MOLES AND MOLE BIOLOGY
Moles are from the family Talpidae which includes moles, desmans, and shrew-moles. The North American moles or New World moles are divided into the Subfamily Talpinae and of this group there are six moles on the continent, seven if you count the shrew-mole. All are insectivores and related on this continent only to the shrew. Parascalops breweri - Scapanus latimus - Scapanus orarius - Scapanus townsendi Scalopus aquaticus - Condylura cristata.
All moles can be damaging but Scalopus aquaticus or Eastern mole is by far the most widespread of the six. It is better described as the common or grey mole. It is the strongest of the group and is most often associated with tunnels and or mole mounds by residential homeowners. The Eastern can be found from the Atlantic to the foothills of the Rockies and from Southern Canada to the panhandle of Florida. Moles are covered by a soft grey pelage that is hinged to allow it to move in any direction. Variegation in color is common with patches of orange or white on some moles. Moles are about the size of chipmunks and can weigh anywhere from three to six ounces. Total length can be six to eight inches. Moles have one litter each year. Litter size can be two to six depending on the health of the female. Latitude seems to play a large part in the timing of male rut and litter deliveries. In Cincinnati I can expect males to rut from about the last week in February through the first week in April. Gestation lasts about five to six weeks which means I can expect litters anywhere from mid April through May. Moles are mammal and nurse the young moles for several weeks. I look for young moles to disperse (newborn expanding off the mother's tunnel system or moving above ground to create or find new tunnels for their own use) from late April through mid June. I imagine this timing can be tempered by unseasonable extremes in temperature or ground moisture. The final dispersal can last through late fall and early winter. Since moles don't hibernate (they store neither food nor fat) final dispersal can result in severe lawn damage until the lawn surface freezes in winter. Newborn females will mate the following spring and the cycle begins anew.
Star-nosed Mole (Condylura cristata) , inhabits low wetland areas. It prefers sandy soils with high water tables. With a diet of aquatic insects, worms, mollusks and small fish, it is not an important lawn pest. I have to confess that I have had little experience with this animal although several of my fellow trappers deal with the starnose on a fairly regular basis. The starnose is a problem throughout Michigan, northern Wisconson and northen Ohio. Its can also be found in some coastal areas along the Atlantic as far south as the Carolinas. See Control - Trapping & Traps.
Because of specialized bone and muscle construction, moles can exert a lateral digging force equivalent to 32 times its body weight. (Arlton 1936) As a comparison, a 150 lb. man would be able to exert a 4800 lb. lateral force.
"For moles to dig one metre of tunnel requires between 400 and 4,000 times as much energy as does walking for the same distance on the surface." (Vleck 1979 University of Arizona.)
A 5 ounce mole will consume 45 to 50 lbs. of worms and insects per year. Godfrey and Crowcroft (1960) Mellanby (1967)
A moles surface tunneling or probes can be dug at about 18 feet per hour. A moles speed through existing tunnels is about 80 ft. per minute. Godfrey (1955)
Moles contain twice as much blood and twice as much red hemoglobin as other mammals of similar size, allowing the mole to breath easily in its underground environment of low oxygen and high carbon dioxide. (Arlton 1936)
TUNNELS & BEHAVIOR
Donald & Lillian Stokes in Animal Tracking and Behavior 1986 state "Moles are believed to remain solitary as adults and avoid contact with other moles. However, there are at least two exceptions. One occurs in the spring, when the males start to move around and leave their range in search of females. They may move about for several weeks, even after all the females in an area have mated. The other exception is that occasionally some tunnels are used by several moles; these tunnels are, in a sense, like highways. This communal use suggests that the social system of moles is more complex than we think."
Terry Yates & Richard Pederson "Moles are probably the least understood major component of the North American mammalian fauna."
These two statements seem to lend a mystic quality to moles and their behavior but moles are creatures of habit and they do behave in fairly predictable ways depending on what they have and what they need. There are a couple of traits that need mentioning before I get into tunnels. The first is that moles will usually take the path of least resistance when tunneling. This is great food for thought the next time you look at a maze of mole tunnels and mounds and wonder why moles do what they do. The second trait reinforces the first in that moles are recolonizing animals and will readily take over existing tunnels or jump homerange. Simply put, trapping the moles that are currently damaging your lawn or landscaping may not be an end-all or permanent solution to a mole problem. Because recolonization is likely, trapping is the only way to keep up with a mole problem. In some Northern states, especially Michigan and Wisconsin, mole tunnels can be used by more than one species of mole. Trapping records show both Eastern and Star-nose taken from the same tunnel system.
