Biological and ecological characterisation of roosting bats and troglofauna in the dark cave conservation site using lidar technology

Abstract

Batu Caves is a habitat island of limestone karst tower surrounded by metropolitan areas located 11 km north of Kuala Lumpur. A total of 20 caves are recognised within the Batu Caves complex and Dark Cave, approximately two kilometres long, is the longest cave system. It supports 151 invertebrates and 22 vertebrates with significant species endemicity. Nine reported caverns were mapped using conventional speleological methods. The cave is known as the most studied tropical cave in Southeast Asia. However, the most detailed biological survey was conducted about 50 years ago, and there has been no up-to-date study on the cave characteristic and detailed biological survey using the latest technology. In this study, the interior of the cave was mapped using three dimensional Light Detection and Ranging (3D LIDAR) laser scanning to produce a 3D model of the caverns. The roosting location of bats were mapped based on LIDAR scans and acoustic data and compared with historical data to detect species trends or any new locations. The location of troglofauna occurrences were marked on the new LIDAR map. The projected 3D point cloud model of the cave was generated after 27 hours of LIDAR data scans that was collected over four site visits which covered 805 m of walking distance. The results produced a more accurate representation of the 3D LIDAR map. The shape and orientation of the underground spaces were similar between the LIDAR map and the latest conventional map. Vertical features (cave height) have provided more precise dimensions of the caverns. The integration of LIDAR-acoustic- visualisation survey methods further confirms only five bat species (Taphozous melanopogon, Hipposideros diadema, H. larvatus, Eonycteris spelaea, and Rousettus leschenaultii) roosting in the Dark Cave. Troglofauna observations found nine species of mammal (including bat), 11 species of invertebrates, five species of birds and 19 species (one genus level) of reptiles were recorded throughout the cave system from 2012 to 2019. Features such as bat roosting locations, speleothem, number of skylights, cave dimensions, man-made structures and seasonal water flowing zones are the map novel features. The spatial information in 3D virtual models can be used repeatedly on post-survey analyses. These outcomes produced a more accurate speleological map of Dark Cave for scientists to conduct long-term monitoring studies and state government together with management authority in managing Dark Cave as an ecotourism, education and conservation site.