slightly less adapted to an underground existence than the moles. The
body is stout, the legs short and the head broad. The tail is short,
sparsely haired, cylindrical and blunt-ended. The fur is soft and dense.
The eyes are small and the ears tiny and naked. The incisor teeth are
external, being separated from the mouth cavity by a furry strip of
skin. Like the pocket mouse and kangaroo rat, the pocket gopher
possesses external, fur-lined cheek pouches. The openings of these begin
just below and posterior to the nostrils, sweep out and down in a
semicircle, and end at the chin posterior to the base of the lower
incisors. They extend laterally to the shoulders and easily accommodate
a fifty-cent piece.
[Illustration: FIG. 95. Northern pocket gopher (_Thomomys talpoides
yelmensis_), from two miles southwest of Tenino, Washington, January
28, 1941. (Fish and Wildlife Service photo by Victor B. Scheffer, No.
1133.)]
The family Geomyidae is composed of eight genera, so similar in
appearance that the name "pocket gopher" is applied to all of them. The
family is confined to North and Central America. Three genera occur in
the United States but only one, _Thomomys_, occurs in Washington.
_Thomomys_ is restricted to western North America where it ranges from
central Canada south to the southern edge of the table land of Mexico.
Several hundred kinds of _Thomomys_ have been described and as
systematic work with this genus has been continued, more and more kinds,
originally thought to be species, are found to intergrade and to be only
subspecies. All of the 17 kinds of pocket gophers occurring in
Washington belong to a single species.
The pocket gopher is principally nocturnal or crepuscular but sometimes
it is active at midday, especially if the day be dark and cloudy.
Pocket-gopher activity is indicated by fresh mounds of earth on the
surface of the ground. Rarely, an observer may see movement of plants as
the gopher molests the roots of the plants, or even see the head and
shoulders of an animal that partly emerges from an open burrow. The
ordinary gopher mound consists of less than a cubic foot of earth. The
earth is forced up from a single opening and usually is pushed out in
one direction. In consequence it forms in a fan-shaped pile about the
opening, and the last load forms a circular plug above and to one side
of the burrow opening. When so much earth has been forced out of one
opening that expulsion of additional loads of earth is overly difficult,
the burrow is extended slightly to one side, or even extended into the
newly formed mound, and another fan formed. Usually not more than three
coalesced fans form a mound, but where the soil is exceedingly soft and
fluffy, hundreds of fans may form a composite mound and the one mound
may include a cubic yard of earth. Large composite mounds probably are
formed gradually over a period of weeks or even months.
The earth in a fresh gopher mound is usually "scratched," and gives the
appearance of having been sieved. Pebbles weighing more than 100 grams
are included in material ejected from burrows. The entrances to the
burrows of gophers are usually solidly plugged with earth. The plug may
be from a few inches to more than a foot in length. At times a burrow
entrance may appear to be open, but in such cases investigation will
usually reveal it to be plugged some distance back--sometimes several
feet.
In contrast to the gopher mounds described above, the mounds of moles
are not fan-shaped but volcano-shaped. The earth from a mole's burrow is
forced straight upwards, whence it falls to either side. Later loads are
pushed up from beneath, raising the entire mound, with the last material
ejected at the center and bottom. The earth of a fresh mole-mound is not
of fine texture but instead is "clotted" and, if damp, gives the mound
a fractured appearance. When mounds are older, perhaps changed by rain
and sun, their identity as of mole-origin or pocket gopher-origin is
more difficult to establish. In such cases, if no fresh mounds can be
found, the observer must rely on the spacing of the mounds. Mole-mounds
are spaced along a burrow, about as far apart as a man can step. Gopher
mounds are irregularly spaced, and the course of the burrow cannot be
traced merely by observing the arrangement of the mounds as can that of
the mole.
