Orthogeomys lanius

Geographic Range

Big pocket gophers are a microendemic species that are native to the subtropical highland of southern Nearctic regions. This species was rediscovered after 100 years in the mountains southeast of Pico de Orzaba in Veracruz, Mexico. The range of big pocket gophers expands throughout higher elevations across central Veracruz, as its lower elevation barrier is limited by a sister species, hispid pocket gopher ( Orthogeomys hispidus ). The small geographic range of big pocket gophers shows very little overlap between other Geomyidae species, therefore, limiting its expansion. Big pocket gophers have historically occupied an elevation range beginning at 1100 and extending well above of 2000 m, with an average elevation of 2400 m. The lower elevation barrier is set by hispid pocket gophers ( Orthogeomys hispidus ) and human alterations on the landscape. A significant portion of their expected geographic range is protected by Parque Nacional Pico de Orbaba.

• Biogeographic Regions
• nearctic nearctic
  • native native

Habitat

Big pocket gophers are terrestrial and fossorial rodents that create self-excavated burrows. Tropical habitats dominated by conifer-hardwood and mountainous terrain are favorable habitats. Big pocket gophers do not co-exist well with humans and prefer habitats that are located at elevations higher than that of human-altered landscapes. The most significant habitat implications for the big pocket gopher includes deforestation and climate change. This species is absent in regions that experience deforestation to produce agricultural fields at lower elevations. Ecosystem alternations associated with climate change result in the expansion of the hispid pocket gopher and push the big pocket gopher into higher elevations.

• Habitat Regions
• tropical tropical
• terrestrial terrestrial

• Terrestrial Biomes
• forest forest
• mountains mountains

Physical Description

Minimal information about the physical characteristics of big pocket gophers is known, however, they have similar characteristics to other pocket gophers ( Geomyidae ). A dense, tubular body with short powerful limbs and short tail assist the species in digging and moving through tunnels. Fore and hind feet have five digits that end with enlarged claws, particularly on the forefeet. Furred lips close behind outward projecting incisors to restrict dirt and debris from entering the mouth when digging. Pinnae and eyes are reduced in size, as with most fossorial species. Pocket gophers ( Geomyidae ) also have enlarged lacrimal glands that are hypothesized to provide fluid to rinse eyes of dirt. A large diastema is also charismatic of rodents . In pocket gophers ( Geomyidae ), the cheek pouches are fur lined and expand from the mouth to the back shoulder to allow for greater food transportation. Pocket gophers ( Geomyidae ) have a relatively large skull with strong zygomatic arches and continuously growing, hypsodont cheek teeth that prevent deterioration through grinding food. The dental formula for the family is 1/1, 0/0, 1/1, 3/3 = 20. Weight in pocket gophers ( Geomyidae ) can be diverse but the two specimens found in the last 100 years weighed approximately 900 g. Orthogeomys species weigh between 300 and 900 g, although big pocket gophers are among the largest species and surpass this upper limit in most cases. Pocket gophers display extreme sexual dimorphism in which females are smaller than males and the species display a male-biased sex ratio. Males continue to grow throughout the duration of their life, whereas female growth is terminated when they reach reproductive maturity, to shift energy production from growth to reproduction. Big pocket gophers are most closely related to hispid pocket gophers ( Orthogeomys hispidus ) which occupy the same geographical range at a lower elevation. These two species differ in size, pelage, and growth. Big pocket gophers are larger with black, thick, woolly pelage, whereas hispid pocket gophers ( Orthogeomys hispidus ) are smaller with brown sparse pelage. The longer hair and woolly composition permit big pocket gophers to withstand cold temperatures at higher elevations. Cranial measurements of the two big pocket gopher specimens were larger than that of the sister species. The color of big pocket gophers demonstrates background matching to assist in camouflage. The diploid number of big pocket gophers is 44 chromosomes compared to the hispid pocket gopher which is 52 or 54. As this species is endemic to this particular location in Veracruz, little variation exists between individuals.

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

• Sexual Dimorphism
• male larger

Reproduction

Limited information is known about mating systems in big pocket gophers. However, pocket gophers ( Geomyidae ) in general are polygynous. Individual pocket gophers inhabit their own burrows limiting interaction between males and females until breeding season. During breeding season, sections of burrows become joint between neighboring males and females. The location of burrows among individuals are important as it plays a role in mate selection. Females are thought to be more likely to select a mate that neighbors their burrow than one that is located further away.

