Ground squirrels are

rodent Rodents (from Latin , 'to gnaw') are mammals of the Order (biology), order Rodentia ( ), which are characterized by a single pair of continuously growing incisors in each of the upper and Mandible, lower jaws. About 40% of all mammal specie ...

s of the

squirrel Squirrels are members of the family Sciuridae (), a family that includes small or medium-sized rodents. The squirrel family includes tree squirrels, ground squirrels (including chipmunks and prairie dogs, among others), and flying squirrel ...

family (

Sciuridae Squirrels are members of the family Sciuridae (), a family that includes small or medium-sized rodents. The squirrel family includes tree squirrels, ground squirrels (including chipmunks and prairie dogs, among others), and flying squirrel ...

) that generally live on the ground or in

burrow file:Chipmunk-burrow (exits).jpg, An eastern chipmunk at the entrance of its burrow A burrow is a hole or tunnel excavated into the ground by an animal to construct a space suitable for habitation or temporary refuge, or as a byproduct of Animal lo ...

s, rather than in trees like the

tree squirrel Tree squirrels are the members of the squirrel Family (biology), family (Sciuridae) commonly just referred to as "squirrels". They include more than 100 arboreal species native to all continents except Antarctica and Oceania. They do not form a ...

s. The term is most often used for the medium-sized ground squirrels, as the larger ones are more commonly known as marmots (genus ''Marmota'') or

prairie dogs Prairie dogs (genus ''Cynomys'') are herbivorous burrowing ground squirrels native to the grasslands of North America. There are five recognized species of prairie dog: black-tailed, white-tailed, Gunnison's, Utah, and Mexican prairie dogs. ...

, while the smaller and less bushy-tailed ground squirrels tend to be known as

chipmunk Chipmunks are small, striped rodents of subtribe Tamiina. Chipmunks are found in North America, with the exception of the Siberian chipmunk which is found primarily in Asia. Taxonomy and systematics Chipmunks are classified as four genera: '' ...

s (genus ''Tamias''). Together, they make up the "marmot

tribe The term tribe is used in many different contexts to refer to a category of human social group. The predominant worldwide use of the term in English is in the discipline of anthropology. The definition is contested, in part due to conflict ...

" of squirrels, Marmotini, a

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

within the large and mainly ground squirrel

subfamily In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end botanical subfamily names with "-oideae", and zo ...

Xerinae The Xerinae comprise a subfamily of squirrels, many of which are highly terrestrial. It includes the tribes Marmotini (marmots, chipmunks, prairie dogs, and other Holarctic ground squirrels), Xerini (African and some Eurasian ground squirrels), ...

, and containing six living

genera Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial s ...

. Well-known members of this largely

Holarctic The Holarctic realm is a biogeographic realm that comprises the majority of habitats found throughout the continents in the Northern Hemisphere. It corresponds to the floristic Boreal Kingdom. It includes both the Nearctic zoogeographical reg ...

group are the

marmot Marmots are large ground squirrels in the genus ''Marmota'', with 15 species living in Asia, Europe, and North America. These herbivores are active during the summer, when they can often be found in groups, but are not seen during the winter, w ...

s (''Marmota''), including the American

groundhog The groundhog (''Marmota monax''), also known as the woodchuck, is a rodent of the family Sciuridae, belonging to the group of large ground squirrels known as marmots. A lowland creature of North America, it is found through much of the Easte ...

, the

s, the susliks (''Spermophilus''), and the

prairie dog Prairie dogs (genus ''Cynomys'') are herbivorous burrowing Marmotini, ground squirrels native to the grasslands of North America. There are five recognized species of prairie dog: black-tailed prairie dog, black-tailed, white-tailed prairie dog ...

s (''Cynomys''). They are highly variable in size and habitus, but most are remarkably able to rise up on their hind legs and stand fully erect comfortably for prolonged periods. They also tend to be far more gregarious than other squirrels, and many live in colonies with complex social structures. Most Marmotini are rather short-tailed and large squirrels. At up to or more, certain marmots are the heaviest squirrels. The

s of the genus ''Tamias'' frequently spend time in trees. Also closer to typical squirrels in other aspects, they are occasionally considered a tribe of their own (Tamiini).

