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Urocitellus

By Kadin Samlaska

Diversity

Twelve species are currently recognized within this genus with 32 subspecies in total. All but Urocitellus undulatus are native to the Nearctic region. All are burrowing ground squirrels but only Urocitellus brunneus is labeled as threatened under the IUCN list. There is evidence of some interspecies competition, but only two of these species occur in the same range. In at least one case speciation has occurred within this genus, thus U.richardsonii split to form the current Urocitellus elegans (Durrant and Hansen, 1954). There is little fossil evidence connected to this genus due to poor fossilization or a lack of collection, so little is known about their evolutionary history (Black, 1972). Many of the species live in high-altitude habitats with a preference for prairie and desert ecosystems. Research is lacking for most of this genus because of their status as pests within agricultural regions including reports of livestock injuries and crop destruction caused by their burrows (Howell, 1938). (Black, 1972; Durrant and Hansen, 1954; "Revision of the North American ground squirrels : with a classification of the North American Sciuridae", 1938)

Geographic Range

Urocitellus includes ground squirrels of the Nearctic with a larger presence in northwestern North America. Their geographic distribution is one of the identifiers for this genus beyond morphological and genetic data. Exceptions to this are Urocitellus undulatus, which is found in the Oriental region, and Urocitellus parryii, which is found in the Arctic regions of North America. Most species have limited geographic ranges, with some being exclusive to mountainous regions. (Durrant and Hansen, 1954; Helgen, et al., 2009)

Habitat

The species that makeup Urocitellus occupy a wide array of habitats, from alpine to prairie ecosystems and meadows. They are primarily herbivorous, eating seeds, grasses, and other available forage (Howell, 1938). In some cases, arthropods are also part of their foraging, particularly during the harsher seasons. The species U. elegans is noted along with U. richardsonii to be found in high altitudes and dry habitats (Durrant and Hansen, 1954). All are colonial species that form a series of burrowing networks that are used for raising young and hibernating. Due to their geographic locations, all are adapted to be either true hibernators or experiencing extended periods of torpor. (Black, 1972; Durrant and Hansen, 1954; "Revision of the North American ground squirrels : with a classification of the North American Sciuridae", 1938)

Systematic and Taxonomic History

Urocitellus was first proposed in 2009 when previously part of the larger genus Spermophilus that included groups such as marmots. In 2009, there was a publication supporting the splitting of Spermophilus into multiple genera including Urocitells. The grouping of Urocitellus is based on genetic data and morphological traits including tail length. Before the split, there were many alterations to the identification of this and other related groups of ground squirrels recorded as early as the 1880s. However, the only current valid synonym is Spermophilus as this term has been used the longest. In terms of relatedness, Urocitellus is closely related to other ground squirrels in the Americas and Europe such as the golden mantel, as well as related to marmots and prairie dogs. (Helgen, et al., 2009; "Revision of the North American ground squirrels : with a classification of the North American Sciuridae", 1938)

  • Synonyms
    • Spermophilus
  • Synapomorphies
    • unknown

Physical Description

Color varies between species, with a few exhibiting a seasonal coat color despite being hibernators. They fall in the medium-size range within f.Spermophilus, and all distinct tails, with one species having a notably long tail U. undulatus. At first glance, they appear very similar to prairie dogs, but are much smaller and have a longer body shape in general. Most species are light to dark brown, with a light-colored belly and a tipped tail in white or black. Coloration is used for predation avoidance and thermoregulation with a lighter ventral side. ("Revision of the North American ground squirrels : with a classification of the North American Sciuridae", 1938)

  • Sexual Dimorphism
  • sexes alike

Reproduction

Males in colonial species are responsible for defending the colony, and a harem structure is thought to be involved. However, in some species like U. columbianus, both the male and female have multiple mates for an increase in fitness. In more distantly spaced species, the males search for a female and defend her from other males doing the same. Verbal and non-verbal attraction is common. Calling and verbal communication are heavily used in this genus with various chirps, squeaks, and screams used. (Durrant and Hansen, 1954; Raveh, et al., 2010)

Mating behavior heavily revolves around hibernation, with males emerging first around early April. Females emerge soon after in mid-April to May, with mating occurring 4 days later. After, females undergo a month-long gestation period before giving birth to a litter. All pups are born blind and naked and will spend a month in a nest burrow in their mother's den before emerging in the late summer. Oddly, while the females are in gestation, the previous year’s litter will emerge sexually mature despite all mating occurring at a single time. For most species, mating takes place underground, but a few species or even subspecies specifically have been observed above ground, and the encounter lasts on average half an hour. (Raveh, et al., 2010)

