We've inherited a Jack Russell pup, he's about 7 months old.

He can't sit. Or stay. Or even respond to his name (his old name, or the new name we've given him). He's basically been left in a backyard/small enclosure alone his whole life. It's really quite sad.

We've taken him on for this week (DH is keen to keep him).

How do I whip his butt into gear? He's done a bit of barking today, which is a HUGE hate for me. I can't stand yappy dogs.
He's come inside a few times. He was great with my parents dog (a 12 year old jack russellxshi tzu x maltese).

If we are going to keep him, what should I know?? He's a pure-bred, but he has no papers or anything.

Also, he's trying to mount everything. It's gross. He doesn't understand 'No' or a firm voice so he just keeps coming back for more.

I know Jack Russells need intense training and it's so sad to see this dog who can't do anything.

He was a hyper little thing when we got him last night and we've taken him on a huge walk and he's alot better. He has tons of energy.

The last thing I wanted 5 months before giving birth was a puppy, but we've saved his life.