They're still pups. Saying that though, alot of people mess dogs up in pens. Even pens as big as 40 acres, dogs get accustomed to running sign and finding hogs within a period of time or a distance and when you get them in the woods they expect the same, so theyll quit sign alot of times because they dont know any better. In your case let the pups hunt and keep em in the woods.
X2 if you want huntin dogs put them in the woods if you want pen dogs keep them in the bay pen