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INTRODUCTION
Resource use and overlap plays a central role in the structuring of vertebrate communities. The mechanisms by which organisms partition resources typically involve differentiation in some combination of habitat use (at both fine and coarse scales), timing of activity and diet. Differences in niche-breadth among competing species are ultimately the result of an evolutionary trade-off between the ability to exploit a wide base of resources and the efficient use of each one (Futuyma & Moreno 1988, MacArthur 1972). Although species occur along a continuum of niche breadth, they are often considered simply as specialists or generalists (Clavel et al. 2010, Julliard et al. 2006). These two resource acquisition strategies have been associated with important life-history traits: in general, specialists have lower dispersal capacities (Brouat et al. 2004), and are more susceptible to stochasticity and environmental change (Clavel et al. 2010, Sol et al. 2002) than generalists. As a consequence, resource specialists are typically more prone to extinction than generalists, and often the first species to be lost when habitats are modified (Boyles & Storm 2007, Dunn et al. 2009, Laurance 1991).
Sloths are mid-sized (2.0-4.5 kg) arboreal mammals that spend the majority of their time in forest canopies. The two phylogenetic groups of sloth, two- (Choloepus spp.) and three-toed sloths (Bradypus spp.), diverged roughly 18-40 Mya (Delsuc et al. 2001, Gaudin 2004), co-occur across much of their distributional range and are ecologically quite different (Pauli et al. 2014). Although both are arboreal folivores, previous authors have broadly described the two-toed sloth as a generalist, inhabiting a range of habitat types and consuming leaves from a number of species as well as augmenting their diet with non-leaf items (e.g. fruits, flowers and animal matter) and possessing large home ranges; the three-toed sloth is considered more specialized, foraging on only leaves from a small number of tree species to the point that individuals appear capable of surviving on a single or a few tree species (Chiarello 2008, Gilmore et al. 2001, Montgomery & Sunquist 1975, 1978; Pauli et al. 2014). Both two- and three-toed sloths use shade-grown agro-ecosystems (Vaughan et al. 2007) but in one well-studied system, only the two-toed sloth appears capable of maintaining self-sustaining populations...