Pocket gopher

Pocket gophers Fossil range: Early Oligocene–Recent PreЄ Є O S D C P T J K Pg N
Botta's pocket gopher (Thomomys bottae)
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Mammalia Order: Rodentia Superfamily: Geomyoidea Family: Geomyidae Bonaparte, 1845
Genera
Cratogeomys Geomys Orthogeomys Pappogeomys Thomomys Zygogeomys

Pocket gopher is the common name for any of the herbivorous, burrowing rodents comprising the family Geomyidae, characterized by a tubular-shaped body, small eyes, reduced external ears, short limbs, and short and almost hairless tail. These are the "true" gophers, although several ground squirrels of the family Sciuridae are often called gophers as well. The many species of pocket gophers are found only in the Western Hemisphere, extending from Canada in North America to Colombia in South America.

The closest relatives of the pocket gophers are the members of the rodent family Heteromyidae, the pocket mice, kangaroo mice, and kangaroo rats. Members of both of these families are characterized by external, fur-lined cheek pouches for storing food, a trait unique from the internal pouches found in many rodents. This feature was used by evolutionist Stephen Jay Gould as support for the conjecture that evolutionary adaptations can come about suddenly rather than by a series of small steps, since it is hard to conceive of an intermediary with just a small crease having any adaptive advantage.

Physical description

Plains pocket gopher

Pocket gophers have a heavily built, tube-shaped body, ranging from 5 to 11 inches (13-36 centimeters) and from about 0.13 to 3.1 pounds (0.06 to 1.4 kilograms) (Hafner 2004). Within any species, the males are larger than the females and can be nearly double their weight (MacDonald 2006). Adapted as burrowing animals living in subterranean tunnels, pocket gophers are characterized by small eyes, small external ears, many hairs around the eyes and ears that restrict the entry of soil, and very strong but short forelimbs that are used for digging (along, on occasion, with the incisors) (Hafner 2004). The hindlimbs are also short. They have a short, almost hairless tail, which they use to feel around tunnels when they walk backwards.

Most gophers have short, brown fur that often closely matches the color of the soil excavated from where they live and helps camouflage it from predators as they move soil to the surface. Their most characteristic features are their large cheek pouches, from which the word "pocket" in their name derives. These external pouches are fur-lined, and can be turned inside out. They extend from the side of the mouth well back onto the shoulders. Used to hold food and nest material for transport (but not soil), these cheek pouches when full can make the head appear almost two times its natural size (Hafner 2004).

Distribution and habitat

Pocket gophers are widely distributed in North America, extending into Central America.

Behavior

All pocket gophers are burrowers. They are larder hoarders, and their cheek pouches are used for transporting food back to their burrows. Gophers can collect large hoards. Their presence is unambiguously announced by the appearance of mounds of fresh dirt about 20 cm (7.9 in) in diameter. These mounds will often appear in vegetable gardens, lawns, or farms, as gophers like moist soil (see Soil biomantle). They also enjoy feeding on vegetables. For this reason, some species are considered agricultural pests. They may also damage trees in forests. Although they will attempt to flee when threatened, they may attack other animals, including cats and humans, and can inflict serious bites with their long, sharp teeth.

Pocket gophers are solitary outside of the breeding season, aggressively maintaining territories that vary in size depending on the resources available. Males and females may share some burrows and nesting chambers if their territories border each other, but in general, each pocket gopher inhabits its own individual tunnel system.

Depending on the species and local conditions, pocket gophers may have a specific annual breeding season, or may breed repeatedly through the year. Each litter typically consists of two to five young, although this may be much higher in some species. The young are born blind and helpless, and are weaned at around forty days.

Classification

There has been much debate among taxonomists about which races of pocket gopher should be recognised as full species, and the following list cannot be regarded as definitive.

