[Vertebrate Pests] Entering the BLZ — the Back Leg Zone

A few months ago in the September issue of PCT magazine, I wrote an article about the interior mouse vulnerable areas (MVAs) of our residential and commercial buildings. If you had a chance to read that article, you might recall there are some types of structures, and certain areas within structures, that are more vulnerable to mouse foraging and nesting activity than others. For example, the house mouse is particularly troublesome inside commercial establishments that in one way or another serve, process and store food (FSEs). A few common FSEs include restaurants, schools, day care facilities, hospitals, hotels and large office building cafeterias.

As you can imagine, FSEs are near-perfect mouse macro-habitats. There are two primary reasons for this. First, it is difficult to clean completely enough to eliminate those size food crumbs or particles on a daily basis that would starve a mouse (recall that an adult mouse requires only about one-tenth [3 g] of an ounce of food). And, I emphasize daily because even if a food establishment is scrupulously clean, and clean enough to deny mice food for several days of any given week, the mouse will gather (grocery shop), and store food reserves in its nest to hold it over until the next less scrupulous cleaning time. Or, it will temporarily extend its foraging range to different zones.

And second, depending on their size and structure, many FSEs often contain hundreds of small voids among the facility’s walls, floors, cabinets, furniture, ceilings and equipment to harbor mice. Many of these voids are warm — an essential environmental resource for the tiny mouse that is always fighting hypothermia. Warm voids close to food — this is the criteria for quality mouse harborage.

THE BLZ. Within the great mouse macro-habitat of the food-serving establishment itself lays a great site-specific mini-habitat. This is the zone that is found around the back legs of commercial equipment and some types of furniture, or appropriately, “the back leg zone.” For the sake of on the job reference, we can use the easy-to-remember acronym, the BLZ.
The highly thigmophilic and cryptobiotic mouse is a frequent forager around the back leg zones within FSEs. Why? There are five good explanations:

1) This area is dark and shadowy (good for escaping detection by predators).

2) It is a hard-to-reach area for humans and their cleaning efforts. Thus, food spills, food items and food films are less often removed. Similarly, wrappers, drinking cups and cardboard items tend to accumulate back here. These items are food and nesting materials. All too often all of these items can remain back here for weeks and even months on end.

3) Because it is a difficult-to-clean area, rodent feces and urine also accumulate here. Rodent excrement often contains pheromones, which in turn, creates various behavioral cues within the areas they are deposited. The back leg itself, and the immediate area around the leg, can become a “marking post,” possibly in a similar way as a fire hydrant to a dog, or certain tree cavities to bats, etc. Note in the figure at right how the floor and corner behind the leg are accumulating months of urine and feces and the leg and the wall are stained with the “smudge trails” of mice. Such trails often contain odors that are used by mice for navigation and orientation, and perhaps other behaviors as well.

4) The BLZ offers a “tight space” between the leg and wall or the wall corner. This is especially attractive for the touch-loving (thigmophilic) mouse.

5) Finally, back leg zones also attract cockroaches, fly maggots and the resultant fly pupae for the same reasons listed in No. 2 previously. The house mouse is a predator upon these animals for additional sources of protein, and learns where they have a good chance of encountering their prey.

So, all in all, the back leg zone is an ideal foraging spot and/or mini-habitat for mice. Relative to the world of the urban mouse in food-serving establishments, I sometimes think of the BLZ in the same way as the watering holes of the Serengeti plains of Africa. Wild game biologists tell us it is highly predictable that elephants, giraffes, hippos, lions and other animals will come to this essential resource on daily or nightly basis — and their predators follow for opportunities to seize prey.
 
ON THE JOB UTILITY. Not only should a pest professional always inspect in the BLZ, he or she always should report any conducive conditions to the client. And, within the golden rule of “let the droppings be the roadmap as to where you install your control devices,” the BLZ area, or along the walls in close proximity to the BLZ area, will pay off in captures or bait feeding.

Note that snap trap stations, or tamper-resistant bait efforts (i.e., only block baits inside tamper-resistant stations), are most appropriate for corners areas. If glue traps are used to supplement the snap traps or baits, they should be installed in the manner in which they are intended; as kinesthetic traps. Thus, glue traps can also be installed along the run ways at least several feet away from any corner, but leading into the BLZs. 
 
EFFICIENT PRODUCTIVITY. On a typical busy commercial pest route, time is money (duh). But efficiency without sacrificing effectiveness is the goal. A mandatory check of BLZs each and every time you service any food serving establishment helps ensure you to more consistently achieve this goal.
As a consultant, I am constantly inspecting for mice inside food establishments of all types trying to solve challenging and recurring mouse callbacks. A favorite mental chant to myself during these inspections: BLZ, BLZ, BLZ.

The author is president of RMC Consulting, Richmond, Ind.