• Mating System
• polygynous polygynous

Two specimens that were collected in late May and early June of 2013, led to the rediscovery of the species. Both specimen were female adults that displayed two pectoral and inaguinal mammae. Others than these specimen, little is known about reproduction in big pocket gophers, although, details can be considered when assessing the Geomyidae family. The hispid pocket gopher, sister species of the big pocket gopher, is capable of breeding throughout the entire duration of the year; however, the highest periods of reproductive activity took place between July and October. As hispid pocket gophers inhabit a lower elevation with more favorable conditions, it may be expected that the big pocket gopher is more restricted for reproduction periods. The mean litter size is two offspring, with an average newborn weight of 15.1g. Offspring exhibit altricial characteristics as their eyes, ears, and cheek pouches are closed at birth. Cheek pouches open at 24 days followed by eyes and ears at 26 days. Offspring remain sheltered within the mothers burrow and are weaned around 40 days.

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

A lack of knowledge exists about reproduction in big pocket gophers. In other pocket gopher species ( Geomyidae ) offspring are altricial and rely on parental care until they are weaned at around 40 days. The breeding male has little involvement in providing care while the female protects young in her burrow and retrieves food. Many male offspring do not survive long enough to reproduce due to male-male competition.

• 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

Lifespan/Longevity

Due to the recent rediscovery of big pocket gophers following a century with no sightings, lifespan has not been identified. In Geomyidae , maximum lifespan is generally five years, although, the average is between one and three years. Females are known to live longer than males due to intermale competition in the breeding season. Big pocket gophers are not found in captivity so lifespan in captivity is unknown.

Behavior

Big pocket gophers are solitary rodents as they inhabit self-excavated burrows. Long, shallow components are used for general transportation while deep components are used for food storage and nesting. In regions were habitat quality is good, burrows will be spaced out evenly; however, in regions with lower quality habitat, burrows will clump together within good quality areas. These burrows are often positioned closely to other burrows. Male burrows on average will be larger and more branched than females allowing them to neighbor many female burrows. This is favorable as females are thought to choose mates from adjacent burrows.

• Key Behaviors
• terricolous
• fossorial fossorial
• diurnal diurnal
• motile motile
• sedentary sedentary
• solitary solitary

Home Range

The home range of big pocket gophers is unknown. Within the Geomyidae family, home range is known to vary drastically between different species and different habitats.

Communication and Perception

Little information is known about methods of communication between individual big pocket gophers. Species within the Geomyidae family have relatively poor hearing sensitivity as subterranean rodents; therefore, vocal expression is not thought to be used significantly. Within the Geomyidae family, tails of pocket gophers are thought to be filled with nerves, muscles, and blood vessels, hypothesized to provide important sensory information about their surroundings.

• Communication Channels
• visual visual

• Perception Channels
• tactile tactile
• chemical chemical

Food Habits

Although big pocket gophers are a fossorial species, they have also been observed foraging above ground. They are herbivorous mammals that feed primarily on succulent roots and tubers below ground, supplemented by leafy vegetation above ground. Forbes and grasses make up their preferred diet; however, diets must shift seasonally based on what is available. Cheek pouches are used for transporting foraged material from above ground back to burrows where they are stashed. Continuously growing incisors suggest pocket gophers are well adapted to a herbivorous diet.

• Primary Diet
• herbivore herbivore
  • folivore folivore

• Plant Foods
• leaves
• roots and tubers
• flowers

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

Predation

Big pocket gophers feature countershading that assists in camouflage. With the dark coloration on top, the big pocket gopher blends into the surrounding soil, making it difficult for owls and birds of prey to identify. Burrows provide safety and are used to escape from predators.

• Anti-predator Adaptations
• cryptic cryptic

Ecosystem Roles

Big pocket gophers play a significant role within soil dynamics. Digging activity transports soil vertically, resulting in increased porosity, slow rate of water runoff, and increased aeration. This activity often creates favorable conditions for growth of herbaceous plants that they prefer eating. A reduction in overall biomass occurs on top of the tunnels but increases approximately 10 cm away. This activity can also counter impacts of soil compaction via grazing in human altered landscapes at their lower elevation regions.

