A male elephant of the forest department that had killed its mahout in Kaziranga National Park last month was kept in isolation after it attacked another mahout with its tusker.

The elephant 'Babul', in a state of 'Musth' attacked 'Dikhudhar', the pachyderm with the largest tusk in the state, along with its mahout Kalia Dey yesterday when it was about to be tranquilised, forest department sources said.

'Musth' is a periodic condition in male elephants which is characterised by highly aggressive behaviour and accompanied by a surge in the reproductive hormone testosterone making the jumbos violent toward humans and other elephants.

'Babul' was, however, tranquilised later and segregated from the other elephants.

"He will be kept in isolation for a month or two till he recovers", the sources said.

'Babul' had on January 29 last suddenly thrown his mahout Nirmal Barman off its back and trampled him to death in the Burapahar Range of the Park when the elephant along with other jumbos were carrying forest guards on patrolling duty inside Kaziranga National Park.