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Dealing with chipmunks

Q: Chipmunks are overrunning our property and causing extensive damage to bulbs and berry bushes. How can we get rid of them?

Chris Michalak, Lake Zurich, IL

Physical barriers deter chipmunks. Bury wire mesh at least 6 inches to keep chipmunks from digging beneath it to attack bulbs. Photo/Illustration: Jennifer Blume

A: Rex E. Marsh, a vertebrate ecologist for the Department of Wildlife, Fish, and Conservation Biology at the University of California, Davis, replies: Although chipmunks are cute, these little rodents can be a gardener’s nemesis when they nibble plant foliage, fruits, and underground bulbs. During good years, when natural food sources such as seeds, nuts, and fungi are plentiful, the chipmunk population may expand dramatically, especially when ample cover and burrow sites are also available. Fortunately, these high populations are somewhat cyclic and may decrease on their own in a couple of years.

Physical barriers that protect plants can reduce chipmunk damage. Wire mesh is useful for protecting bulbs and newly planted seeds. Individual wire planting baskets with covers fashioned from aviary-type wire do a good job of protecting bulbs from chipmunks. Larger beds planted with bulbs can be covered with wire mesh, with the edges buried at least 6 inches to prevent digging under the wire.

You can protect berry bushes or other fruits by covering them with mesh bird netting. This usually works best if the chipmunks’ habitat offers other naturally available alternative foods. The fruit crop must be completely covered by the netting, with the edges well anchored to the ground. Although chipmunks are capable of gnawing through the plastic netting, they rarely do so.

When a physical barrier is not a practical solution, you could try to remove the chipmunks from the area. Chipmunk-size, live-catch traps are available at hardware stores or through garden-supply catalogs. Place several traps close to the chipmunk burrows with the doors of the traps initially wired in the open position and baited with nuts, sunflower seeds, or peanut butter. After the chipmunks become familiar with the unset traps and are readily feeding on the bait, unwire the doors and reset the traps. Trapped chipmunks may be relocated to a similar habitat at least two miles away.

Gardeners who are at their wit’s end may choose to take a more aggressive trapping approach. Ordinary snap-type rat traps will quickly kill chipmunks when set near their burrows and baited with nutmeats or slices of apple. To prevent accidentally killing a bird or injuring a curious pet, cover the set trap with an inverted cardboard box or nursery flat that has been slightly elevated at one end to permit chipmunk access. Check with your state fish and game conservation agency if you have questions about local policies on trapping, relocating, or killing chipmunks.

There are many commercial repellents on the market to ward off small mammals, but, despite some of their claims, they rarely provide relief for a chipmunk problem. The same is true of home remedies made from unpleasant-tasting or odor-producing substances.

From Fine Gardening 73, pp. 96