about deer repellents.

I am about to invest in The Deer Fortress. I've used sonic repellers in the past.
But as the summer progresses, the deer "learn" and don't run away from them.

We are up on an island with mostly rocks. I feed the deer and provide salt, they swim over and bring their fauns. Some give birth on our island too. But there is not much forage for them. When the fauns are bigger they swim back and forth more. I put out feed, but of course it is never enough. And this year the corn situation will be tight. I might have to do sunflower only with rabbit pellets.

I have two big urns near our dock (on both sides) and some flowers
along the dock. I thought a non-smelly intervention might work. We sit there alot and it cannot be offensive. These fortress thingies may work..I could put in the planters?

I also keep things on the porch where they cannot reach. Those are safe.

The first picture is our porch... the deer do not get high enough to eat these, and are too bashful to walk up the narrow steps etc:

Second pic is the old dock, we don't use it anymore as a dock..but as a
deck of sorts. The large planter is right behind these toonies. The deer walk along the shore and eat them.

3rd pic... these are portable planters which we put up on the dock at night,
but a deer came by surprise and got them too last season! (I have 6 of these and usually some seedlings in flats). The deer didn't bother with my seedlings,
but she loved the gazanias!

So the things I want to keep safe are concentrated in one spot, and not a large area by any means.

So do you think the "fortress" things will work?
http://www.deerfortress.com/about.php