Thomomys talpoidesnorthern pocket gopher

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Geographic Range

Thomomys talpoides lives in the dry short-grass prairies, and has the greatest range of any pocket gopher in North America. They occur on both sides of the continental divide, ranging from mid-Manitoba in the north, to New Mexico at the south end. T. talpoides occurs as far west as the east side of the Cascade mountains, and (northern) Sierra Nevada range, and as far east as the Dakota Plains, east of the Black Hills. This area is generally called the North American West and Midwest. (McMahon, 1999)

Habitat

T. talpoides occupies a greater variety of habitats than any other pocket gopher species. They are fossorial, which means they live in tunnels underground. They can be found in mountain meadows, tundra, valley grasslands, sagebrush steppe, and agricultural fields. The uniting feature of these habitats is the absence of significant canopy cover, and abundant ground cover that supplies their nutritional needs. Generally speaking, they prefer deep well drained soils, but are also found in compacted clays and shallow rocky soils. The elevation range of T. talpoides is 915-3750 meters, but they are most common at 1220-2745 meters. (McMahon 1999)

  • Range elevation
    915 to 3750 m
    3001.97 to 12303.15 ft
  • Average elevation
    1220-3745 m
    ft

Physical Description

T. talpoides is highly adapted to a tunneling lifestyle. These pocket gophers have thick, tapering bodies, short limbs with strong claws, loose skin, and reduced eyes and ears. They have sharp and fast growing upper and lower incisors, which are extensively used to help them dig. These rodents have external cheek pouches.

The pelage (fur) of T. talpoides ranges from grayish brown, to brown, and yellowish-brown in color. Complex spring molting patterns create the appearance of waves and bands across the body, from head to tail. The fur is soft and short. It is not as glossy than that of other Thomomys species.

Females are about 10% smaller than males, in both weight and length. The average adult T. talpoides weighs from 60 to 160 grams. Weight varies with respect to elevation. The total body length is 165 to 260 mm, and tail length varies from 40 to 74 mm.

Characteristics that separates T. talpoides from other Thomomys species are: 1) small rounded ears less than 6.9 mm. 2) No sphenoidal fissure in the skull. 3) Smooth anterior surface of the upper incisors.

(McMahon, 1999)

  • Range mass
    60 to 160 g
    2.11 to 5.64 oz
  • Range length
    165 to 260 mm
    6.50 to 10.24 in
  • Average basal metabolic rate
    0.679 W
    AnAge

Reproduction

The mating system of these animals has not been described. They are generally solitary, but males are allowed into female tunnels during the breeding season (Nowak, 1999)

Reproduction occurs in the spring, generally occuring later at higher elevations. The gestation periods last 18 to 20 days. Young are usually born from mid-May to mid June, but births occur later at higher elevations. Pocket gophers are not well developed at birth, and are therefore, altricial. Care of young is an exclusively maternal responsibility, as these are very anti-social animals. Birth weight averages 3 grams. The young are weaned by day 40. Young disperse from the natal burrow around 2 months of age, and reach maturity in 3-6 months. An average mature female T. talpoides will have one litter per year that consists of 4-7 young. (McMahon, 1999)

  • Breeding season
    Breeding occurs in the spring, with births following in late spring or summer.
  • Range number of offspring
    3 to 7
  • Average number of offspring
    5
    AnAge
  • Range gestation period
    18 to 20 days
  • Average weaning age
    40 days
  • Range age at sexual or reproductive maturity (female)
    3 to 6 months
  • Range age at sexual or reproductive maturity (male)
    3 to 6 months

No male parental care has been reported for this species. Females care for their young within their tunnels. The young are nursed for about 40 days. They remain with the mother until they disperse around the age of two months (Nowak, 1999)

Lifespan/Longevity

In captivity, T. talpoides lives 5-6 years. In the "real world" their life expectancy is 18-24 months. Total population replacement occurs in roughly 5 years. Because males tend to uniformly die before females, there are certain times in the late summer where the majority of the population is female. (McMahon, 1999)

Behavior

Pocket gophers tends to dig a lot. They are very territorial, and are aggressive towards each other, except during the mating season. However, their density of up to 20 individuals per hectare can give people a false sense about their sociability. When young are mature, they exit the burrow and disperse by traversing the ground surface to a new area. They have been recorded to move 166-305 meters from the nest. Adult northern pocket gophers have been recaptured about 30-43 m from the previous year's capture location. (Buchner 1979).

