What starts the deer migration?

[freebird63]

Has anyone ever figured out what factors there are to start the mule deer migration to lower elevations?
Is it strictly the depth of the snow?
If it is the depth of the snow, how deep does it have to be??
I've seen elk in pretty deep snow, they were just feeding on a hill side, I would guess at that time the snow was around 36 inches deep.
Does the rut play into the migration?

Chuck in Boise

 

[andrew12gauge]

I think some of the bucks start migrating due to rut but the majority of migrating action takes place based on weather and availability of feed in the high country. The summer ranges some years will only have feed to sustain the animals for so long. Heard a theory that the elk in 39 didn't migrate as early this year due to the late summer rains that caused extra green up this fall

 

[WASHMULEYHUNTER]

Migration of some deer herds in Idaho is even a mystery for the idfg. Take unit 44 for example; they had to open the season to mid September because a majority of deer migrate down to 45 by mid October. Before the rut and weather.

 

[brymoore]

The deer migration is usually triggered by a weather event. Last week I saw no deer driving to work and now I'm dodging 30+ each way. In another week the area will have herds over 100 grazing together.

Elk, on the other hand will stay higher much longer than deer. In my area, the elk didn't migrate much lower than 4K feet last year due to the lack of snow.

 

[freebird63]

I wonder if Whitetails are any different that mule deer as far as migrations go??

Chuck in Boise