Niche Partitioning of 5 Sympatric Bornean Ungulates in Response to Spatiotemporal Variation in Fruit Availability and Resulting Implications for Predator-Prey Interactions

Abstract

Borneo’s rainforests are experiencing some of the fastest deforestation rates worldwide and are home to increasingly vulnerable species, most of which remain poorly understood. Bornean rainforests exhibit dramatic fluctuations in fruit and seed availability during mast-fruiting events which can exert considerable influence on frugivore ecology. Comprehensive spatiotemporal assessments of habitat use, resource partitioning, and responses to fruit availability in mast-fruiting rainforests are lacking for most species, including ungulates. The distribution and habitat use of an apex predator, the Sunda clouded leopard (Neofelis diardi), may be largely shaped by the availability of these ungulates. Yet, factors driving the spatial ecology of this elusive felid remain uncertain. I aimed to quantify spatiotemporal habitat use dynamics of these species and consequently inform effective conservation planning. Specifically, I quantified the effects of human activity, forest type, elevation, and mast-induced fluctuations in resources on the habitat use of lesser mousedeer (Tragulus kanchil), greater mousedeer (T. napu), Bornean yellow muntjacs (Muntiacus atherodes), red muntjacs (M. muntjak), and bearded pigs (Sus barbatus) in Gunung Palung National Park, West Kalimantan, Indonesian Borneo. I applied data from an extensive camera trapping study (n = 42,610 trap nights) to a modified single-season occupancy model to evaluate habitat use over space and time. I then applied estimates of occurrence (Ψ) of the five ungulate species to quantify if habitat use of the Sunda clouded leopard was influenced by prey occurrence and thus if this apex predator responded to bottom-up effects of resource variability. The results from the ungulate modelling revealed that forest type was an important predictor of habitat use of all ungulate species, each preferring different forest habitats. Habitat use estimates were highest in peat swamp forests for lesser mousedeer (Ψ = 0.92 ± 0.05), alluvial bench forests for greater mousedeer (Ψ = 0.52 ± 0.08), lowland granite forests for yellow (Ψ = 0.95 ± 0.07) and red muntjacs (Ψ = 0.98 ± 0.09), and freshwater swamp forests for bearded pigs (Ψ = 0.84 ± 0.07). Bearded pigs exhibited a link between variation in fruit availability and habitat use, indicating an ability to respond to resource variability. Occupancy modelling for Sunda clouded leopards revealed forest type, fruit availability, and bearded pig occurrence as the best predictors of habitat use. The highest estimates were associated with lowland granite forests (Ψ = 0.87 ± 0.09). My results reveal a novel pattern of niche partitioning through both food and habitat resources among five sympatric ungulate species and demonstrate that Sunda clouded leopards may use fruiting events as a cue for abundant prey. My research sheds light on important factors influencing habitat use of understudied ungulates and an apex predator and can be used to refine estimates of habitat suitability across a greater landscape to inform conservation practice amidst continually shrinking remnant forests in Indonesian Borneo.