Because mole tunneling and damage is generally progressive (moles continually adding on new tunnels to the old year after year) the amount or kind of lawn damage at any given time is not indicative of the number of moles present. Current damage also can give no indication as to the number of moles that will have to be trapped out.
Most experts describe two tunnel types. Surface- (probe or gathering) or deep (permanent or producing. These can be broken down into sub groups;
Surface: Exploratory - Mole population adding onto or expanding
system. Male mole rutting pattern ( last week in Feb.
through end March)
Gathering: - As certain biomasses increase seasonally, such as grub or worm concentrations in spring or fall. (Noticed as a literal pumping-up of fairly large areas) These tunnels resemble varicose veins and seem to stem-out in all direction. (A surface feeding area.) The damage is heavy and will come and go seasonally. A permanent tunnel may be constructed to connect these feeding areas.
Deep or permanent tunnels: bolt runs and producing are not too
deep. These tunnels are usually placed along or under man-made borders
such as timbers or foundations. Bolt runs will connect two feeding areas
and will appear fairly straight. (the shortest distance between two points).
They may also be deeper and show up as a series of mounds in open areas.
The producing tunnels do just that, they produce biomass throughout the
Deep producers are indicated by heavy mounding in a small area, such as around tree roots in residential areas. In a natural habitat, the mounding is difficult to see because of woodland debris. The large mounds of dirt associated with deep producers are a result of clay displacement in and around the roots. Some of the producers will eventually work around the root balls of the trees and allow access to the biomass throughout the year, as many insects or larvae (especially periodic cicada) live off of the root moisture and sap.
A complete tunnel system will always connect a combination of all of the tunnel types as well as one or two areas that I can only describe as wet and dry. The wet will hold water and is used during dry periods. The high feeding areas will drain quickly and provide access to biomass during torrential or wet periods associated with spring and fall rains.
Lawn damage from mole activity and tunneling may take several forms. The surface tunneling separates the grass roots from the soil. Besides leaving a mushy or soft feeling when stepped on, the separated roots cause yellowing and dieing patterns in the lawn. Exposed soil along the tunnel ridges allow blowing weed seeds to propagate. (Crab grass and nimble weed often grow along mole tunnels. Deep tunneling, represented by mounding and bulging of soil also will cultivate weed growth.
Winter damage on existing or old tunnels can be severe. Most surface tunnels, especially main or bolt runs, are continually deepened until the tunnels lie an inch or so into the clay beneath the top soil. During winter rains, the water cannot drain properly through the clay and any freezing will heave the tunnels up as the water expands during freezing. When rains are followed quickly by a freeze, which is often the case as cold fronts are preceded by rain, thick ice crystals heave the soil and lay back the sod around the perimeters of the mole mounds. In many cases, deep tunnels that were not visible from above ground during fall or early winter, are exposed during the freeze heaves. The winter of 1996 was tough on old mole tunnels not so much because of temperatures, but because of the many freeze thaw cycles that occurred that winter. Even though trapping removes all of the moles in the lawn, the freeze thaw cycle will make it look like new moles have entered.
Deeper mole tunnels can be used by mice or chipmunks once the moles have been removed. This is common when the moles tunnels are around the foundation or in the mulched areas around houses. Ground hornets or yellow jackets often nest in old mole tunnels.
A mole problem left unattended can reach a stage of complete access for moles, in that over a period of years, the tunneling can reach all areas of the lawn and residence. The tunnels are produced slowly along organic lines such as fence rows, man made borders, tree lines or mulched areas. The resulting system can supply a large and permanent bio- mass that can feed several moles. Effective trapping can remove the resident moles, but the large system can entice other moles to follow. Moles will usually take the path of least resistance, so the empty tunnels make access easy. Moles can and will jump homerange easily. If the tunnels provided for the moles that constructed them, they'll also provide for new moles that happen upon them. Its called recolonization and seems to be a crucial part of mole behavior.
The energy required to construct a permanent tunnel system is great. To protect this investment moles scent mark most of the homerange daily as they travel through the system in search of food. It warns other moles that the system is occupied (protecting territory) and may advertise a females scent when she is ready to mate. The scent can be picked up by a rutting male crossing marked tunnels.