A great way to train a dog to let you know when he needs to go out is to get some bells (those sleigh bells they sell at Christmas time work beautifully - or any other bells that he can jingle with his nose) and tie them to the door handle of the door you use when you take him out. Every time you take him out, make a point of jingling the bells. Encourage him to nudge them with his nose as well to make them ring - then take him out promptly. It will take a little while, but he will eventually understand that when he rings the bells, he goes outside.
My question is - how long of a walk do you take him on in the morning? Maybe you'll need to add some games of catch or just running around playing "I'm going to get you" to seriously tire him out. Consider doggie day care a day or two during the week - or have a pet sitter (or, as it's summer, a neighborhood teenager or something) come walk him 2-3 times a week while you are gone.
Kongs and puzzle boxes are also good. Anything to stimulate his mind. I freeze kongs filled with peanut butter and it takes my dog about an hour to work through one.
Christine
Life is not measured by the number of breaths we take, but by the moments that take our breath away.
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