Evolution and systematics

'' Palaeosciurus'' from

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

is the oldest known ground squirrel species, and it does not seem to be particularly close to any of the two to three living lineages (subtribes) of Marmotini. The oldest fossils are from the

Early Oligocene The Rupelian is, in the geologic timescale, the older of two age (geology), ages or the lower of two stage (stratigraphy), stages of the Oligocene epoch (geology), Epoch/series (stratigraphy), Series. It spans the time between . It is preceded b ...

, more than 30

million years ago Million years ago, abbreviated as Mya, Myr (megayear) or Ma (megaannum), is a unit of time equal to (i.e. years), or approximately 31.6 teraseconds. Usage Myr is in common use in fields such as Earth science and cosmology. Myr is also used w ...

(Mya), but the genus probably persisted at least until the mid-

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

, some 15 Mya. Where the Marmotini originated is unclear. The subtribes probably diverged in the early to mid-

Oligocene The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...

, as primitive marmots and chipmunks are known from the

Late Oligocene The Chattian is, in the geologic timescale The geologic time scale or geological time scale (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the pro ...

of North America. The

fossil record A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

of the "true" ground squirrels is less well known, beginning only in the mid-Miocene, when modern susliks and prairie dogs are known to have inhabited their present-day range already. Whether the Marmotini dispersed between North America and Eurasia via " island-hopping" across the Bering Straits or the

Greenland Greenland is an autonomous territory in the Danish Realm, Kingdom of Denmark. It is by far the largest geographically of three constituent parts of the kingdom; the other two are metropolitan Denmark and the Faroe Islands. Citizens of Greenlan ...

region—both of which were temperate

habitat In ecology, habitat refers to the array of resources, biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species' habitat can be seen as the physical manifestation of its ...

at that time—and from which continent they dispersed to which, or if both continents brought forth distinct subtribes which then spread to the other, is not known and would probably require more fossil material to be resolved. In any case, the fairly comprehensive fossil record of Europe—at the relevant time separated from Asia by the Turgai Sea—lacks ancient Marmotini except the indeterminate ''Palaeosciurus'', which might be taken to indicate an East Asian or western North American origin with trans-Beringia dispersal being the slightly more satisfying hypothesis. This is also supported by the enigmatic Chinese genus ''

Sciurotamias ''Sciurotamias'' is a genus of rodent in the family Sciuridae, found in China. It contains the following species: * Père David's rock squirrel (''Sciurotamias davidianus'') * Forrest's rock squirrel (''Sciurotamias forresti'') References

...

'', which may be the most ancient living lineage of this group, or—if the chipmunks are not included here—close to the common ancestor of the Tamiini and the Marmotini ''sensu stricto''. In any case, expansion of the Marmotini to Africa was probably prevented by competitive exclusion by their close relatives the

Protoxerini The Protoxerini comprise a tribe of squirrels found in Africa. The 30 species in six genera are:Thorington, R. W. and R. S. Hoffmann. 2005. Family Sciuridae. Pp 754–818 in Mammal Species of the World A Taxonomic and Geographic Reference. Johns ...

and

Xerini Xerini is a tribe of ground squirrels occurring in Africa and Asia. With the tribes Marmotini (Holarctic ground squirrels) and Protoxerini (African tree squirrels), they form the subfamily Xerinae. There are five living genera—'' Xerus'', the ...

—the native terrestrial and palm squirrels of that continent, which must have

evolved Evolution is the change in the heritable Phenotypic trait, characteristics of biological populations over successive generations. It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, re ...

at the same time as the Marmotini did.

Size

Ground squirrels can measure anywhere from about in height up to nearly . They can weigh between and .

Habitat

Open areas including rocky outcrops, fields, pastures, and sparsely wooded hillsides comprise their habitat. Ground squirrels also live in grassy areas such as pastures, golf courses, cemeteries, and parks.

