Geomys arenariusdesert pocket gopher

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Geographic Range

Desert pocket gophers are found from extreme western Texas and southwest, southcentral New Mexico (USA) to extreme north Chihuahua (Mexico). This species is commonest in the narrow strip of bottom land along the upper Rio Grande Valley from Chihuahua into New Mexico. ("Geomys arenarius", 1993; Williams and Baker, 1974)

Habitat

Desert pocket gophers are fossorial mammals which prefer sandy and disturbed soils that are excessively drained and easily penetrated. They occupy desert scrub as well as many man-made habitats. They are common along the lowlands of rivers as well as along irrigation ditches. Their use of claws for digging, as opposed to incisors, restricts this species to sandy soils that are less than 30% clay and greater than 40% sand. Desert pocket gophers spend most of their time about 100-200 mm below the surface in underground burrows that exceed 30 meters long. The burrows are made up of many side chambers and associated mounds of earth above ground, as well as a central chamber where all of the passages converge. One observed central chamber was 280mm long, 230 mm wide, and 200 mm deep. (Klingel, 2001; Kays and Wilson, 2002; Klingel, 2001; Lessa and Thaeler, 1989; Nowak and Paradiso, 1983)

  • Range elevation
    1220 to 1520 m
    4002.62 to 4986.88 ft

Physical Description

Desert pocket gophers are heavily built, medium-sized gophers with relatively long, nearly naked tails and pale coloration. Their pelage is drab-brown dorsally, with thinly spread black-tipped hairs. This coloration continues until the abdomen where it may begin to blend with white hairs on the abdomen, chest, and feet.

Desert pocket gophers have massive forelimbs with large olecranon and epicondylar processes and large claws with flexible digits. They are adapted for a strong and powerful mode of digging. They have reduced eyes and pinnae, which enable them to better travel underground and through tunnels. They also have large, external, fur-lined cheek pouches which reach from the side of the mouth back to their shoulders.

Desert pocket gophers can be easily distinguished from other pocket gophers by the lack of sagittal crest, prominent knob over the middle of the jugal on the end of the squamosal arm of the zygoma, and also by checking to see that the rostrum does not exceed the length of the basioccipital. The zygoma of the desert pocket gopher are also unique among pocket gophers in that they has parallel sides in contrast to sides that converge posteriorly. The dental formula is 1/1, c 0/0, p 1/1, m 3/3, and their upper incisors are bisulcate.

There is pronounced sexual dimorphism in desert pocket gophers. Mean external and cranial measurements, excluding interorbital breadth, were all found to be greater in males. Body weights of desert pocket gophers ranged from 198 to 254 g in males, and from 165 to 207 g in females. (Costello and Rosenberger, 2002; Hall and Kelson, 1959; Kays and Wilson, 2002; Lessa and Thaeler, 1989; Williams and Baker, 1974)

  • Sexual Dimorphism
  • male larger
  • Range mass
    165 to 254 g
    5.81 to 8.95 oz
  • Range length
    218 to 302 mm
    8.58 to 11.89 in
  • Average length
    254 mm
    10.00 in

Reproduction

During the reproductive season, males seek a female by either extending their burrows to those occupied by a female, or by searching above ground for an entrance to a female burrow. Because home ranges of males do not overlap, but male home ranges overlap with those of one to four females, the breeding system is polygynous. The highly territorial behavior of desert pocket gophers decreases during the breeding season in accordance with this mating behavior. (Chapman and Feldhamer, 1982; Klingel, 2001; Nowak and Paradiso, 1983; "Desert Pocket Gopher, Geomys arenarius", 2000; Williams and Baker, 1974)

Desert pocket gophers have two reproductive cycles in a year, one in spring and another in summer. The breeding season is also prolonged in the summer months, allowing for the possibility of having more than one litter per year.

The gestation period of G. arenarius is 18 to 19 days and females have 3 to 4 offspring per reproductive effort. Newborn pocket gophers are born altricial with closed eyes, ears, and cheek pouches. At about 26 days the offspring's ears and eyes open and around 39 days the cheek pouches have opened and are able to carry food. At about 100 days molting to adult pelage is half complete. Weaning occurs around 35-40 days of age; however, the young stay with their mother until about the age of 2 months, when they begin to disperse. (Chapman and Feldhamer, 1982; Klingel, 2001; Nowak and Paradiso, 1983; "Desert Pocket Gopher, Geomys arenarius", 2000; Williams and Baker, 1974)

  • Breeding interval
    Desert pocket gophers have two reproductive cycles a year, with a prolonged breeding season during the summer months.
  • Breeding season
    Mating usually occurs during the spring and summer months.
  • Range number of offspring
    4 to 6
  • Range gestation period
    18 to 19 days
  • Range weaning age
    35 to 40 days
  • Average time to independence
    2 months
  • Range age at sexual or reproductive maturity (female)
    9 to 12 months
  • Average age at sexual or reproductive maturity (male)
    1 years

