IT was a cool spring afternoon at the Kanha Tiger Reserve in Madhya Pradesh. I was on a slow drive along the forest road paralleling the grassland and was watching a small herd of gaur grazing close by. These catholic feeders were making the most of the available forage in a characteristically bovine way, unconcerned about being watched. Amid the tranquillity and serenity of the nature reserve, I turned my attention to a bull nearing the road.
Suddenly, the nearby shrub exploded as a stalking tiger leapt out and pounced upon the posterior of the gaur. It was so sudden and forceful that the bull almost stumbled to the ground. I had a full view of the bull’s hindquarters and saw that the tiger had clenched the lower thigh in its strong jaws. The bull, snorting and bellowing in a rage and fear, was swinging its horns and trying to free itself by frequently turning around, almost dragging the tiger. Amid this gruesome drama, the tiger’s grip loosened momentarily, and I saw blood oozing out of the torn muscles of the gaur’s leg. The tiger quickly adjusted its bearings and grabbed the thigh again, sitting down on its haunches and trying to pull the gaur down. The tiger continued gnawing at the thigh, almost completely incapacitating the gaur. Soon, the leg could no longer sustain the bull’s weight. Technically, the tiger had hamstrung the gaur by severing its hamstring muscles just above the knee. These muscles are responsible for movements such as walking and running. The tiger now started eating the tremulously moaning gaur alive. This tiger had to survive and was merely playing the role nature has assigned to it.
Strongly built and the largest wild bovid (family Bovidae) in the world, the gaur weighs almost three times as much as the tiger but it was now reduced to an appalling black heap of live muscle mass. It was also playing its role: food for the tiger. Looking at the issue anthropomorphically, though that is generally frowned upon in conservation, I recalled the pessimism of the German philosopher Arthur Schopenhauer, who once observed: “One simple test of the claim that the pleasure in the world outweighs the pain is to compare the feelings of an animal that is devouring another with those of the animal being devoured.”
A natural world
Speaking generally, a nature reserve is a specially preserved natural area for the conservation, research and study of the floral, faunal, geological and many other region-specific natural attributes of interest. In India, nature reserves are known as protected areas and, depending upon their management importance and legal standing, have been categorised into national parks, core zones or critical tiger habitats of tiger reserves, wildlife sanctuaries, conservation reserves and community reserves.
Kanha can be conceived as a landscape of large mosaics of several vegetal cover and land use types of almost the same crops or different combinations of mixed species, besides grasslands, clearings, hollows, waterbodies and roads. Until some time ago, before the gradual relocation of forest villages, the Kanha core zone also harboured mosaics of habitation and agriculture. All these mosaics are spatially distributed on and across different terrain and types of topography, resulting in horizontal and vertical arrangements of various vegetative and non-vegetative elements. This is a more or less perfect setting for a natural world that has several types of wildlife habitats that can sustain thousands of animals of different species.
The types of vegetation and habitats of wildlife in a nature reserve depend upon its physiography, geology, climate, and precipitation. The physiography of Kanha is characterised mainly by forested shallow undulations, hills with varying degrees of slopes, plateaus and valleys. These physiographical features along with sal, miscellaneous crops and bamboo offer unique settings and ecotones (or transition zones between two different vegetative mosaics), giving rise to diverse types of macro- and microhabitats for various animal species.
Ecological niche
A habitat can be regarded as the address of a species, that is, where it spends its natural lifespan. Species make environmentally appropriate habitat choices, which is a hierarchical process, through many innate and learned behavioural decisions. If a species prefers a habitat or a location therein, there may be more intensive use of the area by individuals of the species. A quality habitat provides a species with relatively appropriate conditions for prolonged usage. Endangered species such as the hard ground barasingha may have special habitat requirements that have to be augmented through managerial interventions.