In addition to mounds, gopher burrows have plugged openings where a
gopher has come to the surface, probably to cut plants. Such entrances
are marked by a plug of earth several inches long. Mounds and feeding
entrances of the gopher burrow are usually not constructed in the main
burrow system itself, but at the ends of lateral burrows of varying
length. If one traces the burrow back from the mound, a junction with
the main, better-constructed burrow is found. The junction is usually
T-shaped, with the lateral burrow at right angles to the main burrow.
More rarely the junction has a Y-shape.
[Illustration: FIG. 96. Giant mounds raised by pocket gophers on Mima
Prairie, Thurston County, Washington, July 13, 1941. (Fish and
Wildlife Service photo by Victor B. Scheffer, No. 1209.)]
The burrow system of the pocket gopher may be divided into three main
parts. These are the laterals, just discussed, the main burrow, and the
deep nesting burrow. The main burrow is a sinuous tube or tunnel at a
relatively uniform depth, that marks the extent of the gopher's home
territory. This tunnel may branch, or even intersect. As it is extended
in one direction, the earth excavated by the gopher may in part be
thrust into an unused portion of the burrow.
The deep, nesting burrows may be used only in the breeding season. They
are connected with the main tunnel system but descend to a greater
depth. Usually they descend into the harder, consolidated layers of soil
below the zone where plant roots penetrate. Here chambers are
constructed in which nests and food are stored. Usually a vertical shaft
is dug in the burrow ahead of the nest to lead rain water away from the
nest.
In areas where gophers live in a thin layer of soil underlain by a more
or less impenetrable layer of rock, clay or gravel, it has been
suggested that they form unique structures known as Mima Mounds. The
formation of these mounds has been discussed in detail elsewhere
(Dalquest and Scheffer, 1942: 68-84). At least in the breeding season
the gophers work mainly and make their nest where the soil is deepest.
In the vicinity of this nest, considerable mounding and cultivation of
soil ensues. This stimulates plant growth in the area. Much observation
indicates that cultivation of earth by gophers stimulates plant growth
to a greater extent than the depredations of the gopher deplete the
ensuing growth. Thus the gopher, by cultivation of the soil in the area
about its burrow, stimulates the growth of vegetation and so increases
his own food supply. Consequently there is but little incentive for the
gopher to leave the vicinity of the nest. The gopher does, however,
construct lateral tunnels into surrounding areas. Earth from these
lateral tunnels is, in part, thrown to the surface in mounds and in part
transported back to fill the abandoned burrows near the nest. The earth
from the burrows about the nest was earlier ejected on the surface.
Slowly, then, earth is transported from surrounding areas to burrows in
the vicinity of the original nest. Each succeeding generation finds in
the vicinity of the original nest, better food and deeper soil, while
areas surrounding the nest possess thinner soil and less vegetation.
Over a period of thousands of generations of gophers, large mounds,
known as Mima Mounds, are formed. Since the removal of earth from the
surrounding areas and its accumulation in the Mima Mound are chance
affairs, the contours of the mound are smooth and flowing while the
contours of the intermound areas are smoothly convex.
The pocket gophers in Washington are economically important. In truck
and flower gardens they are a pest, especially if the crop be bulb
plants. In grain fields they are a pest because their mounds cover
considerable grain and are apt to clog or dull the knife of the mower.
In fields of young alfalfa they are apt to crop back the plant more
rapidly than it can grow. Once the alfalfa plant is well established,
however, the cultivation resulting from activities of gophers, some
persons believe, stimulates the plant to such an extent that it grows
larger and healthier in spite of the gopher's feeding on it. In the
White Salmon Valley, Klickitat County, I examined numerous alfalfa
fields. The most luxuriant growth was invariably in fields where gophers
were common. In these fields, the largest plants were those in the
immediate vicinity of gopher activity. The commensal relation between
the gopher and alfalfa was understood by many farmers, who forbade us to
take gophers for specimens from their fields. Several told us that they
always trapped the gophers from the fields of young alfalfa and from hay
meadows but encouraged their presence in fields of older alfalfa.