Adults emerge first after hibernation to mate and males defend their territories or colonies. During the month that pups stay in the burrows, the female provides food, shelter, and protection. Near the end of the summer period, pups will start to emerge: although fairly independent, they still live in their mother's burrow until after their first hibernation. It is thought that the males are kicked out of the territory after their first year while females either stay or leave on their own. There is not much evidence for group raising of pups, but pups will be independent at emergence from burrows. (Blumstein and Armitage, 1998; "Revision of the North American ground squirrels : with a classification of the North American Sciuridae", 1938)

Lifespan/Longevity

While there is variation between species, overall this genus has a differing lifespan based on sex. There is evidence that males live shorter lives than females, averaging around 4 years. This is based on survival rates before and during hibernation, with females surviving on average 4 to 6 years. There isn't much data on captive lifespans as there is little to no captive care or breeding of this genus. The reason why males don't live as long is not entirely known, but can possibly be correlated to predation, territory disputes, and dispersion patterns. (Michener, 1989)

Behavior

This genus is made almost entirely of social species, though the degree of sociality varies. Species like the Urocitellus parryii are fairly solitary, but maintain territories with multiple females. Species like the Urocitellus elegans and Urocitellus richardsonii have intermingling colonies run by one or two dominant males. All hibernate during the cold seasons of their habitat, with females and males having separate hibernating burrows. Territory disputes can get very aggressive, even between adults and pups, whilst still having a high level of communication within social groups for predators. In habitats that get very hot in the summer, a decrease in activity will occur: burrowing species will go underground and will be most active in the morning followed by a short period in the evening. (Blumstein and Armitage, 1998; Kukka, et al., 2021; "Revision of the North American ground squirrels : with a classification of the North American Sciuridae", 1938)

Communication and Perception

The species of this genus are highly vocal as one can usually hear chatter from colonies throughout the day and even at night. The vocalization varies between species but squeaks, barks, trills, and chirps are commonly used. They are able to communicate mating, predation avoidance, territory disputes, etc. Often there is some visual component to communication with tail movement or body posture. (Blumstein and Armitage, 1998; "Revision of the North American ground squirrels : with a classification of the North American Sciuridae", 1938)

Food Habits

There is not much detail in the text on the diet or feeding behavior on Urocitellus, but there is a fair amount of general information. They are primarily granivores, preferring high alpine grasses and seeds, but have also been observed eating local arthropods including cicadas in the case of U. canus. When present in agricultural areas, they will also feed on crops. This causes damage to the annual yield of the fields. Due to Urocitellus being hibernators, they do not stockpile food. They do, however, store a large amount of body fat during the active season and, depending on the environmental conditions, will either increase their foraging time closer to hibernation or go into an early hibernation if reserves are large enough by that time. In very rare and extreme instances cannibalism has been observed a few times in this genus. All observations involved an adult eating a pup with no other options available for food. (F. Russell and Don E., 2009; Kukka, et al., 2021; "Revision of the North American ground squirrels : with a classification of the North American Sciuridae", 1938)

Predation

Due to being a social species, there is a lot of communication used to avoid predators. There will often be individuals acting as lookouts for threats that will signal to others. Burrows are used to avoid predators, and are most effective against birds. Nearly all species within this genus have contrasting coloration and possess a tan or brown colored dorsal side with a light ventral side. This is a good form of camouflage for their habitat. (F. Russell and Don E., 2009; Hoisington-Lopez, et al., 2012; Kukka, et al., 2021)

  • Known Predators
    • Eagle
    • Weasel
    • Brown Bears
    • Badgers
    • Coyotes

Ecosystem Roles

This information is based on the research of U. canus and U. parryii as there isn't information on the genus level and not all species have had in-depth research on them. Urocitellus are a prey species that primarily feeds on grasses and seeds, which make up the majority of their niche. Small and large predators including wolverines, bears, and hawks feed on these ground squirrels with possible mutualism between the ground squirrels and the other prey item: rabbits. When one group is doing poorly, there is more predation on the other population and vice versa. This, however, is only suggested. Though a mutualistic relationship has been shown between marmots and U. parryii, the nature of this relationship is unknown. In terms of diet, they do provide some seed dispersal, though Urocitellus has not been shown to forage based on abundance but rather on palatability. They display a preference for roots over flowers and more green growth instead of the more abundant dry grass. Vegetation usage or coverage is possibly the reason for speciation within the genus as there are multiple species and subspecies that are distinct despite living right next to each other range-wise. (F. Russell and Don E., 2009; Hoisington-Lopez, et al., 2012; Kukka, et al., 2021; McLean, 2018; "Revision of the North American ground squirrels : with a classification of the North American Sciuridae", 1938)

