Shrew Damage Management

Damage Prevention and Control Methods

Exclusion

A masked shrew, Sorex cinereus

Rodent-proofing will also exclude shrews from entering structures. Place hardware cloth of 1/4-inch (0.6-cm) mesh over potential entrances to exclude shrews. The pygmy shrew (Sorex hoyi) may require a smaller mesh. Coarse steel wool placed in small openings can also exclude shrews.

Cultural Methods

Regular mowing around structures should decrease preferred habitat and food, and may increase predation. Where shrews are eating tree seeds, plant seedlings instead to eliminate damage.

Repellents

No repellents are registered for use against shrews.

Toxicants

No toxicants are registered for use on shrews.

Fumigants

No fumigants are registered for use against shrews. It would be impractical to use fumigants because of the porous nature of typical shrew burrows.

Trapping

Mouse traps (snap traps), box traps, and pit traps have been used to collect shrews. Set mouse traps in runways or along walls, with the traps set at a right angle to the runway and the triggers placed over the runway (Fig. 2a). Small box traps can be set parallel to and inside of runways, or parallel to walls around structures (Fig. 2b). Bait the traps with a mixture of peanut butter and rolled oats. A small amount of bacon grease or hamburger may in-crease the attractiveness of the bait.

Figure 2. Traps and trap placement for capturing shrews: a) mouse trap (snap trap) set perpendicular to wall, with trigger next to wall; b) box trap set parallel to wall; c) pit trap sunk in ground over runway (includes cotton wool).

A pit trap consists of a gallon jar or a large can sunk into the ground under a runway until the lip of the container is level with the runway itself (Fig. 2c). Bait is not necessary. A small amount of bacon grease smeared around the top of the container may be an effective attractant, but this may also attract large scavengers. Pit traps are more effective for capturing shrews than snap traps, although the increased labor involved in setting a pit trap may not be justified when trying to capture only one or two animals. Monitor pit traps daily, preferably in the morning before the temperature gets hot, although Churchfield (1990) recommends checking traps four times in a 24-hour period. Place cotton wool in the pit trap containers to reduce the mortality of trapped animals. This is especially important to ensure the successful release of nontarget animals. Since shrews are generally beneficial in consuming insects, live-captured animals can be relocated in suitable habitat more than 200 yards (193 m) from the capture site.

The traps and placement procedures described above are also effective for catching mice. Note the identification characteristics given above for deter-mining whether the captured animal is indeed a shrew. Sometimes birds are captured in traps set for shrews. If this occurs, try placing a cover over the traps, a cover over the bait, moving the traps to another location, or omitting rolled oats from the bait mixture.

Shooting

Shooting is not practical and is not recommended. It is illegal in some states and localities.

Other Methods

Owls may reduce local populations of shrews in poor habitats, but this has not been documented. Domestic cats appear to be very good predators of shrews, although they seldom eat them (presumably because of the shrew’s unpleasant odor). Cats may be effective at temporarily reducing localized shrew populations living in poor cover around structures. Cat owners may find dead, uneaten shrews brought inside the home. Rather than reduce the shrew population outside to prevent this, simply monitor locations regularly used by your cat, and dispose of dead shrews by placing a plastic bag over your hand, picking up the dead animal, turning the bag inside out while holding the shrew, sealing the bag, and discarding it with the garbage. Using a plastic bag in this manner reduces the potential for flea, tick, helminth parasite, or disease transmission. Use of cats to control shrews is not recommended due to the negative impacts free-ranging cats exert on other species.