Competitive grazing

A herd of Gaur feeding

In Valparai we saw four different kinds of wild plant-eating animals: the huge Gaur (aka Indian bison), the shy barking deer (Indian Muntjac), the rare Nilgiri tahr, and the Nilgiri langur. There were also domesticated cows and buffalos, and a very small number of domestic goats. If all the grazers eat the same food, then the one that eats fastest could starve the others to death. There is the unlikely possibility that the common food plant grows really rapidly, so no species dies out. The more likely possibility is that the different animals eat different plants. In fact, as I looked this up I found that biologists use the word grazing for eating grass, and browsing for eating shrubs and bushes. So avoiding conflict by eating differently is well recognized.

A herd of Gaur feedingWe frequently saw family groups of Gaur grazing among tea bushes, heads down, except when they looked up to keep an eye on us. In forests we found Gaurs to be more cautious, but here on the tea estate they seem to be used to humans. On watching closely, it appeared that Gaur did not touch the tea, preferring to eat grasses, and perhaps other plants, which grew around the tea. I walked among the tea bushes at one point and found that the paths had little other than grass. So this cousin of cattle was eating mainly grass, although they are known to eat a variety of plant material. Maybe they don’t like tea; I don’t much like Nilgiri tea myself.

Barking deer: Indian MuntjacThe barking deer (Indian Muntjac) is a very shy creature. We were lucky to spot one from a road above a sunken meadow. It did not bolt because it never noticed us. It moved through a patch of tea, over the grass, which it completely ignored, looking for something else. An article in the journal Mammalia explains that 80% of its diet comes from shrubs, flowering bushes and trees. Grasses make up only a small part of its diet. The Gaur and the Muntjac occupy the same range but eat differently. This is the classic strategy of two herbivores in the same geography: one grazes, the other browses.

Nilgiri tahr We saw a family of Nilgiri tahr which munched on grass for a while, but then started eating flowers of Lantana bushes growing by the road. An article in the journal of the BNHS claims that this is common. The tahr eats mostly grass, but also a wide variety of flowering bushes. It avoids competition with other herbivores by the fact of being nimble and eating in places where the others cannot reach.

Langurs follow the same strategy. They browse leaves high up on trees, and so avoid competition with other wild herbivores in these places. Domesticated cattle are not so lucky: they eat the same plants that Gaur eat. Sometimes they are seen feeding side by side, and apparently there is occassional conflict. The Gaur is huge: often over a ton in weight and its shoulders are man-high. In a conflict, it is bound to win over domestic cattle. This does not appear to be a serious problem in Valparai, since most people here are involved in tea production and not farming.

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Author: I. J. Khanewala

I travel on work. When that gets too tiring then I relax by travelling for holidays. The holidays are pretty hectic, so I need to unwind by getting back home. But that means work.

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