Ground squirrel

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Ground squirrel
Temporal range: Early Oligocene to recent
Ground squirrel berkeley marina 01.jpg
California ground squirrel (Otospermophilus beecheyi) in the man-made rocky shoreline of the Berkeley Marina: The numerous crevices offer safety and shelter.
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Rodentia
Family: Sciuridae
Subfamily: Xerinae
Tribe: Marmotini
Pocock, 1923
Genera

Palaeosciurus (fossil)
Sciurotamias
Spermophilinus (fossil)

Ammospermophilus

Spermophilus
Notocitellus
Otospermophilus
Callospermophilus
Xerospermophilus
Cynomys

Poliocitellus

Ictidomys
Arctomyoides (fossil)
Miospermophilus (fossil)
Paenemarmota (fossil)
Palaearctomys (fossil)
Protospermophilus (fossil)
Marmota

Eutamias
Neotamias
Nototamias (fossil)
Tamias
Urocitellus
and see text

Ground squirrels are members of the

susliks (Spermophilus), and the prairie dogs (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 8 kg (18 lb) or more, certain marmots are the heaviest squirrels.[1][2]

The chipmunks 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).[3]

The ground squirrel is especially renowned for its tendency to rise up on its hind legs, usually whenever it senses nearby danger, or when it must see over tall grasses. The squirrel then curls its paws flat against its chest and sends a screeching call to warn other family members about the presence of predators.

Evolution and systematics

Palaeosciurus from Europe 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, more than 30 million years ago (Mya), but the genus probably persisted at least until the mid-Miocene, some 15 Mya.

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

fossil record
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 "

Bering Straits or the Greenland region—both of which were temperate habitat 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
, 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

evolved
at the same time as the Marmotini did.

Size

Ground squirrels can measure anywhere from about 7.2 inches (18 cm) in height up to nearly 30 inches (76 cm). They can weigh between 0.09 pounds (0.041 kg) and 24 pounds (11 kg).[4]

Habitat

Open areas including rocky outcrops, fields, pastures, and sparsely wooded hillsides comprise their habitat.

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.[6] They are known to eat rats and mice several times their size.[7]

Subtribes and genera

Watchful "rock chuck" or yellow-bellied marmot (Marmota flaviventris) atop Mount Dana, Yosemite National Park
in California

genera

Subtribe Tamiina: chipmunks (might be full tribe)

Subtribe Marmotina: marmots and prairie dogs

Subtribe Spermophilina: true ground squirrels

Cladogram

Below is a

Marmotini) derived from maximum parsimony analysis.[8]

Notocitellus

N. adocetus

N. annulatus

Ammospermophilus

A. harrisii

A. leucurus

A. harrisii

A. interpres

Otospermophilus

O. atricapillus

O. beecheyi

O. variegatus

Callospermophilus

C. saturatus

C. lateralis

C. madrensis

Marmota

M. monax

M. marmota

M. flaviventris

M. caligata

M. olympus

M. vancouveriensis

M. broweri

M. menzbieri

M. caudata

M. baibacina

M. bobak

M. camtschatica

M. himalayana

M. sibirica

Spermophilus

S. musicus

S. pygmaeus

S. major

S. pygmaeus

S. dauricus

S. xanthopyrmnus

S. suslicus

S. citellus

S. relictus

S. erythrogenys

S. citellus

S. pallidicauda

S. fulvus

S. erythrogenys

S. major

Ictidomys

I. mexicanus

I. parvidens

I. tridecemlineatus

Poliocitellus

P. franklinii

Cynomys

C. ludovicianus

C. mexicanus

C. parvidens

C. gunnisoni

C. leucurus

Xerospermophilus

X. mohavensis

X. tereticaudus

X. spilosoma

X. perotensis

X. spilosoma

Urocitellus

U. townsendii

U. washingtonii

U. brunnenus

U. townsendii

U. mollis

U. townsendii

U. armatus

U. beldingi

U. columbianus

U. undulatus

U. parryii

U. elegans

U. richardsonii

U. parryii

See also

References

  1. ^ Kryštufek, B.; B. Vohralík (2013). "Taxonomic revision of the Palaearctic rodents (Rodentia). Part 2. Sciuridae: Urocitellus, Marmota and Sciurotamias". Lynx, N. S. (Praha). 44: 27–138.
  2. ^ Armitage, K.B.; Blumstein, D.T. (2002). "Body-mass diversity in marmots. Holarctic marmots as a factor of biodiversity". In K.B. Armitage; V.Yu. Rumiantsev (eds.). Holarctic Marmots as a Factor of Biodiversity. ABF Publishing House. pp. 22–32.
  3. ^ Steppan et al. (2004)
  4. ^ Karels, Tim (2004). Grzimek's Animal Life Encyclopedia (Vol. 16: Mammals V. 2nd ed.). Gale. p. 143.
  5. ^ National Audubon Society Field Guide to Mammals
  6. ^ "Squirrels: Diet, Habits & Other Facts".
  7. ^ Ground Squirrel Control, Fort Ord Complex Fort Ord, California. Defense Technical Information Center. 1977.
  8. ^ Helgen et al. 2009, p. 274.

Further reading

External links