Rodent devices at food facilities are typically spaced according to the standards of an auditing body, or a company’s standard operating procedures, or because “that’s just the way we’ve always done it.” Indoors, traps are usually 20-40 feet apart and exterior stations are spaced 50 to 100 feet apart. But, have you ever thought about why we do this spacing and if it’s really the best way to determine where to put your traps or bait stations?

The conventional interval spacing, described above, was established in the 1940s and 50s based on the range that rodents forage for food. Yet, there isn’t a ton of scientific evidence behind this spacing and it also fails to take any other aspect of rodent behavior or conducive conditions into account. So, a recent study investigated this conventional, standard interval trap placement to determine if there are specific building characteristics or rodent behaviors that may influence or enhance trap catches and/or bait consumption.

The researchers evaluated seven food warehouse distribution centers in New York, USA and 5 in Ontario, Canada. Passive multi-catch traps were used indoors and mouse and bait stations with rodenticide were placed outside. All facilities utilized the standard spacing of traps in the interior and then researchers noted characteristics of the building like construction and ecological conditions that would be attractive to rodents. Some examples include the dock door not having a compression seal or the bottom of the door not being rodent proof, if the device was near a product aisle, a heater source, in a drop ceiling etc., with a total of 76 characteristics used to evaluate indoor traps and 27 characteristics outdoors.

The researchers discovered that about half, (45%) of interior devices captured mice and 56% of exterior bait stations had some evidence of rodent feeding. Not surprisingly, certain structural characteristics or conditions resulted in more trap catches or higher feeding in bait stations. Characteristics that resulted in higher activity included areas with warmer temperatures, along pathways, near concrete walls, on the edges or corners of walls, near dense vegetation and in shadows. Basically, warmer areas with more cover and protection should alert someone to spend more time for inspection and be a focal point for device placement.

Moving forward, this research lends to a more assessment-based approach, where an inspection is conducted first to determine the areas that have higher rodent activity and then trap placement based on the assessment of a facility, rather than arbitrary distances. Additionally, this could result in a reduction of rodenticide waste. Almost 40% of bait blocks that were evaluated had no feeding and would have been thrown away. With a more assessment-based approach, some of the stations that were not visited could be moved in areas that will receive activity and eliminate the use of bait that isn’t necessary.

If you want more details, you can read the paper here: https://www.sciencedirect.com/science/article/abs/pii/S0022474X21000771

Frye, M. J., Gangloff-Kaufmann, J. L., Corrigan, R. M., Hirsch, H., & Bondy, D. (2021). Assessment of factors influencing visitation to rodent management devices at food distribution centers. Journal of Stored Products Research, 93, 101838.