Category: Recovery Plans
Published: January 2013
Author(s): Derek W. Stinson
The Mazama pocket gopher (Thomomys mazama), a small fossorial rodent, is a regional endemic found only in western Washington, western Oregon and northern California. Pocket gophers play an important role in ecological communities by altering soil structure and chemistry, affecting plant occurrences, and serving as prey for many predators, and their burrows provide a retreat for a wide variety of other species. Mazama pocket gophers were formerly more widespread on south Puget Sound prairies, but their distribution has diminished as suitable habitat has been lost to development or degraded by Scotch broom and succession to forest. The species was state-listed as threatened in 2006 by the Washington Fish and Wildlife Commission.
In 2001, the U.S. Fish and Wildlife Service (USFWS) designated eight subspecies of the Mazama pocket gopher in Washington as candidates for listing under the federal Endangered Species Act. In 2012, the USFWS proposed adding four of these subspecies (T. m. pugetensis, tumuli, yelmensis, and glacialis) to the federal list of Threatened species and designating critical habitat. The proposal also included a 4(d) rule that would exempt some activities from the Actâ€™s Section 9 take prohibitions, including some existing maintenance activities at airports and farms, livestock grazing, some agricultural activities, and certain activities on single-family residential properties. The proposal is being evaluated and a final rule is scheduled to be published in late 2013.
The Mazama pocket gopher is primarily found on well-drained glacial outwash soils with grassland or herbaceous vegetation. Many of these areas historically supported prairies and savannahs. In addition to historical prairies areas, they occasionally inhabit areas with sandy loam or gravelly soils when the tree cover is removed and herbaceous vegetation is established. Higher numbers of gophers have been found on loamy sand soil types than on the more widespread gravelly soils, some of which may contain too much rock to be suitable. Most of the areas of loamy sand soils in Thurston County are within the city limits or Urban Growth Areas of Olympia, Tumwater and Lacey, and much is already densely developed. In southeastern Mason County, pocket gophers are found on grassland in former prairie areas near Shelton, and they also occur in forest openings, roadsides, and in the ephemeral herbaceous vegetation in recent clearcuts. WDFW conducted extensive Mazama pocket gopher surveys in 2012. These included nearly 950 survey sites in Thurston, Mason, and Pierce counties, and small portions of Lewis, Grays Harbor, Wahkiakum, and Clark counties. The results of the surveys confirmed previous descriptions of the distribution of Mazama pocket gophers in Washington.
Much of the historical gopher habitat of south Puget Sound with appropriate soils and vegetation has been degraded, fragmented, or converted to impervious surfaces. Habitat loss to succession, agriculture and development has eliminated most of the prairie vegetation. Although significant areas remain in grassland, pasture or turf, trends in the human population suggest that available habitat and the quality of habitat will continue to decline without careful management of conflicting uses. The human population in Washington is expected to increase from the current 6.8 million to 7.7 million by 2020, and to 11 million by the mid-21st century. Prairie habitat continues to be lost, particularly to residential development, and Thurston County is projected to have 170,000 additional people and need an additional 50,000 detached single-family housing units, and >25,000 multi-family units by 2040. As the habitat patches become smaller, fewer, and farther apart, the likelihood of each patch continuing to support pocket gophers declines.
The goal of the recovery plan is to secure and maintain self-sustaining populations of Mazama pocket gophers within their current Washington range. Seven areas that have substantial existing habitat and contain significant numbers of Mazama pocket gophers in Thurston, Pierce, and Mason counties are identified for recovery emphasis. Populations in three occupied or formerly occupied areas are not included in recovery objectives for the following reasons: Mazama pocket gophers in Wahkiakum County (T. m. louiei) and a portion of Pierce County (T. m. tacomensi) appear to be extinct; and Mazama pocket gophers in Clallam County (T. m. melanop) are found entirely within Olympic National Park. Because they are within the park, there are no certain threats to the Clallam County population or habitat; however, there may be a need to address tree encroachment in occupied areas.
Conservation of the populations in the seven areas (five in Thurston County, one in Pierce County, and one in Mason County) would preserve representative local populations and subspecies across their range in the south Puget Sound region. Some portions of the range that still host small numbers of gophers were not identified for recovery emphasis because of low potential for long-term persistence. These areas are densely developed or host only small numbers of gophers.
The Mazama pocket gopher will be considered for downlisting to Sensitive status when the following objectives have been met:
- Objective 1. Maintain a stable or increasing population trend for a 10-year period in each of seven Mazama pocket gopher population areas (five in Thurston County, one in Pierce County, and one in Mason County); and
- Objective 2. Conservation agreements, regulations, or other mechanisms are in place that effectively and sustainably protect and provide the habitat extent, connectivity, and condition necessary to meet Objective 1.
Conservation activities will focus on protecting and maintaining habitat, monitoring population trends, maintaining or restoring habitat connectivity between local subpopulations, and conducting research to describe dispersal, demography, population dynamics, and determining what factors limit populations. Population trends will be monitored over time by sampling site occupancy and other indices. Much of the occupied gopher habitat in the Puget Sound is in public ownership, but some has uses that can conflict with the needs of gophers and a number of sites are on private lands. Recovery will involve partnerships with landowners, federal, state, and local agencies, and private conservation organizations. Incentive programs and partnerships are recommended to facilitate the maintenance of functional pocket gopher habitat in rural residential and agricultural areas with the help of private landowners.
Once the recovery objectives are met, an updated status report will be prepared with a recommendation to downlist the species to state Sensitive. After the species is downlisted to Sensitive, a management plan will be prepared.