Impact of coarse woody debris on habitat use of two sympatric rodent species in the temperate Białowieża Forest

Importance of coarse woody debris (CWD) in habitat use of small mammals has not been thoroughly explored, especially for European species. Moreover, despite the growing awareness about the need for protecting CWD resources in forests, their amount is usually quantified with regard to current or desired volume. The area of forest floor covered by CWD is rarely considered, despite its potential importance for habitat use of small mammals. Over a period of three summer seasons (4800 trap-nights), we examined the populations of yellow-necked mouse Apodemus flavicollis and bank vole Clethrionomys glareolus through capture-mark-recapture trapping at three 1-hectare study sites, including both managed forests and a nature reserve in Białowieża Forest, Poland. We applied generalized linear mixed models on a sample of 236 adult individuals of yellow-necked mouse and 173 adult individuals of bank vole to establish that the access to CWD is a significant aspect of their habitat use. Our results suggest that both species prefer a certain minimum amount of CWD. After accounting for different aspects of forest undergrowth, we established that bank vole more frequently used areas with a relatively large amount of CWD (threshold of 0.75 m$^{3}$ CWD per 100 m$^{2}$), together with a propensity to choose areas with debris in the later stages of decay. Yellow-necked mouse was found more frequently in areas with at least 1.5 m$^{2}$ of CWD. We suggest that manipulating CWD distribution, or possibly vegetation characteristics, could be a strategy for managing the abundance and distribution of rodents in forest stands—especially when both CWD volume and coverage are taken into account.