Gradual shrinkage of the all-important grassland in this abode of one-horned rhinoceros has thrown up a challenge before the Park authority. It has raised concern in the authority, which is looking for ways to conserve the grassland here. "Although shrinkage of grassland hasn't become an alarming problem yet it is bound to become one unless we can device an effective mechanism for preservation and expansion of the existing grassland area which is vital for survival of the herbivores in the Park,' says L N Baruah, Assistant Conservator of Forest (ACF), Assam.