The Reproductive Ecology of the Bank Vole Myodes ( Clethrionomys ) glareolus Schreb. in North Periphery of Its Areal: I.
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The Reproductive Ecology of the Bank Vole Myodes (Clethrionomys) glareolus Schreb. in North Periphery of Its Areal: I. Sex Cycles, Course, Dates, and Intensive Reproduction E. V. Ivanter* Petrozavodsk State University, Petrozavodsk, 185910 Russia *e-mail: [email protected] Received February 1, 2019; revised September 18, 2019; accepted November 1, 2019
Abstract—A characterization of long-term station and field studies (1958–2017) on the tiaga in northwestern Russia is given for the population-ecology features of reproduction of the bank vole, including those associated with its habitat at the northern borders of its distribution: reproductive cycles and the timing, course, and intensity of reproduction. According to the dates, including from the results of histological examination of the gonads, under the conditions of the northern periphery of its range, the bank vole has a long breeding period from April to September with the very intensive participation of young fertile voles, especially early spring– summer births. The male reproductive cycle has a stage of passive spermatogenesis with a rapid increase in the epithelium and the appearance of spermatocytes of both orders. From April, active spermatogenesis occurs, during which the epithelium of germinal becomes layered and mature spermatozoa appear in the tubules and appendages of the testis. Ovulation in females, apparently, is spontaneous, as is evidenced by cases of the presence of a false corpus luteum in adult (overwintered) females, as well as in newcomers, the reproduction of which is interrupted by seasonal depression. The average duration of the sexual cycle is 5– 6 days; the maximum is about two weeks. In this article a function of population autoregulation, which depends on the initial population density of the adaptive shift involved in the reproduction of age-related generations of animals, is revealed. DOI: 10.1134/S1062359020050040
INTRODUCTION Despite the unrelenting interest in study of the bank vole, including in connection with its wide distribution and abundance (in the studied region, it is an absolute dominant in the population of small mammals) and important biocenotic significance, ecology, and, particularly, reproduction of this species, it remains insufficiently investigated. The aim of this study is an attempt to fill at least partially a significant gap in the study of the territory of Karelia and the adjacent regions of Eastern Fennoscandia, which is a habitat of the red-backed vole. MATERIALS AND METHODS This study covers East Fennoscandia, which includes the Kola Peninsula, Finland, Karelia, and the Karelian Isthmus of Leningrad oblast. The landscapes of this territory belong mainly to the taiga forest zone and represent the northern periphery of the range for the red-backed vole. The material for this communication included the results of analysis of the reproductive state of >11000 voles of this species obtained over all the years of research. Catching (counting the num-
ber) of animals was carried out by two main methods:
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