I have two 16-week-old Yorkies Grizzly & Scruffy. Grizzly will start barking and howling immediately when he notices he is left alone. Scruffy usually does just fine being alone.

For example, we were all in the same room and Grizzly was playing quietly in his open crate while Scruffy was lying in their dog bed. I needed to get up to go to the other room and take Scruffy with me, and he started whining, barking, and howling almost as soon as we were out of sight. He's usually ok as long as his brother or I am in the room with him, but he can't stand us being out of sight.

I also just left the room for a couple of minutes in the same situation, but I left Scruffy lying in his dog bed, next to Grizzly playing quietly in his crate. I left the room quietly for a few minutes without saying anything and they remained quiet. When I returned I found Scruffy had moved into the crate and snuggled up next to Grizzly. Then when I sat back down, Scruffy returned to his dog bed.

I know I need to start correcting this immediately by increasing the separation time and rewarding him when he's calm, but I'm looking for tips or a good reference for how to do this most effectively. Otherwise, I'm going to have to rename Grizzly "Howling Woof".