Despite such threats both Assam and Nepal -- homes to the densest rhino populations in Asia -- have notched impressive records in curbing poaching.
Rhino tourism in both countries brings in considerable revenue, and the animal is an Assamese icon with the recent spate of poaching sparking a public outcry.
Kaziranga itself is regarded as one of the world's great wildlife conservation victories.
From some 20 rhino at the beginning of the 19th century -- when maharajas and British colonials shot them by the scores -- it now faces the problem of overpopulation.
This Asian Eden also shelters healthy numbers of tigers, elephants, the highly endangered swamp deer and some 500 species of birds.
To keep it that way, Vasu says it's essential to "dominate every inch of the ground" inside the park and link up with area police and civil authorities, a weakness in the past along with continuing corruption.
"In one hour you are set for life," says Polash Bora, a naturalist who has worked in the park for 21 years, referring to the temptation for park guards to abet poaching.
He also notes trafficking kingpins rarely get caught in India's northeast because of their connections with police and other authorities.
But overall, Kaziranga's green front line has drawn widespread praise, patrolling around the clock, living in lonely camps, until recently drawing low pay and regularly attacked, sometimes killed, by tigers, wild buffalo and rhino because they are forbidden to shoot wildlife.
The poachers they encounter now wield sophisticated weapons and communications.
"It's hard to catch them, especially since they come at night. You hear a gunshot and in five minutes they cut off the horn and run away into the tall grass and jungle," says P.K. Barua, a veteran ranger at a four-man camp deep inside the park.
When they use silencers on their guns, a recent development, a dead rhino may not be discovered for days.
"You only know that one has been killed when you see the vultures circling overhead," he says.
