Cat

A working cat is an ordinary domestic cat that lives around the buildings and growing ground rather than in the house, is fed and cared for there, and hunts the rodents that cross its patch. The job it actually does is smaller than the job it is usually given.

Extension sources agree that cats and other predators do not control an established rat population, and a standard manual on rodents in stores does not list cats among the control methods at all. What holds rodent numbers down is taking away their food and their way in: a store swept clean of spilt grain, a metre (3 ft) of clear floor around stacked bags, weeds and rubble cleared from the perimeter, and every opening wider than about 6 mm (a quarter inch) closed with metal or hardware cloth, since a rat squeezes through 12 mm and a mouse through 6. Against that programme a cat works at the margin - discouraging casual reinvasion of a store already clean and sealed, and taking mice and voles in the open ground around it.

The same instinct that catches mice takes birds and small mammals in very large numbers, and a fed cat hunts just as much as a hungry one, so feeding it protects nothing. That puts it at odds with anything built to gather the small wildlife it hunts - a bird bath, a frog pond - which have to be sited well away from where the cat is fed and sheltered. Left unsterilised it stops being one animal and becomes a breeding colony, so sterilising it is the decision that keeps it a working animal. It also needs rabies vaccination, parasite control, food, water and weatherproof shelter; it is not self-supporting, and going hungry does not sharpen its hunting. It can pass on toxoplasmosis and rabies, so its droppings are not a fertility input. An outdoor working life is short, commonly four or five years against the far longer span of a cat kept indoors.