Mazama Pocket Gopher

For over two years PE Consultants LLC has been studying the Mazama pocket gopher in preparation of Habitat Protection Plans, which are prepared to recommend measures that would protect this sensitive species while allowing permitted land use activities. 

Recent Habitat Protection Plans:

• 118-acre Subdivision.  Habitat Protection Plan on a 118-acre proposed subdivision that has been reviewed by biologists at the Washington Department of Fish and Wildlife (WDFW) and subsequently approved by the City of Tumwater.   We performed an extensive field evaluation to identify Mazama pocket gopher colonies through surveying recently formed gopher mounds and through live trapping.  Gopher colonies were delineated, surveyed, and mapped. Gopher density on the site had been relatively low because of the site's poor habitat conditions.  The site had been logged between 10 and 20 years ago to create cattle pasture.  Since then, the Mazama pocket gopher has come onto the site from the nearby airport, where good quality gopher habitat supports a thriving population.  Consequently, juvenile gophers searching for new territory have migrated from their natal territory onto the subject property.  One-hundred or more cattle, horses, and other livestock have grazed the European pasture grasses, buried the site in manure, and compacted the soils while trampling on gopher tunnel systems.  We recommended to set aside a large tract to transform cattle pasture into prairie habitat preferred by the gopher.  In addition, the WDFW would translocate gophers from the areas that would be impacted by development to pristine off-site prairie habitat in the hope of establishing a new gopher population.

• 280-acre Subdivision.  Performed several months of live-capture trapping to determine distribution of gophers on the subject property.  Prepared Habitat Protection Plan on a 280-acre multi-use site in the City of Tumwater.  Several acres of Mazama pocket gopher impacts will occur on this site.  The proposed mitigation is proposed for the wetland buffer, which is an area that will be preserved through wetland regulations.  Mitigation includes eliminating invading tress and shrubs and seeding with native prairie grass species. 

• 40-Acre commercial.  Habitat Protection Plan on a 40-acre commercial parcel that is in the permit review process.  The conditions are similar to that on the 118-acre property.  The Mazama pocket gopher migrated onto the property when the site had been cleared of timber to provide cattle pasture.  A low density pocket gopher colony has been hanging onto live in this inhospitable environment of grazing and trampling cattle.   We recommended that a tract of cattle pasture be transformed into prairie to enhance Mazama pocket gopher habitat.  Cattle would be eliminated from the property, soils would be loosened, native pasture plant species would be seeded, and the enhanced prairie habitat would be maintained through the periodic mowing of shrubs and trees. 

• 26-acre Subdivision.  Habitat Protection Plan on a 26-acre assemblage of low to moderate density single-family lots proposed for subdivision.  Gopher mounds occurred in cleared areas containing homes, access roads, and lawns.  A small population of 11 to 20 gophers had been estimated to occur on the site, based on literature describing research performed to estimate pocket gopher density.  We recommended to set aside some areas within the proposed openspace for gopher habitat restoration, transforming maintained lawns into preferred Mazama pocket gopher habitat.  This project had recently been approved.

• 22-acre Subdivision.  Habitat Protection Plan on a 22-acre assemblage of low to moderate density single-family lots proposed for subdivision.  Gopher mounds occurred in cleared areas containing homes, access roads, and lawns.  We recommended to set aside a contiguous area of openspace near the stormwater pond for gopher habitat restoration, transforming maintained lawns into preferred Mazama pocket gopher habitat. 

• 10-acre Commercial Buildings.   Habitat Protection Plan on a 10-acre commercial site in the Grand Mound Area.  This project is proposed for stages.  Mitigation area occurs adjacent to the stormwater pond and property edge.  The mitigation plan will preserve and enhance Mazama pocket gopher habitat, while optimizing developable area on the site.

• 140-acre Subdivision.  Performed live-capture trapping and detailed GPS locating of gopher mound clusters in the Grand Mound area over the course of several weeks. 

• 141-acre Commercial Tacoma.  Performed a 3-month live capture trapping study of the Mazama pocket gopher on a City of Tacoma site to determine presence or absence of a possible remnant population segment.  Unfortunately, no gophers had been discovered. 

• 0.3-acre Commercial Building.  Performed a Mazama pocket gopher mound reconnaissance near the Olympia Airport.  No Mazama pocket gophers occur on the site. 

Gopher Mitigation Monitoring

118-acre approved Mazama pocket Gopher Mitigation Area	Monitoring Mazama pocket gopher mitigation area
Amended soils and prairie vegetation of mitigation Area in foreground & Construction Area in Background

Mazama Pocket Gopher

By Curtis Wambach, M.S.

