Competition to breed is a must, if the ratio is unbalanced bucks see little need to fight for this right. Assuming the ratio is good rattling is an excellent trick to add to your bag. Pre rut right through to post rut can envoke results. Like most I find pre rut to work really well in combo with sparring simulation though my results have been more immature bucks then mature bucks.BTW, I usesparring the techniquein pre rutforMule Deer and it has worked pretty well. I haven't had much success with rattling Mulie's outside this tech./timeframe.
I find the absolute best time to rattle in mature deer is in the chase phase or late pre rut. While this window is small the result have been great in my area. The key to rattling is setup, I rattle deep in transition as close to the bedding area as possible - I think safety when determining where to hunt. I lalso look for structure such as small meadows, bottle necks, fencelines, etc to set up on. To the rattling itself I grind and twist vs smashing. I start out low toned and low intensity (30-45sec session), I like to add in realismsuch aspawing of the ground and raking of samplings and trees. Grunts, bleats, etc all work in combo with rattling but i make sure to not over use calls either. I wait 15 minutes between sequences and with each time I bring up the intensity and duration slightly, I also start adding in pounding of the ground at the end of the rattling sequence to simulate a deer fleeing after a loss in battle. I pay particular attention to my back door as they like to circle the wagons and have used scents placed in a half moon directly behind my location as a possible mask of my scent to a love sick buck. I will only rattle in one location for 4hour period and never back to back days. Most often then not I rattle between the hours of 10am and 2 pm.
I also have had bucks come in like a freight train and others without a peep, it is because of this that I make my self stay alert and attentive during my rattling attempts. Another reason why 4 hours is the max I have for this technique in one sitting, if i feel myself slipping I stop as i have had more then one deer make a fool out of me while calling.