• Family Geomyidae
  • Genus Cratogeomys; some authors treat this genus as a subgenus of Pappogeomys.
    • Yellow-faced Pocket Gopher (Cratogeomys castanops)
    • Oriental Basin Pocket Gopher (C. fulvescens)
    • Smoky Pocket Gopher (C. fumosus)
    • Llano Pocket Gopher (C. gymnurus)
    • Merriam´s Pocket Gopher (C. merriami)
  • Genus Geomys - eastern pocket gophers; principally found in the south-western United States, east of the Sierra Nevada mountains.
    • Geomys arenarius; two subspecies, the Desert and White Sands Pocket Gophers
    • Attwater's Pocket Gopher (G. attwateri)
    • Plains Pocket Gopher (G. bursarius); two subspecies
    • Jones' Pocket Gopher (G. knoxjonesi)
    • Geomys personatus; 5 subspecies including the Texas, Davis, Maritime and Carrizo Springs Pocket Gophers
    • Geomys pinetis; 4 subspecies, the Southeastern, Cumberland Island, Sherman's and Goff's Pocket Gophers
    • Geomys texensis; 2 subspecies, including the LLano Pocket Gopher
  • Genus Orthogeomys - giant pocket gophers or taltuzas; found in Mexico, Central America and Colombia.
    • Chiriqui Pocket Gopher (Orthogeomys cavator)
    • Cherrie´s Pocket Gopher (O. cherriei)
    • Oaxacan Pocket Gopher (O. cuniculus)
    • Darien Pocket Gopher (O. dariensis)
    • Giant Pocket Gopher (O. grandis)
    • Variable Pocket Gopher (O. heterodus)
    • Hispid Pocket Gopher (O. hispidus)
    • Big Pocket Gopher (O. lanius)
    • Nicaraguan Pocket Gopher (O. matagalpae)
    • Thaeler´s Pocket Gopher (O. thaeleri)
    • Underwood´s Pocket Gopher (O. underwoodi)
  • Genus Pappogeomys; found in Mexico.
    • Alcorn´s Pocket Gopher (Pappogeomys alcorni)
    • Buller´s Pocket Gopher (P. bulleri)
  • Genus Thomomys - western pocket gophers; widely distributed in North America, extending into the northwestern US, Canada and the southeastern US.
    • Thomomys bottae; many subspecies, including the Botta's, Fish Spring, Bonneville, Clear Lake, San Antonio, Pistol River, Mount Ellen, Guadalupe, Limpia, Mearns', Stansbury Island, Antelope Island, Cebolleta, Salinas, Skull Valley, Swasey Springs, Harquahala and Limpia Greek Pocket Gophers.
    • Camas Pocket Gopher (T. bulbivorus)
    • Wyoming Pocket Gopher (T. clusius)
    • Idaho Pocket Gopher (T. idahoensis)
    • Mazama Pocket Gopher (T. mazama); several subspecies including the Western, Gold Beach, Olympic, and Tacoma Pocket Gophers.
    • Mountain Pocket Gopher (T. monticola)
    • Northern Pocket Gopher (T. talpoides); very widely distributed; several subspecies including the Cheyenne Northern Pocket Gopher
    • Townsend´s Pocket Gopher (T. townsendii)
    • Southern Pocket Gopher (T. umbrinus)
  • Genus Zygogeomys
    • Michoacan Pocket Gopher or Tuza (Zygogeomys trichopus)

Some sources also list a genus Hypogeomys, with one species, but this genus name is normally used for the Malagasy Giant Rat, which belongs to the family Nesomyidae.

Control

Geomys spp and Thomomys spp are classed as "prohibited new organisms" under New Zealand's Hazardous Substances and New Organisms Act 1996 preventing it from being imported into the country.

Evolution

Note regarding evolution from Stephan Jay Gould:

"Many rodents have check pouches for storing food. These internal pouches connect to the pharynx and may have evolved gradually under selective pressure for holding more and more food in the mouth. But the Geomyidae (pocket gophers) and Heteromyidae (kangaroo rats and pocket mice) have invaginated their cheeks to form external fur-lined pouches with no connection to the mouth or pharynx. What good is an incipient groove or furrow on the outside? Did such hypothetical ancestors run about three-legged while holding a few scraps of food in an imperfect crease with their fourth leg?" http://www.stephenjaygould.org/library/gould_hopeful-monsters.html [ Stephen Jay Gould, "The Return of Hopeful Monsters," Natural History 86 (June/July): 22-30; Reprinted here with permission from The Panda's Thumb New York: W. W. Norton & Co., 1980, pp. 186-193. ]

References

ISBN links support NWE through referral fees

• Hafner, M. S. 2004. Pocket gophers (Geomyidae). Pages 185 to 198 in B. Grzimek et al., Grzimek's Animal Life Encyclopedia, 2nd ed., vol. 16. Detroit, MI: Thomson/Gale. ISBN 0787657921.

.<ref>{{cite book

 | last = Macdonald (Ed)
 | first = Professor David W. 
 | authorlink =
 | coauthors =
 | title = The Encyclopedia of Mammals
 | publisher = Oxford University Press
 | year=  2006
 | location =
 | pages =
 | url =
 | doi =
 | isbn = 0-19-920608-2 }

External links

• Article on the Animal Diversity Web site

Rodent Families

Template:Geomyidae nav

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