Spermophilus
Spermophilus is a genus of ground squirrels in the 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 the certainly distinct prairie dogs, marmots, and antelope squirrels. As a consequence, all the former "Spermophilus" species of North America have been moved to other genera, leaving the European and Asian species as true "Spermophilus" (the only exceptions are two Asian "Urocitellus"). Some species are sometimes called susliks (or sousliks). This name comes from Russian , "suslik". In some languages, a derivative of the  name is in common usage, for example "suseł" in Polish. The scientific name of this genus means "seed-lovers" (gr. σπέρμα "sperma", genitive σπέρματος "spermatos" – seed; φίλος "philos" – friend, lover). Habitat and behavior. As typical ground squirrels, "Spermophilus" live in open habitats like grasslands, meadows, steppe and semideserts, feed on the low plants, and use burrows as nests and refuge. They are diurnal and mostly live in colonies, although some species also can occur singly. They are found in both lowlands to highlands, hibernate during the colder months (up to 8 months each year in some species) and in arid  regions they may also aestivate during the summer or fall. The distributions of the various species are mostly separated, often by large rivers, although there are regions inhabited by as many as three species and rarely two species may even form mixed colonies. A few species are known to hybridize where their ranges come into contact. Appearance. "Spermophilus" are overall yellowish, light orangish, light brownish or greyish. Although many are inconspicuously mottled or spotted, or have orange markings on the head, overall they lack strong patterns, except in "S. suslicus", which commonly has brown upperparts with clear white spotting. Size  varies with species and they have a head-and-body length of . Before hibernation the largest "S. fulvus" may weigh up to and the largest "S. major" up to almost , but they always weigh much less earlier in the year and other species are considerably smaller, mostly less than even in peak condition before hibernation. All have a fairly short tail that—depending on exact species—is around 10–45% of the length of the head-and-body. Relationship with humans. Ground squirrels may carry fleas that transmit diseases to humans (see Black Death), and have been destructive in tunneling underneath  human habitation. Species. A generic revision was undertaken in 2007 by means of phylogenetic analyses using the mitochondrial gene cytochrome b. This resulted in the splitting of "Spermophilus" into eight genera, which with the prairie dogs, marmots, and antelope squirrels are each given as numbered clades. The exact relations between the clades are slightly unclear. Among these, these exclusively Palearctic species are retained as the genus "Spermophilus sensu stricto" (in the strictest sense). Prehistoric species. Discovery and examination of one of the best preserved Eurasian ground squirrel fossils yet recovered allowed the study of many previously unknown aspects of ground  squirrel cranial anatomy, and prompted a critical reassessment of their phylogenetic position. As a result, three Pleistocene species previously considered members of the "Urocitellus" genus were moved to "Spermophilus": "Spermophilus citelloides" is known from the Middle Pleistocene to early Holocene of Europe. It appears to be most closely related to the living "S. suslicus".