Your cat is showing his gratitude towards you by bringing you whatever
he catches ....

the only thing that is going to keep your cat from hunting is to keep the
cat inside.  There are bells and whistles and collars and doodads that try
to prevent it, but the cat is a smart creature, and will find a way around
them.

I have a feeling though that keeping the cat in is not an option for you.
You might want to close off the cat door in that case, so you have to let
the cat in yourself, and you can check to see if he's coming home with a
present for you

Just a couple of observations and speculations.

The mice that the cat kills are mice that don't manage to get into
your house.  I keep a number of indoor/outdoor cats that keep my home
free of mice (it was infested when I moved in) - yes, sometimes one
brings a mouse or other prey inside, but they almost always kill and
eat it.

I can understand how cats might have evolved through unintentional
selection by humans to bring their catches in to show off.  For
thousands of years, people kept - or barely tolerated - cats because
they kept the mice down and helped preserve the human food supply.
Over these thousands of years, every few years the local pupulations
would have to be culled (this is still true for farm cat pupulations),
and the humans doing the culling would tend to prefer the cats that
they thought were the best mousers, and those would be the ones that
they saw most often with mice, that is, the ones that brought mice to
show to the humans.  A relatively poor hunter  that showed all its
catches to the person doing the selection might well have more of its
kittens survive to breed while the ones that killed more mice but were
not seen doing it had most of  their kittens culled.

T.E.D. (tdavis@gearbox.maem.umr.edu)
SPAM filter: Messages to this address *must* contain "T.E.D."
somewhere in the body or they will be automatically rejected.