Elevational Stratification of Medium- to Large-bodied Terrestrial Mammals in Western Sarawak

Among the threats facing the tropical rainforest in south-east Asia, are fragmenting and isolating the forest patches, threatening species richness and density of animals. To date, the effect of reserve areas, age, and species composition along the elevation gradients in western Sarawak have not been well studied. This study aims to document the spatial distribution of medium to large mammals in the region of Western Sarawak, to understand the species composition along elevation gradient in altitudinal range and activity pattern changes with and within altitudinal range, and influence of vegetation complexity on the species distribution by using camera traps. It also attempted to determine the influence of attractants on the occupancy and detection probability of medium to large mammals. This study deployed one regular camera trap at 209 camera stations using stratified sampling along seven elevation ranges ( 1100 m asl) at six reserves (Santubong National Park (SNP), Borneo Highland Resort (BHR), Kubah National Park (KNP), Bako National Park (BNP), Gunung Gading National Park (GGNP), Gunung Pueh National Park (GPNP)) from November 2014 to April 2017 (30 months) accumulating 29,449 camera trap nights, with only selected camera stations in KNP, baited with 12 types of attractants comprising food, scent and vision lures. This study successfully recorded 33 species of medium to large mammals and subsequently explored the relationships between seven community levels (e.g., carnivores, herbivores and frugivores, omnivores, insectivores, felids, civets, and ungulates). This study acknowledges the effect of reserve areas on the species richness whereby the largest reserve (GPNP) recorded the highest number of medium to large mammals (n = 22). However, this study found no effect of reserve age on species composition. The mammals distributed along elevation gradients showed the highest number concentrated at the mid-altitudinal range (701 – 900 m asl) (n = 24). This study recorded two species (Hose’s Civet and Sunda Clouded Leopard) that are confine their distribution to the highlands (> 700 m asl), while 20 species were distributed throughout the lowlands (< 700 m asl) to the highlands. Multiple sympatric species with similar size deterred their distribution at certain elevation gradient, possibly to avoid inter-species competition, while some sympatric species exhibiting different temporal pattern. In KNP, food baits attracted the greatest number of medium to large mammals (n = 19), followed by scent lures (n = 16) and visual lures (n = 13). Cat pellets and shaved coconut attracted most species among six chosen food baits, the perfume Obsessions for MenTM by Calvin Klein as the most attractive scent lure and CD attracted more species than other visual lures. Attractants that featured with water resistant and pungent smell promise higher detection rate in tropical rain forests. Magna gland was found to be less attractive for tropical mammals, compared to other attractants. The preference of targeted species to lures appear varied with diet behaviours and microhabitat of the sampling area. These findings need to be treated as auxiliary data, in order to enhance future camera trapping survey for targeted species. The relationships between reserve areas, age, elevation gradients, and species composition need to be considered as aspects in preserving an area, especially where the occupancy and detection probabilities are high along these gradients. Keywords: Mammals, western Sarawak, reserve areas, elevation gradients, attractant