Pocket Gophers: The good, the bad and how to deal with them

(SBA) - Although not as notorious in Iowa yards as moles, the plains pocket gopher (Geomys bursarius) can be an unwelcome guest in lawns and fields across most of Iowa, generally becoming less common in the eastern quarter of the state. It is an expert burrower, and its habit of creating dirt mounds and vigorously tunneling through soil on occasion leads to conflicts with property owners, including impairment of drainage tiles and underground utility lines, weakening of embankments along ditches and dikes, damage to mowing equipment, and diminishing the general aesthetics of lawns and other manicured areas. Pocket gophers can clip and girdle the bark of trees and shrubs and can consume the underground and aboveground portions of various garden, commercial, and ornamental plants.

Pocket gophers are a species of conservation concern in Iowa because the loss of Iowa's native grasslands and farm pastures has reduced the amount of habitat for them throughout the state. Therefore, caution should be taken in the control of their populations, and only efforts to reduce or dissuade their presence on your farm should be considered if they are doing economically consequential harm.

Habitat: The plains pocket gopher occupies open, grassy areas, such as prairies, meadows, pastures, hayfields, lawns, cemeteries, golf courses, and sports fields. Generally, pocket gophers are more likely to colonize locations surrounded by extensive grassland. However, the presence of ditches, fencerows, field borders, and other grassy corridors can enable pocket gophers to survive within stretches that would otherwise be uninhabitable. In any setting, soil composition is key: pocket gophers reach their highest densities (6 to 8 gophers per acre) in sites with porous, well-drained, loamy soil. Excessively rocky soils present too many obstacles for burrowing, while shallow or extremely sandy soils are not stout enough for tunnel walls to stay in place. Furthermore, because pocket gophers seal their tunnels off from the surface, they must breathe air that circulates through the surrounding soil. Thus, soils that are excessively compacted, like those with clay or heavy moisture, do not allow for enough air to cycle in and out of the tunnel.

General biology: From a small, compressed head connected to a short, thick neck, to muscular forelimbs armed with long, curved claws, and short hind feet tipped with shorter, straighter claws, nearly every aspect of a pocket gopher’s stocky anatomy makes it a burrowing machine. The extensive tunnels that a pocket gopher creates dominate every aspect of its life cycle – from feeding to sleeping to reproduction. Except when mating or raising offspring, the plains pocket gopher remains solitary. An individual will create and maintain its own tunnel system, although multiple tunnel systems (and therefore multiple gophers) can be present in the same lawn or section of field. As would be expected by their burrowing nature, pocket gophers spend most of their time underground. However, they venture to the surface to feed within close vicinity of their tunnel entrances.

Plains pocket gophers reach breeding age at the end of their first year. After a gestation period of about three weeks, females give birth to a single litter of 3-4 young (sometimes up to ten) some time from April-June. Males may share the female’s burrow for a few weeks to help care for the young before moving on to another burrow. After weaned from the mother, the young disperse outward to establish a new burrow; this often entails a dangerous trek across the surface. Pocket gophers of all ages fall victim to a variety of predators, but they are especially vulnerable to badgers, which are proficient at digging them out of their tunnels. Weasels and snakes (especially bullsnakes) capture pocket gophers within their tunnels; skunks, raccoons, foxes, coyotes, bobcats, domestic dogs, cats, hawks, and owls are among the many animals that dine on pocket gophers that venture onto the surface.

Diet: Unlike moles, which prey on invertebrates, the plains pocket gopher is strictly an herbivore, using its long, sharp teeth to gather grasses (like bluegrass in lawns) and broad-leaved plants (most notably alfalfa), as well as bark and stems of trees and shrubs. During warmer months, pocket gophers frequently consume roots and bulbs that they encounter while digging and eating additional portions of plants they pull down into their tunnel. They also make brief excursions onto the surface, where they extend out as much as a body length from their tunnel to feed on neighboring plants, including the bark of trees in lawns and orchards. During these aboveground forays, especially during winter, they often clip the stems of young trees and shrubs.

