I wonder what the policy for keeping pets in Starfleet is? I know Data had Spot, Zack Kebron in New Frontier has goldfish, and the like. I suppose it depends on the ship, the captain, and the policies thereof, at least canon seems to establish that.
I ask because a Voyager fanfiction character I'm writing had a dog at his last post, an American Staffordshire Terrier, when he was based near the Bajoran frontier on a starbase. He obviously didn't take his dog on the mission, but he does have one.