Western pocket gopher (Thomomys mazama)

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Western pocket gopher digging
IUCN Red List species status – Least Concern LEAST
CONCERN

Top facts

  • The western pocket gopher can close its lips behind its front teeth, preventing soil from entering the mouth when it digs its burrows.
  • The western pocket gopher can move backwards in its tunnels almost as fast as forwards.
  • Two long, fur-lined cheek pouches open on the outside of the western pocket gopher’s mouth. Used to transport food, they can be turned inside out to be cleaned.
  • In winter, the western pocket gopher tunnels through snow and lines the tunnels with soil. When the snow melts, trails of soil are left on the ground.
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Western pocket gopher fact file

Western pocket gopher description

KingdomAnimalia
PhylumChordata
ClassMammalia
OrderRodentia
FamilyGeomyidae
GenusThomomys (1)

Also known as the Mazama pocket gopher, the western pocket gopher (Thomomys mazama) is a medium-sized, stocky rodent with a number of adaptations for its underground lifestyle. Its short, powerful forelimbs are equipped with strong claws for digging (2) (3) (4) (5) (6), and it can close its lips behind its large, curved incisors, allowing it to gnaw at soil without getting any in its mouth (3) (4) (6).

The head and shoulders of the western pocket gopher are heavily muscled, and the body tapers towards relatively narrow hips (2) (4) (6), which are an advantage for moving through burrows (6). The western pocket gopher has small ears and eyes and fairly poor vision, but its short, almost naked tail is highly sensitive to touch (4) (5).

The western pocket gopher has soft, smooth fur (4) which varies in colour from dark, reddish- or yellowish-brown to black with purple and greenish iridescence (2) (3) (6) (7). The underparts of the western pocket gopher are typically grey to buff (3) (6) (7), sometimes with white patches on the chin or chest (2) (7), and the face is greyish to black (2) (6). The feet and the tip of the tail are usually white or light grey (2) (6).

Like other pocket gophers, the western pocket gopher has two long, fur-lined cheek pouches that open externally, on the outside of the mouth (2) (4) (5) (6). These pouches are used for transporting food, and can be turned inside out to be cleaned (4) (6).

The ears of the western pocket gopher are relatively large in comparison to other pocket gophers (3), and there is a large patch of black fur below each ear (3) (7). The size of this black fur patch can help to distinguish the western pocket gopher from the similar-looking northern or Vancouver pocket gopher (Thomomys talpoides), in which it is smaller and less obvious (6) (7).

As in other pocket gophers in the genus Thomomys, the male western pocket gopher is likely to be significantly larger than the female (4). Up to 15 subspecies of western pocket gopher have been described, although their taxonomy is currently under study (8).

Also known as
Brush Prairie pocket gopher, Cathlamet pocket gopher, Gold Beach pocket gopher, Goldbeach western pocket gopher, Louie’s western pocket gopher, Mazama pocket gopher, Olympia pocket gopher, Olympic Mountains pocket gopher, Puget Sound pocket gopher, Rocky Prairie pocket gopher, Rogue River pocket gopher, Roy Prairie pocket gopher, Shelton pocket gopher, Tacoma pocket gopher, Yelm Prairie pocket gopher.
Synonyms
Thomomys helleri, Thomomys hesperus, Thomomys melanops, Thomomys nasicus, Thomomys niger.
Size
Total length: 18 - 23 cm (2) (3)
Tail length: 5.2 - 7.9 cm (2)
Weight
61 - 147 g (2)
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Western pocket gopher biology

Like other pocket gophers, the western pocket gopher spends most of its life underground, where it constructs an extensive burrow system (2) (4) (6). In addition to shallow feeding tunnels, it also digs deeper tunnels which include chambers for nesting, storing food and depositing faeces (2) (4) (6). The nest chamber is usually lined with dry grass (2) (6). Above ground, the western pocket gopher leaves conspicuous, fan-shaped mounds of excavated soil, but unlike most rodents it usually seals the burrow entrances with plugs of earth (2) (4) (6).

The western pocket gopher digs mainly with its strong front claws, but the large incisors may also be used to loosen soil and cut through roots. This species can run backwards through its tunnels almost as fast as it runs forwards (4) (6).

The diet of the western pocket gopher includes underground roots, bulbs and tubers, as well as surface vegetation such as grasses and forbs (1) (2) (4) (5) (6) (7). Woody plants are also occasionally eaten (2), mostly in winter (6). Although the western pocket gopher can forage underground from its burrows, it may also emerge onto the surface in the evening or at night to gather vegetation (1) (2) (4) (6). It rarely ventures far from the burrow entrance, typically filling its cheek pouches with vegetation before taking it below ground (2) (4) (6).

