VERTEBRATE PESTS: Happy Groundhog Day, Part 2

In last month’s column, we covered the biology and behavior of woodchucks. Here, in part 2, we will discuss the management of woodchucks when they become nuisance pests in and around structures.

Although woodchucks can be controlled any time they are out of hibernation, the optimal period for eliminating urban woodchucks is during the spring (mid-March and April). This is because 1) active burrows are easy to find before vegetation covers over the high activity areas; 2) entire woodchuck families may occupy a single den area; and, 3) other wildlife that inhabit woodchuck burrows during the winter months will have likely evacuated the burrow and thus are less likely to be harmed by any control efforts.

LIVE TRAPPING PROGRAMS. When woodchucks construct their dens beneath buildings, the safest and most efficient method of control is to live trap and remove the rodents using heavy-duty wire-mesh animal live-capture traps. In most cases, woodchucks are relatively easy to live trap.

Each of the trap manufacturers (such as Kness Manufacturing, Tomahawk Live Trap Company, Woodstream Corporation and others), make live traps large enough for woodchucks (and most other mammal pests). Still, because the woodchuck is a relatively large and powerful mammal, it is essential the appropriate model trap is employed.

The keys to live trapping woodchucks effectively include locating the trap in paths and locations that maximize the chances of the woodchuck encountering the trap and then installing the trap in a manner that entices the woodchuck to enter the trap. Remember that the woodchuck does not have good vision. Thus, it often moves along familiar pathways and paths of least resistance.
Live traps can be installed next to, or nearby, a woodchuck’s active burrow opening or positioned along well used paths leading from the woodchuck’s burrow and feeding grounds. Traps with two doors should be used and both doors should be set open.

When a trap is placed directly in front of a burrow entrance in an effort to capture a woodchuck upon its departure from the burrow, the trap should be situated as close to the burrow opening as possible. Stones, small logs, branches or some other material should be used on both sides of the trap to construct a specific pathway and prevent the woodchuck from veering left or right just prior to the trap’s entrance. In other words, do not allow the groundhog to have any choice but to go forward and enter the trap.
Creating a natural footing to the trap can provide additional means to encourage a woodchuck to enter the trap. This can be done by working the trap’s base into the dirt or vegetation or by covering the floor with dirt collected from the mound of the main burrow entrance. The odors within this dirt may provide the animal with familiar smells and decrease any aversion to entering the trap.

Because the woodchuck is a vegetarian, nearly any fruit or vegetable can be used for bait. Apple slices, carrots, lettuce, broccoli and beans all are attractive foods. The bait should be placed out in small pieces creating an enticing trail gradually leading into the trap. The largest piece of bait can be installed at the trap’s trigger zone.

Remember, the woodchuck is diurnal, which means it is active early morning, midday and at dusk. On cold days, the woodchuck tends to emerge from the burrow during the warmest part of the day. On hot summer days, the foraging periods are during the cool early dawn hours and at dusk.

TRAPPING AND RELOCATION LAWS. The laws affecting the live trapping of woodchucks and other wildlife species vary from state to state. Before any wildlife live trapping is conducted, all state regulations must be checked. Additionally, different regulations may dictate how nuisance wildlife can be handled, euthanized and/or released once captured.

Considering urban sprawl (often the reasons for woodchuck infiltration to property areas), it has become increasingly difficult to relocate woodchucks to areas where they’re not likely to cause pest problems for other property owners, farmers or park personnel. Nevertheless, large tracts of forest land bordering open fields provide suitable habitat for relocated woodchucks.

Professional euthanizing of captured animals is a must. Live-trapped woodchucks should never be drowned, shot or killed via any other inhumane approach.

BURROW FUMIGATION. Away from buildings, woodchucks can also be controlled via burrow fumigations using gas cartridges or phosphine tablet fumigations. Gas cartridges and smoke bombs are the most commonly used burrow fumigants because they are nonrestricted materials and are readily available to even farmers and homeowners as over-the-counter products.

When ignited, gas cartridges and smoke bombs release carbon monoxide into the burrow system, killing the woodchuck via asphyxiation.

Tablet fumigants containing aluminum phosphide are registered for woodchucks and other burrowing rodents in some states. These tablets release phosphine gas upon reacting with ground moisture. Thus, phosphine tablets are more effective during the spring and fall when the soil is damp more than during the dry days of summer.

Again, it must be stressed that burrow fumigants are not approved for use around buildings. All labels for burrow fumigants must be strictly adhered to. In general, burrow fumigations are most effective when they are conducted on cool, rainy days. All fumigated burrows should be checked the following day to ensure success. And, because vacant burrows may be re-occupied by other woodchucks from adjoining areas, treated burrows should be rechecked every couple of weeks. Fumigation should not be done after September since most woodchucks will be in hibernation and the hibernating chamber is often “walled off,” rendering a fumigation treatment ineffective. Additionally, oftentimes, woodchucks evacuate summer dens and relocate to auxiliary winter dens in wooded and other protected areas, some distance away from the summer den, rendering treatments being a wasted effort.

Coincidentally, this column was written on Feb. 2, Groundhog Day. I read on the Internet today that 40,000 people  turned out to witness Punxsutawney Phil emerge from his burrow to search for his shadow. This big rodent event is better attended than our own national pest management convention and most of our large regional conferences combined! At any rate, Phil did see his shadow (or so said his agents) indicating six more weeks of winter. Imagine that. Do the math. 

The author is president of RMC Pest Management Consulting and can be reached at rcorrigan@pctonline.com or 765/939-2829.