Mole
Mole Damage
The mole, Scapanus species, is a small insect-eating mammal. Contrary to a commonly held belief, it isn't part of the rodent family. In California, moles inhabit the Sierra Nevada, coastal range mountains and foothills, and the entire coastal zone. They aren't usually found in the dry southeastern regions of the state or in much of the Central Valley, except for moist areas where the soil is rich in humus, such as riverbanks.

Moles live almost entirely underground in a vast network of interconnecting tunnels. They frequently create shallow tunnels just below the surface where they capture worms, insects, and other invertebrates. They may infrequently consume roots, bulbs, and other plant material, although rodent species (e.g., pocket gophers, meadow voles, and deer mice) are almost always the cause of such chewing damage. By far the greatest damage from moles occurs through their burrowing activity, which dislodges plants and dries out their roots. In lawns, the resulting mounds and ridges are unsightly and disfiguring.
BIOLOGY AND BEHAVIOR

Moles have cylindrical bodies with slender, pointed snouts and short, bare, or sparsely haired tails. Their limbs are short and spadelike. Their eyes are poorly developed, and their ears aren't visible. The fur is short, dense, and velvety. Moles typically have one litter of three to four young per year. Because moles are antisocial, you will find only one mole per tunnel, except during the breeding season, which typically occurs during later winter through early spring.

Mounds and surface runways are obvious indicators of the presence of moles. The mounds are formed when moles push up soil to the surface from underground runways. The excavated soil may be in small chunks, and single mounds often appear in a line over the runway connecting them.

Surface feeding burrows appear as ridges that the mole pushes up by forcing its way through the soil. Some of the surface runways are temporary. More permanent tunnels are deeper underground and are usually about 2 inches in diameter and 8 to 12 inches below the surface. Moles are active throughout the year, although surface activity slows or is absent during periods of extreme cold, heat, or drought. Greatest mole activity occurs usually after rainfall or watering events when digging new tunnels is easiest.

Trapping

Trapping is the most universally applicable and dependable method of mole control. Several different kinds of mole traps are available at hardware stores, nurseries, or directly from the manufacturer. Keep in mind that the best mole traps differ from those for pocket gophers; very few traps are effective for both animals.

Understanding mole behavior helps improve the efficacy of trapping. To be effective, the trap must be set to catch the mole underground. When a mole's sensitive snout encounters a foreign object in the burrow, the mole is likely to plug off that portion and dig around or under the object. Therefore, traps should be set to straddle or encircle the tunnel or be suspended above it.

Moles are undeterred by soil blocks in the tunnel, which occur naturally from cave-ins, and will continue digging through them rather than around them. The upward pressure of the mole's body or the movement of soil against a triggering plate springs the trap.

Moles are active throughout the year and can be trapped at any time. Before setting mole traps, determine which runways are currently in use. Moles dig a system of deep tunnels that are more or less permanently used as well as a network of surface runs used for feeding. Some of the surface tunnels are only temporary, so they may not make a good trap set. Moles are more likely to be trapped in the deep runways, which they reuse almost permanently.

To determine where moles are active, tamp down short sections of surface runways and mounds. Observe these areas daily and retamp any raised sections, making note of the areas of activity. Selecting a frequently used runway is very important to the success of your control efforts. Set traps at least 18 inches from a mound and only in those runways moles use frequently. You can locate deeper tunnels by probing between or next to a fresh mound with a pointed stick, slender metal rod, or gopher probe. When the earth suddenly gives way, the probe has probably broken through the burrow.

Mole traps are fairly expensive, so most people tend to buy only one. Although one trap may solve the problem, increasing the number of traps will increase the speed and overall success of the trapping program. In California, two major types of mole traps are most commonly used. These are the harpoon type and the scissor-jaw type. Moles have sometimes been caught with certain pincer-type gopher traps set in mole runways, but these are rarely as effective as the harpoon or scissor-jaw mole traps. Trap manufacturers often provide detailed instructions, which should be followed carefully.

