A package arrived the other day. I put it on the floor for the dogs to check out because I knew what it contained: a big supply of smoked cow hooves. Needless to say, they were very interested in that box.
They always, without fail, know when a package has something in it for them. And they get very enthusiastic when the UPS or FedEx truck rumbles over the auto-gate. Every package coming into the house has to go through Doggie Customs!
Dogs pretty much live in their noses. We have about six million smell-receptors, and dogs have 200 to 400-million. A smell-contest wouldn't be a fair fight.
I have no doubt that, if I hadn't retrieved the package and opened it up for them, they would have opened it themselves.