Rats and certain other vermin are difficult to kill with poisons because their feeding habits reflect their place as scavengers. They will eat a small bit of something and wait, and if they don’t get sick, they continue. A good rat poison must be tasteless and odorless in lethal concentrations, and have a delayed effect.
There are several types of rodenticides available. The traditional products are called anticoagulant rodenticides and are discussed here. If one intends to use a rodenticide we encourage you to choose this type over others as there is a readily available antidote for the anti-coagulant rodenticides. Other rodenticides are more toxic and no antidote is available.
In 1921, ranchers were dismayed at the sudden onset of lossage in their herds due to a strange condition: the animals bled to death. Small cuts failed to heal. The roughage cows eat will scratch their digestive systems, but unlike the normal case where such scratches are minor and readily heal, these scratches failed to heal and the animals died from internal hemorrhaging. What seemed odd was that the animals were being fed hay from fields that appeared not dissimilar from that of...