Forest heterogeneity outweighs movement costs by enhancing hunting success and fitness in spotted owls

Abstract ContextThe concepts of habitat fragmentation and heterogeneity are central to the conservation of biodiversity; yet understanding when landscapes transition from heterogenous to fragmented can challenge conservation in practice. Complex and sometimes difficult-to-measure responses of species, and ultimately biological communities, to habitat heterogeneity and fragmentation may reflect the outcome of life-history trade-offs shaped by different landscape properties. ObjectivesHere, we tested the hypothesis that a mosaic of forest stands improved hunting and breeding success for California spotted owls (Strix occidentailis occidentalis). MethodsWe integrated high-temporal-resolution GPS tags, video monitoring of nests sites, long-term assessments of reproductive status, and high-resolution remotely-sensed vegetation data in a mixed-ownership landscape in the Sierra Nevada, California. ResultsSpotted owls made shorter nocturnal movements when medium forest was prevalent in their territory. However, spotted owls delivered prey at a higher rate to nests sites when they had more forest edge in their territory, which presumably provided greater access to large-bodied woodrat prey. Further, spotted owl reproductive output was relatively high in territories that contained a mix of mature and open forest. ConclusionsThus, the benefits heterogenous forests provide to hunting success appear to outweigh costs associated with additional commuting to foraging sites and provide emergent fitness benefits to spotted owls. We suggest that the line between habitat heterogeneity and fragmentation can be a complex one that varies not only among, but within, species. Further, understanding the effects of heterogeneity and fragmentation on biological communities will require more empirical and mechanistic studies of individual species.