ORIGINAL: GMMAT
75 acres is a decent bit of land but by no means is it huge. I think the answers (your bucks) could be found in that 230 acre sanctuary?
But how would you account for seeing them one year and not the next? The property hasn't changed.
True, but the bucks have. As bucks grow older they grow smarter. They may recognized that your 75 acre tract of land as being hunted (it just takes the lightest bit of pressure for a buck to realize he is being hunted) and reverted to the sanctuary where they obviously felt safer.
Did you get any trail cam photos of these deer or still photos? Did you just not see them while hunting or zero sightings of these bucks period?
I'm still stumped. Out of 16 bucks I think you would have ATLEAST seen 2-3.