Landscape connectivity and conservation prioritization for an old forest species with limited vagility

Old forests are often patchily distributed in contemporary forested landscapes leading to conservation concerns for species dependent on these forest types. In the absence of broad-scale recovery of old forests, conservation initiatives have emphasized connecting forested landscapes to facilitate movement of genes or individuals. We assessed forest connectivity for a low-vagile arboreal rodent (red tree vole; Arborimus longicaudus), an obligate of old forests within a distinct population segment that is a candidate for listing under the US Endangered Species Act in the northern Oregon Coast Range (USA). Within the distinct population segment, old forests (>80 years old) have contracted by >80% in the previous century, comprise 10.9% of the contemporary landscape and reside in a matrix of young forests (20-80 years old). We combined complimentary graph and circuit theory metrics into spatial conservation prioritization to provide insights into the composition and function of the contemporary forested landscape and to identify potential conservation and research priorities for this area. Given average distances from patches of old forests (3.4 km), we predicted that connectivity can only be achieved if red tree voles move and settle iteratively through young forest matrix, which is suboptimal habitat. We found that the top 1% conservation priorities were a series of small, spatially central patches and several large patches located where old forest cover was most extensive. Most of these patches were in protected reserves. Up to 30% of the top 10% prioritization were forests outside of reserves, highlighting the potential for these forests to contribute to landscape connectivity for this low-vagile species that is dependent on old forest.