Understanding the co-occurrence of Asian small-clawed otter and smooth-coated otter in a human-dominated landscape

Land conversion threatens many wild species globally, driving multiple populations to extinction. The issue is particularly severe in Southeast Asia, where natural habitats have been continuously modified due to rapid agricultural and urban expansion, consequently forcing many wildlife species to adapt to human-dominated landscapes. This disruption also impacts co-occurring, competing species, affecting both dominant and subordinate species, which can be disruptive to ecosystems. For this reason, understanding how environmental and human factors influence wildlife in human-dominated landscapes is necessary for long-term wildlife conservation in these areas. This study examined the effects of extrinsic factors on interspecific competition between the Asian small-clawed otter (Aonyx cinereus) and the smooth-coated otter (Lutrogale perspicillata) using two-species occupancy models with a continuous-time detection process that can simultaneously account for space and time. Our results supported models suggesting spatial and temporal dependence between these two species in southern Thailand. We found that occupancy was explained by the availability of natural habitat and aquaculture, while co-occurrence between species was better explained by the size of contiguous agricultural patches and the number of urban patches in the landscape. Human disturbance had limited influence on otter occupancy but rather impacted their detection at different scales, depending on the intensity of human disturbance. Otters occupying the most human-disturbed areas responded to humans at the smallest temporal scale, perhaps indicating a degree of habituation to humans when encounters are non-threatening and adequate habitat remain (i.e., high habitat heterogeneity and undisturbed corridors). However, increased overlap between otters and humans might lead to more conflict, and private property regulation is likely challenging for otter conservation. The shrinkage of natural habitats escalates competition between wildlife species. This interspecific competition is a crucial factor that influences behavioral adaptation and geographic distribution for both dominant and subordinate species, especially urban wildlife occupying anthropogenic landscapes that have been persistently changing. Using continuous-time detections from camera traps along the coast of southern Thailand, we investigated the relationship between the Asian small-clawed otter and smooth-coated otter, and their responses to humans through time and space simultaneously. We found temporal avoidance and spatial dependence between the two species of otters; however, their relationship varied with human density levels. Our findings suggest that these distinct otter species can co-exist and adapt to human-dominated landscapes under specific conditions, for example when human encounters are non-threatening, habitat heterogeneity is sufficient, and habitat corridors remain undisturbed.