Monitoring – Rodent Trap Selection

General Considerations

There are many types of rodent traps to choose from. Selecting the best type of trap for your application is important to the success of your monitoring program. Use of an inappropriate trap style can mean fewer captures, lower efficiency in servicing traps, secondary infestation of rodent carcasses by insects, or an animal’s unnecessary pain and suffering. As a result, it may also impact the quality of your monitoring data. For example, rodents may avoid traps that are not positioned properly, or placed outside of natural runways. On the other hand, using remote traps in locations that are difficult to access may reduce servicing time by allowing pest management professionals to focus on known captures and allow them to more efficiently record, clear, and reset traps.

No trap is perfect for all monitoring applications. It is important to match the trap to the needs of a particular situation. Some considerations include:

Presence of known or suspected runways
Proximity to human disturbances (will the trap get bumped or kicked?)
Visibility concerns
Ease of access to the trap location for servicing
Outdoor vs. indoor use
The size or capacity of the trap

Key Resources:

Rodent Trapping Tip Sheet, Museum Pests Working Group

Vertebrates, Museum Pests Working Group

Snap Traps

Snap traps are the preferred method of trapping mice.

Snap Traps should be placed perpendicular to the wall with the trigger against the wall or parallel to the wall, preferably with two traps back to back with the triggers facing outward (see double trapping for more information).
Expanded trigger traps are snap traps with a larger trigger area and are the preferred type of snap traps. They will give you 17% more catches.
Reuse traps if possible, but use gloves.
Place traps in quiet corners in order to catch them when they are slowing down a bit rather than in the middle of their run or along walls.
Gluing snap traps on a board can be helpful for placement and removal once the trap is sprung

Traps should be baited using non-lethal attractants. Options include:

Whatever mice are already feeding on
Cotton balls (females will instinctively seek out cotton for nesting)
Nutella
Tootsie-roll pieces

*Avoid baiting with peanut butter, as it poses allergy concerns in public spaces and is so effective that it can attract more rodents.

Double Snap Traps

The so-called “popcorn response,” triggered when mice sense an issue with the first trap, will cause them to jump to get out of the way of the first trap, falling into the second trap. These tactics work best with snap-traps and expanded trigger traps.

Three options for “double trapping” include:

Set up a first trap abutting a second trap, with both traps parallel to the wall and with triggers to the outside/away from one another.
Set up one trap on either side of a corner, each perpendicular to their own wall with triggers towards the wall.
Set up two traps, both perpendicular to the wall and right next to each other, (double wide-style) with triggers towards the wall.

Key Resource: Mouse Snap Trap Placement Diagram, Museum Pests Working Group

Glue Traps

Flat glue traps are sometimes used to trap rodents. These traps have a thicker glue layer (2 – 4 mm) than those needed to trap insects. Generally other methods such as snap traps or live traps are considered to be more humane for rodents because they are less likely to cause prolonged suffering.

If you are considering using these traps, please check your local regulations to ensure that they are permitted. These are currently banned in the UK.

A rodent glue trap with dead mice and additional insect pests

Photo courtesy of Tom Parker

While snap traps are preferred, occasionally glue traps are also necessary.
Larger, rat-sized boards with a thicker glue layer are best.
Freeze boards first to ease removal of contact paper/release paper.
Low-temp glue boards exist for use in cold (eg: in refrigerators and freezers).
Flat glue boards are better than trays/mice will run around or bypass trays.
Can be used in combination: glue boards alone will get about 70%. You’ll need a combo to get both. Traps and glue boards on a perimeter, traps in the corners, boards along the runs. You can wrap a glue board around pipes – more for rats than mice, because mice eventually come down to eat.
If glue boards are not allowed in your institution during public hours, place them at closing and retrieve them in the morning before opening.
Trap position: place along runs or in areas with smudges (grease markings).
Dead mice will also attract insects; traps should be checked regularly and only used strategically as necessary.

Multi-Catch Traps

While “No Kill” traps may initially appear on the surface to be a more humane option, they can often result in a prolonged, painful death when compared to a quick-kill snap trap solution. Most trapping/monitoring IPM campaigns will not have the resources to be able to check traps in frequent enough intervals. This may require contracted help.

Photo courtesy of Tom Parker

Rodents can die within 6-12 hrs of being trapped.
Multi-catch traps can result in stress, fighting, and even cannibalization for the trapped animals.
Dead mice will also attract insects; traps therefore should be checked regularly and only used strategically as necessary.

Bait Stations

NEVER USE RODENT BAIT inside museums, historic houses, libraries, or archives!

Photo courtesy of Tom Parker

Poisoned rodents often die in hidden voids (behind walls, under floorboards, etc.) leaving carcasses that are difficult to find/remove.
Hidden carcasses attract flies, hide beetles, carpet beetles, clothes moths, and other pests that will attack collections when the carcass is finished.
Many commercial rodent baits come unintentionally pre-tainted with dermestid eggs, which will soon hatch and attack collection.
Do not use bait near buildings if mice may enter afterwards. Performing proper exclusion (sealing up the building envelope) first can reduce the chance of void odors.

Exterior baiting must be managed in consultation with a PMP (Pest Management Professional). Monitor/work with your PMP to ensure:

Correct baits/traps are used and they are well-located

Check local ordinances regarding allowable uses of rodenticide baits.
Do NOT use anticoagulant baits where they may cause secondary poisoning in predators who may ingest dead rodents.
Use products without secondary toxicity to raptors, coyotes and other animals, such as baits using vitamin D3 as the active ingredient.

That the PMP regularly maintains the baits/traps

Check outdoor traps quarterly, if not monthly.
Snap traps or glue boards can be included in bait station units if well-monitored.
That the PMP monitors baits/traps meaningfully
That technicians actually unlock, open, and check each box