Senior Biologist & President

PE Consultants LLC

&

Devoun Cooper

Student at the University of Arizona

14 August 2006

1.0  Mazama Pocket Gopher Biology

Species Description.  Mazama pocket gophers are small (body ~5.5 in) fossorial (live in underground burrows) rodents with short-necked stocky bodies, narrow hips, and short legs (See photo of Mazama pocket gopher in Appendix A). They have cheek pouches that open on the sides of their mouth, which can be turned inside out like pants pockets, and are used for transporting food.  They have small ears and small bead-like eyes. Their front feet are equipped with strong claws and their digits and palms are bordered with a fringe of stiff bristles (Verts and Carraway, 1998).  Their tails are short (~2.5 in) and nearly naked.  T. mazama is a relatively small pocket gopher, smaller than the species commonly found in eastern Washington.  Male T. mazama average 10 – 20% heavier and 5% longer than the females. 

 Moles (family Talpidae) are insectivores and lack the prominent gnawing teeth exhibited by pocket gophers and other rodents.  Moles also have a pointed snout and front claws that differ substantially from pocket gophers. Since both moles and pocket gophers are seldom seen above-ground, most people only see the evidence of their digging.

Species Diet and Foraging.  Pocket gophers eat a wide variety of roots and above-ground plant parts.  T. mazama is particularly fond of bulbs, such as wild onion and wild garlic, and also eat clover (Trifolium spp.), lupines (Lupinus spp.), false dandelions (presumably Hypochaerus radicata), and grasses.  T. mazama forages in the evening on the surface close to their burrows (Stinson, 2005).  Food caches consist of roots of cat’s ear (Hypochaeris radiata), Gairdner’s yampah (Perideridia gairdneri), bracken fern (Pteridium aquilinum), camas bulbs (Scheffer, 1995), and quackgrass (Agropyron repens). 

 Feeding preferences seemed to change with availability, but the most succulent plants available are the most preferred (Stinson, 2005).  The annual diet of T. mazama consisted of aboveground parts of forbs and grasses (40% and 32%, respectively) and 24% roots (Stinson, 2005).  The diet of T. mazama consists of 60% grasses in the winter and 16.6% grasses in the summer (Verts and Carraway, 2000).  Forbs are the preferred forage when in season during the summer months.  Woody plants make up 6% of the diet of T. mazama in the winter and 1.6 % in the summer.  During July, when all forbs were most abundant, pocket gophers prefer forbs over grasses.  In a fallow field and a Christmas tree farm in western Washington, food cache chambers usually contained a single type of root, often thistles (Cirsium spp.) or Scotch broom (Witmer et al., 1996). Scotch broom is probably not a preferred food, since gophers are absent where Scotch broom is abundant (Steinberg, 1996a).  Dandelions can consist of 94% of the pocket gophers’ diet if available (Keith et al., 1959; Laycock and Richardson, 1975).

Habitat requirements and Ecology.  Mazama pocket gophers need open meadows, prairie, or grassland habitat with friable soils that are not too rocky. In general pocket gophers prefer light-textured, porous, well-drained soils, and do not occur in peat or heavy clay soils (Chase et al., 1982).  Gophers tend to favor areas with deeper soils (Baker et al., 2003). The highest gopher densities occur in sites with dark-colored, light-textured soils vegetated with grasses and forbs, especially succulent forbs with underground storage structures.  The availability of forbs may provide nutrients important for gopher growth and reproduction.  Mazama pocket gophers in Washington occur primarily on grasslands of the glacial outwash plain (Dalquest, 1948).  Occupied sites in Washington include airport margins, fallow fields, Christmas tree farms, airport margins, fallow fields, Christmas tree farms, and occasionally in clearcuts.  Provided a source population is available, Mazama pocket gophers may invade an area when the forest cover has been removed; as grass and forbs increase gophers can become abundant for a few years unless or until the area regenerates to forest (Stinson, 2005).  This is what we found on the properties located west of the subject property.  The Mazama pocket gopher invaded neighboring properties when land had been cleared of forest for pasture. 

 Pocket gophers require malleable soils to excavate tunnels.  During the summer months when soils are dry, new tunnels tend to cave in, so tunnel and mound building activity is much reduced during the summer season.  This is analogous to building a sand castle using dry sand.  Rain moistens the soils, making the soil structure more amenable for tunneling.  The best digging conditions occur when the soil moisture is at 10 to 20 percent (Stinson, 2005).  During our 2 years of field studies, we have observed a greater frequency of mound building activities during or following rain events.

