preference for the territories of the males by cropping grass there. The territorial behaviour of antelopes such as blackbuck is probably more primitive than that of the kob.

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