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Geomys arenarius

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA MAMMALIA RODENTIA GEOMYIDAE

Scientific Name: Geomys arenarius
Species Authority: Merriam, 1895
Common Name(s):
English Desert Pocket Gopher
Taxonomic Notes: Analysis of sequence data from the mitochondrial DNA cytochrome-b gene (P. Sudman and D. Hafner pers. comm.) supports both the recognition of Geomys arenarius as a species distinct from G. bursarius (contra Hafner and Geluso 1983) and as a closely related sister taxon to G. knoxjonesi. Preliminary molecular sequence data for ectoparasitic lice (Geomydoecus spp.) indicates that the louse on G. arenarius (Geomydoecus quadridentatus) is distinct from the lineage that includes lice from G. bursarius and G. knoxjonesi (S. Brant and D. Hafner pers. comm.).

G. arenarius has been recognized as a subspecies of G. bursarius, but, in a study of mitochondrial RNA, Jolley et al. (2000) found that G. arenarius appeared as a distinct lineage (although sequence divergence was small). Baker et al. (2003) and Patton (2005) recognized G. arenarius as a distinct species.

Assessment Information [top]

Red List Category & Criteria: Near Threatened ver 3.1
Year Published: 2008
Date Assessed: 2008-06-30
Assessor(s): Hafner, D.J., Timm, R. & Lacher, T.
Reviewer(s): McKnight, M. (Global Mammal Assessment Team) & Amori, G. (Small Nonvolant Mammal Red List Authority)
Justification:
Listed as Near Threatened because, although the species is still reasonably widely distributed, it is dependent upon a patchily distributed habitat; climatic and land use changes could quickly result in this species becoming seriously threatened. Almost qualifies as threatened under criterion B2.

Geographic Range [top]

Range Description: This species has a patchy distribution (D. Hafner pers. comm.), and is restricted to a narrow area of south-central New Mexico, a small section of the north-western Trans-Pecos in Texas (several localities in El Paso and Hudspeth counties), and bordering areas in Chihuahua, Mexico.

Subspecies arenarius: narrow strip of bottom land along the upper Rio Grande Valley from Porvenir, Chihuahua, north to Las Cruces, New Mexico (Williams and Baker 1974). Subspecies brevirostris: Tularosa Basin and adjacent Jornada del Muerta of New Mexico in the vicinity of White Sands National Monument, Gran Quivira (Salinas Pueblo Missions National Monument), and south-east of San Antonio (Williams and Baker 1974; Hafner and Geluso 1983).
Countries:
Native:
Mexico (Chihuahua); United States (New Mexico, Texas)
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: According to Hafner (pers. comm.), it is difficult to estimate the number of occurrences because populations occur in small patches of appropriate habitat. However, there are probably more than 100 occurrences or subpopulations rangewide (D. Hafner pers. comm.). The total adult population size is estimated at over 10,000 individuals occupying over 50,000 acres (D. Hafner pers. comm.).

This species is common within its small range in Texas and New Mexico (Schmidly 1977; Davis and Schmidly 1994). Populations are dense in areas along the Rio Grande, and large populations occur on Gran Quivera and White Sands National Monuments (Hafner, in press). The scant information that is available regarding population trends indicates populations may fluctuate greatly and that intermediate populations may be slightly declining (D. Hafner pers. comm.). In 1981 populations were locally abundant in pinon-juniper habitat at and near Gran Quivera National Monument, along the margins and interior basins of White Sands National Monument, and along the banks of the Rio Grande near Las Cruces. After a prolonged drought in 1982, no pocket gophers were found at White Sands National Monument and only old mounds could be located at Jornada del Muerta (a potentially ephemeral population). On the other hand, activities in the Las Cruces vicinity have improved gopher habitat, and populations are dense in areas in the Rio Grande Valley (Hafner, in press).

According to Hafner (in press), it appears that secure but isolated populations persist along the Rio Grande, at White Sands National Monument, and at Gran Quivera National Monument. However, continued grazing and fire suppression, coupled with warming and drying trends, may result in the extirpation of intermediate, ephemeral populations (Hafner, in press). Some intermediate populations may be lost as drying trends continue, but with the return of wet periods populations are expected to expand (D. Hafner pers. comm.)
Population Trend: Unknown

Habitat and Ecology [top]

Habitat and Ecology: This fossorial species occurs in loose soils of disturbed areas or sandy areas near open water; it is often common along edges of rivers, ponds, or irrigation canals (Schmidly 1977; Davis and Schmidly 1994).
Systems: Terrestrial

Threats [top]

Major Threat(s): The interior valleys of New Mexico have experienced extensive desertification and an increase in shrub cover during this century due to overgrazing and fire suppression, perhaps accelerated by a warming and drying trend. A reduction in quality and expanse of grassland has apparently resulted in increased fragmentation and isolation of G. arenarius populations, which already have a patchy distribution dictated by the availability of appropriate friable soil. Continued grazing and fire suppression, coupled with warming and drying trends, may further isolate the Rio Grande and Tularosa Valley populations temporarily eliminating intermediate, ephemeral populations (Hafner, in press).

Habitat in the Las Cruces area has apparently been improved by Army Corps of Engineers activities. Populations are dense along the Rio Grande and adjacent agricultural fields and pasturelands in areas where the river has been channelized and the natural bosque eradicated (Hafner, in press; D. Hafner pers. comm.). According to Williams and Baker (1974), Cratogeomys castanops may have replaced G. arenarius some areas. In contrast, Hafner and Geluso (1983) found Geomys to be abundant in the White Sands area, while they caught relatively few Cratogeomys. Davis and Schmidly (1994) stated that this species faces no known threats but should be monitored in view of its small distribution. Hafner (pers. comm.) indicated that this species is not very threatened or is unthreatened; it is threatened only in the sense that it occupies a somewhat small range.

Conservation Actions [top]

Conservation Actions: A protected population occurs on White Sands National Monument, but it is vulnerable to droughts (D. Hafner pers. comm.). Inventory needs are as follows: 1. Determine distribution and long-term dynamics of isolated populations located between the established populations (Rio Grande, White Sands, and Gran Quivera). 2. Evaluate the effect of grazing and fire suppression on intermediate populations. 3. Monitor established populations periodically to determine population dynamics (Hafner, in press). 4. Determine if additional populations exist in Texas and Mexico.

Citation: Hafner, D.J., Timm, R. & Lacher, T. 2008. Geomys arenarius. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 01 October 2014.
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