Cross posted:
rec.pets.cats, rec.pets.cats.health+behav, rec.pets.cats.misc, alt.cats

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We have 3 cats. A mother about 8 years-plus and 2 siblings aged 5
years-plus. All have been spayed. The mother was a street rescue
(after the litter) and has outdoor privileges. The sibs are strictly
indoor.

For the most part the mother raised a nice litter. After 4 were
weaned 2 were given away. A 3rd was supposed to go but didn't, so we
kept 2. Life was generally beautiful these last 5-years plus.

Mother cat would occasionally put the sibs in their place. Other than
that its been a peaceful existance. It's a small city apartment but
again, all has been well.

In the last 2 years the mother has ceased going out as much as she
used to. She's gotten used to the indoor life, or better stated,
re-used. She had been owned by a neighbor that abandoned her so after
the litter happened under the porch we took her in ourselves. She
tends to stay in most of the winter now and only ventures outdoors
when the weather is suitable - read warm and fair. As a part of that
increased indoor life we had to get her a separate litter box but the
feeding station which auto-fills has been shared with no hassles to
date.

This past week something changed.

The recessive sibling that has always been submissive to the mother
has taken to attacking her randomly. It starts with a hissing and the
fur fuzzing out and then goes into a full chase with all kinds of
howling and screaming. It's pretty dramatic. We have intervened each
time so far. It seems to happen 1-2 times a day and has been a
regular event since last Saturday. Its now Wednesday. We're puzzled
as to what might have brought this on suddenly.

Now the second sibling is picking up this behavior to some extent
whereas before she was pretty indifferent and independent.

We cannot separate the mother cat from the others all the time due to
space limitations.

I suspect that this is a dominance drama unfolding where the mother is
getting older and the sibs are exerting their dominance but the fights
that we are seeing have a look and feel of someone getting seriously
hurt.

The mother, which had previously been dominant and rather secure in
that, is now cowering and as soon as one of the sibs sees her they
attack.

Right now the mother is locked up in the bedroom but we cannot give
her food and a litter box in there (long story). We are concerned
that she is now not eating right and limiting litter box (her own)
usage.

It seems the newly aggressive sibling only attacks when she sees the
mother cat. If they don't see each other life is beautiful.
Otherwise the sib goes right into that stalking low-profile hunting
walk as if she were chasing a mouse or bird on the ground.

I'm wondering if I should let nature run its course to allow the sibs
to determine who will be dominant or if I will have to find a new home
for the newly aggressive one so as to protect the aging mother. Its a
choice we'd rather not have to make of course.

The sister sibs don't fight at all. They still play-fight or chase
each other on occasion but nothing like what we are seeing with the
mother cat.

Mother has a separate litter box and now a second feeding station of
her own at a respectable distance from the auto-feeder.

Suggestions welcome. What we know about cats is what we have learned
these last 5-plus years of direct observation.

Aside from this behavior change, all three seem normal, are
affectionate, feed and poop regularly. No exibitions of any illness.

Thanks in advance.

D.