Rodent Control (or, how we rely on feral cats)
We moved to this property 21 years ago and the only rat I saw was a 'wood rat', a native species with a braided tail. It attempted to burrow under the back foundation of the barn, but was discouraged by the half-dozen feral cats that lived here.
Other rats in Nova Scotia include the Norway Rat , roof rat and the Black Rat. Since the Norway Rat is the mortal enemy of the plague-carrying black rat, a certain number are encouraged around seaports like Halifax. As a result city poultry owners are at a constant disadvantage in keeping their chicken coops rat-free and must rely heavily on barriers like 1/2" mason wire. Poultry wire (so-called) is useless against rats, red squirrels, mice and raccoons. Of course some people will always blame chickens for rats.
Then, we saw only male ferals and I was told that some barns harbor tomcats and that others shelter the queens. Lately I have regarded this as hogwash because about 10 years ago a queen we lated name 'Elizabeth' (what else?) came to the barn with a litter of 4 kittens. She is still with us and in control of an intact colony of ferals including her offspring and various other cats that she allows to stay. Some of her sons are what I call 'uncle cats' and others become breeders who roam the district.
Elizabeth and her daughters do not seem to mate with their close relatives, in fact they 'encourage' other toms to hang around during the February/march heat periods. As a result we have about 25 cats on the property and seldom see a rodent. To protect the cats, we never use poison or traps to kill rodents.
It has been over six years since I have seen a living mouse near or in the barn. The cats have to travel to a property called the 'Caseylands' to hunt them. They sometimes come in off our property with a baby mole or a red squirrel that has strayed in, unaware that such a formidable guard stands over the red barn. Even when the owner of a nearby property called in an exterminator to drive off Norway rats, not one came our way. It's nice. I don't like the disease issues that rats suggest, and now that we're getting hens I assume the cats will continue to keep a clean perimeter around the barn.
I must add though that you can't expect one or two cats of any kind to rid an existing infestation of rats. I would rid myself of rats by any means possible before allowing cats on that ground or in that coop. Once that is accomplished the cats will keep all rodents away. Coop hygiene is vital in all this, especially in the storing and distribution of food. If you feed them they will come...