Geomys pinetissoutheastern pocket gopher

Geographic Range

The range of G. pinetis extends from southern Georgia and southeastern Alabama to northern and central Florida. Geomys pinetis consists of five subspecies which together form this range. Geomys pinetis austrinus resides in central Florida, G. p. floridanus is in northern Florida and southern Georgia, G. p. goffi was in eastern central Florida, G. p. mobilensis is found in southeastern Alabama and northwestern Florida, and G. p. pinetis is mostly found in southern Georgia. (Pembleton et al. 1978)

Habitat

This pocket gopher generally resides in either the sandhill ecosystem or the xeric hammock ecosystem. Longleaf pines (Pinus palustris) and turkey oaks (Quercus laevis) are the two dominant trees within the sandhill ecosystem. The terrain is rolling and the soil is well-drained. The xeric hammock ecosystem is dominated by live oaks (Q. virginiana) and other hardwood species. The soil contains more organic material and is slightly moister than that of the sandhill ecosystem. In areas where sandhill and xeric hammock habitats are disappearing from modern land-use practices, pocket gophers are adapting by burrowing into road shoulders, power line rights of way, railroad embankments, fields along airport runways, parks, lawns, orchards, cemetaries, baseball fields, and golf courses. (Wilkins 1986, Lee 1980)

Physical Description

This pocket gopher is a medium-sized rodent with a total length of about 290 mm in males and 261 mm in females. This sexual dimorphic species has a size difference of roughly 10%. The cylindrical body has sepia fur, shaded orange-cinnamon on the sides of the shoulders and flanks, with white hairs on the throat and forearms, a white patch from the forehead to the nostrils, and grayish underparts. All pocket gophers' fossorial adaptations include small eyes, reduced pinnae, strong-clawed forelimbs, nearly naked tail, external fur-lined cheek pouches, and a thick body. The teeth are all evergrowing and the cheekteeth have reduced enamel. The large exposed incisors function as picks while burrowing. The dental formula is i 1/1, c 0/0, p 1/1, m 3/3, total 20.

A major distinguishing characteristic of this species is the hourglass-shaped nasals which are constricted near the middle. Geomys pinetis can be further distinguished from some other Geomys as follows: from G. fontanelus by the missing fontanel between the parietal and squamosal bones on the skull; from G. cumberlandius by a greater angled zygomatic arch which is not extended posteriorly; and from G. colonus by a broad V-shaped, rather than U-shaped interpterygoid space. (Pembleton et al. 1978, Lee 1980, Ross 1980)

Reproduction

This pocket gopher breeds throughout the year. Females exhibit two major peaks of activity during February through March and June through August, whereas males display a more constant higher level of activity from January through August. Males have alternating cycles of spermatogenic activity and inactivity, and they produce sperm at a higher rate with increased age. The range of litter sizes is one to three with averages of 1.7 0.51 and 1.52 0.11 in separate studies. Females may produce two litters per year corresponding with their two peaks of sexual activity. Pocket gophers are born tail-end first and average 50 mm and 5.8 g. The eyes, ears, and cheek pouches are closed at birth. Young pocket gophers are usually weaned and dispersed by one month, and reach sexual maturity by the age of four to six months. (Pembleton et al. 1978)

  • Key Reproductive Features
  • gonochoric/gonochoristic/dioecious (sexes separate)
  • sexual

Behavior

The pocket gopher is famous for the clusters of mounds it creates that are about one foot high and 1-3 feet across. Pocket gophers are fossorial and spend the majority of their lives underground within their elaborate burrows. The burrows are usually about 6 inches to 2 feet below the surface and can extend for hundreds of feet. As the loosened soil accumulates within the burrow, the pocket gopher periodically pushes the soil out to the surface, creating the mounds of dirt outside each hole. Mounds are usually placed several feet apart, and there are generally 6-12 or more mounds for a single burrow. The mounds are connected to the burrows by diagonal tubes and are sealed with dirt so that open holes are not visible from the surface. Pocket gophers are solitary, territorial, and extremely aggressive within their burrows. Males and females create separate burrows and only come together in order to mate. Females generally create localized burrow networks, whereas males burrow in straight lines sometimes for hundreds of feet. Burrowing straight gives males a higher chance of running into a females randomly directed burrow while searching for a mate. Males may also use odor to help locate females in estrus. After mating, the male and female seal off their burrows from one another.

Living in sealed burrows has made it necessary for pocket gophers to adapt to living in an atmosphere low in oxygen and high in carbon dioxide. They have a high tolerance to carbon dioxide and has a low metabolic rate to reduce their oxygen requirement and lower respiratory water loss. Body temperature is thought to be further regulated by heat dissipation from their naked tail and feet.

Life below the surface results in a very low mortality rate. Predation from owls, mink, and spotted skunk is greatly reduced and usually only takes place during the rare times that the pocket gopher looks for food close to its mound on the surface. (Avise et al. 1982, Lee 1980)

Communication and Perception

Food Habits

The bulk of this pocket gopher's diet includes roots and other herbaceous material. While burrowing, these pocket gophers collect plant roots, tubers, bulbs, and stems, which they transport in their cheek pouches to underground storage chambers for later consumption. It occasionally emerges above ground and feeds on grasses, forbs, and sedges (Humphrey 1992, Wilkins 1986)

Economic Importance for Humans: Positive

Pocket gophers play several important roles in the functioning of their ecosystems. They return leached nutrients to the surface of the soil, pushing up to 81,600 kg/ha of burrow soil to the surface per year. The soil mounds create numerous small sites for colonization and secondary succession within grasslands, sandhills, and scrub. (Humphrey 1992)

Economic Importance for Humans: Negative

Over 203 articles were published between 1888 and 1976 regarding the damage caused by pocket gophers. Suggestions to control these pests included traps, poisons, anticoagulants, repellents, gas-chambers, and mechanical burrow-diggers. Most pocket gophers are quickly exterminated from lawns, golf courses, parks, and cemeteries. (Avise et al. 1982)

Conservation Status

Four of the five subspecies of G. pinetis are common throughout their range. G. p. goffi was listed as endangered by the Florida Game and Fresh Water Fish Commission in 1990. It is now considered to be extinct and is therefore no longer being considered for listing by the U.S. Fish and Wildlife Service. (Humphrey 1992)

Other Comments

The family name, Geomys, comes from the Greek words Geo and mys, meaning "earth" and "mouse", respectively. The species name, pinetis, comes from the Latin word Pinetum which means "a pine wood". (Pembleton et al. 1978)

Contributors

John Dunn (author), 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

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

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.

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

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.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

References

Avise, J. & Laerm, J. 1982. The pocket gopher. Florida Naturalist. 55(2):7-10.

Humphrey, S. R. 1992. Rare and endangered biota of Florida. Volume 1:mammals. University Press of Florida, Gainesville, Tallahasse etc. 11-18.

Lee, D. S. 1980. The pocket gopher mound probe. Natural History. 89(6):36-41.

Pembleton, E. F. & Williams, S. L. 1978. Geomys pinetis. Mammalian Species. No. 86. 1-3.

Ross, J. P. 1980. Seasonal variation of thermoregulation in the Florida pocket gopher, Geomys pinetis. Comparative Biochemistry and Physiology: A Comparative Physiology. 66(1):119-25.