Waiting for Brown Rats to show themselves can often mean a long and cold wait so take something to sit on and wear warm clothing.
Use baits with a strong aroma or flavour. I find that flake chocolate draws them in and they can't carry it away. Apples are also favoured by Rats, use Apples whole (can't be carried away) crush small amounts to create an aroma. Try cat food such as the tins with peel top lids (do not leave the tin on the ground). Basically Rats prefer anything that is fresh in preference to old and rotten .
Brown Rats have keen hearing, smell, taste, and touch, but poor vision, and they are also colour blind. The adults are nocturnal and like to explore, but they are cautious and shy away from newly introduced objects .Young Rats will often venture out to find food during daylight hours.
Stay motionless as rats will bolt at the first signs of movement, so it is essential that the rifle is pointing almost directly at the place you expect the Rats to emerge.
Place any bait along regular 'runs' and in such a position that the rat has to expose all of its body to get at it. Generally about one or two feet from any rat hole - this way any rats hit but not killed cleanly will not be able to get to cover before you take another shot
Do not handle dead Rats, use a shovel or stick to remove them.
Diseases carried by Brown rats:
Salmonella..carried by all rodents.
Trichinosis..Pork roundworm. Initially the worm lodges in the intestines, but the larvae may invade the muscles to form cysts that are often resistant to drug treatment.
Rat Bite Fever...Murine Typhus spread by lice on the animal, they die of it, but not before they have passed it on.
Hantavirus.. Pulmonary syndrome (HPS) is a deadly disease transmitted by infected rodents through urine, droppings, or saliva. Humans can contract the disease when they breathe in aerosolized virus. Although rare, HPS is potentially deadly. Rodent control in and around the home remains the primary strategy for preventing hantavirus infection.
Weils Disease...Leptospiral Jaundice(Leptospirosis). Symptoms are flu like, with a severe persistent headache and if you think you have been in an area where there are rats, then you should seek immediate medical advice. Affects the liver and kidneys.Needs early treatment.