Dryomys nitedula Pallas - Forest Dormouse
Systematic position.Class Mammalia, order Rodentia, family Myoxidae, genus Dryomys. In the territory of the former USSR, there is only 1 species (2n = 48) with 10.13 subspecies.
Biological group.Pest of fruit crops.
Morphology and biology.The length of head and body is 102-116 mm; the tail is 60-113 mm long, the hind feet are 19-22 mm long. Wool on the upper part of the body is grayish-tan; body ventrum is yellow-white. The tail is fluffy and slightly flattened. A black stripe passes from nose to ear, surrounding eye. Vibrissae are in the form of bushy tuft, one fifth the head length. There are 6 rather large and convex callosities on each palm and foot. In winter, the Forest Dormouse runs into hibernation. Term of reproduction period varies in different geographical areas, appreciably depending on duration of hibernation. In the Caucasian region and Central Asia, this species can produce 2 litters per year. In the European part of the distribution area, the Forest Dormouse breeds once a year. The beginning of reproduction period dates to the first weeks after the hibernation termination; i.e., in the last third of April in the south of the area or in the end of May in its northern part. The gestation period lasts 27-28 days; 2 to 9, more often 4-5, cubs are born. The young dormice open eyes in 14-16 days and feed themselves independently in 20 days; the lactation period lasts about one month; the young animals leave parental nest in 40-45 days. They become sexually mature in the second year of their life. In the Forest Dormouse populations, the sex ratio is practically 1:1, with insignificant predominance of females.
Distribution.The area covers the territory of Europe from the Alps southward, including the Balkan Peninsula, northward to the Baltic Sea, and eastward to Volga and the Ural Mountains. In western Asia, it reaches the Tien Shan Mountains in the east and Transcaucasia and the Kopet-Dag in the south. The Forest Dormouse reaches altitudes up to 3000 m. Its distribution inside the area is sporadic.
Ecology.The Forest Dormouse eats fruits of about 20 tree and bush species, including apricots, apples, cherries, plums, cherry plums, pears, peaches, blackberries, currants, etc. from the beginning of their maturing to full disappearance. In spring after hibernation, the dormice eat green parts of cereals, bean, and other plants, and also their seeds, fruits, young sprouts, etc. Animal food is essential in ration. The most optimum stations in the Forest Dormouse habitats are various plots of deciduous forest with shrubby layer and dense undergrowth. Its population reaches the greatest density in forests of central Moldova, in Transcaucasia, in the mountains of Central Asia; the Forest Dormouse is rather numerous in Belovezhskaya Pushcha and Voronezh nature reserves. In Moldova, the greatest density (23-25 individuals per hectare) has been found in forest belts near agricultural lands with orchards. Abrupt fluctuations of numbers are not characteristic of this species; the annual increase of a population exceeds mortality only a little, which falls basically at the winter period of hibernation, when 60% of young individuals and the majority of old animals in the age of 4 and more years perish. The life interval in this species in nature is probably not more than 4 years. The basis of a population in all parts of the species area is made up of individuals who have wintered 1 or 2 times; on the average, 3.6 to 15.5% of animals hibernate 3 times; thus, full renewal of a population occurs in 4 years. The Forest Dormouse number is reduced by long storm rains causing death of cubs in openly located nests. Furthermore, they may be prey of terrestrial predators (European pine and stone martens, forest cats) and birds (owls, corvids, etc.). Sometimes the Forest Dormouse competes in artificial and natural nests with hazel dormice, fat dormice and birds nesting in hollows.
Economic significance.The pest harms fruit crops, eating and also damaging fruits in all stages of maturation; it eats both pulp and seeds. The Forest Dormouse frightens away insectivorous birds, borrowing artificial nests, ruining their eggs, and eating nestlings. The species is also the natural vector of agents of tick-born encephalitis, leptospirosis, and probably of the Black Death. In the beginning of the 20th century, the dormice caused essential damage to orchards, especially in Central Asia, the Caucasus, Moldova, and western Ukraine. Now the species density is low in the major territory of its area, and it is included in the Red Books of some regions and countries. It is classified as an endangered species in the Red Lists of the World Conservation Union (IUCN). Therefore, scare methods only (biophysical ones, chemical repellents, and sound) are possible as means of orchard protection.
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