A cat falling to the floor PROBABLY means that it sees the pup as harmless at the moment, and even a potential playmate. My cats do this when they want to play with each other in a lazy kind of way. So, without seeing exactly what's going on, I think the flopping over could be a good sign as far as your cat goes - perhaps he's getting used to the idea of the puppy - if it is infact playing out like I see it in my head! If he was REALLY worried he'd stay totally out of sight, or get his claws out.
However, of course you don't want your pup to continue the way he's going, you don't want him to learn that chasing the cat is EVER fun. Maybe a little bit late! But lets do what we can now
First of all you'll want to teach a 'positive interrupter'. When you shout NO! it means precisely nothing to Archie
What you want to do is teach a noise that cuts through his excitement and makes him think "BOY something fun is about to happen right over there where Mum / Dad is!" Here's a tutorial on how you can do this:
http://www.youtube.com/watch?v=TBvPaqMZyo8
Now, you don't want to use this when he IS chasing, because he literally won't be able to hear it - all his senses will be fully focused on the cat. What you want to do is use it when you see his ears perk up and start
thinking about the cat. Do you know the look? I certainly do with mine! She thinks she's the Cat Cop
I would strongly, STRONGLY suggest you couple this with putting him on a training lead on a harness for the whole time he's around the cat. Prevention is going to be a really strong factor here - if he NEVER gets to chase the cat, it's NEVER fun, it's NEVER rewarding. If he DOES get to chase the cat he's only going to get better at it and find it more and more fun! This won't be forever, but if you lay some really strong groundwork here, it will stick for life and the time invested now will pay dividends later
I let my puppy 'play' with my little blue cat, as she's a very motherly cat and always sought out my puppy.... but now the puppy just thinks that she's the greatest elicit toy. I really wish I'd spent more time and effort separating them, so that my puppy had not learned this behaviour, because now I cannot leave them alone together.
Having a house line on can also help diffuse other puppy behaviours, eg. it makes it easy to pick up the lead and move your pup away from whatever naughtiness he's getting into without having to have any confrontation. And, knowing puppies, there's a lot of naughtiness to get upto
Finally, make sure you've got all the obvious things in place... eg. places that the cat can be out the way. Mine have a tall cat tree, and they've got shelves especially for them on my bookcase, little dens with only enough room for the little blue cat to get into, and get their food ontop of it out the way, so it's not tempting for the dog to get to their food. The latter part prevents having a flashpoint for your two creatures too
You can also install baby gates that the cat can get over but puppy can't (assuming it's an agile younger cat!)
Hope this helps.
[edit] I forgot to add! It is also REALLY REALLY important to make sure your pup has loads of mental stimulation. This is probably the most important thing! If he's chasing the cat he's making his own fun. If he's whacked out from playing games and puzzles with you all day long he doesn't have to make his own fun
See our 'exercise the mind' thread for some great ideas that don't necessarily mean you have to be playing WITH him (eg boxes with food in for him to puzzle out) and also it's a great idea to take up clicker training, it's fun for both of you.