The western pocket gopher does not hibernate, and if snow accumulates on the ground it will burrow through it, lining the tunnels with excavated soil. In spring, rope-like trails of soil may be left on the surface when these snow tunnels melt (2) (4) (6).

A primarily solitary species, the western pocket gopher is highly territorial and intolerant of other individuals, except during the breeding season (4) (5) (6). This species is believed to be polygamous, with each male mating with several females (5) (6). The female western pocket gopher gives birth to a single litter of up to 7 young between March and June (1) (5), probably after a gestation period of about 18 to 19 days (4) (5).

The young western pocket gophers are likely to remain in the female’s burrow for about one to two months, before leaving to establish burrows of their own (4). This species reaches sexual maturity at about a year old (4) (5) (6). The western pocket gopher has a number of predators, including owls, coyotes, weasels, skunks, foxes, bobcats, and domestic dogs and cats (1) (2) (4) (6), and few individuals live for more than a year or two (4) (6).

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Western pocket gopher range

The western pocket gopher has a relatively restricted distribution along the Pacific coast of the United States, occurring in Washington, Oregon and northern California (1) (2) (4) (5) (6) (7) (8). The majority of its population is found in Oregon (1), with its populations in Washington being small and patchily distributed (1) (8).

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Western pocket gopher habitat

The western pocket gopher typically inhabits prairies, pastures, alpine meadows and grasslands, and sometimes young, open woodland or forest (1) (2) (3) (6) (7). As a burrowing species, it prefers areas with soft, deep, light-textured volcanic soils (1) (3) (6) (7) which are easy to dig through and not too rocky (6).

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Western pocket gopher status

The western pocket gopher is classified as Least Concern (LC) on the IUCN Red List (1).

IUCN Red List species status – Least Concern

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Western pocket gopher threats

Although the western pocket gopher is not currently considered to be at risk of extinction, its populations are generally declining and many face significant threats (1). A number of subspecies found around the Puget Sound in Washington have small, fragmented populations with restricted distributions, and are considered to be particularly under threat (4) (6) (8). At least two subspecies, Thomomys mazama tacomensis and Thomomys mazama louiei, may already have become extinct (4) (5) (6) (8) (9).

The main threat to the western pocket gopher, particularly in parts of Washington, is the loss and degradation of its habitat, with native prairies now considered to be one of the most highly threatened habitats in the whole of the United States (5) (6). Many of the prairies in the western pocket gopher’s range have been extensively modified or replaced by agriculture and development (1) (5) (6) (8), while the remaining habitat has been degraded by overgrazing and the spread of invasive plants (1) (5) (6). Gravel mining also occurs in some areas (6), while altered fire regimes have allowed the process of succession, whereby the prairies gradually change into forest (6).

The western pocket gopher is sometimes accused of damaging grasslands, but overgrazing by livestock typically does the damage, with the gophers only moving in to take advantage of the conditions it creates (4). However, pocket gophers may feed on crops in agricultural areas and can do damage to young trees (2) (4) (5), and are often poisoned and trapped as a result (2) (6). Persecution, together with predation by domestic cats and dogs, means that this species often cannot persist in residential areas (6).

The small size and isolation of many western pocket gopher populations put them at increased risk of local extinction. As patches of habitat are increasingly hemmed in by roads and suburbs, this species is also increasingly unable to disperse (6).

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Western pocket gopher conservation

The western pocket gopher occurs in a number of protected areas (1), including the Olympic National Park in Washington, where the entire population of the subspecies Thomomys mazama melanops occurs (6) (8) (9).

A number of subspecies of the western pocket gopher are ‘Candidate’ species for federal listing under the U.S. Endangered Species Act (5) (6) (10) and for State listing in Washington, meaning that they are under review for possible listing as threatened or endangered, but are not yet legally protected (6) (8). Recent assessments recommend that the western pocket gopher should be listed as ‘Threatened’ in Washington (6). In Oregon, the subspecies Thomomys mazama helleri has been listed as a ‘Species of Concern’, but this does not give it any legal protection (11).

Conservation measures for the western pocket gopher have included efforts to restore and manage prairies, for example through the removal of invasive plants (5) (6). Population surveys have been conducted, but more are needed (6). Other recommended actions for this species include determining the distribution and status of the different subspecies, clarifying their taxonomic relationships, and preserving remaining prairie habitat (8).

