Habitat linkages or corridors can help facilitate animal movement across fragmented landscapes.
In Peninsular Malaysia, 17 corridors have been identified for increased protection by the federal
government. However, their conservation importance for mammals is uncertain because almost
all have been fragmented by roads and/or forest conversion. Here, we first assessed the
conservation importance of two corridors and investigated how forest use by large mammalian
carnivores, herbivores and omnivores (> 20kg) has been affected by fragmentation caused by
infrastructure and forest conversion. Further, we assessed the potential of 20 road underpasses at
these two corridors to serve as crossing structures for large mammals at two corridors. Our results
show that both corridors are of high conservation importance for native mammals: cameratrapping
spanning 63,750 trap nights detected 40 species (including 17 threatened species) and 36
species (including 13 threatened species) of native mammals, respectively comprising 100% and
75% of Peninsular Malaysia’s 12 extant native large mammals. For seven focal large mammal
species with sufficient data in both corridors, logistic regression models revealed that all
measured fragmentation covariates (i.e. distance to road, reservoir and plantation and forest cover
type) had some degree of effect on habitat use by at least one focal species. The distance to a
reservoir appeared to be the most common threat to focal species in one corridor, while the
distance to the road was the most pervasive threat in the other. When we examined the efficiency
at which underpasses are being used by six large mammal species, by calculating the ratio of
observed to expected underpass use in each corridor, we found that underpass use efficiencies
were sub-optimal for all but one species. Our results suggest that the potential of existing
underpasses to serve as crossing structures by large mammals in fragmented corridors within
Peninsular Malaysia appears limited, especially for carnivores. Regulating infrastructure
development and forest conversion around the underpasses to prevent declines in surrounding
forest use by large mammals appears to be the most obvious and urgent mitigation measure.