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 Don’t overlook cardboard boxes as potential harborage sources for mice and other pests.
In residential and commercial accounts with chronic mouse problems, many pest management professionals (PMPS) find themselves periodically wondering where the mice come from. They might find themselves telling a client, "The mice probably are coming in from the outside, beneath one of your doors”. But most times, it’s difficult to be certain mice are immigrating from the exterior. How do PMPs find out, for example, that the mice aren’t originating from overlooked interior harborage sources? If a client were to pose this question, how should a PMP respond? One of the most frequently overlooked indoor sources of mice that cause chronic mouse sightings is cardboard boxes. In almost all commercial facilities, the cardboard box is one of the most taken-for-granted objects in the daily lives of humans. The cardboard box presents a unique, urban ecological niche to mice and other urban pests such as cockroaches, silverfish, bed bugs, mites, psocids and various grain insects. PMPs can help clients and themselves when managing mice by carefully managing boxes. Ecology of mice and cardboard boxes Ecology is a branch of biology that deals with the relationship of organisms to one another and their physical surroundings. The origin of the word ecology is from the Greek word oikos, meaning house. The cardboard box is a near-perfect house for the house mouse. When a mouse infestation becomes established within almost any type of human structure containing cardboard boxes, there’s an excellent chance that mice will select a suitable box and move in. The following eight factors are associated with a mouse selecting one box over another, and what they offer ecologically: 1. Harborage. A cardboard box essentially substitutes for the natural harborages - tree trunk cavities, fallen logs, rock crannies, ground burrow crevices available to rodents in the wild. Similar to these harborages, a cardboard box protects mice from temperature shifts, the elements and natural predators, including humans, cats, dogs and rats. 2. Sound deadening. Mice are among the prey species that are constantly exploring to find harborages in which they have protection. Constant disturbance from the vibrations and noises of larger animals cause prey animals to be on high alert continuously, which is an energy- wasting and stressful state. Boxes — especially those containing cans, packages and smaller boxes — dampen relatively loud noises around the outside of the box. Imagine how quiet it is in the center of a pallet of boxes that are packed with highly dense items such as rice, marshmallows, birdseed or multiple cans of soup, drinks and vegetables. Many other boxes containing similar goods are stacked onto this box. Sound could be absorbed before it might reach a mouse nest within the interior zones of a box or two. In addition, when unknown sounds are deadened, the frequency of stressful periods is reduced. This results in mice being able to devote more energy toward rearing their young, and more rest to build body strength. 3. Insulation. Many cardboard boxes are constructed of corrugated panels, which have air pockets formed within the tunnels of the corrugation along the panels. Air pockets are among the best insulators from cold and heat, and cold temperatures are a constant threat to a mouse’s survival. 4. 0n·site dining. The hotel industry learnd that if it provided shelter and food under one roof, many travelers will remain in the hotel to eat. If a single box (see Figure 2), or a case of boxes, contains food, why would mice leave the safety and dependable food of the box or pallet? 5. Food spills and odors. Boxes that used to contain food items are prone to the spills and breaches of the boxes around them, or from the packages within. Cardboard retains the odors of food residues, and such odors will attract mice and other pests to the boxes initially into which they might move. 6. Colony odors. As mice hide within or travel on boxes, they urinate, defecate and smudge-rub onto the surfaces. Because it is an absorbent surface, cardboard collects these odors —— some of which contain individual, family and colony pheromones. In tum, the pheromones communicate a range of different messages to the mice, including for other mice to investigate a box or to encourage new mice to invade other boxes nearby. 7. Spatial separation. Boxes containing items that divide them into smaller components (cardboard panels, cans, other boxes, cardboard dividers. etc.) are beneficial to social mammals. By nesting within a large case full of boxes of granola bars, for example, a mouse has its own space to protect it from other, perhaps more aggressive mice that might be living within the same box. 8. Human practices. People shove boxes into crowded and cluttered storerooms and stack them on top of refrigerators, stoves, shelves, furniture and a wide range of nooks and crannies within attics, garages, basements and garden sheds. Because boxes fit snugly into corners and slide easily below things, these storage practices facilitate mice being out of sight and mind. A consequence of stacking is that one box quickly becomes concealed behind, below or above other boxes of the same type, providing more protection for mice. For example, a cat food box is placed behind 10 other identical cat food boxes, which were on the top shelf rendering the back boxes out of reach and sight. When mice emerged from their box, they exited to the rear and climbed down the back side of the grocery shelves. The mice escaped detection by the store employees and thousands of shoppers for months. In this particular store, many other top shelf back boxes in other aisles were infested. The servicing PMP told the store manager the ongoing mouse problem was caused by mice entering with deliveries and/or from the exterior through open doors. But these were resident mice. This misread of the situation cost the pest management company significant headaches, costly callbacks and, ultimately, the account. In summary, cardboard boxes are one of the most taken-for—granted and valuable inventions around but mice use them for their own benefit. Boxes must be considered a critical infestation source in the daily inspections of PMPs. The next time you’re frustrated at a rodent account, certain that the client is leaving the doors open and allowing mice to enter, do a gut check. Maybe they’re leaving the doors open, but first you must confirm whether you’ve taken the time to rule out resident mice that could be living right before the client’s eyes behind those nearby cardboard boxes. |
