[Vertebrate Pests] Reading A Yard For Moles

Features - PCT News

June 9, 2004

"Mole season" has arrived for many areas of the country. Disfiguring dirt mounds and raised tunnels are appearing in hundreds of thousands of yards, parks, golf courses and other turf areas in many states.

Seven species of moles occur in the United States. But only three are of any real pest significance. The Eastern mole (Scalopus aquaticus) occurs throughout many areas of the eastern half of the country and is overall, the most numerous and widespread mole pest in America. On the coast of Oregon and Washington, the relatively large Town-send’s mole (Scapanus townsendii) can be troublesome, while in some areas of California, the broad-footed mole (Scapanus latimanus), causes problems. Four other species of moles occur in the United States, but they are of minor or no pest significance. Regardless of the species, moles have similar biology and behavior.

Attempts to control moles have varied from the silly to the serious. Pest professionals over the years have tried spraying for grubs, using smoke bombs, tablet fumigants and toxic grain baits (similar to rodent baits). Thus far, all these approaches have not proven effective on a consistent basis. Homeowners have tried chewing gum, spinning daisies, flooding and various electronic gizmos all to no avail.

The most reliable mole control thus far has proven to be trapping conducted by experienced and skilled trappers. Over the past two years, however, mole baits that incorporate new technology, active ingredients and formulations have emerged on the market. The Scimetrics Corporation released an anticoagulant bait three years ago. And now in 2004, Bell Laboratories is cued up to release a completely new non-anticoagulant mole bait this summer.

But for both traps or baits, success is dependant upon working within high-activity zones of the moles. This is an important point, because moles construct different types of "runways." Some runways are used by the mole many times during the course of a week; these are referred to as "main runways." Other runways are used intermittently or are abandoned after only one pass through on a feeding frenzy.

The point is a lot of time and money can be wasted trying to control moles without first understanding the mole’s foraging behaviors.

An easy analogy would be to consider the ineffectiveness of placing bait stations for burrowing rats on the third floor of a grain elevator when the rats are getting all their food at ground level.

Thus, the key for professionals performing mole control is being able to read a property to identify a mole’s high activity zones. Service time is too expensive to "guess" where to place mole traps or baits.

The following are six helpful field tips for pest professionals to facilitate being able to quickly "read a property" for the mole’s high activity areas.

RUNWAYS AND TERRITORIES. The deep mole runways in which soil mounds are excavated out to the top of the ground are usually activity runways. Moles use these deep runways to travel to and from the feeding runways and as pathways that connect to the nest. Depending on the species and local soil environment, deep runways may be constructed as deep as 36 inches. The Eastern mole usually constructs its deep runways within 3 to 12 inches of the surface.

Adult, sexually mature moles are territorial within their areas. In environments that offer moles abundant food resources, several mole territories may overlap to varying degrees. Young moles born into a territory in early spring may occupy the mother’s burrow system for several months before becoming independent and establishing their own territories relatively nearby in the fall. Yards and areas surrounded by or adjacent to large tracts of forested land or weedy fields may be sources of several dozens of moles. Should a mole’s territory become vacant due to a death or abandonment, other moles living nearby will usually "absorb" the vacated territory into their own.

MOLES FOLLOW LINES. Moles use specialized tactile hairs on their feet, tail and nose to help them travel about and find food in their dark tunnels. Moles also use these tactile hairs to guide them along different types of linear surfaces. Some "lines" used by moles in and around yards include fencerows, building foundation perimeters, walkway and driveway edges and large tree root systems.

Each of these linear zones is attractive to moles for a couple of reasons. First, the areas at the bases of fencerows and structural edges are often less traveled upon by humans and animals and thus the soil remains less compacted and easier to tunnel through. Second, these areas are more difficult for people to thoroughly remove vegetation via mowing and weedwacking. Unmanaged lush vegetation protects the soil from the hot sun, which in turn conserves soil moisture compared to surrounding areas. This moisture, in turn, results in the food sources of moles such as earthworms and grubs gravitating towards these areas, which in turn attracts moles to follow along these lines.

MULCH BED MCDONALD’S. Similar to lush and thick vegetation found along unmowed areas, mulch beds provide a protective cover to the desiccating sun, as well as insulating the soil from hot sun or temporary variations in cold temperatures during late winter and early spring. Thus, sub-mulch soil is attractive to worms, slugs, snails, millipedes, grubs and other invertebrate animals moles use for food.

Consequently, mole tunnels are nearly always found beneath mulch beds. Main runways will often be found connecting two mulch mounds in yards (e.g., between two different mulched tree bases or garden beds).

Perhaps as a mole "cruises" around in its territory, mulched areas are used by the mole as its own version of the local fast food "drive thru." Over a billion worms eaten — no doubt about it.

BIRD FEEDERS. Moles seem to always forage beneath bird feeders, although the reasons for this are not fully understood. Because the mole employs specialized tactile hairs to detect vibrations from its prey as they move through the soil, it may be that the mole is attracted, in part, to the areas below bird feeders as a result of all the vibrations created by the feet of feeding birds. Moles likely utilize some of the fallen seeds as a supplemental food source. Moles also occasionally capture and eat small birds.

Whatever the reason, runways leading to active bird feeders are often used on a daily basis, especially during the winter and early spring.

LONG, STRAIGHT RUNWAYS. Runways that run in straight lines for relatively long distances in an area (e.g., 20 to 60 yards) are high activity runways by moles. These runways contain many "side-street" runways that branch off the main lateral runway. Long straight runways are also used by the mole to connect higher terrain areas to lower terrain areas.

During the wet season, higher terrain areas often contain nest sites (i.e., good drainage for maintaining a dry, warm nest). From these areas, the mole travels the straight runways to connect to the foraging zones in the lower terrain areas where the invertebrate food sources attracted by moist soil are found.

MOUND-CONNECTING RUNWAYS. Because the deeper main runways result in the mole having to excavate out mounds of soil, the subsurface deep runways that connect two large mounds are typically main runways used by the mole on a daily or regular basis.

CONCLUSION. Mole control has often been characterized as "difficult" by many pest professionals and thus they are hesitant to venture into mole control as an add-on service. But with good traps and perhaps the advent of efficacious mole baits, combined with guidance for "zeroing in" on active moles, maybe mole control as a profit source should be reconsidered.

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