Tropical pocket gopher
| Tropical pocket gopher | |
|---|---|
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Rodentia |
| Family: | Geomyidae |
| Genus: | Geomys |
| Species: | G. tropicalis |
| Binomial name | |
| Geomys tropicalis Goldman, 1915 | |
The tropical pocket gopher (Geomys tropicalis)
Pocket gophers are of the order Rodentia, and of the Geomyidae family, they are sister to the new world Heteromyidae.[2] They are fossorial herbivores, and they occur in small, isolated demes and possess an overall lack of agility as well as conservative morphology, these rodents pose various issues with respect to their taxonomy, systematics, evolutionary history, and intra- generic affinities.[2] The Pocket gophers family currently have 40 named species, 20 of them occur in Mexico.[3] Thirteen of these 20 species (nearly one-third of all extant pocket gopher species) are endemic to México.[3]
Description
The tropical pocket gopher is cinnamon to brown on its back and head. Its underparts have white fur, and its tail is mostly naked. They have large front feet, along with small eyes and a thick body.[4] Males are on average larger than females.[5]
Pocket gophers are adapted to live in subterranean tunnels, and so their body shape is tubular which allows them to move fast both forwards and backwards in tunnels.[6] Their ears, and eyes are reduced in size, and are surrounded by numerous hairs which protects them from the entry of soil.[6] Their limbs are short, and they have almost a hairless, short tail.[6] Digging can be accomplished using the claws of their strong forefeet, and their procumbent, blade-like incisor teeth used sometimes for digging.[6] While digging, the soil is prevented from entering their mouth by the closure of their lips behind the incisors.[6]
The name of the pocket gopher is derived from the fact that Pocket gophers have cheek pouches that open external to the mouth and extend from the mouth region to the animal's shoulders.[6] These commodious pouches are lined with fur and are used to transport food and nest material (but not soil) within the burrow system.[6] When full, the pouches make the Pocket gopher's head appear almost twice its natural size.[6] The color of the Pocket gopher fur varies widely within species, and it ranges between generally light brown to almost black depending on the color of freshly excavated soil.[6] This matching of the fur and the soil color appears to be an adaptation to hide the animal from aerial predators such as hawks when the pocket gopher is pushing excavated soil onto the surface.[6]
Behavior
Pocket gophers live alone in their burrow systems, and the are very asocial mammals. Food availability limits their population density in different habitats.[6] They can have population size of 50 or less individuals, to several hundred individuals per acre.[6] All geomyid are known to be solitary and aggressive, coming together only to mate.[3] Pocket gophers are crepuscular which means they are active mainly at down and dusk, so they live mainly in darkness.[6] They are nocturnal, active year long, and does not hibernate.[6]
Numerous changes of the land scape are due to the remarkable amount of burrowing activity done by pocket gophers.[6] Their burrowing activity moves a big amount of soil per year which alters both physical and biotic processes in the local environment, and they also play a major rule in the excavations on soil nutrients.[6] They spread roots, tubers, and other plant parts as a result of their burrowing activity, so they contribute to the distribution of plant life in their communities.[6] Their subterranean lifestyle is energetically expensive but its important for the pocket gopher's survival because it protects them from predators and extreme climatic fluctuations.[6]
Pocket gophers are restricted to specific habitat preference which is severely fragmented by agriculture and industrialization, and it is vulnerable to further encroachment.[7] Also their small range size makes them threatened by intrinsic factors.[7] Threats to the pockets gophers occur naturally in low abundance within restricted habitats which include competition from other gopher species and, in the case of Geomys tropicalis, loss of habitat caused by urban expansion of humans.[6]
Evolution and Genetics
Fossil records of Pocket gophers are extensive, and they have been dated back to the late Oligocene or early Miocene of North America, approximately 25 million years ago.[6] Members of the Heteromyidae family are the closest living relatives to pocket gophers. Including the kangaroo rats (Dipodomys) and Pocket mice (Chaetodipus and Perognathus).[6] Two major lineages are comprised by the pocket gophers that are living. One lineage contains only a single living genus, Thomomys, the other containing the living genera Geomys, Cratogeomys, Orthogeomys, Pappogeomys, and Zygogeomys.[6]
There has been a compartion of relationships between species of Pocket gophers and relationships among species of chewing lice that live in the pocket gopher's fur. Which led to a phenomenon known as speciation; which means that the relationship of the louse is almost exactly mirror the relationships among their host. This phenomenon suggests that pocket gophers and lice have been living together for many millions of years.[6]
The tropical pocket gopher has a diploid number of 38. This is low compared to similar species. This could help them adapt to their restricted habitat. Since their numbers are low there is a high risk of them losing too much genetic variability to survive.[8] In numerous phylogenetic studies of rodents, nucleotide sequences from mitochondrial genes have been successfully useful, especially the mitochondrial cytochrome b gene which has been used to study relationships among species of geomyid rodents in the genera Orthogeomys, Cratogeomys, and Pappogeomys.[9] The research finding of this specific gene suggests that geomyid rodents appear to evolve at a faster rate than other rodent lineages.[9] However, within the superfamily Geomyoidea, little rate heterogeneity is evident, suggesting clock-like behavior and a potential means of dating time since divergence among lineages of pocket gophers.[9]
