"Why is this cat growling and hissing at me??"

It’s always very hard to help with behavior problems at a distance. But based on the cat "hiding" under your bed and hissing at you, I’d say it’s simply scared. It certainly sounds like the cat is displaying fear aggression.

Why the cat would be comfortable and trusting with you when it first entered your home but then changed, I have no idea. One possibility is that your cat and this cat have met (while you were sleeping?) and it didn’t go well. But whatever the cause was, since you’ve got to deal with the situation for three more weeks the best suggestion I can give is ignore the cat as much as possible. Give it space and hopefully, with time, it will adjust to its new surroundings.

If you attempt to interact with it the cat is likely to interpret this as aggression on your part. So the best thing to do in these situations is to try to ignore the cat.

Cats can interpret an unblinking stare as aggression. (If you've ever seen two feral cats meet they will often start by simply sitting and staring at each other. Each is trying to intimidate ... stare down ... the other.) Try not to look directly at the cat or look at it through half-closed eyes. Slow blinking is also said to help relax a cat. (Hey, it's worth a try, no?)

Make sure food, clean water, and especially a litter box are available in your bedroom. Move anything the cat might damage, for example knick-nacks on a dresser that might be damaged if knocked to the floor. Then leave, close the door and let the cat be. If you have a radio in the room you might consider leaving it set at a low volume to a local classical music station. Check the food, water, and litter once or twice a day, but otherwise just give the cat space so it feels secure enough to calm down.

If you’ve got a studio apartment then I’m not sure what to tell you other than to try to partition off an area in it where the cat would feel safe to come out for food and to use the litter box. You can sometimes fashion something ugly, but adequate enough from large cardboard boxes thrown out by supermarkets and other stores.

Here’s a link to the brochures web page at the Cornell Feline Health Center. It’s possible that their Feline Behavior Problems: Aggression brochure may have ideas that are useful to you.

Good luck and please let us know how this turns out.

pet him when you first brought him into your house was more than likely because Money didn't realize what was going on.  I suspect he knows you from your friendship with his owner and at first was startled when brought into your home but because he is familiar with you did not make a big fuss.  But then you left for awhile and Money is wondering where he is, where is his owner and can smell the presence of another cat.  He hides under the bed because it is dark and safe to him.  He is telling you to watch out by the growling and hissing because he is afraid and very stressed. 

Just be patient with Money.  Make sure you leave food and fresh water out for him every day.  I would not try to force him out from under the bed as this can traumatized him even worse.  When he gets hungry enough I believe he will come out.  I'd keep my other cat away from him for now also.  They may fight if brought together.  It wouldn't hurt to just sit in that room and talk to Money (or yourself) so he can hear your voice and that may eventually bring him out from under the bed also.

If Money and your cat have not interacted at all, then my guess is that Money has gotten sick. The sudden hiding and growling often indicates that the cat is feeling lousy, and is in pain. He could have developed a urinary tract infection, or pancreatitis, or many other problems that can come on rapidly. Ditto with the not eating. Please take Money to the vet as soon as possible, and have him checked out.

On the other hand, when you say that Money and your cat "haven't really met yet", if there is any chance that they interacted unsupervised, like while you were gone, then Money may be hiding and growling out of fear and/or anxiety. It really doesn't matter that your cat is female, or even who is the bigger cat; if they tangled, and Money lost, it could explain the radical behavior changes. After all, your house is *your* cat's territory, and cats often take offense when a new cat encroaches on "their" area. If you are sure that Money is not sick or in pain, you might try moving him to another room, with a soft bed or pillow and his own litter box, food, and water, and see if his behavior improves. Be sure that the door to the room stays closed at all times, so that your cat can't get in there. The closed door will probably make your cat crazy for a while, but she will get used to it. Make sure that you spend time with Money in "his" room, and try to entice him into playing with you, using a cat fishing pole, a piece of string (but be sure to put it away, so that he can't use it unsupervised), or some other interactive toy. If it is a fear or anxiety reaction, you should see improvement, once Money figures out that he is in a safe environment. Keep in mind that being in your house is already stressful for Money, especially since his owner has disappeared on him, to his way of thinking.

I hope this helps!
Katherine

Da Bird is a *great* interactive toy; it makes a humming noise when you twirl it in a circle that drives cats bonkers! Beware of imitators, though--it has to be a genuine Da Bird!

Maybe the person that had the cat was mean to it and it was abused.  See if your vet knows anyone who deals professionally with these problems, there are some.    Also I had to baby sit a friends cat for two weeks and never saw it.  The food was gone and the littler box was full each day I came back (twice a day)  Some cats are just afraid of new surroundings be patient and keep it in a room by itself until it can get adjusted to new surrounding's.  Sometimes it takes a long time like a month or two.  Don't give up the kitty may turn out to be your best buddy. Your big and it's small.  Scampie