‘Orang Sungai’ (literally “people of the river”), most of them living in the north and center of Sabah, live mainly along rivers a . Another group belonging to the same family is the Ida’an, who live along the east coast and converted to Islam as far back as the 15th century. In the past, both the Orang Sungei and the Ida’an practiced cave burials, and it is still possible to see the remains of wooden coffins and burial urns in some of the caves and rocky overhangs along Sabah’s east coast, including in the Danum Valley region.
The Ida’an (Idahan), however, have a far more important use for caves. For centuries, they have been harvesting valuable birds nests from the limestone caves between Semporna and Lahad Datu. Twice a year during the collecting season, the usually empty village at the mouth of a cave comes to life as collectors, owners of rights to harvest the nests, itinerant traders, cooks, families and family pets take up residence for six to eight weeks.