Set the scissor-jaw trap in the mole's main underground tunnel, which is usually 8 to 12 inches below the surface. Using a garden trowel or small shovel, remove a section of soil slightly larger than the trap width, about 6 inches. Build a plug of soil in the center of the opened runway for the trigger pan to rest on. Moist soil from the opened tunnel or from a nearby fresh mound can be squeezed together to build the plug. With the safety catch in place, set the trap and wedge it firmly into the opened burrow with the trigger placed snugly against the top of the soil plug. Next, scatter loose soil onto the set trap to about the level of the top of the tunnel. This excludes light from the opened burrow and probably makes the mole less suspicious of the plugged tunnel. Release the safety catch, and the trap is completely set.

The harpoon trap will work in deeper tunnels if you set it on a soil plug as described for the scissor-jaw trap. It can also be set on the surface over an active runway ridge that has been pressed down under the trigger pan.

Repellents

Many home remedies have been suggested to solve mole problems. These remedies include placing irritating materials such as broken glass, razor blades, thorny rose bush branches, bleach, mothballs, lye, castor oil, and even human hair in the burrow in an effort to drive moles away. "Frightening" devices such as mole wheels, vibrating windmills, and whistling bottles are also commonly recommended in garden literature as repellent techniques. Some garden literature advises using the gopher and mole plant, Euphorbia lathyris, as a repellent. Various electrical devices that vibrate soil, produce sound, or do both are frequently advertised for mole control, but research doesn't support their effectiveness. None of these approaches has proved successful in stopping mole damage or in driving moles from an area.

Commercially available mole repellents, usually castor oil solutions, are also available. Research on the effectiveness of these castor oil commercial repellents has shown some efficacy for eastern moles. No research has been done on moles in the western United States, so their effectiveness on these species remains unclear. However, repellents work by moving animals from one location to another by deterring their presence in the area where the repellent is applied. As such, they may have limited utility in residential areas, as "repelled" moles will simply move to neighboring lawns and gardens and will continue to cause damage in these areas.
Toxic Baits

Because the mole's main diet consists of earthworms and insects, poisoning with traditional grain-based baits is rarely effective. However, several new forms of toxic control have been developed that better mimic the moles natural food source. One example is a new gel-type warfarin anticoagulant bait (Kaput Mole Gel Bait, Scimetrics Ltd. Corp.) that is squeezed directly into the tunnel. Another example is a worm-shaped gel containing bromethalin (Talpirid, Bell Laboratories Inc.) that can be placed directly into the tunnel. Although rigorous testing is still needed to better estimate their effectiveness, limited studies have indicated these gel-type baits are more efficacious than grain baits and appear to be a viable alternative for mole control. Be sure to follow label instructions when applying these baits.
VOLES
Vole
Vole Damage
IDENTIFICATION

Voles are mouselike rodents somewhat similar in appearance to pocket gophers. They have a compact, heavy body, short legs, a short-furred tail, small eyes, and partially hidden ears. Their long, coarse fur is blackish brown to grayish brown. When fully grown they can measure 5 to 8 inches long, including the tail.

Although voles spend considerable time aboveground and you occasionally can see them scurrying about, they spend most of their time below ground in their burrow system. The clearest signs of their presence are the well-traveled, aboveground runways that connect burrow openings. A protective layer of grass or other ground cover usually hides the runways. The maze of runways leads to multiple burrow openings that are each about 1-1/2 to 2 inches in diameter. You can locate the runways by pulling back overhanging ground cover. Fresh clippings of green grass and greenish-colored droppings about 3/16 inch long in the runways and near the burrows are further evidence of voles. With age, the droppings lose the green coloring and turn brown or gray.