Not much is known about the parental care of desert pocket gophers. Newborns are atricial when born, requiring some parental care to survive. Young stay with their mother for almost a month after weaning, however the reasons for such extended care is unknown. Male parental care is either absent or unknown. (Chapman and Feldhamer, 1982)

  • Parental Investment
  • altricial
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
    • protecting
      • female
  • pre-independence
    • protecting
      • female

Lifespan/Longevity

There is no information about the lifespan of desert pocket gophers; however, a study conducted on a closely related species, T. talpoides, provides some data about the longevity of pocket gophers. In a five year field study that was conducted on a population of T. talpoides, the oldest female collected was 4 years and 9 months old, and the oldest male was 3 years of age. The mean lifespan for the population of interest was found to be about 13.6 months for males and 18.3 months for females. Ninety-six percent of the pocket gophers where 2 years old or less when last trapped. (Chapman and Feldhamer, 1982)

Behavior

Desert pocket gophers are solitary, fossorial animals. Individuals live alone, each within their own burrow system, and are intolerant of members of their own species. The exception to this behavioral pattern is during the breeding season when males extend their tunnels or go above ground to seek a female. When a desert pocket gopher is angry or introduced to a strange gopher they begin to make hissing sounds by breathing rapidly, and will violently fight with one another. They will also occasionally cry out if injured.

When burrowing below ground, desert pocket gophers create large ejecta mounds by pushing the excess soil from their burrow. They alternately push out the soil in three different directions (to the left, right and directly in front of the burrow) creating a large fan-shaped ejecta mound.

When foraging above ground, desert pocket gophers collect food and store it in fur-lined cheek pouches to be brought back to the burrow. Upon re-entering the burrow, desert pocket gophers plug the opening, thus allowing for better climate control inside the burrow as well as keeping predators out.

Desert pocket gophers collect and store food underground for winter use. (Costello and Rosenberger, 2002; Kerley, et al., 2003; Nowak and Paradiso, 1983; "Desert Pocket Gopher, Geomys arenarius", 2000; Vaughan, et al., 2000)

Home Range

The home range of Geomys arenarius is equivalent to its burrow size and territory except for during the breeding season. They are extremely sedentary animals and, once established, they make only minor shifts to their territories due to external forces such being crowded by a large animal.

The territories of desert pocket gophers have been found to be a variety of shapes and sizes, depending on the availability of food and soil conditions in the area. (Chapman and Feldhamer, 1982; Nowak and Paradiso, 1983)

Communication and Perception

Desert pocket gophers have small eyes and ears as an adaptation for moving through underground tunnels. They do not rely heavily on visual or acoustic perception channels. They mainly perceive their environment through the vibrissae covering their body, and through their sensitive tail, which they use as a guide when moving backwards out of a tunnel. Chemical cues are also very important.

Little is known about the communication habits of desert pocket gophers in the wild. Pocket gophers in captivity make grinding, chattering noises with their teeth, eliciting similar clicking noises from other pocket gophers nearby. (Chapman and Feldhamer, 1982; Nowak and Paradiso, 1983; Vaughan, et al., 2000)

Food Habits

Desert pocket gophers are strict herbivores. They are opportunistic feeders and will eat a wide variety of plants including underground roots, rhizomes, and bulbs they encounter within their burrow system. They also feed on above ground vegetation that is easily accessible from their burrows. They will eat any part of the plant including stems, roots, leaves, flowers, needles, buds and seeds. They also eat alfalfa as well as a variety of grass species. Desert pocket gophers obtain adequate amounts of water from the moisture in the vegetation they feed on. They rarely require fresh water to drink. (Chapman and Feldhamer, 1982; Klingel, 2001; Nowak and Paradiso, 1983)

  • Plant Foods
  • leaves
  • roots and tubers
  • wood, bark, or stems
  • seeds, grains, and nuts
  • fruit
  • flowers

Predation

The effect of vertebrate predators on desert pocket gophers is not well understood. This is because they are fossorial mammals and only subject to predation when above the ground. It appears that avian predators are the greatest threat to desert pocket gophers, however Canis, Mustela and Crotalus appear to have some effectiveness as predators as well. (Chapman and Feldhamer, 1982)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

The main influence of desert pocket gophers on the ecosystems in which they live is through their continuous working of the soil. Desert pocket gophers increase the mixing and aeration of soils they inhabit, increasing soil fertility and stimulating vegetation growth. The vertical cycling of soil through desert pocket gopher activity also increases soil fertility in that it loosens and aerates the earth as well as mixes organic matter into the soil, through such things as fecal materials and vegetation stores underground. However, this continuous working of the soil can also accelerate soil erosion on overgrazed ranges. (Chapman and Feldhamer, 1982; Nowak and Paradiso, 1983)

