
Hi Sarah,
I'd recommend they try and use a "swap system" with him - if this is isolated to things he picks up outdoors on walks, they should always have extra special treats for such occasions. Not just dog biscuits, something particularly tastey that he normally isn't given such as baked liver or kidneys (roast chicken, cheese and hotdogs may also work but then he may get them randomly at home ;) ). As they offer the treat in exchange for the stick, for eg, they should use a command word such as "give" / "leave" / "drop" - something which wont be confusing to other words in his training. They also have to ensure that their reactions are 100% consistent with the dog in these situations - confusion leads to poor or improbable learning in the dog.
I'd add that they also need to be firm with him - a very abrupt, sharp toned "Ah! Ah!" for any inappropriate vocal behaviour usually works.
NB I'd also check carefully with them if they have been in the habit of taking things off him - such as his food bowl - just "to check they can" :rolleyes: Often owners do this and fail to realise they are
encouraging defensive / guarding behaviour by proving to the dog that they are indeed a threat to his most valued resource.
It would probably also be useful if they could focus him on a toy which he can have for his walks rather than allow him to collect sticks (which are potentially very dangerous anyway). That way if he has a special "for walks only" toy they can carry an equally admired one or even a replica and should they *need* to remove it from him temporarily they can then operate the swap system with either the other toy or aforementioned irresistable treats ;)
HTH, regards Teri :)