 Pocket gopher populations are reported to undergo occasional extreme fluctuations (Case et al., 1982) and are characterized by local extinction and re-colonization (Baker et al. 2003).  Territoriality and extreme weather may influence pocket gopher populations more than any other factors.  Pocket gophers are not long-lived and many live only to one year.  Research has concluded that the maximum age reached by the Mazama pocket gopher is 4 to 5 years with an average of 2 years, although many in the studies did not survive longer than one year (Stinson, 2005). 

Gopher Biology.  The Mazama Pocket Gopher is a small burrowing mammal that eats roots, tubers, bulbs and some surface vegetation (see Section 3 for more detailed information on gopher biology).  Feeding occurs primarily underground.  However, the pocket gopher also feeds above ground on forbs and grasses during the evening and nighttime or during dimly-lit overcast days.  When feeding above ground, the pocket gopher bends down grasses to collect the seeds.  An area of intensely foraged grasses and forbs near their mound structures is an indicator of pocket gopher high use. 

Gopher Habitat.  The Mazama pocket gopher prefers prairie habitat.  Historically, the Native Americans maintained prairie habitat in western Washington through burning the shrubs and trees off the land.  Native Americans harvested camas and other crops, which grew abundantly in western Washington prairies.  Since burning the fields became a thing of the past, forests and farms replaced much of the prairie ecosystem.  Currently, only scattered remnants of this once human-maintained ecosystem remain in western Washington.  Many of these areas are zoned for high-density development by local cities and counties.  One of the last high quality habitats for the Mazama pocket gopher is at the Olympia International Airport.  The Airport is a source of gopher dispersion near the subject property.  Juvenile gophers seeking their own territory may wander into less desirable habitat away from the airport, as they have migrated onto the subject property and the neighboring cattle pasture. 

Gopher Mounds.  The Mazama pocket gopher produces characteristically crescent-shaped mounds of soil above the ground.  Typically, mounds have a plug of soil closing the burrow entrance at the center portion of the crescent-shaped mound.  Mounds are commonly found in lines marking the underground route of the burrow system.  In contrast, moles produce larger conical-shaped mounds that appear more randomly distributed in the landscape.  The pocket gopher burrow system is located just below the surface.  However, brooding chambers and food caches are located as deep as 6 feet below the surface. 

Mound Identification.  Because moles often create mounds interspersed with gopher mounds, species-specific mound identification is an essential component of the study.  Moles and pocket gophers live their lives almost completely under ground.  Their tunneling activity results in mounds of dirt being excavated and left on the surface.  Fortunately, mole and pocket gopher mounds can be identified in the field by easily observable characteristics.  Basically, moles create round or conical-shaped mounds in contrast to the Crescent or kidney shaped mound of the pocket gopher.  Another key difference is that only moles create surface runs, pocket gophers don’t.  The entrance to the mole tunnel system is in the center of the conical-shaped mound, while the entrance for the pocket gopher tunnel is beneath a plug located on the inner side of the crescent-shaped mound.

Gopher Dispersion.  Although, home ranges are very small, juvenile pocket gophers sometimes wander up to 1,000 feet or more in search of territory.  After several generations of these short-lived rodents, dispersion could extend a mile or more from the original natal territory.  While searching for territory, juvenile pocket gophers may create individual or scattered mounds in poor habitats while probing for new territory or foraging areas.  Individual wandering pocket gophers may create ‘explorer mounds’ outside of the primary mound complexes through the dispersal of juveniles or less commonly, adults searching for new foraging opportunities.  The separation distance for suitable habitat is a compromise between the sedentary habits of these mammals and the search for new territory as juveniles strike out on their own.  Two occupied mound complexes separated by less than a few kilometers of suitable habitat could represent two independent territories.  Because of these wandering individual juvenile gophers searching for territory, there may be explorer mounds between two mound complexes or in areas of unlikely gopher habitat, such as in wetlands, forests, or in cemented glacial till. 

Study Limitations.  The limitations of the study include:  1) timing of the field study during the dry summer months when gophers limit mound-producing activities, 2) length of the field study, and 3) lack of trapping for confirmation of gopher presence.  Mound-producing activity occurs more frequently in moist soils.  Rain moistens the soils making its texture malleable for tunnel building.  New mounds are formed much less during the dry summer months.  Hence, few new mounds were available for observation during the site reconnaissance.  Many old mounds were readily available for observation.  To overcome these limitations, our firm drew on our 2 years of field research experience gained in the preparation of several other Mazama pocket gopher Habitat Protection Plans.  The City of Tumwater and the Washington Department of Fish and Wildlife have approved our Habitat Protection plan on the 118-acre site bordering the western boundary of the subject property.  Our firm has performed extensive field research on this and other neighboring properties, expanding our knowledge and experience in identifying gopher use areas during any time of the year.  Field research on neighboring properties included mound identification and live trapping.  The live trapping was to confirm presence in areas of high mound concentrations.  We have learned that pocket gophers typically are found in areas of densely spaced mounds.  The field research for the 93^rd Avenue Assemblage study focused on the identification of gopher mound formations to determine gopher presence. 

