Rodenticide

Rodenticides, colloquially rat poison, are typically non-specific pest control chemicals made and sold for the purpose of killing rodents.

Some rodenticides are lethal after one exposure while others require more than one. Rodents are disinclined to gorge on an unknown food (perhaps reflecting an adaptation to their inability to vomit), preferring to sample, wait and observe whether it makes them or other rats sick. This phenomenon of bait shyness or poison shyness is the rationale for poisons that kill only after multiple doses.