Mule deer migrate from low elevation winter ranges to high elevations summer ranges. Although not all individuals in populations migrate, some will travel long distances between summer and winter ranges. Researchers discovered the longest mule deer migration in Wyoming spanning 150 miles from winter to summer range. Multiple US states track mule deer migrations.
Mule deer migrate in fall to avoid harsh winter conditions like deep snow that covers up food resources, and in spring follow the emergence of new growth northwards. There is evidence to suggest that mule deer migrate based on cognitive memory, meaning they use the same path year after year, even if the availability of resources has changed. This contradicts the idea that animals will go to the areas with the best available resources, which makes migratory paths crucial for survival.