Habitat use by the Great Indian Rhinoceros (Rhinoceros unicornis) and the other sympatric large herbivores in Kaziranga National Park

Abstract

A study on the habitat use by the Great One horned rhinoceros (Rhinoceros unicornis) and three other sympatric ungulates was carried out in Kaziranga National Park (KNP), Assam during December 2000 to April 2001. KNP supports more than half the world's population of the Indian Rhinoceros, a highly endangered species. Since this park also supports a high diversity and density of herbivores coexisting in a typical floodplain habitat, it was an ideal place to conduct the following study. The study aimed to determine how 4 large herbivore species rhino, wild buffalo, swamp deer and hog deer achieve spatial and temporal separation across two seasons. The study also investigated how nutritive content of the forage determines habitat selection by these species. KNP was an ideal place to study habitat use patterns by these four sympatric species due to the seasonal variation of forage quality caused by the practice of annual burning. Sampling for animal abundance within each habitat type over two seasons was done by monitoring transects. Feeding observations were obtained by scan sampling. Laboratory analysis was done to determine the nutritive content of the available forage during winter and summer. Seasonal and spatial differences observed in habitat occupancy patterns by the ungulate species within KNP seem to be a way of partitioning resources in order to minimize competition. During the winter season all ungulates selected the short grasslands for feeding. The wild buffalo and the swamp deer showed no variation in the habitat occupancy patterns showing a positive selection for the short grasslands. However, rhinos and hog deer were observed to prefer the tall, burnt and sprouting grasslands in summer for feeding during summer. When habitat occupancy patterns were correlated with the nutritive value of the forage it was found that all ungulates tracked high crude protein levels in available forage. Rhinos and hog deer formed an association that exploited areas that have high crude protein and low silica content. Wild buffaloes and swamp deer show less flexibility in habitat occupancy patterns and were observed to feed in short grasslands where there was a relatively high amount of crude protein available during both the seasons. The study revealed that crude protein played an important role in determining habitat use by hog deer, which shows a linear relationship with crude protein. Forage volume, an indicator of available food played a significant role in determining habitat use patterns for the large bodied ungulates, namely the rhino and the wild buffalo which is in keeping with their physiology and body requirements. There seems to be partitioning of space by the ungulates on the basis of body size and dietary separation. Rhino and hog deer were observed to formed one guild whereas wild buffalo and swamp deer formed another one. These two groups differed in the pattern of habitat occupancy suggesting that ecological separation in Kaziranga National Park, perhaps occurs on the basis of differential use of the habitat by ungulates that have a similar body size. There was an observed complementation of body sizes within each association. A large bodied ungulate associated with another ungulate that was much smaller in size. and therefore, had different ecological needs.