The influence of the root diseases Armillaria solidipes and Inonotus sulphurascens on the distribution of mule deer during winter

Abstract

Armillaria (Armillaria solidipes) and laminated root diseases (Inonotus sulphurascens) are two wide-ranging fungal pathogens that occur in the southern half of British Columbia (BC), Canada, and can infect economically and biologically important tree species such as interior Douglas-fir (Pseudotsuga menziesii var. glauca). In northern, temperate locations, Douglas-fir forests serve as winter habitat for ungulates. When these fungal infections are in Douglas-fir forests, core components of winter ranges are altered, including canopy cover, snowpack and understory vegetation. In this study, we investigated how Rocky Mountain mule deer (Odocoileus hemionus hemionus) of central BC used winter range habitats that included root disease (A. solidipes and I. sulphurascens) centres. We used remote camera-traps to collect data from September 2017 to April 2019, and we assessed those habitats in which the cameras were located during the summer and winter of 2018. We used logistic regression and an information theoretic approach to test a series of factors hypothesised to influence the use of root disease centres by mule deer. Our results show that mule deer use root disease centres less than control forests as well as negatively respond to the deeper snow packs found in root disease centres, especially in late winter. Our cameras also detected higher vertebrate diversity in root disease centres. We suggest that forest policy-makers should acknowledge heterogeneous habitat features such as root disease centres within ungulate winter ranges and consider adjusting estimates of habitat capability for deer based on our findings.