2.0    Mound Identification

Gopher mounds can be distinguished from mole mounds by their shape and observable characteristics (Table 1).  Pocket gopher mounds are generally crescent or kidney-shaped and made of finely sifted and cloddy soil (Illustration 1 & 3).  Pocket gopher mounds are often built in a line, whereas moles leave more randomly placed mounds.  Moles form conical or volcano-shaped mounds that are often made up of larger clods of soil in contract to the finely sifted pocket gopher mound (Illustration 1 & 2).  The mole mounds are pushed up from the deep tunnels and may be 2 to 24 inches (5 to 60 cm) tall.  The entrance to the pocket gopher tunnel extends generally 5 to 10 inches of the surface to the main tunnel that extends laterally in both directions.

 Table 1.  Pocket gopher verses mole mound.

Pocket Gopher mound	Mole Mound

 3.0 Distribution and Dispersion

Distribution.  Pocket gophers are found across most of the United States, with the exception of the northeastern states, and from central Alberta south to Panama (Chase et al., 1982).  Pocket gopher ranges generally do not overlap because one species will competitively exclude the other (Chase et al., 1982; Verts and Carraway, 2000).  They are usually not represented by more than one species at any one site.  Mazama pocket gophers are restricted to western Washington, western Oregon, and a portion of northern California (Stinson, 2005).

Mazama pocket gophers are patchily distributed in open non-forested habitats in parts of western Washington (Stinson, 2005).  Their center of abundance is on the south Puget Sound prairies of Pierce, Thurston, and Mason counties. The species is also found on subalpine meadows of the Olympic Mountains.

Home Range.  Males and females both hold territory.  The home range of males covers between 73 and 143 m² of area, while that of females covers 47 and 150 m² of area (Verts and Carraway, 2000).  The area encompassing an individual’s territory varies greatly, depending on the age of the gopher, resources available, suitable soil conditions, and other factors.  Gophers are relatively solitary with exception during breeding season (October to June) when males and females can be found in the same tunnel system.  T. mazama is polygynous in that males will mate with multiple females that enter the male’s burrow system during breeding season.  The larger size of males prevents them from entering the smaller burrow systems tunneled by females.  Hence, females choose males by entering the male’s burrow system (territory).  An individual territory is sedentary once established.  Territories are clustered in preferred areas favored for bountiful resources and suitable environmental factors.  The close proximity of individual territories forming a colony allows for breeding success and for re-occupying abandoned tunnel systems.  Field studies performed by PE Consultants LLC over the last several years has identified high use areas that resemble a colony of gophers, as well as some individual mounds formed in less desirable environmental conditions, presumably left by juveniles searching for individual territory. 

Density.  The Mazama pocket gopher averages 20 individual gophers per acre within a dense gopher colony (Stinson, 2005).  Other studies estimated approximately 11 individual gophers per acre (Smallwood and Morrison, 1999).  The larger the study area, density tends to decrease because the gophers tend to cluster in high density colonies.  Smallwood and Morrison (1999) pointed out that the conventional study method is to estimate density for a dense cluster of gophers (colony); as the study plot size is increased, more gopher-free area is included and estimated density decreases. 

Juvenile Dispersion.  Females produce an annual average litter size of 5 offspring during the October to June breeding season (University of Michigan Museum of Zoology, http://animaldiversity.ummz.umish.edu/site/accounts/informational/thomomys_mazama.htm).  Gestation takes 1 month and then shortly after, the juveniles leave their natal brooding chamber to seek their own territory.  The gopher’s relatively short lifespan creates an urgency to find territory and reproduce.  The mates with the best territory presumablkey have a better mating success.  Pocket gophers reach sexual maturity within one season and the average life span extends only 2 years (Maximum life span 5 yrs for males & 4 yrs for females). 

Juvenile pocket gophers can wander from the natal burrow system almost 1000 feet in search of individual territory.  Daly and Patton (1990) reported that vacant habitat within a few hundred meters is rapidly colonized.  They further reported that 20% of juveniles wandered 120 to 300 feet of their natal territory.  About half of that percentage moved up to 1000 feet or more of their natal territory.  Juvenile pocket gophers disperse above ground from their natal burrows (Chase et al., 1982).  Most gophers that disperse far from their home range are males, as typical in small rodents (Stinson, 2005).  After several generations of these short-lived rodents (within several years), dispersion could extend a mile or more from the original natal territory.