Thomomys mazamawestern pocket gopher

Geographic Range

Thomomys mazama is found in the Pacific Northwest of the United States. Populations occur in Washington, Oregon, and California (Verts and Carraway, 2000).


Thomomys mazama usually occupies a narrower array of niches than other species of Thomomys. Thomomys mazama is found in a variety of soil types in prairies, meadows, orchards, and abandoned farms. They are not frequently found in dense forest. Common vegetation in the habitats of T. mazama includes bracken fern, Douglas fir, perennial grasses, red sorrel, and western strawberry.

Physical Description

Thomomys mazama is highly fossorial. It is adapted for this mode of life with heavily muscled shoulders and head tapering to relatively narrow hips. It has short limbs with five toes on each of the four feet. The toes on the front limbs have much longer curved claws than the hind limbs. The eyes and ears are small. The skull is flattened dorso-ventrally and has wide spreading zygomatic arches. The mandibles are heavy (Verts and Carraway, 2000).

The dorsal pelage of T. mazama exhibits a large range of colors in various subspecies. It is a shiny iridescent black in the subspecies T. m. niger. In T. m. tumuli and T. m. pugetensis it is blackish brown. The fur is dark brown in T. m. fuscus and T. m. louiei; reddish brown in T. m. hesperus, T. m. mazama, T. m. helleri, and T. m. melanops; reddish tan in T. m. couchi and T. m. tacomensis; light yellowish brown in T. m. nasicus, T. m. premaxillaris, and T. m. glacialis; and light brown in T. m. oregonus and T. m. yelmensis. The nose and face are dusky or black. The chest often has white splotches. The tip of the tail is lighter colored, usually buff, white, or light gray and may be almost naked.

Male T. mazama are generally larger than females. The total average length of T. mazama is 204 mm for females and 213 mm for males. The average tail length is 62 mm for females and 64.5 mm for males. The baculum is commonly used to differentiate between juveniles and adults. It is long and slender. The minimum length to be classified as an adult is 21-22 mm, but it can reach a length of about 26 mm. The dental formula for T. mazama is i 1/1 c 0/0 p 1/1 m 3/3 with a total of 20 teeth. The premolars are figure eight shaped. Chewing is propalinal (Verts and Carraway, 2000). (Verts and Carraway, 2000)

  • Sexual Dimorphism
  • male larger
  • Range length
    204 to 213 mm
    8.03 to 8.39 in


There is little information on the mating behavior of T. mazama. Individuals seem to rely on encountering each other through normal daily movement (Scheffer, 1938).

Mating has not been observed in captivity for T. mazama, but reproductive behavior can be inferred from individuals taken in from the wild. The females produce one litter per year during the October to June breeding season. The average litter size is five. The period of gestation is about one month and depends on environmental factors. Under extreme stress, one or more embryos may be reabsorbed (Scheffer, 1938).

  • Average number of offspring
  • Average number of offspring
  • Average gestation period
    30 days
  • Average gestation period
    30 days
  • Average age at sexual or reproductive maturity (female)
    1 months
  • Average age at sexual or reproductive maturity (male)
    1 months


Thomomys mazama leads a fossorial life, spending most of its time in burrow systems it constructs or finds unoccupied. These burrows are 3.8-4.4 cm in diameter and are generally 10-15 cm below the surface. A vertical tunnel goes to deeper burrows that include the nest. Crescent shaped mounds of earth are formed when earth is excavated and lie at the surface. Nests are about 25 cm in diameter and 15 cm high and are lined with dry grass and root cuttings. Feces are left in nearby waste chambers. Individuals are generally solitary and are found together in burrows only during mating season. Thomomys mazama forages underground by snipping off roots while in their burrows. They sometimes forage above ground at night. They stay close to the openings of their burrows while they load their cheek pouches with vegetation before quickly going back underground. They repeat this process throughout the night. They do not eat while on the surface (Verts and Carraway, 2000).

The average home ranges of T. mazama are 97 square meters for females and 108 square meters for males (Witmer, 1996).

Communication and Perception

Food Habits

Grasses compose the largest portion of the diet of T. mazama annually. Woody plants such as Ponderosa pine were consumed mostly in the winter. Roots were eaten mostly in the autumn and spring and compose a large portion of the diet during these periods. Forbs are preferred when many food sources are available. In general, consumption of various species of plants corresponded to their abundance (Verts and Carraway, 2000).


Anti-predator adaptations are primarily behavioral. Thomamys mazama lives underground and emerges only briefly at night to forage. If threatened it retreats underground (Verts and Carraway, 2000).

Ecosystem Roles

Thomomys mazama may play an important role in the aeration, mixing, and drainage of soil. They also contribute to the distribution and succession of plant species and communities. They are a source of food to many mammals and birds. Their burrows are used and inhabited by many other species. Their ecological importance is suggested by the fact that there is an ecological equivalent to the gopher on almost every continent (Witmer, 1996).

Economic Importance for Humans: Negative

Thomomys mazama can cause the failure of forest plantings because they eat the roots, leaves, and stems of the seedlings. This has led to efforts to control and eliminate gopher populations with repellents and toxins (Witmer, 2000).

  • Negative Impacts
  • crop pest

Conservation Status

As of 1998 T. mazama was listed as a candidate species by the Washington Department of Fish and Wildlife and as a species of concern by the U.S. Fish and Wildlife Service but was not included in lists of threatened species from the Oregon Department of Fish and Wildlife or the California Department of Fish and Game (Verts and Carraway, 2000).

Other Comments

There are many subspecies because they are easily isolated by rocky, wet, or very compact soil; by frequent agricultural plowing of the land; or by dense forest (Whitmer, 1996).


Corie Hanna (author), University of Michigan-Ann Arbor, Ondrej Podlaha (editor), University of Michigan-Ann Arbor.



living in landscapes dominated by human agriculture.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


uses smells or other chemicals to communicate


animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.


union of egg and spermatozoan

internal fertilization

fertilization takes place within the female's body


having the capacity to move from one place to another.


active during the night

seasonal breeding

breeding is confined to a particular season


reproduction that includes combining the genetic contribution of two individuals, a male and a female

soil aeration

digs and breaks up soil so air and water can get in


lives alone


uses touch to communicate


that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).


Living on the ground.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.


A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.


Scheffer, T. 1938. Breeding records of Pacific Coast pocket gophers. Journal of Mammalogy, 19: 220-224.

Verts, B., L. Carraway. 2000. Thomomys mazama. Mammalian Species, 641: 1-7.

Witmer, G. 1996. Biology and Habitat Use of the Mazama Pocket Gopher (Thomomys mazama) in the Puget Sound Area, Washington. Northwest Science, 70: 93-98.