Karst Records of Quaternary Fauna and Environments in Peninsular Malaysia: A Literature Review

Karst landscapes of Peninsular Malaysia preserve some of the most important terrestrial archives of Quaternary fauna and paleoenvironmental indicators. Due to its location in between the Indochina and Sundaic subregions, the peninsula is critical for assessing faunal dispersal, landscape contiguity, and climatic fluctuations effects on the ecosystem. Published fossil and geochronological evidence from cave sites across the peninsula are synthesised to evaluate the faunal habitat structure and ecological variation from the Middle Pleistocene to the Last Glacial Maximum (LGM).

Early Quaternary research in the peninsula was largely conducted through geological, sedimentological, and palynological records, often in placer tin-mining pits. It was suggested that vegetation cover during the LGM and earlier glacial phases was reduced and more open relative to the present day. Pollen preserved within alluvium deposits indicates cooler, drier climates, with grassland–savanna and pine woodland corridors. These interpretations were embedded within broader landscape evolution models including deep weathering of exposed basement in Mio-Pliocene time during the maximum extent of the Sundaland continent, regolith mobilisation after the initiation of slumping due to the rise of sea levels and precipitation, braided fluvial aggradation, episodic interglacial downcutting, the development of peneplanation and pedogenesis followed by the establishment of modern fluvial, infill of V-shaped valleys in association with high-sea level deposits along the coast during the Late Pleistocene.

Numerically dated karst cave fossil assemblages provide a new insight to complement these open-site models. The persistence of orangutan (Pongo sp.) at Batu Caves until ~60 ka implies continued lowland forest cover along the west coast during the last glacial phase. Pleistocene small mammal assemblages from Semadong Cave, located in the northern peninsula, feature environmental variability with the co-occurrence of grassland- and forest-affiliated taxa suggesting a mosaic vegetation model under cooler and drier conditions. Reflected by the occurrence of arboreal mammals including Pongo and colobine monkeys, the Middle–Late Pleistocene Layang Mawas Cave represents an assemblage that is dominated by species closely tied to tropical forest habitats.

Notable recent finding includes the first reported occurrence of Stegodon in Peninsular Malaysia, which was discovered together with a Pongo within the same Middle Pleistocene stratigraphic unit. Based on the ecological tolerances of modern Pongo and stable isotope evidence from fossil Pongo and Stegodon elsewhere in Southeast Asia and adjacent regions, it is reasonable to infer that the palaeoenvironment at this site was either under continuous forest cover or comprised a mixed landscape, with forest patches interspersed within more open vegetation. Recent studies on palaeoecological records across Southeast Asia and pollens from South China Sea during the LGM further challenge the “savanna corridor” paradigm and support the concepts of “forest” and “mosaic vegetation” across Sundaland.

Collectively, karst cave archives in Peninsular Malaysia add critical faunal constraints to existing sedimentary and palynological frameworks. Future combination of stable carbon and oxygen isotope data on fossil remains, with high-resolution rainfall and monsoon proxies will further refine paleoenvironmental reconstructions in the peninsula, subsequently contribute to a better understanding of the paleoenvironment in this region.