I have a 3 year old cat, Sam, that does the same thing to my 12 year old, Kitty.  Kitty
was a lap cat when I took her in at 4 years old but since Sam has been here she mostly
sticks to the bedroom which is her territory because if Sam sees her out he is right after
her. He can be sleeping and sense her being out and away he goes.  If Sam goes in there
while chasing her she will stop once there cross the door and she will chase him back out.
He knows he is doing wrong because if I tell him "Sam - no" he will set and just look at
me. But once he starts the chase forget stopping him !!  Bad thing is that the other 3
year old, Rascal, and the 4 year old, Margie, have picked up Sam's habit.

I have tryed squirt bottles, load noises, me chasing the others, throwing one of their
small soft toys in their direction to distract them, ETC.  It may stop them that time but
the next time Kitty comes out and they (Mostly Sam) see her off they go again.  I finally
gave up and told Kitty that she will have to put them in their place.  She does if they
chase her in HER bedroom but not otherwise.  GO FIGURE !!

http://users.ameritech.net/lestark/

Hi Ed,

Before you remove the aggressive cat, do give it some more time. It can
take a full year for them to get things worked out (cat time). I have
two and one is definitely the alpha and she can do some chasing from
time to time. We had a rather terrible introduction time, but now at 2
years together, they are really very good friends. While there is an
aspect of letting them work it out - at 10 months, you should be
enforcing that you don't want the aggressor chasing the other two. In
addition to verbally scolding (which has no actual consequences for the
cat), try addressing each incident that you witness with a prompt
timeout in the bathroom. When a cat is chasing and pouncing, the last
thing in the world it wants is to be suddenly contained and if the cat
understands that is going to happen (for 15 mins or so), then it may
rethink
the wisdom of setting off after his roommates. The key, as with any
discipline, is consistency and doing the time out every time it
happens.

The other issue may relate to space inside the home. Does each cat have
a few places of it's own to sleep and hang out? Or are they competing
for a small number of spots? Sometimes an extra cat tree, or a few
kitty beds tossed around can greatly increase the amount of usable
space in the home and take some of the pressure off. Add another cat
tree, if you can manage it. It, combined with the time-out training,
might make all the difference in the world.

Good luck!

Tracy