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Geomys bursarius Cladus: Eukaryota Name Geomys bursarius (Shaw, 1800) References * Geomys bursarius in Mammal Species of the World.
* North American Mammals: Geomys bursarius [1]
Plains Pocket Gopher, Geomys bursarius Geomys bursarius, also known as the Plains Pocket Gopher, is one of thirty-five species in the mammalian family, Geomyidae.1 This family is in the largest order of mammals, known as Rodentia. They are commonly called “pocket gophers” in reference to their externally located, fur-lined cheek pouches. Pocket gophers are the most highly fossorial rodents found in North American.2 Biogeography and Paleontology Plains pocket gophers are found throughout the Great Plains of North America ranging from southern Manitoba (Canada), and eastern North Dakota south to New Mexico and Texas in the United States, and as far east as the extreme western parts of Indiana. Fossil remains have been found as far south as Tennessee, indicating a late Pleistocene, early Holocene population.3 This would support the hypothesis that drier environmental conditions with extensive prairies extended further south during the Late Wisconsinan glacial period, supporting populations of Geomys and other prairie species such as Thirteen-lined ground squirrels and Prairie Chickens.4 Description G. bursarius has short fur with brown to black coloration to it’s upper pelage, while the ventor surface tends to be a lighter brown or tan in coloration. Whitish hairs cover the tops of the feet while the short, tapered tail is nearly naked. Fossorial adaptations include small eyes, short, naked pinnae, and heavily clawed forefeet. Zygomatic arches are widely flared, providing ample room for muscle attachment.5 This is important, as the curved incisors are also used to assist the feet in digging. The lips close behind these grooved teeth to help keep dirt out of the mouth. The external cheek pouches, which distinguish this family from other mammals, can be turned inside-out for grooming purposes. They are used for carrying food up to 7 cm in length and open forward facing.6 Other interesting and important adaptations to a fossorial lifestyle include a low resting metabolic rate and high conductance, a tolerance for low oxygen levels and high carbon dioxide levels, and a decreased water intake. (G. Bursarius rarely drink water.)7 Measurements: Total length: 235–310 mm; tail length: 63–90 mm; hindfoot length: 30–37 mm; ear height: 6–9 mm; weight: 200-400g.8 Ecology The Plains Pocket Gopher prefers deep, sandy, crumbly soils from open fields to sparsely wooded tracts. This facilitates its fossorial lifestyle and herbivorous diet of plant roots. A long-term controlled study of tunnel excavation by G. bursarius found that the rate of tunnel construction ranges from a high of 2,059 cm/week of new tunnels to a low of zero over several weeks during the summer. 30 – 50 meters of tunnels were open at any one time. Factors affecting the size of the tunnel system appeared to be influenced more by the amount of energy needed to maintain and patrol it rather than the amount of vegetation present.9 Predation
Plains Pocket Gophers show no seasonal change in activity, except for an increased level of activity during mating season. They do show a bimodal pattern of activity during the day with increased activity occurring from 1300-1700 and then again from 2200-0600.11 Even though burrow temperature did not vary more than 4oC, this bimodal pattern of activity was thought to be reflective of burrow temperature. For a fossorial animal with a metabolically expensive lifestyle (360-3400 times as much as terrestrial creatures), planning daily activity around burrow temperature, where lack of air flow and high humidity lead to a decrease in evaporative and convective cooling, becomes much more important.12 G. bursarius spends 72% of their time in their nests. Territorial and aggressive, especially in male-to-male interaction, these rodents appear to use their greatly increased sensitivity to soil vibration to maintain their solitary lifestyle.13 Males leave their burrows in early spring to mate, but then return to their solitude. Females are monestrous, giving birth to 2-6 young following a gestation period of 18–51 days. The wide variation in observed lengths of gestation is reflective of the small amount of data available in this particular area. It could also indicate the possibility of some form of delayed fertilization, delayed implantation, or delayed zygote development. Further study, though difficult on fossorials, is needed. Economic Impact Though pocket gophers are considered to be no more than pests by farmers and suburban lawn owners, they play active roles in soil aeration, flood control via improved drainage, and soil and plant diversity.14 (For a more thorough discussion on the positive impact of gophers in maintaining and/or restoring disturbance-dependent elements of native plant communities, see Reichman, 2002.) Conservation status Least concern (per IUCN, Oct. 26, 2008) Due to the widespread distribution of this species, it’s adaptability to suitable habitat, the lack of any major threats, and an apparently stable population, G. bursarius has a conservation status of “Least Concern.” Prognosis for this species is good, and there are no plans of action toward conservation at this time.15 References 1. ^ Linzey, A.V. & NatureServe (Hammerson, G.) (2008). Geomys bursarius. In: IUCN 2008. IUCN Red List of Threatened Species. Downloaded on 29 January 2009. Database entry includes a brief justification of why this species is of least concern Benedix, Jr., J. H. (1994) “A predictable pattern of daily activity by pocket gopher Geomys bursarius.” Animal Behavior. 48:501-509. Kurta, Allen. Mammals of the Great Lakes Region, Revised Edition. The University of Michigan Press. 1995. Reichman, O.J., et al. (2002) “The role of pocket gophers as subterranean ecosystem engineers.” TRENDS in Ecology & Evolution. 17:44-49. Sullivan, Robert M. (1981) “A late Pleistocene population of the pocket gopher, Geomys cf. bursarius, in the Nashville Basin, Tennessee.” Journal of Mammalogy. 62:831-835. Teeter, K. (2000) “Geomys bursarius” Animal Diversity Web. Downloaded on 26 October 2008 at http://animaldiversity.ummz.umich.edu/ Thorne, David H. et al. (1990) “Long-term soil-disturbance pattern by a pocket gopher, Geomys bursarius.” Journal of Mammalogy. 71:84-89 Vaughan, Terry A. et al. Mammalogy, 4th Edition. Thomson Learning, Inc. 2000. GOPHERS Source: Wikipedia, Wikispecies: All text is available under the terms of the GNU Free Documentation License |
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