Identifying migration corridors of mule deer threatened by highway development

Abstract

ABSTRACTHighways are hazardous to migratory ungulates world‐wide, causing direct and indirect impacts to ungulate survival. Moreover, significant financial costs are incurred in damage from wildlife–vehicle collisions and in building and maintaining wildlife passage structures. Information is needed to link ungulate movements to collision occurrence to prioritize needed construction of wildlife crossings on highways. We simultaneously documented mule deer (Odocoileus hemionus) migration corridors and mule deer–vehicle collisions (DVCs) in South‐central Oregon, USA, over 6 years (2005–2011). We calculated Brownian Bridge Movement Models for 359 migrating mule deer equipped with Global Positioning System technology. We modeled DVC counts as functions of probability of use during migration, annual average daily traffic (AADT), and habitat characteristics. Probability of use during migration was the strongest predictor of where DVCs occurred (r = 0.93). Predicted DVCs also increased with AADT but peaked at approximately 8,000 and then decreased. Where AADT was above approximately 8,000, fewer deer attempted to cross the highway and DVCs decreased because, over time, deer either abandoned the migration route or were killed trying to cross this busy highway. Our results suggest that managers should focus on migration corridors or high‐density DVC locations to identify where fencing and under/overpasses could be most effective for maintaining migratory corridors when confronting increasing traffic and development that bisect seasonal ranges of mule deer. © 2015 The Wildlife Society.