Posted on November 16, 2018 by Dr. Dale Rubenstein.
Has this ever happened to you? You bring Tiger in for his annual exam, but when you get home and let him out of his carrier, your other cat Fluffy suddenly hisses, growls and swats at Tiger. Normally they’re best friends! And they were just snuggled up together two hours ago! Now they don’t even know each other. What happened? This sudden aggression between cats in their own household is actually quite common.
Veterinary behaviorists call this phenomenon “Non-Recognition Aggression.” Whether this is labeled as a type of “territorial” or “redirected” aggression, all you know is that your cats now can’t be left alone. But let’s try to understand why this occurs, and what we can do to keep the peace in our 4-legged families.
Cats recognize by smell, not sight
When Tiger and Fluffy act like they’ve never seen each other before, you are surprised. Tiger doesn’t look any different than he did an hour ago. But cats don’t really use sight as their main means of recognition, they sniff each other. And because the sense of smell is so important to cats, when the scent normally associated with the cat who was out of the house changes, he suddenly becomes a threat. Maybe alcohol was used where he had a blood test, or a staff member was holding him for the exam. Suddenly the returning cat is no longer Tiger but some different, unknown cat, possibly dangerous.
Fluffy doesn’t know how to respond directly to the threat or fear she smells, so she lashes out at the nearest substitute, which is Tiger. On the other hand, Tiger can’t respond directly to his own fear from his experience out of the house, so he takes it out on Fluffy. The cats react aggressively toward each other, sometimes for an extended period of time.
Warning signs of aggression include flattened ears, staring, growling with hitting/swatting or attacking the other cat. Dilated (fearful) eyes and raised hair along the back and tail (“Halloween cat”) may also be observed.
The best step is to separate the cats as soon as possible. Allowing them to “fight it out” may lead to extended inter-cat aggression in the household. Hopefully you only need to separate the cats for a few hours. But in some cases, the separation needs to be days to weeks.
If one cat was anesthetized for a procedure, you may want to keep that cat in a separate room overnight. This allows for a full recovery from anesthesia, as well as a chance to take on “home” vs hospital smells.
Reduce stress to reduce changes in smell
At A Cat Clinic, we try to make your cat’s visit as low-stress as possible. Lower stress handling means fewer fear or stress hormones and somewhat limits the change in smell. A stressed cat may also express its anal glands, which are on either side of the anal area, similar to the scent glands in skunks. This smell will further antagonize the other cat, worsening their already tense interactions.
If your cat is prone to anxiety during visits, we recommend giving a safe medication, Gabapentin, prior to bringing your cat to us. It may help to use Feliway ® spray or wipes in the carrier. If possible, get your cat used to the carrier and riding in a car well before your visit. This can be tough for many of us, since our indoor cats may only ride in a car a couple of times per year.
If all else fails, start over…
If the sudden aggression between cats does not resolve quickly, you need to view the situation as if you were introducing two cats who have never met before. Keep them separated. Rub towels on each cat, then swap towels, so the cats can get used to the other cat’s scent. Feliway diffusers, spray or calming collars may be helpful. Some behaviorists recommend swapping litter boxes.
And, if the situation does not resolve within a couple weeks after using the above suggestions, we would recommend scheduling a consultation exam. Dr. DeBernardis has a special interest in feline behavior and with guidance and sometimes medication, we will work to get your two cats back to being family!