I have common walnut “Juglans Regia” trees, that are approx 20 years old. They have nuts on every year. But when the nuts get to ‘walnut’ size, they all disappear in a few days. No evidence on the ground of any being eaten. It is as thou the nuts have been ripped off the stem, with the stem tip then keeling over and ultimately dying. The tree does not seem to mind, it puts on new growth. But no nuts.
The ‘experts have told me it must be squirrels, as opposed to any flying animals ie Jays, Magpies or Crows. This has started my quest to solve the problem. Last year it was the use of Kania 2000 squirrel traps laced with peanut butter. Must have cleared a couple of dozen.
This slowed the problem down a touch, but all of the nuts went in the end. So this year I am onto the ultimate. Clear all the overhanging branches so that a squirrel cannot jump from one tree to another, and clear all the ground scrub, to stop them jumping up off the ground.
Then wrap around the trunk some galvanised sheeting, that is approx 1m tall.
There should now be now excuses for any lose of me walnuts this year ???!!!