Commensal/Parasitic Species

Economic Importance for Humans: Positive

Humans benefit from desert pocket gophers through their cycling of the soil. This cycling process allows for soil aeration and blending of organic matter into the soil which in turn increases soil fertilization. (Nowak and Paradiso, 1983; "Desert Pocket Gopher, Geomys arenarius", 2000)

Economic Importance for Humans: Negative

Desert pocket gophers are considered pests by humans because of the great economic loss they can cause in agricultural areas. Their burrowing and ejecta mounds can damage crops as well as lead to the depletion of grazing ranges. Some crops that are particularly damaged through desert pocket gopher activity are sweet potatoes, sugar cane, and peas. Desert pocket gophers can also cause erosion through their mounds and tunnels and are considered a nuisance by home gardeners. (Chapman and Feldhamer, 1982; Nowak and Paradiso, 1983; "Desert Pocket Gopher, Geomys arenarius", 2000)

  • Negative Impacts
  • crop pest

Conservation Status

The conservation status of Geomys arenarius is described as near threatened.

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Jessica Templeton (author), University of Michigan-Ann Arbor, Phil Myers (editor, instructor), Museum of Zoology, 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.

World Map

acoustic

uses sound to communicate

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

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

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.

folivore

an animal that mainly eats leaves.

fossorial

Referring to a burrowing life-style or behavior, specialized for digging or burrowing.

herbivore

An animal that eats mainly plants or parts of plants.

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).

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.

pheromones

chemicals released into air or water that are detected by and responded to by other animals of the same species

polygynous

having more than one female as a mate at one time

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

scrub forest

scrub forests develop in areas that experience dry seasons.

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"

tactile

uses touch to communicate

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).

terrestrial

Living on the ground.

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

visual

uses sight to communicate

viviparous

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

References

The University of Texas at El Paso. 2000. "Desert Pocket Gopher, Geomys arenarius" (On-line). Chihuahuan Desert. Accessed March 20, 2006 at http://museum.utep.edu/chih/theland/animals/mammals/geoaren.htm.

Smithsonian Institution. 1993. "Geomys arenarius" (On-line). Mammal Species of the World (MSW). Accessed March 20, 2006 at http://nmnhgoph.si.edu/cgi-bin/wdb/msw/names/query.

Chapman, J., G. Feldhamer. 1982. Wild Mammals of America; Biology, Management, and Economics. Baltimore, Maryland: The Johns Hopkins University Press.

Costello, R., A. Rosenberger. 2002. "Geomys arenarius" (On-line). North American Mammals. Accessed March 20, 2006 at http://www.mnh.si.edu/mna/image_info.cfm?species_id=100.

Grohol, J. 2006. "Pocket gopher" (On-line). Accessed April 07, 2006 at http://search.psychcentral.com/psypsych/Geomyidae.

Hall, R., K. Kelson. 1959. The Mammals of North America. New York: The Ronald Press Company.

Hanney, P. 1975. Rodents, Their Lives and Habits. New York, New York: Taplinger Publishing Co, Inc.

Kays, R., D. Wilson. 2002. Mammals of North America. Princeton, New Jersey: Princeton University Press.

Kerley, G., W. Whitford, F. Kay. 2003. Effects of pocket gophers on desert soils and vegetation. Journal of Arid Environments, 58: 155-166.

Klingel, J. 2001. "BISON Species Account 050270" (On-line). Accessed April 07, 2006 at http://www.fw.vt.edu/fishex/nmex_main/species/050270.htm.

Lessa, E., C. Thaeler. 1989. A Reassessment of Morphological Specializations for Digging in Pocket Gophers. Journal of Mammalogy, 70/4: 689-700. Accessed March 21, 2006 at http://links.jstor.org/sici?sici=0022-2372%28198911%2970%3A4%3C689%3AAROMSF%E2.0.CO%3B2-B.

Mauk, C., M. Houck, R. Bradley. 1999. Morphometric Analysis of Seven Species of Pocket Gophers (Geomys). Journal of Mammalogy, 80/2: 499-511. Accessed March 21, 2006 at http://links.jstor.org/sici?sici=0022-2372%28199905%2980%3A2%3C499%3AMAOSSO%3E2.0.CO%3B2-S.

Nowak, R., J. Paradiso. 1983. Walker's Mammals of the World. Baltimore, Maryland: The Johns Hopkins University Press.

Vaughan, T., J. Ryan, N. Czaplewski. 2000. Mammalogy. United States of America: Thomson Learning, Inc.

Williams, S., R. Baker. 1974. Geomys arenarius. Mammalian Species, 36: 1-3. Accessed March 20, 2006 at http://www.science.smith.edu/departments/Biology/VHAYSSEN/msi/.