For decades, Borneo's once extensive and pristine forests have been increasingly exposed to a suite of anthropogenic disturbance and deforestation processes as a result of selective and illegal logging, hunting, droughts, fires and the conversion to plantations, chiefly oil palm. Such disturbance is likely impacting the Sunda clouded leopard, Neofelis diardi, and other threatened, sympatric Bornean felids, yet few studies have attempted to address these issues. In this thesis, I used data from intensive camera trap surveys throughout Sabah, Malaysian Borneo and high-resolution GPS data from tagged Sunda clouded leopards to examine the influence of forest disturbance on the abundance, distribution, movements and population connectivity of Sunda clouded leopards and other sympatric felids on Borneo, and to provide some of the first data regarding the ecological interactions and patterns of coexistence among this felid assemblage. I showed that Sunda clouded leopard movement was facilitated by forest cover with high canopy closure, and highly resisted by oil palm plantations with low canopy closure. Models of population connectivity across Sabah identified a number of isolated populations of these felids, which may be particularly threatened with extinction. Analysis of camera trap detection data revealed that the Bornean felids exhibit evidence of resource segregation along the temporal, spatial and prey niche axes, and showed that Sunda clouded leopards, bay cats, Catopuma badia, and marbled cats, Pardofelis marmorata exhibited broad scale avoidance of disturbed habitats but varied in their selection of optimal foraging habitat at fine scales. Conversely, leopard cats, Prionailurus bengalensis, were associated with forest disturbance and likely benefit from such changes. I developed some of the first estimates of population density for Sunda clouded leopards and the first such data for marbled cats. The results are discussed in the context of the conservation of these felids on Borneo.

Niche separation may be the key to promoting the long-term coexistence of introduced and native species. Physical alterations to the environment (habitat manipulation) or re-introducing native species to former habitats can exploit the maladapted traits of introduced species to create a refuge for native species. No two species have identical niches because evolutionary constraints differ between species with different evolutionary histories. Our objectives were to determine if cold temperatures could promote coexistence between native least chub and introduced western mosquitofish. We used individual scale and population scale experiments to test four hypotheses: 1) colder temperatures would reduce the aggressive behavior and predatory effects of western mosquitofish on least chub, 2) colder temperatures would reduce the effect of western mosquitofish on the habitat use, activity, and feeding of least chub, 3) western mosquitofish would not be able to overwinter without warm refuges, and 4) western mosquitofish reproduction would be delayed or absent at colder temperatures, whereas colder temperatures would not inhibit least chub recruitment. At the individual scale cold temperatures reduced the aggression and predation of western mosquitofish on least chub. However at the population scale there was little recruitment in the cold treatment and juvenile least chub did not survive the winter in the cold treatment. Adult least chub successfully overwintered at freezing temperatures whereas western mosquitofish had no recruitment in the cold treatment during the summer and no western mosquitofish survived the winter. There is adequate niche separation among the adults to promote coexistence but the juveniles of both species require warm habitat in the spring and summer to survive freezing winter temperatures. Habitat manipulation may reduce the availability of warm winter refuges for western mosquitofish while leaving warm habitats during the spring for least chub spawning and recruitment. Transplanting least chub to former cold habitats could eliminate western mosquitofish because of niche separation between the species along a temperature gradient. We suggest that the niche separation hypothesis has general application for the restoration of a variety of threatened native species.

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