Mammal Species Composition and Activity Patterns Shift While Richness Remains Constant Across Elevational Gradients in Western Sarawak, Borneo

Abstract

Changes in species composition and diversity along elevational gradients remain poorly understood for many tropical taxa. Here we elucidate the distribution of mid- to large-bodied mammals along elevational gradients in northwestern Borneo. We deployed camera traps at 209 stations using stratified sampling across seven elevation categories at six protected areas from 2014 to 2017, recording 33 mammal species. Species richness was not statistically related to elevation, but species composition shifted in response to opposing effects of elevation on the occurrence of different taxa. No species were restricted to the lowlands, but occurrence of common palm civets (Paradoxurus hermaphroditus), thick-spined porcupine (Hystrix crassispinis), and long-tailed porcupine (Trichys fasciculata) was higher at low elevations. In contrast, occurrence of masked palm civet (Paguma larvata), pig-tailed macaque (Macaca nemestrina), and Malay weasel (Mustela nudipes) increased with elevation, and two species - Hose's Civet (Diplogale hosei) and Sunda Clouded Leopard (Neofelis diardi) - were only detected in the highlands (>700 m). Species tended to shift their activity patterns in low versus high elevation forests, though the magnitude of these effects was small. Most species that we detected currently have broad elevational ranges; nevertheless, protecting forest across elevational gradients remains critical so that if climate change forces species to abandon the lowlands, they have habitat connections to higher-elevation refugia