Factors explaining the occurrence of the Siberian flying squirrel in urban forest landscape

Urban forests are often modified and fragmented by human land use and the original habitat might exist only in remnant patches. Due to their specific habitat requirements and unwillingness to move through matrix many forest-dwelling mammals are susceptible to changes in landscape structure. It is important to understand how the availability of suitable habitat and landscape fragmentation affect species distributions, and what landscape characteristics are essential to the persistence of a given species to conserve urban wildlife. We investigated the effect of landscape composition and configuration on the occurrence of the Siberian flying squirrel, a small-sized arboreal rodent, in a partly urbanized area of Eastern Finland. All suitable and potential forest patches were searched to determine the presence or absence of species, and the landscape characteristics of occupied sites were compared to those of unoccupied sites. Flying squirrels occurred both at the edges of large suitable forested areas, but also in small forest fragments within residential areas. Surprisingly, urban areas did not have a negative effect on the flying squirrel occurrence. Occurrence probability was not either associated with the proportion of suitable habitat, but occupied sites contained larger amount of movement habitat and had shorter distances to nearest occupied sites than unoccupied sites. Our results show that flying squirrels can exist in urbanized landscape and near residential areas, but more detailed information on habitat use and survival is still needed to determine the long-term persistence and viability of the urban populations.