Lethal removal of animals can be a very contentious issue, especially when one species is killed for the conservation of biological diversity. Barred owls recently expanded into the range of northern spotted owls in the Pacific Northwest and are now linked with continued population declines of spotted owls. Removal of barred owls is being evaluated as a management option to conserve spotted owls. With a patchwork of ownership throughout the Pacific Northwest, removal areas would differ in size, distribution, and effort allocated towards detecting barred owls. We developed a spatially explicit, individual based population model that incorporated dispersal mechanisms to explore how the size and distribution of removal areas would influence the efficacy and efficiency of removals. Removals were simulated under varying levels of effort, which represented the probability of detecting and subsequently removing a barred owl.
Our simulation model illustrated that as the size of a removal area increases, fewer territories are occupied by barred owls and fewer owls are removed per territory for a given level of removal effort. To a lesser extant, as a fragmented removal area is consolidated into a single removal area, barred owl occupancy may be slightly lower and fewer owls will likely be removed for a given level of removal effort. A deterministic occupancy model without spatial dynamics did not capture the benefit that may be provided by a large removal area. As lethal removal of barred owls is further evaluated to help conserve northern spotted owls, managers should consider the size and distribution of removal areas across the ownership patchwork of the Pacific Northwest and beyond.