[Illustration: FIG. 97. Food cache of northern pocket gopher
(_Thomomys talpoides tacomensis_), from chamber four inches below
surface of ground, Tacoma, Washington, December 1, 1940. Contents
575 grams (about 2 liters) of roots, principally quackgrass,
_Agropyron repens_. (Fish and Wildlife Service photo by Victor
B. Scheffer, No. 1119.)]
Another economic factor is the gopher's removal of certain weeds from
grazing land. A number of introduced weeds form dense rosettes that
prevent the growth of grass from several square inches of ground and
themselves lie so close to the ground as to be unavailable as food to
grazing stock. These weeds seem to be favored food of gophers which cut
not only the rosettes but the roots of the weeds as well.
In irrigated parts of eastern Washington the gopher is a serious pest.
It burrows in the banks of the main ditches, causing cave-ins and
occasional breaks with resultant water loss. The mounds of gophers fill
in the smaller channels and divert the streams. Constant attention is
necessary to keep the ditches free of gopher mounds.
In uncultivated land the gopher is a distinct asset unless the land is
near enough to cultivated land to serve as a reservoir of pests. In the
mountains and on the desert the gopher cultivates and keeps the soil
soft and stimulates the growth of water-retaining vegetation, thus
preventing rapid run-off and erosion and keeping the flow of springs and
streams constant. Boulders, logs, and other obstructions are undermined
and, as a result of gopher activity, in time sink under the surface of
the ground. Thus a larger surface is available for plant growth. Lastly
the gopher furnishes an important food source for certain fur-bearing
mammals and eases the predator pressure on game species.
The subspecies of pocket gopher occupying the Puget Sound area are
highly restricted in their habitat preference; they occur only on the
grassy prairies of the glacial outwash aprons. They do not occur in
woods, brush or even small openings on the borders of the prairies. The
alpine forms occupy the mountain meadows and are slightly less selective
in their habits. It should be noted that in western Washington the
forests are far more open at higher altitudes than at low elevations.
The races inhabiting the desert are found in open areas, often in sandy
places. They occur more rarely in areas where the soil is baked and
claylike, and then usually in the vicinity of springs or watercourses.
The race _T. t. fuscus_ has a wide range of tolerance as regards
environmental factors; it occurs near Wenatchee in essentially desert
conditions, in alpine meadows of northeastern Washington, and in many
habitats at intermediate elevations. It occurs also in brushy areas and
is often abundant in open pine forests.
Since the gopher usually has a narrow range of tolerance as regards its
environmental adaptations, this has resulted in considerably more
isolation than is the case with other mammals, and has probably
contributed to the formation of the many subspecies. Within the range of
almost every race, microgeographic races, or local populations with
distinctive characters, are found. Many subspecies of _Thomomys_ are
probably the result of chance fixation of genetic characters already
present in a more genetically variable ancestral population, and the
loss of other genetic factors. Such races might be considered
degenerative (see Dalquest and Scheffer, 1944: 24).
[Illustration: FIG. 98. Distribution of the northern pocket gopher in
Washington. A. _Thomomys talpoides devexus._ B. _Thomomys talpoides
columbianus._ C. _Thomomys talpoides aequalidens._ D. _Thomomys
talpoides wallowa._ E. _Thomomys talpoides fuscus._ F. _Thomomys
talpoides yakimensis._ G. _Thomomys talpoides shawii._ H. _Thomomys
talpoides immunis._ I. _Thomomys talpoides limosus._ J. _Thomomys
talpoides douglasii._ K. _Thomomys talpoides pugetensis._ L. _Thomomys
talpoides tacomensis._ M. _Thomomys talpoides glacialis._ N. _Thomomys
talpoides tumuli._ O. _Thomomys talpoides yelmensis._ P. _Thomomys
talpoides couchii._ Q. _Thomomys talpoides melanops._]
The history of the pocket gophers of Washington has been traced
previously (Dalquest and Scheffer, 1942, 1944). It may be briefly
summarized as follows: At the close of Vashon-Wisconsin times, gophers
were found in the southern Cascades, on the Simcoe Bridge, the Columbian
Plateau, and in southeastern Washington. Following the retreat of the
ice, the gophers in the Mount Rainier area spread westward on the
outwash of the Nisqually and perhaps other glaciers to the Vashon
Outwash about southern Puget Sound and thence to the Olympic Mountains.
