Mallis Handbook Excerpt: Snap Traps & MCTs for Rodent

The common rodent snap trap is familiar to nearly everyone and is one of the oldest devices for controlling rodents. In an effort to capitalize on Ralph Waldo Emerson’s advice "if you build a better mouse trap, the world will beat a pathway to your door," inventors have been attempting to build a better trap for more than 140 years.

In fact, to date, about 3,500 mousetrap patents (and counting) have been awarded by the U.S. Patent Office. Several different types of snap traps have evolved from the originals and are available to professionals and homeowners alike. (See Figure 1 on page 30.)

Trapping is appropriate for those situations where the use of rodenticides is unwarranted or might pose a hazard. Traps also can be used where the odor of the decomposing rodents might be unacceptable. Snap traps also have several disadvantages.

First, success with snap traps depends on the skill and determination of the trapper.

Second, trapping often requires more time and effort than some other methods of control.

Third, traps cannot be placed where children, pets or unknowing feet wander.

Fourth, if not secured to a surface, a rodent caught by the tail or a foot, may drag the trap away. And finally, once sprung, snap traps are ineffective until they are reset.

SNAP TRAPS FOR MICE. Mouse snap traps can be highly effective tools — especially when used by an experienced professional.

Below are several useful tips that pest management professionals can use to effectively trap mice:

1) Tying the bait securely to the trigger prevents the rodent from licking or nibbling the bait without setting off the trigger. If a bait is used that cannot be tied (e.g., chocolate syrup), it is best to use small amounts.

2) Sensitivity of the trap is adjusted by bending the long, narrow metal prong that touches the trigger. In areas where vibrations are a problem, the trap must be made less sensitive.

3) The key to success using mouse traps is to use many traps. For only a couple of mice in a residence, 12 or more traps are not too many.

4) Traps should be placed close together (approximately 6-foot spacing) in double sets in areas of activity.

5) In situations where contamination is not a problem, traps can be reused after captures. Odors from previous odors will not repel mice and are sometimes more attractive to rodents.

6) The professional, expanded-trigger mouse traps should be used for best trapping results.

7) Trap baits can be varied. The success of any bait depends largely upon how much other food is available and what the rodent is accustomed to eating. Oatmeal, whole oats, salami, freshly fried bacon and chocolate flavor extracts are but a few of the items that can be successful.

In areas with numerous mice, the use of a variety of baits (e.g., meats, fruit, candy, cereals, etc.) among all the traps may entice a wide range of mice within the colony during any one trapping event.

Also, it may be a good strategy to use nuts in a meat packing facility and meat in a flour mill, so mice are offered a food that is not otherwise available. Peanut butter and/or nutmeats also are good baits provided they are not used in residences or other areas (e.g., schools, day care centers, hospitals) where there may be children or individuals with peanut allergies.

8) Effective baits are also small pieces of thread or cloth which mice use for nesting materials (dental floss is convenient to use and carry). Female mice exhibit intensive nest building activity just prior to the onset of the cold weather and within a day or two of birthing a new litter (Bronson 1979). Nesting material will not spoil, nor will it be consumed by ants or cockroaches.

With the expanded trigger model snap trap, it is often possible to trap mice without using bait merely by placing the treadle in a position next to the wall where the rodent may step on it. Corrigan and Weber showed that the professional model trap had a capture rate of 53 percent as compared to 37 percent for the standard trigger model. Both models exhibited about equal "escape rates" (traps set off without any capture) of about 12 percent to 14 percent.

Also, bait stealing did not occur with the professional level trap, yet occurred at 16 percent rate with the standard trigger traps.

Traps are effective when set next to a wall beneath a runway made by leaning a board against the wall. The trigger end of the trap should be situated next to the wall. Several traps set together will prevent the rodents jumping over them.

Because rats can be neophobic of objects, traps should not be set directly in front of a hole where the rat gains entrance to the room.

Old traps should be scraped and kept clean. Dipping traps in melted paraffin lengthens wear, deodorizes them and may make them spring more readily.

MULTIPLE-CATCH LIVE TRAPS. Multiple-catch mouse traps (MCTs) are also known as "curiosity traps" and are now available in several brands comprised of two basic types: a wind-up trap and a low profile trap-door trap. One winding of the wind-up models permits the capture of numerous mice. The trap door models offer a low-profile design and employs an entrance tunnel with a one-way trap door that allows a mouse to enter but not escape. (See Figure 2 on page 31.) Both types of traps are made by different manufacturers; some are made of metal, some of plastic. The greatest number of these traps are used in the food and warehousing industry, but they are also used in a wide variety of commercial facilities. Multiple catch traps are rarely used in residential settings.