BIOLOGY AND BEHAVIOR

Voles are active day and night, year-round. You’ll normally find them in areas with dense vegetation. Voles dig many short, shallow burrows and make underground nests of grass, stems, and leaves. In areas with winter snow, voles will burrow in and through the snow to the surface.

Several adults and young can occupy a burrow system. The size of the burrow system and foraging area varies with habitat quality, food supply, and population levels, but in most cases it is no more than a few hundred square feet.

Vole numbers fluctuate from year to year, and under favorable conditions, their populations can increase rapidly. In some areas their numbers are cyclical, reaching peak numbers every 3 to 6 years before dropping back to low levels. Voles can breed any time of year, but the peak breeding period is spring. Voles are extremely prolific, with females maturing in 35 to 40 days and having 5 to 10 litters per year. Litter size ranges from 3 to 6 young. However, voles seldom live longer than 12 months.

Voles are mostly herbivorous, feeding on a variety of grasses, herbaceous plants, bulbs, and tubers. They eat bark and roots of trees, usually in fall or winter. Voles store seeds and other plant matter in underground chambers.

Voles are poor climbers and usually don’t enter homes or other buildings. Instead, they inhabit wildlands or croplands adjacent to buildings or gardens and landscaped sites with protective ground cover. Most problems around homes and gardens occur during outbreaks of vole populations.

DAMAGE

Voles cause damage by feeding on a wide range of garden plants including artichoke, beet, Brussels sprouts, cabbage, carrot, cauliflower, celery, lettuce, spinach, sweet potato, tomato, and turnip. They also can damage turf and other landscape plantings such as lilies and dichondra. Voles will gnaw the bark of fruit trees including almond, apple, avocado, cherry, citrus, and olive. Vole damage to tree trunks normally occurs from a few inches aboveground to a few inches below ground. If the damage is below ground, you will need to remove soil from the base of the tree to see it. Although voles are poor climbers, if they can climb onto low-hanging branches, they can cause damage higher up on trees as well.

Gnaw marks about 1/8 inch wide and 3/8 inch long in irregular patches and various angles along with other signs including droppings, runways, and burrows indicate vole damage. If voles gnaw completely around the trunk or roots, it will disrupt the tree’s flow of nutrients and water, a process known as girdling. Girdling damage on trunks and roots can kill trees. Signs of partial trunk or root girdling can include a prolonged time before young trees bear fruit, reduced fruit yield, abnormal yellowish leaf color, and overall poor vigor. Where snow cover is present, damage to trees can extend a foot or more up the trunk. Damage that occurs beneath snow cover often escapes notice until it is too late.

MANAGEMENT

To prevent vole damage, you need to manage the population in your area before it reaches high numbers. You often can achieve this by removing or reducing the vegetative cover, making the area unsuitable to voles. Removing cover also makes detecting voles and other rodents easier. Once vole numbers begin to increase rapidly, the damage they do to ornamental and garden plants and to trees can be quite severe.

Monitoring Guidelines

Be alert for the presence of voles. Look for fresh trails in the grass, burrows, droppings, and evidence of feeding in the garden and surrounding area. Pay particular attention to adjacent areas that have heavy vegetation, because such areas are likely sources of invasions.
Habitat Modification

One way to effectively deter vole populations is to make the habitat less suitable to them. Weeds, heavy mulch, and dense vegetative cover encourage voles by providing food and protection from predators and environmental stresses. If you remove this protection, their numbers will decline.

You can reduce the area from which voles can invade gardens or landscaped areas by regularly mowing, spraying with herbicides, grazing, or tilling grassy areas along ditch banks, right-of-ways, or field edges adjacent to gardens. If feasible, weed-free strips can serve as buffers around areas requiring protection. The wider the cleared strip, the less apt voles will be to cross and become established in gardens. A minimum width of 15 feet is recommended, but even that can be ineffective when vole numbers are high. A 4-foot-diameter circle around the base of young trees or vines that is free of vegetation or a buffer strip 4 feet or more along a row of trees can reduce problems, because voles prefer not to feed in the open.