In the southern Cascades, gophers spread westward on glacial terraces of
the Columbia River to the vicinity of Vancouver, Clark County. The
establishment and growth of the forests split up the original
populations, and continued spread of forest has exterminated many units.
All the races in the lowlands of western Washington face extermination
as the prairies are reclaimed by forest.
Pocket gophers also invaded northeastern Washington from Idaho and
spread westward to the Cascades, thence southward until the native
gophers were encountered north of Mount Rainier and in the Yakima
Valley. The invading gophers nearly surrounded the Columbian Plateau.
T. H. Scheffer (1938B: 220-224) found the gestation period of the pocket
gopher to be approximately 28 days. No second brood is raised in
Washington. Near Kennewick, Yakima County, the young are born from
February to April. The average number of embryos found in 76 female
gophers was 6.3. Near Olympia, Thurston County, the young are born from
March to June. The average number of embryos from 312 females was 5.0.
=Thomomys talpoides devexus= Hall and Dalquest
_Thomomys talpoides devexus_ Hall and Dalquest, Murrelet, 20:3,
April 30, 1939.
_Thomomys talpoides ericaeus_ Goldman, Jour. Mamm., 20:243, May
15, 1939 (type from Badger Mountains, Douglas County, Washington).
_Type._--Obtained 1 mile west-southwest of Neppel (now Moses Lake),
Grant County, Washington, by W. W. Dalquest on May 30, 1938; type
in Museum of Vertebrate Zoölogy.
_Racial characters._--Size medium; ears tiny; color of upper parts
pale brownish gray; underparts white; postauricular spots dark.
_Measurements._--Two male and 4 female topotypes average,
respectively: total length 184, 184; length of tail 54, 55; hind
foot 25, 25; weight 89, 71 grams.
_Distribution._--The Columbian Plateau. Marginal occurrences of
the races of pocket gophers occurring in Washington are not listed
here because they have recently been placed on record (Dalquest
and Scheffer, 1944: 308-333, 423-450).
_Remarks._--This is the smallest and palest race of pocket gopher found
in Washington.
=Thomomys talpoides columbianus= Bailey
_Thomomys fuscus columbianus_ Bailey, Proc. Biol. Soc. Washington,
27:117, July 10, 1914.
_Thomomys columbianus_ Bailey, N. Amer. Fauna, 39:106, November
15, 1915.
_Thomomys talpoides columbianus_ Goldman, Jour. Mamm., 20:234, May
15, 1939.
_Type._--Obtained at Touchet, Walla Walla County, Washington, by C.
P. Streator on September 10, 1890; type in United States National
Museum.
_Racial characters._--Larger and brighter in color than _devexus_.
Near ochraceous orange in color.
_Measurements._--Five male and three female topotypes average,
respectively: total length 213, 209; length of tail 60, 58; hind
foot 29, 28.
_Distribution._--Walla Walla County, between the Snake River and
the Oregon boundary and from the Columbia River east to the
Columbia County line.
=Thomomys talpoides aequalidens= Dalquest
_Thomomys talpoides aequalidens_ Dalquest, Murrelet, 23:3, May 14,
1942.
_Type._--Obtained at Abel Place, 2,200 ft., 6 miles south-southeast
of Dayton, Columbia County, Washington, by S. H. Lyman, on April 6,
1934; type in Museum of Vertebrate Zoölogy.
_Racial characters._--Large size, very dark color.
_Measurements._--The average of four male topotypes and the
measurements of one female topotype are, respectively: total
length 202, 201; length of tail 57, 59; hind foot 26, 27.
