We discussed this in detail on the QDM board during the summer - its excellent reading - it may take a while for the link to come up because its archived - its worth the wait:

http://forum.hunting.net/bbs/topic.a...44&FORUM_ID=10

Basically, most studies indicate that of male deer that disperse - 25% do so in the spring, the balance in the fall, just prior to the rut. This explains the influx of "new" yearling bucks we see just as the hunting opens, and the "disappearance" of many yearlings we watch during the summer months.