Using thresholds to determine priorities for apex predator conservation in an urban landscape

Abstract

As landscapes are increasingly modified due to anthropogenic processes such as urbanisation or development for agriculture, the need to understand wildlife habitat requirements is imperative. This is particularly pertinent for species that are threatened, or apex predators with specific nest, den, or food requirements. Identifying responses to habitat with thresholds can provide an understanding of what resources species are using or avoiding, and their interactions with the surrounding environment. In this research we investigated space use and habitat requirements of the threatened apex predator, the powerful owl (Ninox strenua) in Greater Melbourne, Australia. We deployed GPS devices to 21 urban powerful owls over five years and found owls had an average home range size of 397 ha, and an average core-range of 84 ha. Home range size and positioning was driven by tree cover and urban land cover, while core ranges were restricted to treed environments with a limited area of impervious surfaces and housing. We used thresholds to identify-three priorities for powerful owl conservation in Melbourne. Priority 1: Ensuring river corridors and public open spaces are adequately protected. Priority 2: Limit property densities near rivers and protected areas. Priority 3: Finding opportunities for revegetation to expand and enhance habitat over time. Our research demonstrates how species-specific thresholds can inform land use planning to ensure wildlife species are maintained within highly modified environments.