_Distribution._--Southeastern Washington east of the range of
_columbianus_ and north of the higher parts of the Blue Mountains.
=Thomomys talpoides wallowa= Hall and Orr
_Thomomys quadratus wallowa_ Hall and Orr, Proc. Biol. Soc.
Washington, 46:41, March 24, 1933.
_Thomomys talpoides wallowa_ Goldman, Jour. Mamm., 20:234, May 15,
1939.
_Type._--Obtained at Catherine Creek, 7 miles east of Telocaset,
3,500 ft., Union County, Oregon, by R. T. Orr on June 29, 1932;
type in Museum of Vertebrate Zoölogy.
_Racial characters._--Similar to _devexus_ but much darker.
Similar (in Washington) to _aequalidens_ but much smaller.
_Measurements._--Four males and 4 females from Mountain Top and
Stay-a-while Spring, Columbia County, average, respectively: total
length 191, 180; length of tail 56, 52; hind foot 26, 25.
_Distribution._--The higher parts of the Blue Mountains.
_Remarks._--Washington specimens referred to this race are intermediate
between _wallowa_ and _aequalidens_ but are colored like _aequalidens_.
=Thomomys talpoides fuscus= Merriam
_Thomomys clusius fuscus_ Merriam, N. Amer. Fauna, 5:69, July 30,
1891.
_Thomomys myops_ Merriam, Proc. Biol. Soc. Washington, 14:112,
July 19, 1901 (type from Conconnully, Okanogan County,
Washington).
_Thomomys fuscus fuscus_ Bailey, N. Amer. Fauna, 39:126, November
15, 1915.
_Thomomys talpoides fuscus_ Hall and Dalquest, Murrelet, 20:4,
April 30, 1939.
_Type._--Obtained at the head of Big Lost River, Custer County,
Idaho, by B. H. Dutcher on September 23, 1890; type in United
States National Museum.
_Racial characters._--Similar to _devexus_ but upper parts rich
tawny in color.
_Measurements._--Three males and 2 females from Newport, Pend
Oreille County, average, respectively: total length 189, 186;
length of tail 54, 57; hind foot 27, 26.
_Distribution._--Along the eastern border of the state to the
north of the Snake River, northeastern Washington, and the
northeastern Cascades.
=Thomomys talpoides yakimensis= Hall and Dalquest
_Thomomys talpoides yakimensis_ Hall and Dalquest, Murrelet, 20:4,
April 30, 1939.
_Thomomys talpoides badius_ Goldman, Jour. Mamm., 20:242, May 15,
1939 (type from Wenatchee, Chelan County, Washington).
_Type._--Obtained at Selah, Yakima County, Washington, by P.
Burgner, on November 27, 1938; type in Museum of Vertebrate
Zoölogy.
_Racial characters._--Similar to _fuscus_ but more orange, less
red.
_Measurements._--Four male and 3 female topotypes average,
respectively: total length 209, 191; length of tail 60, 56; hind
foot 27, 26.
_Distribution._--The eastern edge of the Cascades from the
Wenatchee Mountains south to the Simcoe Anticline.
=Thomomys talpoides shawi= Taylor
_Thomomys douglasii shawi_ Taylor, Proc. Biol. Soc. Washington,
34:121, June 30, 1921.
_Thomomys talpoides shawi_ Hall and Dalquest, Murrelet, 20:4,
April 30, 1939.
_Type._--Obtained at Owyhigh Lakes, Mount Rainier, Pierce County,
Washington, by G. G. Cantwell, on August 9, 1919; type in United
States National Museum.
_Racial characters._--A large, tan-colored pocket gopher, similar
to _aequalidens_ but paler.
_Measurements._--Two male and 7 female topotypes average,
respectively: total length 227, 213; length of tail 72, 64; hind
foot 32, 30.
_Distribution._--The higher Cascade Mountains from Mount Rainier
southward. Southern limits of range unknown.