Ecological niche is an important concept that helps one understand relationships between habitats and different wildlife species. Niche is a profession or role played by each species in its natural habitat. As such, it can only be described in terms of the interaction between the environment and the species. While some species have broad niches that help them exist in a wide variety of habitat types, others have narrow niches and can only survive in limited habitat types. That is why species are known as food generalists or food specialists, with the latter having to struggle for survival. Such species are gradually prone to be rendered endangered. For instance, the hard ground barasingha at Kanha is a food specialist that is almost totally dependent on grasslands. This is unlike the chital, which is both a grazer and a browser. If the grass dries up in the high summer, the chital can switch to browsing on leaves.
Each species has a certain average lifespan determined by heredity and genetics beyond which it cannot survive even in the most favourable of natural conditions. Most animals in good zoos are expected to reach their upper natural age limit because of the hygienic conditions under which they live and the good veterinary care and nutritious food they receive and, of course, the lack of predation. A zoo is an example of exsitu , or off-site, conservation, while a nature reserve is an insitu, or on-site, conservation location where conservation practices aim at maintaining species diversity and preventing species extinction in a natural way.
Survival games
Kanha supports at least four major carnivore and nine herbivore species. Now imagine the coexistence of thousands of these animals exploiting overlapping resources of food for survival. There exists a natural segregation amongst them on the basis of ecological niche partitioning that includes food habits, habitat separation and specific ecological requirements. The very basis of inter-species relationships in Kanha can be understood through the concept of the ecological pyramid, which is a graphical representation of ecological niche partitioning and shows which species consumes which other species.
Species-specific niches help reduce competition, and no two species, carnivore or herbivore, occupy the same niche in a habitat for the same resources. In case two species compete for the same resource, natural selection will reduce the dependence of these species on this overlap. If, however, no species evolves and reduces the competition, then the species that successfully exploits the overlapping resource will do well and the other may decline and finally become locally extinct.
Nature has helped species evolve different feeding strategies to reduce inter-specific competition. The body size and metabolic rates of different ungulate species also have an important role to play in this. Besides, geographic barriers have resulted in the creation of several habitat pockets characterised by large aggregations of ungulates at Kanha. Generally, valley meadows and undisturbed habitat mosaics of some forest ranges support such huge assemblages. Conversely, some ridges, rugged terrain and biotic pressure prone areas of the some forest ranges sustain only small assemblages of herbivores. The distribution of carnivores is also regulated by the presence and movements of these ungulate species.
The predator-prey relationship maintains the dynamics and health of the Kanha wildlife ecosystem, and any serious disturbance may cause either population explosions or crashes, which are unnatural. The Kanha ecosystem supports the tiger as the main predator and the leopard and the wild dog as co-predators. These predators rank as such in the predation hierarchy and each has a distinct niche of its own.
Tigers, generally, prey upon large-sized ungulates and travel long distances in their home ranges, away from habitations. While the tiger kills a wide range of ungulate species, sometimes even an adult bison or a langur or even a python with a freshly swallowed ungulate, the bulk of its annual consumption is the chital. Besides, tigers also prey upon livestock in the peripheral areas of the Kanha core zone.
Leopards generally have smaller and almost stable home ranges close to human habitation. There seems to be no competition between the tiger and the leopard, and they follow the tactics of mutual avoidance. The leopard, however, is sometimes known to operate close to the tiger’s range. Leopards generally kill small-sized prey, including domestic dogs, goats and birds.
Wild dogs are transients and travel in packs over large distances. Although their home range overlaps those of tigers and leopards, their presence is so fleeting that they seldom come into conflict with the other two predators. Other lesser predators such as foxes and jackals prey upon small herbivores, rodents and birds.
At Kanha, various intra- and inter-specific relationships among different species of carnivores and herbivores affect their survival. Ecologically, these interactions result in the adjustment of equilibrium. In predation, one sees the killing of prey, which is generally smaller in size than the predator. In some areas, when two species, for instance, tigers and leopards or barasingha and chital, enter into direct competition, the inhibition of one species is observed. There is also indirect competition between ungulates and cattle for the overlapping resources in villages close to the core zone. This usually results in the inhibition of ungulates in the peripheral areas of villages. Chital and langur show mutualism through ecological facilitations that benefit both, which is known as probiosis.
Rakesh Shukla is a Research Officer at the Kanha Tiger Reserve.
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