Geomys pinetis

Geographic Range

The range of southeastern pocket gophers extends eastward from southern Georgia and southeastern Alabama to northern and central Florida. Geomys pinetis consists of six subspecies, which together form this range. Geomys pinetis austrinus is distributed in central and western Florida, G. p. cumberlandius is restricted to Cumberland Island in Georgia, G. p. fontanelus is known from an isolated population near Savannah, Georgia, G. p. colonus is restricted to coastal plains in Camden Co., Georgia (previously recognized as a distinct species), G. p. floridanus is distributed from central and northwestern Florida eastward into Georgia and Alabama (and includes the previously recognized subspecies G. p. mobilensis , and the now-extinct G. p. goffi ), and G. p. pinetis is mostly found in central and southern Georgia. Recent research, however, indicates that the Apalachicola and Suwannee Rivers may be serving as a river barrier within G. pinetis , thus future taxonomic changes may be necessary.

• Biogeographic Regions
• nearctic nearctic
  • native native

Habitat

Southeastern pocket gophers generally reside in either sandhill or xeric hammock ecosystems. Longleaf pines ( Pinus palustris ) and turkey oaks ( Quercus laevis ) are the two dominant trees in sandhill ecosystems. The terrain is rolling and the soil is well drained. Xeric hammock ecosystems are dominated by live oaks ( Quercus virginiana ) and other hardwood species. The soil contains more organic material and is slightly moister than that of the sandhill ecosystem. In sand pine scrub and longleaf pine flatlands habitats, southeastern pocket gophers occur less commonly. In areas where sandhill and xeric hammock habitats are disappearing due to modern land-use practices, southeastern pocket gophers are adapting by burrowing into road shoulders, power line rights of way, railroad embankments, fields along airport runways, parks, lawns, orchards, cemeteries, baseball fields, and golf courses.

• Habitat Regions
• temperate temperate
• terrestrial terrestrial

• Terrestrial Biomes
• forest forest
• scrub forest scrub forest

• Other Habitat Features
• urban urban
• suburban suburban
• agricultural agricultural

Physical Description

Southeastern pocket gophers are medium-sized rodents with a total length of about 290 mm in males and 261 mm in females. Based on age composition, they are broken into three groups: juveniles, weighing 45 to 80 g; sub-adults, weighing 70 to 150 g; and adults, weighing 130 to 390 g. The species is sexually dimorphic and displays a size difference of roughly 10%, with males larger than females. The cylindrical-shaped bodies of these pocket gophers have 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. Coloration can vary among juvenile and sub-adult individuals: juveniles have gray pelage and molting sub-adults have a range of coloration from gray to brown pelage. Like all pocket gophers, southeastern pocket gophers have fossorial adaptations, including small eyes, reduced pinnae, and strong-clawed forelimbs, as well as nearly naked tails, external fur-lined cheek pouches, and thick bodies. The large exposed incisors function to dig and move soil while burrowing. The daily growth rate of incisors average 0.35 mm (upper) and 0.67 mm (lower). Enamel on the incisors are typically bisulcate; however, it is common for the species to have additional grooves. The dental formula is 1/1,0/0,1/1,3/3 = 20. A major distinguishing skull characteristic of southeastern pocket gophers are their hourglass-shaped nasals, which are constricted near the middle.

• Other Physical Features
• endothermic endothermic
• homoiothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• sexes alike
• male larger

Reproduction

There is little available information on reproduction in southeastern pocket gophers, but they are most likely polygynous, as are other gopher species.

• Mating System
• polygynous polygynous

Southeastern pocket gophers breed throughout the year. Females exhibit two major peaks of activity during February through March and June through August, whereas males have 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. Litter sizes ranges from 1 to 3 with averages of 1.7 ± 0.51 or 1.52 ± 0.11. Females may produce two litters per year corresponding with their two peaks of sexual activity. Southeastern pocket gophers are born nearly naked, tail-end first and average 50 mm and 5.8 g. The eyes, ears, and cheek pouches are closed at birth and the teeth are not yet erupted. Young southeastern pocket gophers are usually weaned and dispersed by one month, and reach sexual maturity by the age of 4 to 6 months.

• Key Reproductive Features
• iteroparous iteroparous
• year-round breeding year-round breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• viviparous viviparous

There are no detailed data available regarding reproductive investment in southeastern pocket gophers. Given the mating system (polygynous) and time to weaning and dispersal, the female likely provides sole care for altricial young for a time period of approximately one month.

• Parental Investment
• altricial altricial
• female parental care female parental care
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female
• pre-weaning/fledging
  • provisioning
    • female
  • protecting
    • female

Lifespan/Longevity

No data are available on the longevity of southeastern pocket gophers but, based on other species ( Thomomys bottae and Geomys bursarius ) and a study by Brown (1971), longevity is likely around 2 years.

