[Vertebrate Pests] The house mouse: The perfect stowaway, part II

Wouldn’t it be so cool if somehow we were able to get an accurate measurement as to how many mice actually enter commercial buildings from the outside beneath doors or via structural gaps and holes, compared to how many mice arrive as stowaways within incoming items and supplies?
Practically speaking, this question is impossible to answer — at least an answer that is representative of the entire commercial sector. Nevertheless, there are plenty of real-world occurrences and observations to confirm that we know mice arrive in many urban structures as stowaways on a fairly common basis.
And as discussed in last month’s column (see “The perfect stowaway, part I”), we cannot completely prevent mouse stowaways from periodically arriving at those operations in which hundreds, even thousands of items, arrive every week from a multitude of places. These include warehouses, supermarkets, retail stores, restaurants, shopping malls, large hospitals, and mega-office buildings to list just a few.

SIMILAR CHALLENGES. Remember, the earliest transported mice began as stowaways, accessing the packs of mules and wagons in various places along the grain traders’ routes, covering hundreds of miles. It is essentially the same today, only the rate and means that has changed. Mice may become stowaways at the point of origin of a box of goods or virtually anywhere along the route of a semi-trailer truck, rail car, or airfreight building. In fact, trailer trucks and railcars are often stationary for several hours, if not entire days, in lots, roads and rail yards that are surrounded by fields and woods (e.g., picture a typical Interstate rest stop).
Thus, the take-home message of this two-part stowaway article for both pest management professionals and our commercial clients is that a pregnant mouse (or a family of mice) might arrive at any time from any place. But through pro-active inspection services, pest management professionals can significantly reduce the number of stowaway mice that might later establish a “foothold” and go on to grow into potentially serious infestations. 
Therefore, the following are service and operational considerations for pest management professionals and commercial facility personnel alike — especially those in food-handling and distribution operations:
• Regardless of how tight any commercial structure may be, the chances are good that mice will occur periodically inside commercial structures.
• Although all perimeter wall traps and exterior bait stations may repeatedly show no activity, this does not guarantee mice are not present in the facility. Therefore, an interior inspection program of those areas away from walls must be part of a quality service.  
• In warehouses and other storage facilities, approximately 20 percent of the interior aisles should be pro-actively inspected on a monthly basis (or bi-weekly for sensitive environments) for mouse signs (i.e., droppings, smudge marks, mouse holes in boxes, etc.). The areas being inspected should be selected randomly each service visit and represent the entire floor space, unless there is some operational reason for checking certain areas more often than others (e.g., a previous history of mouse problems in an area or with a particular product).
• Warehouse managers should be encouraged to avoid storing slow-moving items (especially if they are seasonal hold-over products such as grass/bird seeds, grain products, etc.) on the upper racks of warehouses. Elevated stored, slow-moving items become vulnerable to mouse invasions because of low disturbance, and because they are now out of sight of the pest professional and warehouse staff. If such products cannot be shelved in low areas, servicing pest professionals (or appointed building staff)  must target these products for pro-active inspections.
• Should mice or mouse signs be observed upon an arriving delivery truck,  the load, of course, should be rejected.  Additionally, the product label and the trailer company should be flagged for caution for all future deliveries. As we all know, certain manufacturers, distribution centers, trucking companies, pallet trucks and truck routes are more prone to harboring pest stowaways than others. If the product from these “marked” companies or carriers is stored in a particular area of a building, that area should be inspected and pest monitoring traps installed to identify infestations before they become severe.
• Products especially prone to mouse stowaways include grass seed, bird seed, bulk pet foods and fresh fruits and vegetables (e.g., pumpkins, watermelons, pineapples, etc). In part, this is due to the natural attraction of the product itself to mice, but also to the way these products are often packaged. For example the common five-pound box of grass seed or boxed pet treats when stacked 12 or 24 to a case provide both ideal mouse harborage and unlimited food. In these types of products and arrangements, mice can establish a “nested nest” (i.e., the mouse is in a box within a box). Within the large fruit items, mice will literally bore out holes on the bottom fruits and establish nests within the fruit or the bottom bag of fruits. Such nest locations no doubt provide the mouse with a strong sense of protection as threatening “predator” sounds and vibrations are significantly deadened.
• Be especially alert to stowaway mice during the field harvest months (September thru November). During these months, mice will to escape the oncoming winter and stowaway onto vehicles onto trucks and trains from roadsides and fields.  Obviously, these are the same months we usually note spikes in “field mice” entering structures the world over.
For us as pest professionals, stowaway mice are a double-edge sword. Newly arriving mice may prompt a business to hire a pest professional.  On the other hand, even with an excellent pest management service and all the perimeter wall traps and bait stations well-serviced, a facility can still bring in stowaway mice and an infestation may occur.   Once these mice emerge from their hiding places, or in the cases of warehouses,  if they are shipped out to the warehouse’s customers, you’re likely to get a callback, or worse. The customer may question whether or not you are “doing your job” (i.e., “if we have a pest service, why should we be seeing mice ? ”).

BE PROACTIVE. Professional mouse management services for commercial facilities inherently includes a pro-actively designed and implemented inspection service as part of the service.  If a technician simply checks and services installed equipment and relies on the clients’ feedback” as to whether or not there are mice based on positive or negative client sightings, then that facility is more of a service “stop” in the truest sense of the word, compared to a professional servicing of that facility. 
We’ve learned from history, some of it costly and painful that we can’t underestimated the mouse’s potential in commercial buildings.  The house mouse is not only the perfect stowaway.  Due to some of the expensive and time-consuming litigation and fines, this mouse can also create the perfect storm — for your clients and for you.

Note: If the subject of pests (of all sorts) secretly arriving into business accounts is important to you or to your customers, a related discussion but a different aspect was covered in my column “ Trojan Horses” (PCT, April 1999).

The author is president of RMC Pest Management Consulting and can be reached at rcorrigan@giemedia.com or 765/939-2829.