=Thomomys talpoides immunis= Hall and Dalquest
_Thomomys talpoides immunis_ Hall and Dalquest, Murrelet, 20:4,
April 30, 1939.
_Type._--Obtained 5 miles south of Trout Lake, Klickitat County,
Washington, by W. W. Dalquest on July 27, 1937; type in Museum of
Vertebrate Zoölogy.
_Racial characters._--Similar to _shawi_ but paler and grayer.
_Measurements._--Two males and 2 females from Morrison Springs
Ranger Station, Skamania County, average, respectively: total
length 211, 212; length of tail 64, 58; hind foot 28, 29.
_Distribution._--The Cascade Mountains from the vicinity of Mount
Adams north. The zone of intergradation between _shawi_ and
_immunis_ is in the rugged, inaccessible mountains between Mount
Rainier and Mount Adams.
=Thomomys talpoides limosus= Merriam
_Thomomys limosus_ Merriam, Proc. Biol. Soc. Washington, 14:116,
July 19, 1901.
_Thomomys talpoides limosus_ Goldman, Jour. Mamm., 20:235, May 15,
1939.
_Type._--Obtained at White Salmon, Klickitat County, Washington, by
J. A. Loring on June 26, 1897; type in United States National
Museum.
_Racial characters._--Similar to _immunis_ but darker with
smaller, shorter skull.
_Measurements._--One male and 13 female topotypes average,
respectively: total length 210, 198; length of tail 55, 56; hind
foot 30, 28.
_Distribution._--The lower Columbia River Valley, from the type
locality east to the Columbian Plateau.
=Thomomys talpoides douglasii= (Richardson)
_Geomys douglasii_ Richardson, Fauna Boreali-American, 1:200, 1829.
_Geomys fuliginosus_ Schinz, Syn. Mamm., 2:136, 1846 (type from
"Habitat ad fluvium Columbia").
_Thomomys douglasii_ Allen, Bull. Amer. Mus. Nat. Hist., 5:66,
April 28, 1893.
_Thomomys douglasi douglasi_ Bailey, N. Amer. Fauna, 39:116,
November 15, 1915.
_Thomomys talpoides douglasii_ Goldman, Jour. Mamm., 20:234, May
15, 1939.
_Type._--Obtained at Fort Vancouver (now the city of Vancouver),
Clark County, Washington, by David Douglas, probably in 1825.
Probably not now in existence.
_Racial characters._--A medium-sized, yellowish gopher with tiny,
pointed ears and very small postauricular patches.
_Measurements._--Two male and 10 female topotypes average,
respectively: total length 227, 213; length of tail 68, 63; hind
foot 30, 30; and weight 148, 117 grams.
_Distribution._--Known only from Clark County.
=Thomomys talpoides glacialis= Dalquest and Scheffer
_Thomomys talpoides glacialis_ Dalquest and Scheffer, Proc. Biol.
Soc. Washington, 55:97, August 13, 1942.
_Type._--Obtained 2 miles south of Roy, Pierce County, Washington,
by W. W. Dalquest, on December 19, 1941; type in United States
National Museum.
_Racial characters._--A dark, yellowish-brown gopher with
orange-tinged underparts.
_Measurements._--Twenty male and 17 female topotypes average,
respectively: total length 225, 220; length of tail 72, 71; hind
foot 30, 30; and weight 128, 116 grams.
_Distribution._--Known only from Roy Prairie, Pierce County.
=Thomomys talpoides tacomensis= Taylor
_Thomomys douglasii tacomensis_ Taylor, Proc. Biol. Soc.
Washington, 32:169, September 30, 1919.
_Thomomys talpoides tacomensis_ Goldman, Jour. Mamm., 20:235, May
15, 1939.
_Type._--Obtained 6 miles south of Tacoma, Pierce County,
Washington, by G. G. Cantwell on December 24, 1918; type in United
States National Museum.