Integrating multi-source forest inventory and animal survey data to assess nationwide distribution and habitat correlates of the Siberian flying squirrel

Modern intensive forestry worldwide is posing serious threats to old-growth forest specialist species. Cost-effective conservation can only be achieved when the ecology and distribution of species are well understood. The present distribution of the Siberian flying squirrel (Pteromys volans), a vulnerable species in Finland (and Europe), is poorly known, and its ecology studied only locally. We conducted a nationwide survey of the species to assess its distribution and derived habitat variables from the National Forest Inventory dataset to study its habitat requirements. We performed separate logistic regression models of the species occurrence at two separate spatial scales, small (9 ha plot) and landscape (1 km radius) extent. At the small scale, occurrence increased with average forest age and volume of spruce trees. At the landscape scale, occurrence was positively related to cover of mature spruce/mixed forests, density of suitable habitat patches and, rather unexpectedly, agricultural fields. Occurrence of flying squirrel was generally higher in restricted regions of central-western Finland, where the forested landscape is more fragmented by agricultural fields, compared to the rest of the country. Our findings indicate that the species can make use of fragmented habitat mosaics including forests and the interface between forests and fields. Conserving spruce dominated mature stands in these landscape mosaics is a key to maintaining adequate habitat for the species. We conclude that conservation efforts should also be directed to the most highly man-modified landscapes, where the preservation of habitat patches of good quality for the species should be integrated within the forest management plans. (C) 2012 Elsevier Ltd. All rights reserved.