RE: When the mast crop fails..................
Deer will eat just about anything.....the trick is finding their " preferred" food. Deer have been living through mast failures for thousands of years....they are the masters of adaptation.
Apples, twigs, leaves, bark.....if they can reach it, chances are they can eat it.
Some of the more interesting things I have seen deer eat.....last year I watched two does eat a strip after strip of greenbriers....I guess the thorns didn' t bother them. Just a few weeks ago, I watched a small buck take care of my poison ivy problem.....the pickets on the one side of my property have been cleaned off better than any herbicide could do. Over the summer I saw two deer standing in the middle of an old pond....you could see them sticking their heads under water then coming up with a huge mouthful of algae. Look like something you would expect a moose to do!
At any rate...suggestion would be to figure out where they bed and fan out from there....bound to be a food source somewhere nearby or the deer wouldn' t be there.
Good luck!