JAKARTA, March 5, 2009 (AFP) - New infra-red footage released Thursday captures hitherto unseen images of elusive Javan rhinos, the most endangered mammal in the world with less than 60 individuals believed to remain alive.

The grainy video was released by environmental group WWF which has been monitoring the rhinos for about 20 years in the rugged Ujung Kulon National Park on the southern tip of Indonesia's Java island.

They show mothers and calves and a single large male wallowing in various mud holes, revealing behaviour researchers had never seen before and helping with the identification of individual animals.

"These rhinos are very shy. In the last 20 years our team has only seen rhinos two or three times with their own eyes," WWF Asian rhino coordinator Christy Williams told AFP.

He said WWF had previously operated still cameras in the dense jungle but the rhinos were often frightened by the shutter and fled the area or attacked the cameras.

Under an expanded project to film the animals, 34 cameras with infra-red triggers which take video every time they sense movement in the forest have been painstakingly installed in likely rhino haunts.

Typically they are concealed in trees overlooking wallowing ponds and streams and most of the clips released Thursday show the animals wading or wallowing in mud.

"The videos are showing a lot of young animals but not many calves so even though there is evidence of breeding it is not enough," Williams said.

"A healthy rhino population should be increasing at about seven percent a year or about three or four calves, but here we are getting three or four calves every four or five years."

He said the WWF was identifying other suitable rhino habitat areas on Java with a view to resettling some individuals from Ujung Kulon to boost their chances of survival.