FBG, get/borrow a game camera. They are motion activated and will take a picture of you unwanted guest helping themselves to your berries. You never know just what you will see on there. I saw a news clip last year where someone put one up just to watch their back yard and here they caught a thief cleaning out their house a few days after it was put up.
Miss Jane's idea struck me as a lot of fun. Along with the No Trespassing signs, we will be posting WARNING; Experimental pesticides in use. Consumption of fruits and vegetables may cause serious illness and/or death. Symptoms may take months to manifest themselves. Have your doctor contact Monsanto and the CDC.
I don`t think I would put that "serious illness and or death" line,, just in case the neighbor read it and scared him so bad he had a heart attack or something !! Try saying they had an experimental dye added that will cause the tongue to turn blue or purple and will be permanent without an antidote !!
FBG--You could go to your various neighbors and explain what happened (raspberries disappeared) and ask folks if they saw any animals or strangers in the area and specifically in your yard. If the culprits are human, that may give them pause before doing it again.
Some one stole two 6ft Norfolk Island pines from my front porch, (You have to cross a serious drainage ditch to reach my porch) I now have a pack of dogs (6) and what ones does not hear the others will. I say its my alarm system going off.