Although it can sometimes do damage to crops and trees, the western pocket gopher plays an important role in its habitat, improving soil aeration and water flow through its burrowing, and maintaining plant diversity by its activities (1) (4) (5) (6) (8). The burying of its food stores and faeces deep underground also improves soil fertility (4), while its burrows provide shelter for a range of other species, and the gopher itself is an important prey item for many predators (1) (6). However, unless large, stable, interconnected populations are established in suitably managed habitat, this burrowing rodent could be at risk across much of its range (6).

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Find out more

Find out more about the western pocket gopher and its conservation:

More information on prairie conservation:

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Authentication

This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
arkive@wildscreen.org.uk

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Glossary

Forb
A herb with broad leaves that grows alongside grasses in a field, prairie or meadow.
Genus
A category used in taxonomy, which is below ‘family’ and above ‘species’. A genus tends to contain species that have characteristics in common. The genus forms the first part of a ‘binomial’ Latin species name; the second part is the specific name.
Gestation
The state of being pregnant; the period from conception to birth.
Hibernate
Hibernation is a winter survival strategy in which an animal’s metabolic rate slows down and a state of deep sleep is attained. Whilst hibernating, animals survive on stored reserves of fat that they have accumulated in summer.
Incisors
The front or cutting teeth.
Polygamous
Mating with more than one partner in the same season.
Prairie
An extensive area of flat or rolling, predominantly treeless grassland, especially the large tract or plain of central North America.
Subspecies
A population usually restricted to a geographical area that differs from other populations of the same species, but not to the extent of being classified as a separate species.
Succession
The progressive sequence of changes in vegetation types and animal life within a community that, if allowed to continue, results in the formation of a ‘climax community’ (a mature, stable community in equilibrium with the environment).
Taxonomy
The science of classifying organisms, grouping together animals which share common features and are thought to have a common ancestor.
Territorial
Describes an animal, a pair of animals or a colony that occupies and defends an area.
Tuber
In plants, a thickened stem or root that acts as an underground storage organ. Roots and shoots grow from growth buds, called ‘eyes’, on the surface of the tuber.
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References

  1. IUCN Red List (June, 2012)
    http://www.iucnredlist.org/
  2. Verts, B.J. and Carraway, L.N. (2000) Thomomys mazama. Mammalian Species, 641: 1-7. Available at:
    http://www.science.smith.edu/msi/pdf/641_Thomomys_mazama.pdf
  3. Kays, R.W. and Wilson, D.E. (2009) Mammals of North America. Second Edition. Princeton University Press, Princeton, New Jersey.
  4. Nowak, R.M. (1991) Walker’s Mammals of the World. The Johns Hopkins University Press, Baltimore and London.
  5. U.S. Fish and Wildlife Service, Washington Fish and Wildlife Office: Species Fact Sheet - Mazama pocket gopher (June, 2012)
    http://www.fws.gov/wafwo/species/Fact%20sheets/MazamaPocketGopher_final.pdf
  6. Stinson, D.W. (2005) Washington State Status Report for the Mazama Pocket Gopher, Streaked Horned Lark, and Taylor’s Checkerspot. Washington Department of Fish and Wildlife, Olypmia. Available at:
    http://wdfw.wa.gov/publications/00390/wdfw00390.pdf
  7. Reid, F.A. (2006) A Field Guide to Mammals of North America. Houghton Mifflin Company, New York.
  8. Hafner, D.J., Yensen, E. and Kirkland Jr, G.L. (1998) North American Rodents: Status Survey and Conservation Action Plan. IUCN/SSC Rodent Specialist Group, IUCN, Gland, Switzerland and Cambridge, UK. Available at:
    http://data.iucn.org/dbtw-wpd/edocs/1998-039.pdf
  9. Lidicker Jr, W.Z. (1989) Rodents: A World Survey of Species of Conservation Concern. IUCN/SSC Rodent Specialist Group, IUCN, Gland. Available at:
    http://data.iucn.org/dbtw-wpd/edocs/SSC-OP-004.pdf
  10. U.S. Fish and Wildlife Service (June, 2012)
    http://www.fws.gov/
  11. U.S. Fish and Wildlife Service, Oregon Fish and Wildlife Office (June, 2012)
    http://www.fws.gov/oregonfwo/Species/Data/default.asp
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Western pocket gopher digging  
Western pocket gopher digging

© William Leonard

William Leonard
mollusca1@comcast.net

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