22 months, won't stop hitting our pets. Timeouts and talking about why hitting is mean doesn't seem to be working.

My son has started a nasty phase of hitting our pets. We have 4 cats and 2 dogs so there's constantly an animal in striking distance.What we've been doing so far:Calmly but firmly tell him hitting hurts, it's mean, makes them sad, please be nice, and 1 warning for timeoutTimeouts consist of sitting in the corner for 2 minutes with a timer, each additional timeout adds an extra minuteAfter timeout, talk again about how hitting hurts, dogs are sad, and only want to play with him when he's niceIt's been going on for about a month and the only progress we've seen is once in awhile the warning for timeout deters him. But that usually only works after he's already had a timeout or 2.I know we need to stay consistent, but what else can we do to help the situation? We don't spank and even when we play rough together we only wrestle and don't pretend to hit. I know hitting it's a common phase, but I'm hoping there's other things we can do to bring it to an end faster.Just as a side note: so far his hitting is only directed at the pets, never us or other kids. It's usually when he's bored and not done out of anger, it seems like he has fun watching their reactions. Or maybe it's fun for him because he feels dominant. Idk, but it sucks and I'm tired of it :/Edit: I'm terrible at putting my thoughts into words. Just so there's no confusion, we aren't being super soft with our warning, it's very stern and serious so he knows we aren't messing around. And we act immediately; after 1st hit we warn him about timeout and talk about why it's mean. If he hits again he's going into the corner immediately. Maybe it's time to cut out the warning and go directly to timeout. via /r/Parenting http://ift.tt/2sivTGT