It is endemic to Sarawak, Malaysian Borneo, where it is known from a small number of locations, including the eponymous Mount Saribau.

Coloration varies from light to dark brown and includes some darker markings.

[3] Alcalus sariba occurs along seepage areas close to small streams as well as in leaf litter in primary forest; it does not tolerate habitat disturbance.

Breeding biology is unknown but presumably involves direct development (i.e, there is no free-living larval stage[5]), as in other Alcalus.

Furthermore, Santubong National Park is facing encroachment from housing and tourism development.