Rodents, Rats and Mice Oh My!

November 1, 2003

7 Min Read
Rodents, Rats and Mice Oh My!

Here are a few things you probably didnt know about rodents:

  • An average-size rat can squeeze through a gap about the width of your pinky finger, an adult mouse through a gap the thickness of this magazine.

  • A healthy female rat can give birth to six litters per year, with as many as 20 baby rats per litter. Each new female is ready to breed at about three months of age.

  • Many fire investigators say one quarter of all structure fires of undetermined origin are caused by rodents gnawing on electrical wire.

  • Even today, rats can transmit the Bubonic Plague to humans.

  • Groups of rats are called packs. (You thought Sinatra just made that up off the top of his head?) Rats and mice arent all that fond of cheese.

What You Can Do

Unless you consider simply embracing the presence of rodents at your self-storage facility as some form of enlightened social consciousness, there are four basic steps to a rodent control program. To be effective, all four steps must be taken in the order described here.

The Inspection

Short of seeing a live rat or smelling a dead one, the most obvious sign of the non-rent-paying creatures is their droppings. Rodent droppings vary in size, from one-eighth of an inch to a half-inch. They are about the same shape and texture of a popular rice breakfast cereal (the lawyers for which would probably take exception to my using the brand name to make the comparison).

Other less-obvious indications are gnaw marks in electrical or PVC conduits, rips or holes on the coverings to heating and cooling ducts, and open burrows filled with nesting materials. A pest-control professional may use a black light in a darkened area to detect the presence of urine trails or special powders to track little footprints.


This generally tends to be less of an issue in self-storage facilities. No doubt you have rules as to what your tenants can and cannot store in their spaces. Obviously, food for human or animal consumption should be strictly regulated if not completely prohibited. Tenants should be required to dispose unwanted items and trash off-site. The facility dumpster or trash containers should be secure to prohibit use by tenantsof both the two- and four-legged variety.


By the time this issue of the magazine hits your desk, you are probably already thinking about weather-proofing (or wondering why you waited this long to think about it). There is no more important issue in rodent control than a tight building.

The same measures you should take to keep your energy costs down will help keep rodents out of your buildings. Always use the strongest, most durable materials to seal your doors and utility openings. It will not always be cost-effective to completely seal off the structure. Although rodents are particularly persistent and adept at exploiting structural weaknesses, the harder you make them work, the better the chances they wont get in.

Here are a few tips on rodent-proofing a structure:

  • Trim vegetation away from the structure. Never allow overhanging tree braches to contact the building or roof.

  • Expanding foam is just a quick fixalways use heavy-gauge hardware cloth or flashing to cover holes and gaps.

  • In wooden roof structures, check for water damage or soft spots. (See comment above about rodents exploiting structural weaknesses.)

  • Employ self-closing exterior doors wherever possible.

  • Maintain screens on all windows that can be opened.


One hundred and fifty years ago, it took two months to deliver a document from New York City to San Francisco. Today it takes two seconds. One hundred and fifty years ago, it took six weeks to travel from New York City to London. Today it takes less than six hours. One hundred and fifty years ago, the best way to kill a rat was a spring-loaded metal trap mounted on a scrap of wood. Today, well, the best way to kill a rat is a spring-loaded metal trap mounted on a piece of wood.

Ok, best might not be the right word for those not inclined toward handling dead rodents. It remains, however, the most effective method to quickly eliminate an established population. It also requires the least expertise and expense.

The most efficient way to set snap traps is to place them where you and the rodent can easily access them. Rodents normally travel the same path over and over to move about their surroundings, so if you see droppings, chances are your little friend will be back by soon. Simply coat the business end of the trap with a small amount of chunky-style peanut butter and place on a flat surface. DO NOT arm the trap until you are ready to place it. (I have armed a trap before I was sure where I wanted to put it, and I have the X-rays to prove it!) Ideally, you will place the trap perpendicular to a wall, with the business end facing inward. In warmer weather, check the traps daily, otherwise, check them every other day. Be patient. Rodents are sensitive to new objects in their environment, and it may take them a few days to get used to the traps, even if they smell yummy. If you are successful, simply dispose of the dearly departed and the trap together. Keep at it until the traps collect dust quicker than they collect rats.

There are a number of live-catch options available to the general public; however, these devices tend to be expensive and require some expertise. The larger the target rodent, the less effective these things are.

Another option is sticky trap or glue board. Basically, it is a piece of plastic or cardboard coated with a glue-like substance. This is placed much like snap traps. Sticky traps tend to be ineffective against larger rodents, as even professional-grade sticky stuff isnt strong enough to mire any rat with some sense of self preservation. It generally will hold a mouse or young rat. Just be prepared to deal with a very unhappy little camper if its still alive.

No primer on rodent control is complete without a word about electronic pest-control devices. Sometimes called ultrasonic or electromagnetic pest repellers, they tout high-frequency sound waves or eltro-magnetic pulses as a means of controlling rodents, insects and a variety of other unwanted wildlife. They all have one thing in common: They dont work.

In a number of cases, manufacturers of these devices have been prosecuted by the federal government for making false claims and fraud. Consider this bit of wisdom taken from official Department of Defense policy: Electromagnetic exclusion or control devices, ultrasonic repellent or control devices ...will not be procured or maintained with public funds, and personnel should discourage the use of such devices by pointing out their relative ineffectiveness. Now, go unplug them, put them in a bag, and hide them at the bottom of your dumpster, and no one will be any the wiser.

Sorry, Mickey, but the best way to control a rodent population is to kill as much of it as you can. This brings us to the subject of controlling pests with poison. There are a number of products available for use by the general public (e.g., De-Con). I cant stress strongly enough that toxic substances to control pests, sold for use by John Q. Public, should never be used in a commercial environment.

If it isnt illegal where you do business, just ask your insurance carrier what it thinks about the idea. If you are considering using either poison baits or fumigants at your self-storage facility, the limiting factor is not expertise or legality but liability. Poison baits and fumigants are a highly effective means of eliminating rodent populations, but should only be applied by a licensed, insured professional.

Ken Berquist is a field representative at R&D Pest Services in San Diego. For more information, e-mail [email protected].

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