Season starts oct. 1 here and I start grunting at bucks immediately if I can see them. You kind of go by thier reaction then. If they stop and look or take a few steps give it to them again in the same tone, if they ignore you give it to them again more aggressive. Once they start coming let them come until they stop or change course.
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I like to start rattling around Oct. 20 or about two weeks before rut starts. Bucks are battling for territory then and does are not quite ready.
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I will switch to esterious can call and buck tending grunts during rut and have had good success with both. If I have a buck in site I will can bleat at it ( this has worked best) if he ignores it I will bleat again and give some tending grunts this usually at least gets his attention. Then just go with what he seems to like.