Very often, I am asked to consult with a family whose mature, middle aged cats suddenly stop getting along. Typically, the cats had gotten along splendidly. In fact, they are often siblings that have been together for years. Then, chaos suddenly erupts.
One cat chases the other in a frenzied manner. The two are often separated for a few hours for safety. In many cases, the moment the cats are reintroduced, another chase ensues. In some cases, there appears to be a calm period of several hours, to even a day, then the fighting resumes.
Occasionally, the onset of the aggression is not observed, but people return to find one cat hiding under a bed, the other one poised for pursuit. There may even be a trail of urine, feces or fur as evidence of a chase.
How unsettling for a family! The victim is clearly disturbed, having lost his or her best friend for no apparent reason. The humans are distraught, needing to create barriers for safety. Many couples wind up sleeping separately, so that no cat need be alone.
Why would a cat suddenly turn on his housemate? In many cases, the aggression is redirected. Something aroused the aggressor. Since he could not get to that stimulus, he instead turned to the closest living creature. The victim could have been any housemate including a person or dog. But it seems the target is most often another cat.
There are many potential triggers for redirected aggression. Occasionally, families report that there was construction nearby, that the outside of the house was being painted, or that the window washers were there that day. Very often, the trigger is an outside, non-resident cat that comes just a little too close for comfort. Since the indoor cat cannot attack the outdoor cat, he instead attacks his buddy who is sitting calmly nearby.
Once there is an attack, further episodes may occur, even though the trigger is long gone. It seems that the sight of the victim somehow recalls the fight itself and the aggressor now attacks his housemate upon sight. At this point, each cat is afraid of the other and the aggression, initially redirected, is maintained by this fear.
In some cases, fear actually appears to be the primary driving factor for the initial fight.
If the aggressor is a nervous cat, the initial fight may be triggered when he is startled.
Many times, the initial episode of aggression follows a veterinary visit. Typically, one cat remains home and when his housemate returns from the hospital, a fight occurs.
Rule Out Medical Causes
Of course, whenever a behavior problem erupts suddenly, a medical cause must be considered. The victim may be ill, with a condition that can be detected by his housemate. The aggressor may be threatened by the change in scent or appearance of the other cat. Examples of conditions that might generate fear in a housemate include infection of the anal sacs, diabetes mellitus, renal disease and lameness.
It may be the case that the aggressor is the one who is suffering from a medical condition. Pain and neurological dysfunction are two possibilities to consider, as either could change a cats threshold for tolerating fear.
Which brings us to treatment of this challenging problem. The medical examination must be the first step. Then, once the cats are deemed healthy, the behavior can be addressed. In most cases, a period of separation is required. It is best to be conservative with this separation. It may be more difficult to reintroduce cats after a series of failures than after one single episode. In general, separation should continue for several days – even a week.
The week need not be wasted though. The cats should be allowed to roam through the house one at a time. That way, they continue to encounter each others scents. It may be helpful to rub the cats with a common cloth or soft brush, as though they were grooming one another.
After a quiet week, it is time to attempt a reintroduction. This is best accomplished through a systematic desensitization with counterconditioning. Little by little, over a period of days or weeks, the cats will be permitted to see one another while being kept safe by virtue of leashes or other barriers. It is essential to progress very slowly: Both cats should be calm at the end of any session.
Once the situation has returned to normal, remember that an ounce of prevention is the key. Learn the trigger if possible. Board the cats when the house is painted, use outdoor cat repellents, and rub both cats with a feline cologne after a veterinary visit.
Be patient. The process may be very slow, even though the cats had been best friends.