Distribution, habitat an diet
The distribution of the tropical pocket gopher is restricted to a small area near the Southeastern tip of Tamaulipas, Mexico. Field parties from the Universidad Nacional Autónoma de México found a relationship between G. tropicalis distribution with soil texture, specifically with sandy loam soils. Besides cave for this species was founded in spiny scrub and adjacent to soils modifiyed by pipeline.[10] Field parties from Texas Tech University. Also, the pocket gophers are limited to a range in the Western Hemisphere which extends from southern Canada through western North America, southward to northwestern Colombia in South America.[6] Habitats that doesn't flood, and has variable soil are suitable for Pocket gophers to live in such as meadows, prairies, woodlands, alpine forests, valleys, deserts, rainforests, and agricultural fields.[6] They can live in any of these areas and their distribution is not affected by neither elevation nor temperature.[6] They can live in hot desert habitats at sea level and also in cold, high elevation habitats near timberline.[6] Pocket gophers lives in an isolated and small populations that are close to fertile valleys that are usually converted to agricultural production.[3] The Geomys prefers open or sparsely wooded areas with loose, deep, sandy soils, and they are restricted to certain habitats (regosol and cambosol).[7] Pocket gophers are described as fossorial animals that spend most of their lives underground, and they live alone with each animal having its own burrow system.[7] Pocket gophers are well adapted to the subterranean lifestyle, and their cylindrical bodies, reduced eyes, and well-developed forearms are used for digging.[3] They like habitats with deep soils which allows them to achieve deeper burrow systems.[3]
Their Diet includes underground vegetation (roots, bulbs and rhizomes), and sometimes they eat surface vegetation close by their burrow entrance.[7] They feed on roots and tubers of various plants, and they are abundant in agricultural fields, and they prefer alfalfa, potato, banana, and sugar cane crops.[6]
Significance to humans
Pocket gophers are damaging to agriculture and so they are considered to be agricultural pests.[6] A family's garden can be destroyed by a single pocket gopher in less than a month.[6] They are often poisoned or trapped by commercial agriculturalists regularly to limit loss of crops.[6] Also pocket gophers are known to be consumed by Early Native Americans and in some areas of Latin America it has been reported that the meat of pocket gophers as a delicacy.[6]
Reproductive biology
Breeding of Pocket gophers generally happen once per year (usually in spring), and sometimes they breed twice during (spring and fall) depending on the condition.[6] Reproductive, mature females breed during the breeding season by allowing males to enter their burrow systems for short mating encounters.[6] In the smaller species, the gestation period is about18 days but it is more than a month for larger species.[6]
Their litter size varies between pocket gophers species from 1-10 young per litter.[6] The young stays in their mother's burrow for one to two months, then they start digging their own burrow system.[6] The litter average range from 3 to five young.[6] The breeding age for pocket gophers is three months, and in some others is nine to 12 months of age.[6]
References
- ↑ Álvarez-Castañeda, S.T.; Castro-Arellano, I.; Lacher, T. & Vázquez, E. (2008). "Geomys tropicalis". IUCN Red List of Threatened Species. Version 2008. International Union for Conservation of Nature. Retrieved 29 January 2009. Database entry includes a brief justification of why this species is of critically endangered
- 1 2 Sudman, Philip D.; Wickliffe, Jeffrey K.; Horner, Peggy; Smolen, Michael J.; Bickham, John W.; Bradley, Robert D. (2006-08-24). "Molecular Systematics of Pocket Gophers of the Genus Geomys". Journal of Mammalogy. 87 (4): 668–676. doi:10.1644/05-MAMM-A-349R2.1. ISSN 0022-2372.
- 1 2 3 4 5 6 Fernández, Jesús A.; Hafner, Mark S.; Hafner, David J.; Cervantes, Fernando A. "Conservation status of rodents of the families Geomyidae and Heteromyidae of Mexico". Revista Mexicana de Biodiversidad. 85 (2): 576–588. doi:10.7550/rmb.36710.
- ↑ Goldman, E.A. 1915. Five new mammals from Mexico and Arizona. Proc. Biol. Soc. Washington 28:133-137.
- ↑ Alvarez, T. 1963. The recent mammals of Tamaulipas, Mexico. Univ. Kansas Publ. Mus. Nat. His. 14:363-473.
- 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 Grzimek, Bernhard; Schlager, Neil; Olendorf, Donna; American Zoo and Aquarium Association; Thomson Gale (Firm) (2003-01-01). Grzimek's animal life encyclopedia. Detroit: Gale. ISBN 0787677507.
- 1 2 3 4 5 IUCN. "Geomys tropicalis: Álvarez-Castañeda, S.T., Castro-Arellano, I., Lacher, T. & Vázquez, E.". IUCN Red List of Threatened Species. doi:10.2305/iucn.uk.2008.rlts.t9056a12954274.en.
- ↑ Davis et al. 1971. Chromosomal studies of Geomys. Jour. Mammal.52:617-620.
- 1 2 3 Jolley, Ted W.; Honeycutt, Rodney L.; Bradley, Robert D. (2000-11-01). "Phylogenetic Relationships of Pocket Gophers (Genus Geomys) Based on the Mitochondrial 12s rRNA Gene". Journal of Mammalogy. 81 (4): 1025–1034. doi:10.1644/1545-1542(2000)081<1025:PROPGG>2.0.CO;2. ISSN 0022-2372.
- ↑ Márquez-Huitzil, R. 1994. Distribución ecológica y Geográfica de una tuza (Geomys tropicalis) endémica de México. Tesis de Biología. Facultad de Ciencias, Universidad Nacional Autónoma de México.