Defense mechanisms

Ground squirrels have developed several defense mechanisms to protect themselves from predators. When threatened, they emit high-pitched warning calls to alert others in their colony. This alarm call serves as an early warning system, allowing nearby squirrels to seek cover. The squirrels spend about one-third of their time standing to watch and when a predator is in sight, they stop and watch 60% of the time. Ground squirrels are also known for their burrowing behavior. They have intricate tunnel systems with multiple entrances, which provide escape routes from predators. When a threat approaches, they quickly retreat underground, where they are safe from most predators. Their burrows are designed with multiple chambers and ranges between , making it challenging for predators to reach them. This combination of vocal warnings and burrow construction makes ground squirrels highly adapted to evade danger and survive in the wild. California Ground Squirrel

Diet

Ground squirrels are omnivorous, and not only eat a diet rich in fungi, nuts, fruits, and seeds, but also occasionally eat insects, eggs, and other small animals.

Subtribes and genera

Basal and ''

incertae sedis or is a term used for a taxonomy (biology), taxonomic group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of open nomenclature, uncertainty ...

'' genera * '' Palaeosciurus'' (

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...

) * '' Callospermophilus'' * '' Notocitellus'' * '' Otospermophilus'' (American rock squirrels) * '' Poliocitellus'' (Franklin's ground squirrel) * ''

...

'' (Chinese rock squirrels) * ''

Urocitellus ''Urocitellus'' is a genus of ground squirrels. They were previously believed to belong to the much larger genus ''Spermophilus'', but DNA sequencing of the cytochrome ''b'' gene showed that this group was paraphyletic to the prairie dogs and m ...

'' * '' Xerospermophilus'' Subtribe Tamiina: chipmunks (might be full tribe) * ''

Eutamias ''Eutamias'' is a genus of chipmunks within the tribe Marmotini of the squirrel family. It includes a single living species, the Siberian chipmunk (''Eutamias sibiricus''). The genus is often treated as a subgenus of ''Tamias'', which is now res ...

'' * ''

Neotamias ''Neotamias'' is a genus of chipmunks within the tribe Marmotini of the squirrel family. It contains 23 species, which mostly occur in western North America. Along with '' Eutamias'', this genus is often considered a subgenus of ''Tamias ''Ta ...

'' * ''

Nototamias ''Nototamias'' is a genus of fossil ground squirrels from the Miocene of North America. Species include ''Nototamias hulberti'' Pratt and Morgan, 1989; ''Nototamias ateles'' (Hall, 1930); and ''Nototamias complicatus'' Korth, 1992. Although the g ...

'' (fossil) * ''

Tamias ''Tamias'' is a genus of chipmunks in the tribe Marmotini of the squirrel family. The genus includes a single living species, the eastern chipmunk (''Tamias striatus''). The genus name ''Tamias'' () means "treasurer", "steward", or "housekeeper ...

'' Subtribe Marmotina: marmots and prairie dogs * '' Arctomyoides'' (fossil) * '' Miospermophilus'' (fossil) * '' Paenemarmota'' (fossil) * '' Palaearctomys'' (fossil) * '' Protospermophilus'' (fossil) * '' Marmota'' * '' Cynomys'' (prairie dogs) Subtribe Spermophilina: true ground squirrels * '' Spermophilinus'' (fossil) * '' Ammospermophilus'' * '' Ictidomys'': Thirteen-lined ground squirrel and related species * ''

Spermophilus ''Spermophilus'' is a genus of ground squirrels in the Sciuridae, squirrel family. As traditionally defined the genus was very species-rich, ranging through Europe, Asia and North America, but this arrangement was found to be paraphyletic to ...

Cladogram

Below is a partial

cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...

of ground squirrels (tribe Marmotini, but excluding the Tamiina subtribe and some basal genera) derived from maximum parsimony analysis.

References

External links

{{DEFAULTSORT:Ground Squirrel 01 Rodents of Asia Rodents of North America Extant Rupelian first appearances Taxa named by R. I. Pocock