[Vertebrate Pests] Pest issues of detached storage containers, Part I

It seems that we humans never have enough storage space. We are always overfilling our kitchen drawers, closets, attics, garages, cubicles, back rooms, car trunks and so forth. As evidence of this consider how successful the many different types of “U-Store-It” lockers and facilities have become around your own neighborhood. 
In residential environments, many single-family homes in suburban neighborhoods construct detached storage/garden sheds. The detached garage meant for the car, over time, often becomes relegated to an extra storage building. Recently, drop/pickup storage containers (mini versions of the commercial sector’s shipping containers) have become popular rental items to alleviate homeowner storage problems.
For the commercial sector, such as market stores, warehouses, food plants, super centers and the like, detached storage containers of all types are employed. But most of these types of accounts have taken to employing the trailer beds of the common semi-trailer. When more important items need to be stored, or for the situations requiring longer-term storage, commercial operations often employ the heavy-duty overseas shipping containers. These days, it is common to note at least one trailer bed associated with commercial stores. But with the new “Super Center” stores and operations, several storage trailers are often parked on the property lot year round, or new ones are rotated in and out on a regular basis.
For the purposes of this column, regardless of whether the storage containers are the small “garden storage shed” of the suburban home, or the larger commercial tractor trailer employed by mega-stores, they all can be referred to as detached storage containers (DSCs).  
In Part I this month, we’ll examine how detached storage structures are affected by pest issues and the dynamics of how pests utilize these structures. Next month, in Part II of this column, we’ll discuss the types of pro-active and remedial services pest professionals can offer their residential and commercial clients that use detached storage containers and structures.

PEST SHELTER SUBSTITUTES. To us pest professionals, it is fairly predictable as to the outcome of employing the various detached storage structures around our buildings.  Animal pests of all types during their opportunistic exploration of property areas are likely to find any “big box” an attractive shelter from the elements and their enemies.
Pests that commonly invade detached storage structures in residential environments include mice, squirrels, rats (Norway, roof and packrats), tree squirrels, ground squirrels, solitary bats, raccoons and opossums.
In the commercial environment of semi-trailer beds and shipping containers, any of these same mammals may occur, but in the majority of cases, it is mostly house mice and “field mice (deer mice and white footed mice) that invade the trailers and containers.
From the animal’s perspective human storage structures are convenient substitutes for hollow trees, logs on the ground, rock outcrops, rock piles, cave vestibules, or some other natural harborage environment necessary for their protection from the elements, nesting locations and/or hibernation sites in which to survive the cold winter.

PEST ISSUES. Vertebrate pests moving into detached storage containers and structures are often overlooked or under-appreciated by our clients (and by some service professionals as well?).   In residential situations, animals moving into storage buildings can ruin the stored items via gnawing damage, or from defecation on the stored items. The storage structures themselves can be damaged as well from gnawing damage from tree squirrels.
Perhaps of greater concern are the potential health concerns associated with the feces of invading mammals — especially when homeowners initiate “spring clean-ups” of their storage structures and areas.
In commercial situations, the damage concerns may be the same as for those in residential but, of course, a significant amount of money may be at stake.
When various stores (especially those that are food-handling establishments)  are not proactive about managing pests in their storage systems, they may introduce “Trojan horse” rodents into their stores and warehouses on a regular basis throughout the year (which in turn, the servicing pest professional is now obligated to eliminate).
Even without any live rodents being brought into a store, for example, rodent feces may be transported on pallets and items and these alone can cause a commercial client and servicing pest professional headaches (i.e., it may be difficult to determine if the feces are from newly invading mice, or the feces are old and not associated with any current infestation at all). Of course, such feces also will be of concern to any health inspector.
It is common around supermarkets and super center-style stores for storage trailers to be parked along the outer edges of the property lines. Frequently, empty lots, weeds, woodlots, rail lines, ditch banks and the like border these areas — and often they contain rodent and/or other pest populations. Mice will readily invade any trailers that are not pest-tight. This is especially true with the onset of the colder months.  Moreover, mice will gather natural foods (seeds, berries, bugs, nuts, etc.) from the outside and cache the foods inside the trailers inside boxes, whatever items are being stored, or within the walls of the trailer itself.
When you consider that the average semi-trailer bed contains approximately 4,000 cubic feet of space  (many measure about 9 feet high by 8 feet wide by 53 feet long, but vary slightly depending on their purpose and manufacturer), this is an incredible amount of harborage space for small mammals.   As such, several families of mice may become established in trailer beds simply for the purposes of harborage.
But then commercial clients occasionally can make the disastrous mistake of holding onto rejected bulk foods, or certain types of bulk grass seeds or bird seeds for seasonal sales, not realizing how extremely attractive these type of items are to rodents. When such items are held over in decrepit trailers for only a few months, the results are predictably disastrous (at least to us pest management professionals) because not only do the rodents have everything they need in the trailer, but none of their natural checks and balances are present to offset their reproductive potential (e.g., cold, predators and plenty of space to minimize stress from intra-specific competition). In just a few month’s time, such trailers essentially become rodent-rearing trailers.
When you hear these trailers being guided to a receiving door via the ordinary “come on back” call, once that door is opened, what ensues is anything but ordinary — especially to the receiving clerk. And here again, it often is the pest management professional that is called in to “control” the mice scurrying in a hundred different directions into the back room, warehouse, or wherever (and often such mice are not susceptible to rodent devices along perimeter walls.)
OPPORTUNISTS & OPPORTUNITIES. As previously mentioned, pests to a large degree are opportunists when they utilize human storage containers and structures for shelter. And their invasions of DSCs can pose significant health concerns and/or economic concerns to the residential and commercial client alike.
But these invasions also present opportunities for pest management professionals. Homeowners and commercial clients employ detached storage containers and practices for the same reason: there are items and materials and goods that have value, or items need to be kept for all kinds of personal or economic reasons. Pest professionals play a key role in that protection. Protecting detached storage containers from pests is a very important service indeed.
Next month, in Part II, we’ll discuss the professional services of inspecting and servicing residential and commercial detached storage containers and structures. 

The author is president of RMC Pest Management Consulting and can be reached at rcorrigan@giemedia.com.