Damage identification: Although tunneling can occur at just about any time of year, spring and fall are prime seasons. A single pocket gopher is capable of establishing a long series of tunnels (up to 200 yards per individual) and mounds made in quick succession (1 to 3 per day, leading to as many as 70 in a month or 200 in a year). The poorer the soil and food base, the longer the tunnel system needs to be to support a pocket gophers life cycle. However, high-quality habitats lead to higher densities of gophers, even if the individual tunnels are less extensive and the mounds less numerous. In any case, look for the following distinctive signs of pocket gophers:

Large, crescent or fan-shaped dirt mounds. Gopher mounds differ considerably from the conical (volcano-shaped) mounds made by moles.
1-3 inches wide
Sunken slightly from the surface
Contain a hole, plugged with dirt, that serves as a tunnel entrance and exit
Many are often found in close proximity
Extensive network of underground tunnels that are NOT visible from the surface
Main tunnel is 4 to 12 inches below surface
Additional tunnels for breeding and nesting 18-24 inches down
Up to 200 yards in length per individual gopher
Patches of dead vegetation may appear irregularly between mounds
Distinct from the raised ridges of soil created by moles

In addition to considering the tunnels and mounds excavated by moles, one should also make sure to rule out the narrow, surface-level pathways that meadow voles make when moving among their golf ball-sized burrows in lawns, pastures, golf courses, and other grassy habitats.

Costs and benefits of pocket gopher activity
Negative impact of pocket gophers
Cause economic loss by consuming roots, bulbs, and aboveground portions of plants. Studies in Nebraska showed a 35% loss in irrigated alfalfa and a 46% decrease of production of non-irrigated alfalfa; hay fields with grass (e.g., timothy) have shown declines ranging up to 30% in various locations.

Girdle the bark on trunks of saplings; clip off the stems of seedling trees and shrubs
Weaken or cause washouts of embankments, ditches, dikes, and levees Disfigure and diminish the aesthetics of lawns, golf courses, and other managed areas Tear through and impair drainage tiles and underground utility lines Lead to equipment damage when plows and mowers encounter mounds in fields and lawns.

Benefits of pocket gophers
Reduce compaction and improve aeration by moving and mixing considerable amounts of soil (up to 1 ton or 2,000 pounds per year per individual)
Create tunnels that in turn move more water and wait to roots of plants
Fertilize soil via defecation and bringing plants underground to decompose
Decrease surface water runoff via formation of tunnels that draw water from the surface
Stimulate topsoil formation and weathering by bringing soil to the surface
Serve as an important food source for animals in prairies, meadows, and other wild habitats
Damage control: removal of nuisance pocket gophers
In instances where pocket gophers become especially troublesome, trapping of individuals to remove them from the area can be an effective way to address damage. The first key is to find the main tunnel, which is usually located 12-18 inches away from the plug on the crescent-shaped mound. Once you have found the main tunnel, you can then place traps in the secondary tunnels, which run laterally off the main tunnel.
Locating the best place to trap or bait gophers:
Use a metal rod to probe the ground until you find the main tunnel, located 12-18 inches from the plug on the crescent-shaped dirt mound.
Once the tunnel is detected (no soil resistance on the metal probe), use a trowel to dig out soil above tunnel, typically 4-12 inches downward.
Place your bait or traps in each direction from your excavation (see details below).
Trapping to eliminate gophers: Although not particularly feasible across broad expanses like hayfields or golf course, trapping is a proven means of removing problematic pocket gophers from smaller patches, such as lawns and ditch embankments. Multiple trap styles exist, including Macabee gopher trap, Death Klutch 1 gopher and mole trap, and Victor Gopher-Getter, as well as various homemade traps.
Trap during spring and fall when gophers are most actively tunneling and mound-building.
Follow the aforementioned instructions to locate the main tunnel and to dig out a spot to place the traps.
Set and place two traps facing away from each other in both directions.
Trial and error: either leave tunnel open, thus ensnaring the gopher when it returns to repair the opening, or, like with bait placement, repair the opening yourself to keep the gopher from inadvertently burying the trap; either method can be useful, depending on the individual gopher.
Anchor flags and/or stakes with flagging to make traps easily visible when you return.
Check the trap every few hours; find a new location for any trap that fails after 48 hours.