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Travis complains that most people simply do not realize what attracts rats. Rich-smelling fried food left in an empty room is bait. So are dishes in the sink. So is the feeding of dogs, cats, squirrels and birds in the backyard. Among the worst offenders are construction workmen who throw away luncheon leftovers. "There hasn't been a building put up in Washington in 15 years that the rats didn't move into before the people," says Travis. "You have the exterminator working on the first floor by the time they're laying concrete on the second."
Since rats will eat anything, they should be easy to poison. But they are not. Psychologists explain that rats have two contradictory traits: along with a willingness to sample anything potable or edible, they have a deep suspicion of whatever is new. So exterminators give the rats time to get used to the sight and smell of their traps and baits before they expect results. Dogs and cats, despite their reputation, are not very effective as rat exterminators.
Arsenic, strychnine, phosphorus and thallium salts are effective rat poisons, but far too dangerous where there are children or pets. Probably the oldest of rat poisons is about the most effective and also the safest: red squill, from the ground root of a European plant. Mixed with freshly ground meat or fish baits, it is harmless to children, cats, dogs and even squirrels.
Perhaps still more potent, and still relatively safe, is the anticoagulant drug warfarin. Less than 1/500th of an ounce is enough to make an adult rat die of internal bleeding. Ironically, the brown rats' white kin in laboratories helped University of Wisconsin researchers develop warfarin anticoagulants as lifesavers for men and killers for rats.