By Dr. Leonard Perry, Horticulturalist in Residence
If you’re like me, or the gardener’s in the King’s Garden, you’ve experienced a banner year for chipmunks in the garden. I’ve been lucky—they’ve merely uprooted new plants and seedlings. In the King’s Garden they’ve not only done this, but climbed flower stalks to end buds of lilies and other perennials!
Chipmunks may be cute to many, especially if they’re not damaging gardens or aren’t present in large numbers. Otherwise, they can be a serious nuisance. Knowing a few facts about chipmunks may help prevent them from eating or relocating spring bulbs you may plant this fall, damaging young plants, or even causing more serious structural damage.
I find it amazing that chipmunk burrows may extend 20 to 30 feet. There is no soil around the openings because chipmunks carry it away from the burrows in their cheek pouches and scatter it away from the openings. The burrows are complex, usually with chambers for nesting, food storage, side pockets, and escape tunnels.
Usually there are two generations of chipmunks born per year, with two to five in early spring and again in late summer. So if your landscape seems to have many, this is why. They may range over about a half-acre, but only defend about 50 feet around their burrow opening.
Chipmunks gather and store food, often seeds, throughout the year. If you have seen clumps of sunflowers coming up in flower pots or the lawn, or small bulbs blooming far away from where you planted them, you can thank a chipmunk! This is one of their purposes in natural woodlands– to sow seeds for forest regeneration. Although chipmunks mainly eat seeds, berries, nuts, insects and mushrooms on the ground, they also can climb trees to gather these or to prey on young birds and bird eggs.
Chipmunks do not hibernate during fall and winter as woodchucks do, but remain rather inactive, subsisting on their stored food. You may see them active on warm, sunny days. In addition to their damage in gardens, chipmunks can cause structural damage from burrowing under stairs, retention walls, or foundations. They may kill flowers from burrowing under them.
Exclusion can be used to keep chipmunks from buildings and some flower beds. Fill openings at building foundations, fill and caulk openings, or use one-quarter inch mesh hardware cloth. Cover annual flower beds with this hardware cloth, at least a foot past the edges. You can cover the wire lightly with soil to hide it.
Where bulbs may be damaged, if planting a whole bed, first dig out all the soil. Then line the bed with similar hardware cloth before refilling and planting. Cover the top with the mesh cloth until spring when the bulbs emerge. If planting bulbs in individual holes, place some sharply crushed stones or shells in each hole before refilling. This will help deter their digging. Such products often can be found, just for this purpose, at feed and garden stores.
Habitat modification may lessen chipmunk damage. Try not to continuously connect, through vegetation and plantings, wooded areas with garden beds and homes. Such areas, wood piles, and debris provide protection for them, plus their openings are hard to find under such cover.
Spilled bird seed from feeders is a common attractant for chipmunks, as around my own home. Place bird feeders 15 to 30 feet from buildings or gardens. Keeping grass cut short around such areas will provide little cover for them and encourage them to burrow elsewhere.
Taste repellents, such as those for squirrels, can be used for chipmunks too and may be a good first line of defense. These can be used on bulbs, seeds, and foliage not meant for human consumption. These need to be reapplied, can be expensive over time, and generally don’t provide complete control.
Trapping is an effective means of control around homes and gardens. Common rat snap-traps are used by some. If using these, place boards or a box over, with small opening for the chipmunk, to prevent children, pets, birds or other non-target wildlife from getting caught. I like to put an upturned, large clay pot over such—they’re more attractive in gardens (just don’t leave them out over winter or the clay will get wet and crack when frozen).
Many prefer to use a live-catch wire mesh trap, then transport them several miles away so they don’t return. While relocating chipmunks is not illegal in Vermont (as is the relocation of most larger wildlife), it is in some states. This generally is not recommended, though, as they may not adapt well or even survive in a new site. Another alternative for live-trapped chipmunks is to humanely euthanize them. If relocating to a property other than your own, make sure you have the landowner’s permission. In New York state it is illegal to relocate animals to a property other than where they were caught (http://www.dec.ny.gov/animals/81531.html).
If using traps, a variety of baits can be used including peanut butter, seeds, raisins, or breakfast grains. Place traps in areas, and along routes, where the chipmunks are seen. You may want to fix the traps open a couple days to condition the chipmunks to them, before setting. Check traps often to remove captured chipmunks and to release non-target animals such as birds from live traps.
If chipmunks are in your garden and landscape, and aren’t a big problem, start with exclusion and deterrents from your flowers and vegetables. If they’ve become a serious nuisance, and you seem overrun with them, then you may need to resort to traps. Learn more about chipmunk biology and controls, as well as many other wildlife problems, from publications from Penn State Extension (extension.psu.edu/natural-resources/wildlife).