Mice enter MCTs as a result of their opportunistic behavior to investigate new holes and harborages they encounter in their travels. Once they are trapped inside, the mice succumb to a loss of body heat (hypothermia) and/or deprivation. The amount of time it requires for a captured mouse to expire depends on ambient temperatures, the condition of the mouse and whether or not any other mice are inside the trap (that can be used as food).

To maximize results with multiple catch live traps, the following considerations and tips may prove helpful:

1) No difference in capture rates has not been found between the wind-up and non-wind up model traps. However, operational and design factors (high- or low-profile design, handling time, ease of inspecting, cleaning, see-through inspection plates, etc.) should be evaluated to ensure selecting the trap of choice for the particular situation or needs of the pest management professional. Additionally, some models offer various advantages (e.g., escape prevention designs, construction design, etc.) for their specific brand. Consequently, "comparative shopping" for best long-term value among the different brands is important.

2) Metal traps are prone to rusting, warping and denting, resulting in gaps and warping at doors, hinges and lids. This type of damage not only allows captured mice to escape but also renders the traps difficult to open and handle and these traps are more likely to be skipped by busy pest management professionals. Metal traps must be inspected regularly and repaired or replaced as needed.

3) Items should be pulled away from walls to encourage mice to investigate the traps.

4) Waxing the lids of some models will allow them to slide more easily. This facilitates that the pest management professional cleans the inside of the trap when it gets dirty and/or when removing dead rodents trapped inside.

5) With the wind-up models, the trap should be placed either parallel to the wall with about 2 to 3 inches (50 to 76 mm) from the wall or perpendicular and flush to the wall. No evidence exists that one position is clearly superior to the other.

6) Winding traps too tightly can break the winding mechanism or cause the spring mechanism to "spin out" rendering the trap ineffective. The Ketch-All™ trap offers a no-fault winding operation.

7) If a wind-up trap is wound half-way, the mice are "gently" flicked into the holding area. This affords a better chance the mouse will remain alive for several hours. Although no scientific evidence has proven this fact, it appears a live mouse in the trap attracts more mice than would a dead mouse. However, it has been proven that recently weaned mice of a litter follow the mother or their siblings on feeding and exploring forays, and thus it is common to find entire litters and/or family units inside the trap during the course of one night of trapping. As many as 19 mice have been captured in a single multiple catch trap in one night.

8) Traps should be located in the high activity runways of mice, on either side of doorways and all other possible entry points (e.g., utility lines into a building). For preventive programs in the food industry, the traps are usually installed along allocated spacings around the entire interior perimeter wall.

9) Around the exterior of food-processing facilities, mouse control programs can be supplemented by placing multiple-catch live traps outdoors near entrances with the goal of trapping mice prior to their entry. For long-term performance, exterior traps should be protected from dirt, dust, debris and the elements. Plunkett’s Exterminating Company of Minneapolis, Minn., uses a "Mouse House" in which the multiple catch trap is installed inside a metal rat-sized bait station.

10) A putty knife, rags and wire brush are effective for dry cleaning of multiple catch traps.

11) Tools such as a screwdriver and especially needle-nose pliers are essential on the job repair tools.

12) Most food plants run multiple catch traps weekly or more often in sensitive areas. In food and pharmaceutical facilities, dead rodents, feces and/or hair left in traps constitute a sanitary concern and such traps should be checked frequently and cleaned of any or all of capture residues.

13) For facilities where contamination is not an issue, successful traps need not be thoroughly washed regularly because this removes the urine odor that is attractive to mice. (Unfortunately, a synthetic urine formulation does not exist to "pre-season" rodent traps.)

14) Inexpensive cardboard glue traps can be placed within the multiple catch mouse traps. This results in "trap synergy." When glue traps and a multiple catch trap are combined, this two-in-one trap now works as both a mouse trap and an industrial-strength monitoring station for both insects and a glue trap effectively will contain the carcass, hair and feces of the captured rodent, thereby reducing the biohazards and potential contaminants associated with trapped mice. The body of the multiple catch trap in turn protects the glue trap from dust, dirt and moisture.

15) Pest management professionals servicing multiple catch traps should wear protective disposable gloves whenever cleaning traps that contain mouse carcasses or fecal material. Many pest management professionals prefer to wear leather work gloves while performing routine weekly servicing of metal brand multiple catch traps to avoid cuts and abrasions. Wearing a respirator (to protect against inhaling a microbial pathogen, such as hantavirus — see related story on page 36) is not necessary unless the multiple catch traps are being installed in areas where the deer mouse is prevalent.

Bronson, F.H. 1979. The reproductive ecology of the house mouse. Quart. Rev. Biol. 54:265-299.

Corrigan, R.M. and M. Weber. 1991. Of mice and mousetraps. Pest Control Technology. Vol 19 (3):28-33.