Joining the dots: How does an apex predator move through an urbanizing landscape?

Abstract

Examining the movement of apex predators is difficult in urban environments due to private land ownership; however, understanding their movement is critical given the current and rapidly increasing rate of urbanization globally. Of equal importance is the understanding of what landscape factors allow these movements to occur. We used the powerful owl (Ninox strenua), an urban apex predator in Melbourne, Australia, as a case study to understand their movement ecology in urban environments.Owl movement was recorded using automated GPS logging devices deployed on ten powerful owls, resulting in 10870 GPS locations. In combination with these positions, four environmental covariates, and a priori understanding of owl ecology were used to assign movements to three different states (prey handling/eating, foraging and transitory) based on step length and turning angles between sequential locations in a hidden Markov model.We demonstrate that the environmental covariate combination of time of night, Euclidean distance to riparian vegetation, and NDVI best described movement states. Owl movement states changed across the night. Shorter movements with many turns were made towards the beginning of the night in riparian areas with high NDVI. This behavior is most likely linked to prey handling, suggesting powerful owls are more likely to hunt early in the evenings and as such travel short distances while carrying large prey items. Transitory movements with limited changes in turning angles were the dominant movement state towards the end of the night. As owls leave areas of high NDVI, they quickly travel long distances across cleared land and impervious surfaces to connect to the next habitat patch where they then transition back into shorter step lengths where NDVI is higher.This research highlights the critical importance of riparian vegetation and high NDVI areas in driving powerful owl movement and foraging in urban landscapes. Conservation priority should be placed on retaining and restoring riparian corridors as areas not only for powerful owls and their prey, but also for many other species that utilize similar resources.