Thomomys bottaeBotta's pocket gopher

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Geographic Range

Thomomys bottae ranges from southern Oregon and central Colorado to southern Baja California and central Mexico (Nowak 1991).

Habitat

Valley pocket gophers are primarily fossorial. They burrow in various habitats including high mountain valleys, deserts, and sometimes in agricultural areas with artificial irrigation in the milder climate areas (Grzimek 1990).

Physical Description

Valley pocket gophers have a body length of 11.5 to 30 cm, and a tail length of 4 to 9.5 cm. Males are considerably larger than females. One study showed that average male weight was 141 g, while females weighed 90 g ( Daly 1986). The fur is short, smooth, and soft. The underside fur is only somewhat paler than the dorsal. Many of the 185 subspecies aredistinguished by color, which varies from grey, to brown, to tan to almost black. Thomomys bottae has a robust body and has short legs with long front claws. It has small eyes and ears and a tail that is naked at the tip (Grzimek 1990). Pocket gophers are characterized by deep fur-lined cheek pouches, and the genus Thomomys is characterized by upper incisors that lack frontal grooves (Grzimek 1990).

  • Average mass
    115.5 g
    4.07 oz
    AnAge
  • Average basal metabolic rate
    0.67 W
    AnAge

Reproduction

Female valley pocket gophers are monestrous, producing only one litter per year, after a gestation period of 19 days. The litter size ranges from 3-7, but the average is 5.7 for the species. The young are small at birth, weighing between 2.8 and 4 g. Once born, the young are weaned between the 36th and 40th day. Cheek pouches open after 24 days, and eyes and ears open after 26 days (Grzimek 1990). The young do not leave their mother until after 60 days, and young valley pocket gophers grow the coat of adults after 100 days. They reach an adult weight between 5 and 6 months, and reach sexual maturity the following breeding season, usually at 9 to 12 months of age (Daly 1896). Thomomys bottae live an average of 2.5 years.

  • Key Reproductive Features
  • gonochoric/gonochoristic/dioecious (sexes separate)
  • sexual
  • Average number of offspring
    5.5
    AnAge
  • Average gestation period
    19 days
    AnAge
  • Average age at sexual or reproductive maturity (female)
    Sex: female
    319 days
    AnAge
  • Average age at sexual or reproductive maturity (male)
    Sex: male
    319 days
    AnAge

Lifespan/Longevity

  • Range lifespan
    Status: wild
    4.8 (high) years
    AnAge

Behavior

Thomomys bottae is generally a solitary animal that "likes to dig" and spends a large portion of its life underground. The home range of T. bottae is about 150 sq. meters, but some animals wander 100 meters in search of more favorable conditions (Bandoli 1987). The burrow system that these pocket gophers create consists of deep permanent burrows and shallow tunnels used for feeding. The deep lodge systems are usually 1-3 meters below ground and can contain several nesting and storing chamber. The specialized chambers may be 20-250 cm in diameter (Grzimek 1990). The feeding tunnels radiate outwards from the central permanent burrows. These tunnels are 5 cm in diameter and 13 to 46 cm deep. The nesting chambers are cushioned with dried grasses, while the other large chambers are relatively bare and are probably used for the purpose of storing food (Grzimek 1990). Pocket gophers do not leave raised ridges above the ground like moles, rather they throw up fan shaped mounds of soil at the side of the entrances. The entrances are generally kept blocked with soil (Nowak 1991).

During the day, valley pocket gophers do not wander far from their burrow entrances, but at night they move out above ground to some extent (Grzimek 1990). The Valley pocket gopher was found to be most active during the afternoon and less active at night, and the species has been found to have an average of 16.1 activity periods during the day. In comparison to other geomyids, activity (measured by proportion of time spent away from the nest) was low at 18.8% (Bandoli 1987). They are active at all times during the year and do not hibernate (Nowak 1991).

Valley pocket gophers are solitary and territorial during times during the year except during the reproductive season. Territoriality decreases during the mating season of the spring, and rises in the late summer and fall.

Communication and Perception

Food Habits

Valley pocket gophers generally eat roots, bulbs, tubers, and occasionally above ground plant parts. When in areas inhabited by humans, valley pocket gophers eat cultivated crops. Thomomys bottae do not drink water and get their needs for moisture from "juicy" vegetable matter. Valley pocket gophers may eat plants above ground, but often times they burrow under the plant, bite off the roots and pull the stem into the burrow for further preparation. Once in the burrow, they cut the vegetation into smaller pieces and push it into the cheek-pouches with their front claws. When placed in the deep cheek-pouches, a large quantity can be carried to a storage or eating place.

Pocket gophers have large stomachs and caeca, and the amount of food that can be contained in the digestive tract at one time can exceed 21% of the animals total weight.

Economic Importance for Humans: Positive

Valley pocket gophers are valuable to humans in many ways. The burrowing that the species does helps to keep the earth porous and (friable). The burying of vegetation enriches the soil. In mountain meadows, their holes allow runoff from snow to sink deep into then earth, conserving water and soil (Nowak 1991).

Economic Importance for Humans: Negative

Although valley pocket gophers, along with other pocket gophers, are accused of damaging grasslands, overgrazing by domestic livestock does most of the damage. The gopher population is attracted by the conditions the livestock create (Grzimek 1990). Also, pocket gophers are considered pests in agricultural areas where they eat crops and cut the roots of young trees (Nowak 1991).

Conservation Status

Thomomys bottae are not endangered.

Other Comments

Valley pocket gophers wear their claws down at a fast rate due to constant digging. In order to cope with this, the middle claw grows twice as fast as the other claws. (Grzimek 1990) Owls prey on them at night, and badgers, coyotes, and foxes dig them out of their burrows to consume them. The oldest tagged wild individual was 4 years old, but they usually do not live past their second year, possibly due to predation. Predation, though, does not have an effect on the species' numbers (Grzimek 1990).

Contributors

Noni Greene (author), University of Michigan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

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Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

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.

chemical

uses smells or other chemicals to communicate

endothermic

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.

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

sexual

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

tactile

uses touch to communicate

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.

savanna

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.

References

Bandoli, J. H. 1987. Activity and plural occupancy of burrows in Botta's pocket gopher, Thomomys bottae. The American Midland Naturalist, vol. 118. pp. 10-14 Daly, J. C. 1986. Growth, reproduction, and sexual dimorphism in Thomomys bottae pocket gophers. Journal of Mammalogy, vol. 67. pp. 256-65

Grzimek, B. 1990. Grzimek's Encyclopedia of Mammals. Volume Three. McGraw-Hill Publishing Co., New York, N.Y.

Nowak, R. M. 1991. Walker's Mammals of the World. Fifth Edition. Johns Hopkins University Press, Baltimore, MD