Siamese attacking my other cats/dog

Question
I sure hope you have any answer for my proplem.  I just
adopted an 8 mth old siamese female 2 days ago and today
she has attacked my dog and l cat and growls at them
all.  I have 4 male cats and l female dog. It seems to be
a vicious attack, she keeps jumping a them until I break
it up. They were all mellow until this happened.  
ANY HELP?

Answer
Joanne,

Introducing a new cat "cold turkey" will often have this effect.  A couple of things to keep in mind are that any human interference in how cats inter-relate with each other is generally counter productive.  Also, we poor humans have no idea how cats truly inter-relate to each other.

So, what to do.  One, if the female is not spayed, have that done immediately.  We are full into breeding season in the Northern hemisphere, and her hormones may make her more aggressive.

Cats and dogs have very tough skin, so the cat is not really going to hurt any of the other cats.  They may make a lot of noise and even loosen up some fur, but that is about all that will happen.  It is best if cats are left to their own devices to figure out how to get along with each other.  The only thing the dog needs worry about is that cats do have sharp claws (unless you clip them every other week) and so can intimidate a dog.  It is crucial that the cat have somewhere she can go to get away from the dog who is naturally curious about the new arrival.  If the Siamese has never seen a dog before, she is probably frightened of the dog.  When cats are frightened they seem to "attack".

You also need to give this weeks, not two days for everything to settle down.  With time there will be a new dynamic established for all the pets which may or may not be as peaceful as you would like.  Humans cannot control any of this, and so should just stay back and let things happen on their own.

So, as counter intuitive as it may seem, I would suggest gritting your teeth and let them work it all out amongst themselves.  Ignore the noise (some of the "fighting" may turn out to be play), do not interfere in any way.

Hopeful signs will be things like the cats playing chase, even if it ends up in a noisy "fight". You might consider having another litter pan in another part of the household as cats can be very territorial about litter pans.  If they are eating off common food dishes and will share the litter pans, these, too, are hopeful signs.

Please let me know how it goes.

Best regards... Norm.