In summer and winter there are brief periods of inactivity, but there is no true hibernation. T. talpoides constructs elaborate tunnel networks. An individual can dig up to 150 meters worth of tunnel. The tunnels are usually kept plugged with soil, except to air them out during nice weather. Two distinct levels of tunnel are created. The top level, (20-45 cm from surface) is primarily used to store feces. The lower level, (up to 2 meters deep,) is used as a nesting and food storage area. In winter, T. talpoides digs through snow and lines these snow tunnels with soil. (McMahon, 1999)

Communication and Perception

Vision and hearing are very poor in T. talpoides. Their senses of touch and smell are their primary means of communication. (McMahon, 1999)

Food Habits

Northern pocket gophers are best described as generalist herbivores. They primarily consume the roots, corms, rhizomes, and stems, of forbs and herbs. They tend to avoid woody vegetation. Fruits of Opuntia species are a favorite, if available. At certain times of year, grasses may compose up to 50% of their diet, although they prefer agricultural crops, if available. Overall, the diet of T. talpoides is composed of 80% areal plant material. They search under and above ground, and typically pull the entire plant under ground. One northern pocket gopher was witnessed stuffing its pouches so full of alfalfa that the pouches were dragging on the ground! This species is known to eat its feces, and to cache food. (McMahon, 1999; Lacey, 2000)

  • Plant Foods
  • leaves
  • roots and tubers
  • seeds, grains, and nuts
  • fruit

Predation

Predation upon T. talpoides is best performed by efficient digging carnivores, such as badgers. Other predator species include: coyote, skunk, weasel, great horned owl, bobcat, fox, some snakes, some hawks, etc. Northern pocket gophers are a "keystone species" that many other regional animals depend upon. Specific anti-predator adaptations are not known for this species, although their subterranian existence is probably a way in which they avoid the predatory birds to which so many rodents fall prey. (McMahon, 1999)

Ecosystem Roles

Northern pocket gophers serve a critical role in maintaining the bio-diversity, habitat structure, and functionality of the ecosystems they inhabit. They attain population densities of up to 20 per hectare. For this reason alone, they are a significant food source for larger vertebrates.

Even more important is the manner in which T. talpoides improves site productivity. It has been estimated that T. talpoides turns over 8-15.7 Megagrams of soil/hectare. (11.2-85.1 Mg/ha has been reported in extreme cases.) This means several things: Burrowing activities loosen and aerate soils, deliver organic material to the subsoil (thereby improving its fertility), hasten the soil forming processes, deepen the soil profile, expand the plant-available water-holding-capacity of the soil, and generally improve the biological chemical and physical aspects of soils. The result is that relative to unaltered soil, there are more plant species and higher plant densities on soil that has altered by T. talpoides. In several locations, visual evidence of northern pocket gopher activities is present, on up to 40% of the ground surface area. (McMahon, 1999; Lacey, 2000)

Economic Importance for Humans: Positive

In the long term, T. talpoides is beneficial to farm fields and pastures because of the soil fertility maintenance roles that are described in the ecology section. Over a 31 year study in central Utah, northern pocket gophers increased soil porosity, organic matter, total nitrogen, and total phosphorous. Another study has shown significant increases in soil calcium, soil potassium, and soil moisture, due to northern pocket gopher activity. Percieved direct-crop herbivory by pocket gophers may not be as costly as prevoiusly estimated, if we quantify how much less productive that land would be without them (in the long term). When looking at multiple scales, researchers have shown that a similar species, T. bottae, may actually increase overall productivity in a California alfalfa field. I love to quote my Soil Science teacher who says: "...although we may not like them while they are there, it's good to have had gophers in your field." (Hauxwell, 1999. Personal communication; Lacey, 2000; Litaor, 1995; Smallwood, 1997)

