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Characteristics of Clethrionomys glareolus and Apodemus flavicollis individuals recruited to isolated populations on Crabapple Island (Masurian Lake District, Poland)

Dudek D., Alcheikh B.

Polish Journal of Ecology

2002

Vol. 50, nr 1

57-68

Crabapple Island, a 4-ha island covered with a mixed forest dominated by Tilio-Carpinetum Traczyk 1962, is situated on Lake Bełdany (53 stopnie 42 min.N, 21 stopni 35 min. E) at a distance of about 120 m from the mainland. Materials were collected by using the CMR (catch-mark-release) method during five 7-day censuses conducted each year in 1994-1998. The recruitment of new individuals to the trappable part of the bank vole and yellow-necked mouse populations was compared with respect to the number of new-captured individuals, their age, and reproductive status. The age of new-captured individuals was estimated from growth curves. It was observed that when the populations of the two species were more abundant, the first-captured individuals were older than when population numbers were lower. The proportion of mature individuals (including pregnant females) in the groupm of all individuals captured for the first time was higher for the yellow-necked mouse than for the bank vole (48 and 15%, respectively). In both species, the number of mature new-captured individuals was negatively correlated with the total number of conspecific females present in the population. In the case of the bank vole (probably also of the yellow-necked mouse), this may be related with territoriality of mature females. As yellow-necked mice were first captured at an older age than bank voles, this may be a source of errors in estimates of numbers of immature individuals and, consequently, in the analysis of the population structure of this species.

Trappability of Clethrionomys glareolus and Apodemus flavicollis inhabiting Crabapple Island, Masurian Lakeland, Poland

Alcheikh B.

Polish Journal of Ecology

2001

Vol. 49, nr 4

407-425

Populations of two rodent species were studied during 1996-1998 on a 4-ha island covered with a mixed forest. Population sizes varied within and between years. In total, the material consisted of 10 839 captures of 1925 bank volesand 2941 captures of 881 yellow-necked mice. The redonts were categorised as immature males, mature males, immature females, mature non-pregnant females, and mature pregnant females. It has been found that the weather did not influence trappability (measured as the reciprocal of the mean time that elapsed between successive captures of a bank vole or a yellow-necked mouse. The trappability of different categories of individuals was related to the social systems of the two species. This is indicated by the dependence of the trappability of all categories of individuals on the population size (it was lowest at the highest population numbers), and also by the dependence of trappability on body weight (positive in male voles and negative in male mice). The trappability of immature females and mature males of the bank vole increased with increasing home range size, whereas in other categories of individuals, like in all categories of the yellow-necked mouse individuals, an increase in home range size was not accompanied by changes in trappability. Thus, there is no trappability typical of the whole order of rodents; it should always be related to the species and to the character of its social system.