Species conservation profile and revision of Rhinolophus acuminatus (Chiroptera, Rhinolophidae) from Southeast Asia.

Background: Rhinolophus acuminatus was first evaluated for its conservation status in 1996, with subsequent assessments conducted in 2008 and most recently in 2019, during which it was categorised as Least Concern. These evaluations, however, were largely based on limited occurrence records and a general list of countries where the species was known to occur. Recent discoveries have documented new distribution records, indicating a broader geographic range than previously recognised. Additionally, the availability of a more precise locality data has contributed to a more comprehensive understanding of the species distribution and ecological context. New information: This study provides novel insights into the distribution of Rhinolophus acuminatus, including newly-documented localities, an updated elevational range and refined regional records. Notably, Sarawak (Malaysian Borneo) and Brunei were not previously recognised as part of the species' range during its most recent IUCN assessment. We report the first confirmed occurrence of R. acuminatus in Sarawak, specifically within Gunung Mulu National Park, a UNESCO World Heritage Site, known for its exceptional biodiversity and extensive limestone karst systems. Additionally, a new locality record from Melilas in Brunei further expands the species' known distribution on the island of Borneo. The record from Sarawak represents a newly-documented extant range within Malaysian Borneo, while the Brunei record constitutes a new country record for R. acuminatus. This study also presents the most comprehensive and detailed locality data for the species since its last detailed assessment in 2019. The species' elevational range has been revised from the previously reported maximum of 1,676 m above sea level (a.s.l.) in the 2019 IUCN assessment to a new upper limit of 3,943 m a.s.l., based on records from Mount Kinabalu in Sabah, Malaysian Borneo, indicating the species' presence in upper montane forest habitats. Furthermore, this study provides the first quantitative estimates of the species' Extent of Occurrence (EOO), calculated at 6,957,361.5 km², Area of Occupancy (AOO) at 608 km² and 149 number of locations. EOO mapping further illustrates the species' broad distribution across the Southeast Asian region. Collectively, these findings offer critical data for future reassessments of the conservation status of R. acuminatus under the IUCN Red List criteria.