How did the owl cross the road? Movement patterns and behaviour of a threatened apex predator

Abstract

The road network is crucial in facilitating the transportation needs of society; however, its establishment and expansion comes at a significant cost to biodiversity, particularly through habitat loss, fragmentation, movement barriers, vehicle strike and disturbance. Apex predators are highly susceptible to the negative impacts of roads given that they are highly mobile, have large home-ranges and must connect fragmented habitat to obtain resources for survival, where traversing roads is often unavoidable. Here, we utilised GPS tracking data collected from 37 powerful owls (Ninox strenua) occurring throughout an urban-agricultural-forest gradient in Victoria, Australia, to understand how the movement ecology of this threatened apex predator responds to roads. We found that powerful owls from all landscape types are interacting with the road network, however, they are significantly adjusting their movement behaviour in response to roads. Despite urban and urban-forest owls residing in landscapes containing high road densities, all owl landscape types had similar low road densities in their core-ranges, suggesting road avoidance behaviours in critical habitat areas. Powerful owls switched into and stayed, in a faster more directional movement state when interacting with the road network and tended to cross roads more frequently towards the end of the night (>5 am). Owls preferred to cross roads near watercourses and in areas containing high amounts of dense tree cover. To prevent movement constraints and other road-related effects, it is critical that apex predators are considered in road management projects to strengthen effective impact mitigation and conservation management outcomes.