What can cause rats to become bait shy?

Rats can become bait shy when they consume a sublethal amount of acute poison because this can lead to a negative association with that particular bait. When rats ingest a toxic substance, even if the amount does not prove fatal, they may experience discomfort or illness as a result. This can condition them to avoid that bait in the future, as they associate it with their unpleasant experience. Bait shyness is a defense mechanism aimed at protecting the animal from potential harm, as they learn to avoid foods that have previously made them feel unwell.

In contrast, the other options deal with factors that may not necessarily lead to the development of bait shyness. For instance, a dislike for the taste of the prebait indicates a preference issue rather than a learned aversion from a negative experience. Similarly, consumption of multiple dose rodenticides or anticoagulants over several days may not cause immediate rejection of the bait, particularly because these substances require continuous feeding for effectiveness, and the rat may not make the connection with harmful effects immediately. Therefore, the most compelling reason why rats develop bait shyness is the negative experience associated with ingesting a sublethal dose of poison.