I think I have read someone before that the mature does are the ones that typically have twins or sometimes triplets which increases their odds of producing bucks. The yearling does are more apt to only have one fawn which reduces the odds of producing bucks. Some people believe it is best to shoot yearling does instead of mature does, but obviously if you eradicate your yearlings does, your number of mature does in the future will dwindle. So I think I agree with the biologists, don't target any one age group.