Behavior

Southeastern pocket gophers are fossorial and individuals spend the majority of their lives underground in their elaborate burrow systems. Five phases of mound building have been described as the following: prospecting, groundbreaking, excavation, mound building, and plugging. Completion of the five phases of mound building can range from 5 to 53 minutes. 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, southeastern pocket gophers periodically push 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 to 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. Southeastern pocket gophers are solitary, territorial, and extremely aggressive within their burrows. Males and females create separate burrows and only come together to mate. Males may use odor to help locate females in estrus. After mating, the male and female seal off their burrows from one another. Females generally create localized burrow networks, whereas males burrow in straight lines sometimes for hundreds of feet. Burrowing straight lines gives males a higher chance of running into a females' burrow system for potential mating. Increased mound production seems to occur during low temperatures, and may be the result of increased search efforts for food due to plant dormancy. Living in sealed burrows has made it necessary for southeastern pocket gophers to adapt to living in an atmosphere low in oxygen and high in carbon dioxide. Based on oxygen consumption, basal metabolism is approximately 74% of that predicted for mammal of comparable size. They have a high tolerance to carbon dioxide and 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.

• Key Behaviors
• fossorial fossorial
• nocturnal nocturnal
• motile motile
• sedentary sedentary
• solitary solitary
• territorial territorial

Communication and Perception

Southeastern pocket gophers are morphologically adapted for a fossorial lifestyle. Due to the lack of visibility underground, sight is not essential resulting in a reduction of eyes. External ears also are often reduced to decrease friction, although hearing may be important. It is possible that pocket gophers may use chemical, vibrational, and tactile communication to perceive their environment. No data regarding vocalizations of southeastern pocket gophers are known, although it is presumed they make a variety of audible grinding, clicking, and chattering noises, as do other pocket gophers .

• Communication Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• vibrations vibrations
• chemical chemical

Food Habits

The bulk of the southeastern pocket gopher diet includes roots and other herbaceous material. While burrowing, they collect plant roots, tubers, bulbs, and stems, which they transport in their cheek pouches to underground storage chambers for later consumption. Peak activity is from dusk to dawn and southeastern pocket gophers are active year long. Individuals occasionally emerge above ground to feed on grasses, forbs, and sedges.

• Plant Foods
• leaves
• roots and tubers
• wood, bark, or stems

• Foraging Behavior
• stores or caches food stores or caches food

Predation

Life below the surface results in a very low mortality rate for southeastern pocket gophers. Predation from owls, mink, and spotted skunks is greatly reduced and usually only takes place during the rare times that these pocket gophers look for food close to their mounds on the surface.

• Anti-predator Adaptations
• cryptic cryptic

Ecosystem Roles

Due to the fossorial life history of southeastern pocket gophers, they have many commensal relationships: approximately 60 species of arthropods, mostly insects, have been found in their burrows, 14 of which are considered to be obligate commensals. For example, camel crickets ( Thyphloceuthophilus floridanus ) act as scavengers feeding on fecal matter and organic debris. One species of ectoparasitic louse, Geomydoecus scleritus , has been reported on southeastern pocket gophers. Southeastern pocket gophers may influence soils, microtopography, habitat heterogeneity, and diversity of plant species and primary productivity due to their mixing and moving of soil to create burrow systems.

• Ecosystem Impact
• creates habitat
• soil aeration soil aeration

Economic Importance for Humans: Positive

Southeastern pocket gophers play several important roles in the functioning of their ecosystems. They are known to promote plant growth, increase water penetration, increase availability of helpful nutrients, aerate the soil, and enhance plant diversity. Humphrey (1992) observed the return of 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. Southeastern pocket gophers are also well-known model systems for studies of coevolution.

• Positive Impacts
• research and education

Economic Importance for Humans: Negative

Over 203 articles were published between 1888 and 1976 mentioning 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. The burrowing behavior of pocket gophers can leave soft spots and holes in the soil that may cause injuries in livestock and damage crop and agriculture lands.

• Negative Impacts
• crop pest

Conservation Status

Southeastern pocket gophers are listed as high priority species in Georgia. Three of the six subspecies are threatened by habitat destruction by human development of limited habitats: Geomys pinetus colonus , Geomys pinetus fontanelus , and Geomys pinetus cumberlandius . Geomys pinetus 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.

Other Comments

The genus 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". According to Sudman et. al., G. pinetis is most closely related to Geomys breviceps and is the most basal lineage of all species groups within Geomys (e.g., Geomys breviceps , Geomys personatus , and Geomys bursarius species groups).

Additional Links

Encyclopedia of Life

Contributors

Alicia Byers (author), Texas A&M University, Jessica Light (author), Texas A&M University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

References

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