There is a considerable size difference between rodent bait stations intended to control rats versus those designed to control mice. Is it OK to only use the larger of the two bait stations to control both rats and mice?

Rodent bait stations are specifically manufactured in different forms and sizes in order increase their appeal to the rodents they are intended to control. For example, larger stations designed for Norway or roof rats have a wide entrance and large internal compartment to accommodate the rats’ bigger body size. Additionally, they can house enough bait for multiple feeding rats to consume a lethal dose of the product. The reduced size of mouse bait boxes encourages feeding by providing mice with a smaller compartment that mimics a natural feeding location. Their smaller size also facilitates placement in tighter, more cluttered sites where mice are most likely to forage. So, while a larger bait station may provide equal access for both large and small commensal rodents, it may not encourage feeding equally across species. Therefore, the appropriately sized bait station should be used for the target pest to ensure that you maximize the effectiveness of your rodent management program.

I have been battling a mouse infestation inside a pet food store for months and I don’t seem to be getting control.  I think it’s because they are feeding on dog food that has been fortified with vitamin K and it’s counteracting the rodenticide bait I have been applying.  What do you think?

You are correct; vitamin K1 is a treatment for anticoagulant poisoning.  Vitamin K1 is the preferred method of treatment for poisoning with anticoagulant baits, since vitamin K3 is not as effective at reversing the acute effects of anticoagulants. However, the levels of vitamin K in processed pet foods are typically not high enough to counteract the effects of anticoagulant baits.  At best, increased levels may slow the onset of lethal symptoms, but the end result will be the same.

I do suspect however that the rodent’s diet may have something to do with the challenges you are encountering with your control efforts.  The abundance of competing food sources may be limiting the effectiveness of your baiting program.  If you haven’t done so already, make recommendations to your client about promptly cleaning up spilled food.  If they don’t already have a deep cleaning schedule, suggest that they develop a plan to periodically disassemble shelving and clean food debris that may have become hidden inside or underneath.

Additionally, you should consider a trapping program to “knock down” the population quickly.  Traditional snap traps are one of the most effective ways to remove large numbers of mice in a short period of time.  Consider placing multiple snap traps in all of the areas that droppings or mouse activity has been observed.  In public areas of the store, you may need to wait until after hours to place the trap then remove them early the next morning.  Remember to use plenty of traps.  If there are 100 mice in the account and you only place 50 traps, the best you can do is catch 50% the first night.  You might also consider baiting the traps with non-food items that might be attractive as nesting material like a small bit of yarn or a cotton ball.  As for food baits, try using their normal food (dog chow) and some novel baits, like chocolate, peanut butter or anything else that the mice may not have encountered recently.