• Ecosystem Impact
• soil aeration soil aeration

Economic Importance for Humans: Positive

Positive economic impacts of big pocket gophers lack research. Because they exist at elevations often higher than human establishment, and there were no sightings for a century, little positive economic importance is expected. Digging activity at the lower elevation range may help to counter impacts of soil compaction caused through grazing activity and promote growth of natural vegetation.

Economic Importance for Humans: Negative

Negative economic impacts of big pocket gophers are not explicitly known; however, can be related to that of the Orthogeomys . These species have negative implications in regards to agriculture and are considered to be an agricultural pest. Hispid pocket gophers ( Orthogeomys hispidus ) are a nuisance at elevation levels lower than big pocket gophers.

• Negative Impacts
• crop pest

Conservation Status

Big pocket gophers are listed as critically endangered under the IUCN Red List and threatened under Mexican legislation. Factors contributing to their population decline include deforestation and climate change.

Other Comments

The taxonomic classification of Orthogeomys lanius has been discussed many times since its initial discovery in 1904. Level of relatedness to Orthogeomys hispidus species as well as other pocket gopher species have been repeatedly altered. The most recent study performed in 2014 using the two specimens indicating their rediscovery, has confirmed the big pocket gopher to be a sister species to hispid pocket gophers , not a subspecies.

Additional Links

Encyclopedia of Life

Contributors

Kathryn Yarchuk (author), University of Manitoba, Annemarie van der Marel (editor), University of Manitoba, Tanya Dewey (editor), University of Michigan-Ann Arbor.

References

Demastes, J., M. Hafner, D. Hafner. 1996. Phylogeographic variation in two Central American pocket gophers (Orthogeomys). Journal of Mammalogy , 77/4: 917-927.

Escalante, T., V. Sánchez-Cordero, J. Morrone, M. Linaje. 2007. Deforestation affects biogeographical regionalization: a case study contrasting potential and extant distributions of Mexican terrestrial mammals. Journal of Natural History , 41: 13-16.

Fernández, J., M. Hafner, D. Hafner, F. Cervantes. 2014. Conservation status of rodents of the families Geomyidae and Heteromyidae of Mexico. Revista Mexicana de Biodiversidad , 85/2: 576-588.

Hafner, M., D. Hafner, E. Gonzáles, J. Demasters, T. Spradling, F. Cervantes. 2014. Rediscovery of the pocket gopher Orthogeomys lanius (Rodentia: Geomyidae) in Veracruz, Mexico. Journal of Mammalogy , 95/4: 792-802.

Hartenberger, J. 1995. The Tertiary Record of Rodents in North America. Journal of Evolutionary Biology , 12: 319.

Macdonald, D. 2009. Pocket Gophers. Princeton Encyclopedia of Mammals , Vol. NA, 1 Edition. London UK: Windmill Books (Andromeda International). Accessed November 28, 2019 at https://uml.idm.oclc.org/login?url=https://search.credoreference.com/content/entry/bbbprinmam/pocket_gophers/0?institutionId=1217 .

Myers, P. 2001. "Geomyidae Pocket Gophers" (On-line). Animal Diversity Web. Accessed November 27, 2019 at https://animaldiversity.org/accounts/Geomyidae/ .

Peterson, T., S. Egbert, V. Sánchez-Cordero, K. Price. 2000. Geographic analysis of conservation priority: endemic birds and mammals in Veracruz, Mexico. Biological Conservation , 93/1: 85-94.

Rezsutek, M., G. Cameron. 2000. Vegetative edge effects and pocket gopher tunnels. Journal of Mammalogy , 81/4: 1062-1070.

Spradling, T., J. Demastes, D. Hafner, P. Milbach, F. Cervantes, M. Hafner. 2016. Systematic revision of the pocket gopher genus Orthogeomys. Journal of Mammalogy , 97/2: 405-423.

Villa-Cornejo, B., R. Engeman. 1995. Reproductive characteristics of the hispid pocket gopher (Orthogeomys hispidus hispidus) in Veracruz, Mexico. Southwestern Naturalist , 40/4: 411-414.

Wilkins, K., J. Roberts, C. Roorda, J. Hawkins. 1999. Morphometrics and functional morphology of middle ears of extant pocket gophers (Rodentia: Geomyidae). Journal of Mammalogy , 80/1: 180-198.