While we're on the topic, some Caribbean and Central American ports definitely have sniffer dogs when you get off the ship. On my last umpteenth stops in Cozumel they've been there, and passengers are required to lower any bags to the dogs' level so they can smell them.
On some lower tier cruise lines (e.g. Carnival) it's shocking to see the amount of food, especially whole fruit, piled in the trash cans or on the tables after it's been found by the sniffer dogs.