Rats live in colonies. You need to have enough bait to totally control their numbers otherwise due to their short gestation periods of 18 – 23 days their numbers would grow back as soon as the bait is out. Bromarat kills them after 3-4 days post consumption and this is deliberate to enable you eliminate the whole colony and avoid bait shyness. Keep checking the bait station and add Bromarat to the station as per consumption.