Dear Dr. Fox:

About four years ago, my husband and I adopted a 21/2-year-old Jack Russell terrier/whippet mix, Zero, from the Humane Society. He apparently had been abused and, initially, was extremely fearful of my husband.

By now, he is quite obedient (he comes when called, obeys "sit" and "down") in the house, but if he gets away from the leash outside he gets very aggressive, tries to protect us and, in the process, has bitten several people. Outside, he is also not approachable and runs away when we try to catch him. It seems his entire personality changes when he is off the leash. He also gets aggressive when someone comes to the door of our house. If I expect visitors, I try to meet them outside so we can enter the house together. Then he is fine.

Needless to say, his behavior has caused us a lot of trouble so far. I have tried training him with a trainer who specializes in behavior problems in dogs, but it really didn't help much at all. He is very good with our old cat and also loves to have our grandchildren (ages 1 and 6) around.

Do you have any suggestions?

L.N., Bethesda

Since your dog has had a history of prior abuse, he is most likely expressing defensive, fear-based aggression toward strangers. Since one behavior therapist/trainer was not able to modify your dog's conduct, I suggest you try another animal behavior expert that your veterinarian or local animal shelter might recommend. If that fails, then have your veterinarian put your dog on a trial prescription of one of several psychotropic medications that help reduce fear and anxiety or elevate the dog's mood, such as Valium, Xanax or Prozac. If this approach fails or is not acceptable to you, your dog should wear a muzzle at all times when outdoors, except in hot weather when he is very active.

Dear Dr. Fox:

Our cat (age 5) Tasi has always been high-strung and difficult. She was born with a deformed leg and, when she was old enough, we got her surgery to correct her knee and hip. We always attributed her attitude to the stress of her disability and surgery.

When two new kittens joined us, Tasi became like a devil -- always chasing them, always attacking Isu -- and began spraying and urinating all over the house. We were at our wits' end and our vet wanted to put her on Prozac. My husband and I were against medicating her, so we decided to look into alternatives. We heard about Feliway and bought a diffuser for every floor.

What can I say? She is like a new cat! She is affectionate with us and is beginning to play with Sina. She still terrorizes Isu, but it is more chasing and verbalizing -- rarely does she attack him with her claws. I think it is mainly because Isu is now twice her size and she feels the need to remain dominant over him. We can tell, within a few days, when we need to refill the Feliway diffusers because Tasi becomes mean again.

The diffusers are expensive, but I feel it is so much more worth it to use a more natural cat aromatherapy than medicating her with drugs (and the other cats benefit from the Feliway as well). After over six months of using Feliway, it is great to have four calm cats, with no urination wars and fewer catfights. I highly recommend it!

W.O., Centreville

Dear Dr. Fox:

I have three cats. The youngest two have never been outside and have never sprayed in my house. The oldest cat (12 years) used to be an outdoor cat. For many good reasons, when she was around 7, I decided I needed to convert her into an indoor-only cat. She reacted very badly to not being able to go outside, became extremely agitated, nervous and desperate to go out. She sprayed everywhere (curtains, heating vents, beds, rugs, walls, furniture, stove, refrigerator). I tried all sorts of cleaning products and deterrents, but to no avail. After several years of this, my vet put her on Valium. She stopped spraying all right, but was so drugged-out she could not move (literally) and gained a ton of weight. That was obviously not a solution.

As a last resort, I tried Feliway and it worked right away! I could not believe how effective it was. Once a week (more often in the beginning) I spritzed it on all the places she was spraying. It wasn't long before my cat totally stopped spraying and I no longer needed to use the product. When I moved to a new house temporarily, I sprayed Feliway there, just in case, to prevent any spraying that might be caused by stress in the new environment and to protect new furniture. I have since moved back to the first house and have had no need to use Feliway because my cat has been broken of the impulse. The product is expensive but worth every penny.

C.M., Kensington

Thanks to both of you for your confirmation of the effectiveness of this new pheromone product that I encourage more veterinarians and people with various cat behavior problems to use. I have no financial interest in this product, but I do advocate greater use of products that are safe, have no harmful side effects or adverse environmental consequences -- problems associated with many pharmaceutical products today.

Michael Fox, author of many books on animal care, welfare and rights, is a veterinarian with doctoral degrees in medicine and animal behavior. Write to him in care of United Feature Syndicate, 200 Madison Ave., New York, N.Y. 10016. The volume of mail received prohibits personal replies, but questions and comments of general interest will be discussed in future columns.

(c) 2005, United Feature Syndicate Inc.