Demographic parameters and variations in numbers of the common vole

Abstract

Nabagło L., 1977: Demographic parameters and variations in numbers of the common vole. Acta theriol., 22,.Observations were made for two years of the demographic variations in two enclosed populations (A and B) of the common vole Microtus arvalis (Pallas, 1779), by means of the CMR method. Variations in numbers followed a similar course in both populations, population A reaching a lower maximum number than B. Both populations were more numerous in the second study year (1972). The greatest rate of increase in numbers (tn = 0.23) took place in May. Maximum increase was found in the number of individuals (f r =0.5-1.0/week/l $) during the period from May to July. In the early summer period the rate of increase in numbers in the populations was found to be limited by the high degree of mortality among the youngest animals. During the reproductive period turnover was 60%-90°/o of the population per month. The ratio of females to males in the population varied from 0.25 to 2.35. The greatest percentage of females was observed during the period of intensive reproduction, and was correlated with the number of recruits to the population. The predominance of females results in higher recruitment and better survival. During the growing season over 60% of the population was formed by individuals which had spent less than one month outside the nest. During autumn of the year with higher numbers the populations were younger than was the case in the year with lower numbers. The more numerous population (B) was younger than the less numerous (A). During the reproductive period the females were older than the males. The study populations were in the phase of rapid population growth, which was accompanied in successive years by longer-lasting numerical predominance of females over males, prolongation of the reproductive period and better survival of new individuals.[Inst. Ecol., Polish Acad. Sci., Dziekanów Leśny, 05-150 Łomianki, Poland].

Population dynamics of Microtus arvalis in a weed strip

“…A more plausible cause for the differences in population dynamics could be related to sex ratio. In 2000, the trend in sex ratio was similar to that described by AdamczewskaAndrejewska and Nabaglo (1977), who studied a vole population in an alfalfa field. In 2000, a quite balanced sex ratio in spring was followed by a surplus of females in summer.…”

Somatic characteristics and reproduction of common vole, Microtus arvalis (Microtus arvalis

“…Sex ratio in common voles generally varies between trapping periods and years. For example in 2000, Briner et al (2007) found that the ratio of males and females oscillated between 1:1 and 1:2 except for September and October, when males were slightly more numerous (the trend in sex ratio was similar to that described by Adamczewska-Andrejewska & Nabaglo 1977). In 2001, males were less abundant throughout the year and in late summer females were 7-8 times more numerous than males.…”

Comparison of enumeration and Jolly-Seber estimation of population size in the common voleMicrotus arvalis

“…We have shown that the enumeration method ("minimum number alive" or "calendar of catches"), a technique that has been widely used in central Europe to estimate population size of the common vole (Wojciechowska 1969, Adamczewska--Andrzejewska and Nabag³o 1977, Mackin-Rogalska 1979, Adamczewska-Andrzejewska et al 1981, Nabag³o 1981, consistently gave lower estimations of population size when compared to the JS model. The negative bias increased with density, decreased with increasing capture probability and was more pronounced in males at high density.…”

“…Specifically, the Jolly-Seber model (JS; Jolly 1965, Seber 1965) and its special model variants have turned out to be particularly useful in long-term microtine studies, as they allow estimation of population size at each sampling time as well as survival rates and birth numbers between sampling times (Pollock et al 1990). However, the capture-recapture data on common voles have been almost exclusively evaluated by means of the enumeration estimators (eg Adamczewska-Andrzejewska and Nabag³o 1977, Mackin-Rogalska 1979 yielding population size estimates, which also are known as minimum number alive (MNA; Krebs 1966) or calendar of catches (Petrusewicz and Andrzejewski 1962). Unlike the JS method, which handles recaptures within the clearly defined framework of probabilistic models based strictly on a statistical theory, the enumeration method uses recaptures only as a means of establishing that a marked individual was alive in some previous sampling period when it was caught (Pollock et al 1990).…”