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Earth Notes: mule deer fall migration

Arizona Game and Fish Department/George Andrejko

It’s fall and mule deer are on the move from summer to winter range on the Colorado Plateau.  These large charismatic mammals are faithful to fixed routes during their seasonal travels.  And it turns out a few are doing marathon migrations.  

In 2008, biologists with the Arizona Game and Fish Department started a tracking project to see how deer could navigate hazards along their set routes--especially crossing busy Highway 64 between the San Francisco Peaks and the Grand Canyon.

About a dozen animals were fitted with GPS collars that pinpointed their positions as they moved. Along with locations, biologists were surprised to see a few members of the herd moving 50-plus miles along the migration corridor.

But the batteries on those older collars gave out within a year. Research resumed in 2019 in partnership with the Mule Deer Foundation and later with the U.S. Geological Survey. Another 45 mule deer from a herd of thousands around the San Francisco Peaks--were fitted with collars with better batteries.

Among this group, one deer journeyed 80 miles one way, one of the longest land migrations documented in the state. It was a doe, Number 9073, following an almost identical route every year between the Flagstaff area and the Grand Canyon. It’s a route she will likely show her fawns.

The project will continue as long as the collars last, contributing information to a larger mapping study in several western states. The findings will aid conservation of these animals—and their critical migration corridors.