[Vertebrate Pests] The perfect stowaway, part I

Perhaps you know that the house mouse is considered by mammalogists to be the second most successful mammal on Earth (arguably man is the most successful). Considering there are about 5,000 different species of mammals among 26 orders, this is no small feat. But how did this tiny mammal achieve such success as a species? Let’s look at a little bit of history and characteristics of the “mighty” mouse.

WHERE DID THEY COME FROM? Scientists estimate the house mouse originated in Central Asia (now the country Turkmenistan) nearby the Caspian Sea. Here it existed on the grassy steppes as a burrowing rodent. Its primary food was the scattered wind-blown seeds which it had to chase down and collect (thus the “nibbling” and carrying and caching behavior of the mouse to which we are all so familiar).
From Asia, the house mouse eventually dispersed to all parts of the globe. In fact, it now has the widest distribution on Earth of any mammal second only to the human, occupying all the major landmasses and most of the minor ones. This mouse can be found on cold islands near Antarctica, as well as in the tropical isles in the Caribbean; on open cold tundra, dry hot deserts and salt marshes. It exists in coal mines 1,800 feet below the surface and at elevations of 15,000 feet up in the Andes Mountains. Inside urban structures, infestations have developed in heating ducts in the upper stories of tall skyscrapers as well as within frozen meat lockers at temperatures of -10°C.
For sure, the mouse is a master at adapting to all these different areas. But for dispersing to all the different geographic regions, the mouse is entirely dependant on humans. The intriguing question, however, is how can a rodent that is so repulsed by humans (steals and fouls our foods, damages our goods and objects, transmits illness, and frightens many people) be at the same time, such a successful travel companion to humans and disperse itself throughout the globe?
The answer? The house mouse is the perfect stowaway.
In a broad use of the definition, a stowaway is a person or animal that hides on a mode of transport such as a wagon, ship, plane, train, automobile and so forth, and is taken somewhere unbeknownst to the travelers.
The house mouse may have been among the very first mammalian stowaways when it hid within the mule packs and wagons of the earliest grain traders. Some historians suggest that if you follow the trade of wheat Westward, through the Middle East and into Europe, you are also following the early dispersal of the house mouse.
From European shipping ports, the house mouse sailed overseas via the early trade and explorer’s ships. In fact, the ship records of some of the explorers and European settlers mention mice (and on some ships, rats) destroying or fouling the crew’s rations stored in the holds. Upon landing in the “New World,” the mouse then dispersed west via the wagons and river boats of the fur traders and new frontier settlers. And now, the house mouse is transported on a relatively rapid pace within countries and around the world via delivery trucks, planes, trains, ships, tractor-trailers, mobile homes, cars, and even the backpacks and purses of individuals.

WHY A PERFECT STOWAWAY? So what characteristics facilitate being a perfect mammal stowaway?
1. Small, non-descript and secretive. The size and color of the mouse aids in allowing the mammal to remain undetected. The adult mouse is tiny relative to the specific transport environment in which it hitches a ride. An adult mouse’s body averages only 3 inches in length (in this context, the 3-inch tail is moot). And, weighing a mere half an ounce, no one ever notices any additional weight, even for an entire family of mice in a bag, backpack or box. The mouse’s color ranges from a dark brown to brownish gray. These earthy colors don’t exactly stand out among grains, brown cardboard boxes, jute sacks or shadowy corners.
2. Humans are clutter-prone. The small non-descript mouse can also take full advantage of the behavior of humans. For example, when humans move long distances, they jam-pack moving vans, trailer trucks, cars, etc., often in a cluttered messes. On a commercial scale, we move supplies and goods in quantities of up to thousands of boxes of all shapes and sizes, stacked on pallets, or in a multitude of arrangements in transport vehicles of all sorts. The result in both cases is the mouse is able to take advantage of a myriad of mouse-friendly nooks and crannies.
3. A specialist in secrecy. The mouse is active when people are inactive, i.e., during the night, or at other times when human activity is minimal. Additionally, when the mouse is active, it moves quickly (about 7 feet per second) and lithely, gravitating towards the protection of shadows. This behavior among boxes and supplies allows the mouse to move about undetected.
4. Stays put in transport. Under normal conditions in typical building infestations, the home range of the mouse is small (e.g, a 10-30 foot radius from the nest). But when food exists very close to the mouse’s nest, the foraging range of a mouse may be only a few feet. Most experienced pest management professionals know that it is common for mice to not exit from commercial pallets and/or boxes and large bags of seeds, pet foods, cereals, and other products.
5. Quick reproduction. Where food is readily available, the mouse can multiply quickly. And as long as materials are available for constructing nests, mice can reproduce under seemingly impossible conditions, such as within frozen meat lockers. Thus, the chances of a family of mice surviving in the bottom of boxes of virtually anything we transport is relatively good.
6. Requires little or no water. Finally, because the mouse originated in a semi-desert environment, it has a kidney system similar to that of the desert rat. As a result, the mouse is able to conserve and/or produce its own water when free water is scarce or temporarily unavailable (e.g., huddled up in the bottom of a box during periods of transport).
With all these factors in combination then, you can see how it is so difficult to detect and stop the house mouse before it has already penetrated our modes of transport, food manufacturing and serving establishments, and all their associated warehouses. Nevertheless, we can implement strategies and procedures to reduce stowaway occurrences and severity, a topic that will be discussed in Part II of this column in the May issue of PCT.
Remember the children’s television series Mighty Mouse (and the accompanying song)? ”Mighty Mouse is on his way!”? No joke. He is.
And most times, we could also sing,  “And Mighty Man is unaware”  See you next month.

The author, a frequent speaker at industry conferences and educational events, is president of RMC Pest Management Consulting, Richmond, Ind. He can be reached at rcorrigan@giemedia.com or by calling  765/939-2829.