Their is huge demand for rhino horns which sells for minimum 1 crore at international market. According to the latest census there were 2,329 rhinos at park. Recently Assam Government introduce the remote-controlled Unmanned Aerial Vehicle (UAV) to keep watch on the poachers. But I guess that too not sufficient to protect the park from poachers and hunters.
News Controversy - IBM Live - http://ibnlive.in.com/news/assam-2-rhinos-killed-in-kaziranga-national-park/415985-3-251.html
About Kaizranga National Park -
UNESCO designated Kaziranga National Park as a World Heritage site in December 1985. Almost two third of rhinos are stayed at Kaziranga National Park only. The park remained closed between June and October because of heavy rainfall. This is may be main cause for poaching as less security during on Monsoon. Kaziranga National Park is witness many visitors around the world.