On Wolf Haven’s mounded prairie, there is an underground movement happening that largely goes unnoticed — bioturbation (the movement of soil) by Mazama pocket gophers (Thomomys mazama) excavating their homes. At only eight inches long and weighing less than 100 grams, Mazama pocket gophers are forces of nature. The typical pocket gopher can move 3–7 tons of soil every year as they build and maintain their territories, which consist of a network of tunnels with separate chambers for storing food, nesting, and depositing excrement.

Wolf Haven’s prairie is covered with mima mounds — small, domelike hills with a mysterious origin. Dozens of hypotheses have been proposed about their creation, including pocket gopher activity, events associated with glacial melt, earthquakes, even aliens! Despite decades of inquiry, there is still no consensus on how they were formed but pocket gopher activity continues to be argued as a possibility.

Mazama Pocket Gopher. photo courtesy of WDFW, USFW, Wolf Haven

In some areas, however, non-native forbs outcompeted native species around pocket gopher mounds. Soil disturbance often favors early successional species, many of which are weedy exotics that effectively exclude native species. Local conditions and surrounding plant communities likely influence the prevalence of native verses non-native species found around mounds. There is still much to be learned about the synergy between pocket gophers and plant community dynamics in supporting healthy ecosystems.

Mazama pocket gopher’s movement of soil contributes to the hydrological system. As they excavate their tunnels, they loosen and aerate the soil, increasing water infiltration and percolation. Their tunnels and surface mounds also move and redistribute water to help control runoff and soil erosion.

Many critters also benefit by sharing the landscape with pocket gophers. Numerous amphibians, reptiles, small mammals, and invertebrates use unoccupied burrows as refuge from predators and/or retreat from the elements. In areas where pocket gopher numbers are high, they are a food source for predators, such as coyotes, fox, bobcats, weasels, snakes, hawks, and owls.

Mazama Pocket Gopher. photo courtesy of WDFW, USFW, Wolf Haven

While Mazama pocket gophers are not restricted to prairie habitat, soil conditions affect where they can carve out a living. Soils that are rocky and/or have a high clay content can create numerous obstacles. Mazama pocket gophers are vigorous critters, but large rocks can be a struggle to move and can decrease burrowing efficiency. Soils that are high in clay have very low permeability and often become waterlogged, which can result in periodic flooding of burrows. Waterlogged soils also deprive both pocket gophers and plant roots of oxygen. Furthermore, while clay particles bind well with nutrients, it is hard for plants to extend their roots through them, affecting plant productivity and subsequently Mazama pocket gopher nourishment.

Pocket gophers are well adapted to their largely subterranean life. They have strong claws on their front feet and prominent incisors to dig through the soil and cut roots. They can close their mouth behind their incisors, allowing them to loosen soil with their teeth without swallowing dirt. External, fur lined cheek pouches on both sides of their mouth enable them to transport seeds and plant material gathered while foraging underground. Narrow hips, short limbs, and loosely attached skin facilitate their movement through tunnels, including turning around in tight spaces. They can even move backwards almost as fast as they move forward. They have tiny eyes and ears, but sensitive whiskers and a sparsely haired tail provide the sensory awareness needed to move through the darkness. Life underground, however, can be energetically expensive. Movement through soil costs far more energy than traversing the same distance on the surface. Pocket gophers fuel their activity by consuming large quantities of plant material, primarily roots, but also surface vegetation.

Mazama pocket gophers are highly asocial. Males and females maintain their own burrow systems and are intolerant of other pocket gophers in their burrows, except during the mating season and prior to weaning young, who typically disperse around two months. If young pocket gophers are unable to expand from their mother’s burrow system to establish their own territory, they are sometimes required to move above ground to locate and secure a new territory. This can be a dangerous endeavor because movement above ground makes pocket gophers extremely susceptible to predation.

While Mazama pocket gophers are rarely seen above ground, signatures of their movement are scattered around Wolf Haven’s prairie. Their mounds are visual microsites of soil disturbance that, to the untrained eye, can be confused with mole mounds. A few characteristics, however, can help distinguish them. Pocket gophers push soil up from inclined lateral tunnels, creating fan-shaped mounds whereas moles push soil up from vertical shafts, creating dome- or volcano-shaped mounds. Pocket gopher mounds tend to be distributed in irregular piles while mole mounds are more evenly distributed. And, unlike moles, pocket gophers maintain a sealed burrow system by plugging entrances with soil, which helps deter predators. Sealed burrows create an environment low in oxygen and high in carbon dioxide, which pocket gophers are physiologically adapted to tolerate.

Life moving through the underground often escapes our attention but if you are patient and observant, you may catch a glimpse of something extraordinary. It may be a slight wiggle in the vegetation, followed by the entire plant disappearing underground. Perhaps you are among the lucky few that witness a pocket gopher briefly emerge on the surface, quickly cram its cheek pouches full of food, then vanish again. Even if you miss them though, their mounds remind us there is a mighty movement happening under those piles of dirt and that movement plays a key role in healthy ecosystem functioning.

Introducing… The Mazama pocket gopher: The story of 4 threatened subspecies in South Puget Sound, Washington. US Fish and Wildlife Story Map. This overview is a good visual accompaniment to the above article. It also shows on a map where Mazama Pocket Gophers call home.

Mazama pocket gopher vs. coast mole ID Card

Mazama Pocket Gopher Recovery Plan and Periodic Status Review.

The Influence of Pocket Gopher Disturbance on the Distribution and Diversity of Plants in Western Washington Prairies.

Young Mazama pocket gophers struggle to find their place in a new world.

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