If you go for humane traps make sure you wash your hands, and anytime
that comes into contact with the animals or traps, thoroughly. Rats
carry Leptospirosis (Weil's disease) and you can get infected from
their urine - rats are pretty filthy animals. The risks are low but it
can be fatal.

For more info: http://www.caving.org.uk/wdic/

Rats occupy territories between 50 and 100m in diameter. Once you
remove one animal, another will move in. Given the number of rats
around, you can expect to continue your control methods ad infinitum.

Moving the feeders away from cover and keeping them clean would appear
to be the best approach. If any rat is adventurous to venture out into
the open to get to the feeders then any friendly neighbourhood owl or
cat can take care of the problem.

Stuart
--
Stuart MacKay, Seattle, WA, USA