Most commercial baits are registered for rats and mice, although level of susceptibility to the toxicants, as well as the attractiveness and palatability of the bait formulation varies between the species and even between individuals of the same species. No rodent bait ingredient is universally highly acceptable, and regional differences are the rule rather than the exception. Bait Selection and Formulation Contrary to popular belief, rats prefer fresh, high-quality foods and will reject spoiled or inferior food items when given a choice. Usually corn, oats, wheat, or barley are the grains most preferred by commensal rodents.
Preference varies between rodent populations and among individuals.
Baits similar to foods that rodents are accustomed to eating are often a good choice, particularly if their normal foods are limited or can be made less available to them. Baits are then checked during the next few days to determine which foods are preferred. Rodenticides are available in various formulations. These packets keep bait fresh and make it easy to place baits into burrows, walls, or other locations. Rodents will gnaw into these bags to feed on acceptable baits.