Poison shyness - a behavioural phenomenon observed in animals.
When pest control (by means of poisoned baits) is in use some animals (insects and mammals alike), which previously ingested sublethal doses of poison can subsequently detect and therefore avoid these poisoned baits in the future.
It is believed, that the animals can make the connection between the odour of the toxic substance (released partially by the chemical processes occurring in food) and its toxicity - this allows them to detect and avoid the poison next time. In order to prevent this, a special form of poison is used. Namely, the chemical compound is not toxic as such and it is odourless. When the food is ingested, the active component is transported to liver, where it is in vivo oxidised to a toxic substance, which then kills the animal. With such a solution the animal cannot make the connection between the smell of the food and its toxicity, hence prevents occurring of the poison shyness. [1]