Exclusion

Wire fences at least 12 inches above the ground with a mesh size of 1/4 inch or smaller will help to exclude voles from the entire garden. These fences either can stand alone or be attached to the bottom of an existing fence (Figure. 3). Bury the bottom edge of the fence 6 to 10 inches to prevent voles from tunneling beneath it. A weed-free barrier on the outside of the fence will increase its effectiveness.

You can protect young trees, vines, and ornamentals from girdling by using cylinders made from hardware cloth, sheet metal, or heavy plastic that surround the trunk. Support or brace these devices, so they can’t be pushed over or pressed against the trunk. Also make sure they are wide enough to allow for tree growth and, in areas with snow, are tall enough to extend above snow level. Bury the bottom of the protective device below the soil surface to prevent voles from digging beneath it. You can cut out both ends of individual milk cartons, tin cans, or plastic soda bottles and fit them over small plants. You’ll want to frequently check protective devices to make sure meadow mice haven’t gnawed through or dug beneath the cylinders and are hiding inside the tree guard while they feed on the tree.

Trapping

When voles aren’t numerous or when the population is concentrated in a small area, trapping can be effective. Use a sufficient number of traps to control the population. For a small garden a dozen traps is probably the minimum number required, but for larger areas, you might need 50 or more. You can use a simple, wooden mouse trap baited with a peanut butter-oatmeal mixture or apple slices, although often you won’t need to use bait, because voles will trigger the trap as they pass over it.

Trap placement is crucial. Voles seldom stray from their runways, so set traps along these routes. Look for burrows and runways in grass or mulch in or near the garden. Place the traps at right angles to the runways with the trigger end in the runway. Examine traps daily, removing dead voles or resetting sprung traps as needed. Continue to trap in one location until you stop catching voles then move the trap to a new location 15 to 20 feet away. Destroy old runways or burrows with a shovel or rototiller to deter new voles from immigrating to the site.

Bury dead voles, or place them in plastic bags in the trash. Because voles can carry infectious pathogens or parasites, don’t handle them without rubber gloves; you can use a plastic bag slipped over your hand and arm as a glove. Once you have removed the vole from the trap, hold it with your “bagged” hand and turn the bag inside out while slipping it off your arm and hand. Be sure to keep small children and pets out of areas where you have set traps.

Baiting

When voles are numerous or when damage occurs over large areas, toxic baits can be the quickest and most practical means of control. Take necessary measures to ensure the safety of children, pets, and nontarget animals, and follow all product label instructions carefully.

Anticoagulants, often referred to as multiple-feeding baits, interfere with an animal’s blood-clotting mechanisms, eventually leading to death. They probably are the safest type of rodent bait for use around homes and gardens, because they are slow acting, must be consumed during a period of 5 or more days to be effective, and have an effective antidote, vitamin K1, making it safer to use around children and pets. Anticoagulant baits are available at many county agriculture commissioners’ offices as well as at retail stores.

You can’t use some anticoagulants such as brodifacoum and bromadiolone because of the potential risk they pose to predators such as cats and dogs. These are common over-the-counter rat and mouse poisons. Check the label carefully to ensure it lists that the bait is suitable for use on voles or meadow mice.

Because the pest must feed on anticoagulant baits during a period of 5 days, the bait must be available until the vole population is under control. Usually baiting every other day for a total of 3 applications is effective. As with trapping, bait placement is very important. Place the recommended amount of bait in runways or next to burrows, so voles will find it during their normal travels. Generally, spot treating—placing bait in a specific place, such as a runway—is the preferred method of baiting, but in areas of heavy ground cover or if the area you are treating is quite large, broadcasting might be a better option if the label allows it. When broadcasting bait, be sure to spread it evenly over the infested area. If you use this technique, you probably will have to broadcast every other day for a total of 3 or 4 applications.
MOLES
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