  • Positive Impacts
  • produces fertilizer

Economic Importance for Humans: Negative

According to many farmers T. talpoides is a "bad" species, because they are known to eat up to 245 kg of plant material per year, and because they love agricultural fields. Their mounds can dull the blades of farm machines, and they tend to re-route irrigation water, causing localized flooding. For these reasons, farmers try to control T. talpoides by poisoning and trapping them. Modern techniques of controlling T. talpoides populations include the spreading of predator feces, urine, and scent gland secretions. Another strategy is to inject pepper oil extract (capsicum) into the soil. This irritant is effective in making gophers avoid that area. Gopher contol is expensive, and can also have direct negative effects on crop plants. (McMahon, 1999; Sterner, 1999; Smallwood, 1997)

  • Negative Impacts
  • crop pest

Conservation Status

Not a species of concern.

Other Comments

Environmental and monetary costs associated with attempting to control pocket gopher populations deserve serious questioning. Pocket gopher removal does decrease the population, but it also increases population growth rates.

T. talpoides has an unsettled taxonomy. There are 50 sub-species. Many of these sub-species may eventually be placed in their own species. (McMahon, 1999; Smallwood, 1997)

Contributors

Scott Long (author), Humboldt State University, Brian Arbogast (editor), Humboldt State University.

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.

World Map

agricultural

living in landscapes dominated by human agriculture.

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

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

coprophage

an animal that mainly eats the dung of other animals

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.

female parental care

parental care is carried out by females

fertilization

union of egg and spermatozoan

folivore

an animal that mainly eats leaves.

frugivore

an animal that mainly eats fruit

granivore

an animal that mainly eats seeds

herbivore

An animal that eats mainly plants or parts of plants.

internal fertilization

fertilization takes place within the female's body

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

keystone species

a species whose presence or absence strongly affects populations of other species in that area such that the extirpation of the keystone species in an area will result in the ultimate extirpation of many more species in that area (Example: sea otter).

motile

having the capacity to move from one place to another.

mountains

This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

native range

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

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

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

solitary

lives alone

stores or caches food

places a food item in a special place to be eaten later. Also called "hoarding"

suburban

living in residential areas on the outskirts of large cities or towns.

tactile

uses touch to communicate

taiga

Coniferous or boreal forest, located in a band across northern North America, Europe, and Asia. This terrestrial biome also occurs at high elevations. Long, cold winters and short, wet summers. Few species of trees are present; these are primarily conifers that grow in dense stands with little undergrowth. Some deciduous trees also may be present.

temperate

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).

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tundra

A terrestrial biome with low, shrubby or mat-like vegetation found at extremely high latitudes or elevations, near the limit of plant growth. Soils usually subject to permafrost. Plant diversity is typically low and the growing season is short.

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

References

Buchner, Richard, , Rorabaugh, Jim. March, 1979. The Mountain Pocket Gopher and Some Implications for Timber Management.. U.S. Government Printing Office: El Dorado National Forest. Forest Service. U.S. Department of Agriculture..

Lacey, E., J. Patton, G. Cameron. 2000. Life Underground - the biolkogy of subterranean rodents. Chicago, London: The University of Chicago Press.

Litaor, I., R. Mancinelli, J. Halfpenny. 1996. The influence of pocket gophers on the status of nutrients in Alpine soils. Geoderma, 70: 37-48.

McMahon, J.A., 1999. Smithsonian Book of North American Mammals. Washington and London: Smithsonian Institution Press, in association with The American Society of Mammalogists.

Smallwood, S., S. Geng. 1997. Multiscale influences of pocket gophers on alfalfa yield and quality. Field Crops Research, 49: 159-168.

Sterner, R., K. Hollenbeck, S. Schumake. 1999. . Capsicum-laden soils decrease contact time by northern pocket gophers. Physiology and Behavior, 67 (3): 455-458.