Citellus (Urocitellus) undulatus Pallas, 1778. Long-Tailed Ground Squirrel, or Eversmann.s Souslik.
Systematic position.Class Mammalia, order Rodentia, suborder Sciuromorpha, family Sciuridae, subfamily Marmotinae, genus Citellus, subgenus Urocitellus. The species includes 6 recognized subspecies.
Biological group.Rodent pests.
Morphology and biology.Body length reaches 315 mm; tail length reaches 163 mm (usually more than 4/10 of the body length; the tail with apical hairs is half as long as the body). The dorsum coloration is ochre-brownish; the head is darker. Light pattern of dense, small spots covers the entire body. The venter coloration is sometimes rather bright, ochre-reddish, appearing along body sides. The tail is dark (from dorsal view), black-grayish, with prominent, light edge stripe. Diploid set of chromosomes: 32. Inhabits plain and submontane steppes (up to 3100 m above sea level), montane and flood meadows, light pine forests, edges of birch groves, clearings, and agricultural lands. Depth of refuges depends on soil type. Depth of holes is 3 m in sandy (light) soils; the total length of underground passages reaches up to 15 m; there is usually one burrow outlet. Depth of holes reaches up to 2 m in clay (heavy) soils; the total length of underground passages is 5-7 m; the number of burrow outlets is 2-3.
Distribution.Within the former Soviet Union, the main part of the distribution area is located in Eastern Siberia in two distinct areas: southeastern Yakutia and the southern Amur Region. Species is also found in Mongolia and in northwestern and northeastern parts of China.
Ecology.The seasonal activity period is longer than that of other large ground squirrels; animals awaken earlier (the end of February-March), and fall into hibernation later (September-October). Daily activity begins after sunrise, ceases during midday hours and then lasts until sunset. Duration of outdoor stay changes depending on the ages of the animals. The rodents differ in degree of activity. Individual plots overlap, and the territory is shared by a group of rodents. Colonial settlements are well-defined, especially on open landscapes and in mountains; in taiga zones, the settlements consist of single holes separated by long distances. About one month after awakening, the rodents produce one brood. The average number of young animals is usually 5 to 8 per brood, but the number varies in different parts of the area, increasing towards the north. Young animals move to the surface at the age of 27-28 days. Vegetative feeding supplies the majority of the food ration. The ratio of vegetative parts of plants and seeds changes distinctly by season: the rodents feed on bulbs and roots in early spring and on seeds in autumn. They create large stores of grain cereal seeds, up to 6 kg or more. Animal food is also present in food rations and has great nutritional value.
Economical significance.The Long-Tailed Ground Squirrel is a harmful pest of agriculture on recently developed lands. First of all, it damages grain crops at all developmental stages, from shoots to full ripeness. Readily eats shoots of sunflower and corn as well as vegetable crops, such as potato, carrot, onion, cucumbers and others. Causes noticeable damage to pastures as well, entirely destroying the most valuable fodder crops through constant digging, thereby severely worsening the soil quality. Abrupt decrease of pest control measures may provoke a rise in its potentially harmful activities. The species is a natural vector of many pesthole diseases, including plague, leptospirosis, brucellosis, and mite rickettsial typhus fever infections. It is the second most popular species of the genus Citellus (after the Yellow Souslik) used in the fur trade.
Related references:Gromov I.M., Bibikov D.I., Kalabukhov N.I., Meier M.N. 1965. Terraneous Marmotinae. Fauna SSSR. Mlekopitayushchie. Vol. III, No.2. Moscow, Leningrad: Nauka. 467 pp. (in Russian).
Gromov I.M. Erbaeva M.A. 1995. Mammals of Russia and adjacent territories. Leporines and rodents. St.Ptersburg: ZIN RAN. 522 pp. (Opredeliteli po faune Rossii, izdavaemye Zoologogicheskim institutom RAN, No 167) (in Russian).
Solomonov N.G., Anufriev A.I., Sedalishchev V.T. On reasons of population reduction of souslik - Citellus undulatus in Yakutia (in Russian) 2003: ( http://www.sevin.ru/menues1/index_rus.html?../agreements/teriofauna/331-340.html )
Ustyantsev M.M. 1937. To bioecology of EversmannТs souslik in Eastern Siberia. Sbornik trudov po zashchite rastenii Vostochnoi Sibiri. Irkutsk. N 5, pp. 96-127 (in Russian).
Vinokurov V.N., Akhrimenko A.K. 1982. Ecology of Long-Tailed Soulik population in Yakutia. Yakutsk: SO AN SSSR, Yakutian branch. 164 pp. (in Russian).