In terms of space usage, Urocitellus burrows and usually inhabits large meadows and plains over forests. This is because they need well-drained soil to burrow in. This may initially cause a decrease in diversity in the nearby areas of the burrows: long-term burrowing allows for higher diversity in plant growth and even increases water retention of the soil. On top of that, the burrows may provide second-hand homes for other species including foxes, badgers, or other rodents. While they are not a keystone species, they can be landscape drivers for ecosystems and allow for more niches and diversity within habitats. (F. Russell and Don E., 2009; McLean, 2018)

Mutualist Species
  • Marmots
Commensal/Parasitic Species

Economic Importance for Humans: Positive

There is still work being done to determine whether or not some of the species could be used as an ecosystem indicator for disturbances. However, these species do not have a significant positive impact on the economy. ("Revision of the North American ground squirrels : with a classification of the North American Sciuridae", 1938)

  • Positive Impacts
  • research and education

Economic Importance for Humans: Negative

Nearly all references to ground squirrel species are done in the light of them being pests. It is incredibly common to find detailed accounts of ground squirrels being responsible for damage to both crops and livestock with their burrowing behavior. In all, they don't have a positive reputation in the public eye and all the preliminary research of many of the genera has been on how to dispose of them or reduce their presence in agricultural landscapes. U. elegans in particular has little research beyond how they are a pest and how to get rid of them. There have been some cases of ground squirrels carrying plague among other infections, but not all species within the genus act as carriers to the same degree. (Durrant and Hansen, 1954; Hoisington-Lopez, et al., 2012; "Revision of the North American ground squirrels : with a classification of the North American Sciuridae", 1938)

Conservation Status

The majority of Urocitellus are considered stable or of least concern. However, a couple of species are marked as either vulnerable or endangered. U. townsendii subspecies U. townsendii nancyae are currently on a downhill trend in their population. U. brunneus and its subspecies are endangered but seem to be improving. On a broader scale, Urocitellus live in ecosystems that will see an increase in threats due to climate change, urban development, and wildfires now and in the future. It is currently unknown if these species will adapt well or become more vulnerable in the coming years. (Catzeflis, 2000; Spahr, 1991)

  • IUCN Red List [Link]
    Not Evaluated

Other Comments

Urocitellus as a whole needs more research to be done. Taxonomically the relationship between the oriental species and the Nearctic species is of interest, as well as their ability to adapt to ecological threats. It is one of many examples of commonality resulting in a lack of interest despite the potential knowledge gained. (Helgen, et al., 2009)

Contributors

Kadin Samlaska (author), Colorado State University, Audrey Bowman (editor), Colorado State University, Tanya Dewey (editor), 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

acoustic

uses sound to communicate

agricultural

living in landscapes dominated by human agriculture.

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

aposematic

having coloration that serves a protective function for the animal, usually used to refer to animals with colors that warn predators of their toxicity. For example: animals with bright red or yellow coloration are often toxic or distasteful.

carnivore

an animal that mainly eats meat

causes or carries domestic animal disease

either directly causes, or indirectly transmits, a disease to a domestic animal

colonial

used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

diurnal
  1. active during the day, 2. lasting for one day.
dominance hierarchies

ranking system or pecking order among members of a long-term social group, where dominance status affects access to resources or mates

female parental care

parental care is carried out by females

fossorial

Referring to a burrowing life-style or behavior, specialized for digging or burrowing.

granivore

an animal that mainly eats seeds

herbivore

An animal that eats mainly plants or parts of plants.

hibernation

the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.

holarctic

a distribution that more or less circles the Arctic, so occurring in both the Nearctic and Palearctic biogeographic regions.

World Map

Found in northern North America and northern Europe or Asia.

insectivore

An animal that eats mainly insects or spiders.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

mountains

This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oriental

found in the oriental region of the world. In other words, India and southeast Asia.

World Map

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

polygynous

having more than one female as a mate at one time

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

soil aeration

digs and breaks up soil so air and water can get in

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

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.

tundra

A terrestrial biome with low, shrubby or mat-like vegetation found at extremely high latitudes or elevations, near the limit of plant growth. Soils usually subject to permafrost. Plant diversity is typically low and the growing season is short.

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

References

United States Department of Agriculture: Bureau of Biological Survey.. Revision of the North American ground squirrels : with a classification of the North American Sciuridae. 56. Washington D.C: Washington, Govt. Print. Off.. 1938.

Barbosa, S., K. Andrews, A. Goldberg, D. Gour, P. Hohenlohe. 2021. The role of neutral and adaptive genomic variation in population diversification and speciation in two ground squirrel species of conservation concern. Molecular ecology, 30: 4673-4694. Accessed February 05, 2022 at https://onlinelibrary-wiley-com.ezproxy2.library.colostate.edu/doi/full/10.1111/mec.16096.

