The behavior of this primate has been intensively studied in some habitat types, such as mangrove, fresh water peat swamp and riverine forests, of either natural or protected areas. However, in some sub-districts of South Kalimantan Province the author found that the proboscis monkeys live in three different habitat types. This could be a new record which is not known by many people. In Marabahan sub-district (part of Barito Kuala district), this primate inhabits swamp forest dominated by galam Melaleuca cajuputi. In Tabalong district, it inhabits rubber (Hevea brasiliensis) forest or traditional rubber plantations and was found in limestone hill forests. There were four factors that threaten the sustainability of proboscis monkey, i.e. habitat conversion, habitat fragmentation, the presence of the monkey in non-protected (cultivated) areas, and poor treatment.