Black, C. 1972. Holarctic evolution and dispersal of squirrels (Rodentia: Sciuridae). Evolutionary biology, 6: 305-322. Accessed February 05, 2022 at https://link.springer.com/chapter/10.1007%2F978-1-4684-9063-3_10.

Blumstein, D., K. Armitage. 1998. Life history consequences of social complexity: a comparative study of ground-dwelling sciurids. BEHAVIORAL ECOLOGY, 9: 8.

Bryan, M. 2018. Urocitellus parryii (Rodentia: Sciuridae). Journal of mammalogy, 50: 84-99. Accessed April 17, 2022 at https://academic.oup.com/mspecies/article/50/964/84/5099029#121374867.

Catzeflis, . 2000. North American Rodents. Status Survey and Conservation Action Plan. Biological conservation, 95: 119.

Durrant, S., R. Hansen. 1954. Distribution patterns and phylogeny of some western ground squirrels. Systematic Zoology, 3: 82-85.

F. Russell, C., W. Don E.. 2009. Urocitellus canus (Rodentia: Sciuridae). The American Society of Mammalogists Mammalian species, 834: 1-8. Accessed April 16, 2022 at https://www-jstor-org.ezproxy2.library.colostate.edu/stable/mammalianspecies.41.834.1?sid=primo&seq=5.

Helgen, K., R. Cole, . Helgen, D. Wilson. 2009. Generic Revision in the Holarctic Ground Squirrel Genus Spermophilus. Journal of mammalogy, 90: 270–305. Accessed February 03, 2022 at https://academic.oup.com/jmammal/article/90/2/270/894719.

Herron, M., T. Castoe, . Parkinson. 2004. Sciurid phylogeny and the paraphyly of Holarctic ground squirrels (Spermophilus). Molecular phylogenetics and evolution, 31: 1015-1030. Accessed February 03, 2022 at https://www-sciencedirect-com.ezproxy2.library.colostate.edu/science/article/pii/S1055790303003786.

Hoisington-Lopez, J., L. Waits, J. Sullivan. 2012. Species limits and integrated taxonomy of the Idaho ground squirrel (Urocitellus brunneus): genetic and ecological differentiation. Journal of mammalogy, 93: 589-604. Accessed February 05, 2022 at https://academic.oup.com/jmammal/article/93/2/589/925220.

Kukka, P., J. Werner, L. Andresen, C. Krebs, T. Jung. 2021. Landscape drivers of site occupancy by remnant populations of arctic ground squirrels (Urocitellus parryii). European journal of wildlife research, 67: (6). Accessed February 05, 2022 at https://link-springer-com.ezproxy2.library.colostate.edu/article/10.1007/s10344-021-01534-x#article-info.

Leger, D., S. Berney-Key, P. Sherman. 1984. Vocalizations of Belding's ground squirrels ( Spermophilus beldingi). Animal behaviour, Vol.32 (3): p.753. Accessed February 26, 2022 at https://www-sciencedirect-com.ezproxy2.library.colostate.edu/science/article/pii/S0003347284801517.

McLean, B. 2018. Urocitellus parryii (Rodentia: Sciuridae). Mammalian Species, vol 50: 84–99. Accessed April 28, 2022 at https://academic.oup.com/mspecies/article/50/964/84/5099029#121374867.

Michener, G. 1989. Sexual differences in interyear survival and life-span of Richardson's ground squirrels. Canadian journal of zoology, vol. 67: p.1827-1831. Accessed February 26, 2022 at https://cdnsciencepub-com.ezproxy2.library.colostate.edu/doi/abs/10.1139/z89-260.

Raveh, S., D. Heg, S. Dobson, D. Coltman, J. Gorrell. 2010. Mating order and reproductive success in male Columbian ground squirrels (Urocitellus columbianus). Behavioral ecology : official journal of the International Society for Behavioral Ecology, Vol. 21: p.537-547. Accessed February 20, 2022 at https://academic.oup.com/beheco/article/21/3/537/218913?login=true.

Spahr, R. 1991. Threatened, Endangered, and Sensitive Species of the Intermountain Region. Ogden, Utah: U.S. Dept. of Agriculture, Forest Service, Intermountain Region.

Wilbur, S., B. Barnes, A. Kitaysky, C. Williams. 2019. Tissue-specific telomere dynamics in hibernating arctic ground squirrels ( Urocitellus parryii ). Journal of experimental biology, 222: Pt. 18. Accessed February 05, 2022 at https://journals-biologists-com.ezproxy2.library.colostate.edu/jeb/article/222/18/jeb204925/223475/Tissue-specific-telomere-dynamics-in-hibernating.

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Classification

  • This scientific name is not yet recognized in our classification database.