dynamics in a primeval deciduous forest (Białowieża National Park) in relation to weather, seed crop, and predation. Acta theriol. 38: 199 -232. (Schreber, 1780) and yellow-necked mice Apodemus flavicollis (Melchior, 1834) were studied in 1959 -1991 in the pristine mature forest dominated by hornbeam Carpinus betulus and oak Quercus robur in Białowieża National Park (eastern Poland). The whole 33-year series, and particularly the detailed data from 1971 -1991, were related to weather data and seed crop o f hornbeam, oak, and maple Acer platanoides. Rodent numbers were very low in spring (April), then grew through summer due to repro duction. The annually highest numbers o f both species were recorded in autumn. W inter mortality was on average 77% o f autumn numbers of voles and 86% o f mice. Multiannual variations in numbers were large; the combined numbers of voles and mice showed a regular pattern of 2 years o f outbreak-crash (triggered by heavy mast production) and 4 -7 years of moderate, though variable, densities. Heavy seed crops (synchronous in oak, hornbeam and maple) occurred at 6-9-year intervals (in 1958, 1967, 1976, 1982, and 1989), and were triggered by warm June -July temperature in the preceding year (bud formation year). Outbreaks o f rodents were always preceded by winter breeding in mice and sometimes also in voles. Rodents reached highest numbers in autumn o f the year following the mast peaks. Then, they declined rapidly over winter to extremely low numbers in the following spring, summer and autumn. Such crashes were recorded after 4 out o f 5 outbreaks. In moderate years, summer and autumn numbers o f rodents correlated with food-related factors (seed crop, temperature affecting vegetation biomass), whereas spring numbers were shaped by density dependent winter mortality. Summer (July) numbers of mice in moderate years were a direct function of spring numbers o f overwintered adults ( R = 91%). Autumn (September) numbers o f mice were determined by tree seed crop o f the previous year (R = 32%). Summer numbers of voles depended on temperature in June -July ( R 2 = 29.5%), which most probably acted through an increased production o f herba ceous vegetation biomass. No ambient factors were found to explain variation in autumn numbers o f voles. In both species, the intensity of reproduction in autumn was inversely related to autumn numbers. In bank voles, high temperature in JulySeptember was conducive to prolonged breeding. Winter mortality of rodents was density dependent ( R 2 = 99% in mice and 92% in voles). Mast increased overwinter survival o f mice but not voles. Snow cover increased survival of bank voles. Density -dependent predation was the main agent o f rodent mortality in moderate years, whereas its role in outbreak-crash years has not yet been studied. The described pattern o f population dynamics o f forest rodents is regarded as typical for the decidu ous forests with Quercus in lowland, temperate Europe. Review o f literature showed that the heaviest seed crops of oaks (a...

No abstract

[With 7 Tables and 3 figures]The absolute and relative (in percentages of brain weight) lipids and fat-free dry rest contents in the brain of S. araneus were determined. The water content in the brain was determined from the difference between the sum of the above values and the weight of the fresh brain. Seasonal and age variations in the weight of the brain were found to occur realy in material which had not been fixed. Variations in the weight of water, lipids and dry rest were stated. These indices are smaller in the winter than in the summer by respectively 23.7%>, 11.8% and 6.8%. The water content exhibits a relation in direct proportion to the mass of brain, i.e. a significant loss in the winter (of 3.8%) and repeat increase in old adults (in spring) was found. The dry rest is in reverse proportion to variations in water content. The lipids content is lowest in young adults in the summer, increases in the winter and spring, then decreases in old adults in the summer and autumn. These data indicate that seasonal variations in the brain weight of shrews are conditioned primarily by variations in water content, and also in fat-free dry rest and lipids contents. I. INTRODUCTIONThe phenomenon of seasonal variability in shrews, discovered by D e h n e 1 (1949), has become a starting point for many elaborations, both morphological and physiological. The mechanism of seasonal variations in the height of the brain-case has been explained in studies by Pucek (1955;1957). The suggestions made by this author (1955) that variations in the skull constitute a secondary phenomenon directly dependent on seasonal differences in the capacity of the brain-case, and in consequence in the volume of the brain, were confirmed in further studies of Sorex miv.utus Linnaeus, 1766 (Gabon, 1956 and Sorex araneus Linnaeus, 1758(Bielak & Pucek 1960. Many authors have confir-

of Ondatra zibethica (Linnaeus, 1766) [ With 8 Tables & 11 Figs.]Examination was made of the degree of population differentiation in skull measurements and also in the formation of the skull during individual development, on the basis of a collection of muskrat skulls (n=352) from three Polish populations and one Czech population, divided into four age classes. The muskrats from the three populations differ significantly by reason of their larger dimensions and different proportions of the skull, and also the statistical distances of shape and size, from animals from the central part of Bohemia. Differentiation was also found in the correlation structures of skull dimensions of muskrats from different populations. The number of differences found increases with the animals' age, and also with increasing distance in both space and time from the population closest to the place in which the muskrat was originally introduced into Europe. The skull of the muskrat is distinguished by a slight degree of sex dimorphism in dimensions which increases with the animals' age. Intensive increase of the majority of its dimensions ends in the second calendar year of the animals' lives. Age changes in skull dimensions of the muskrat are also reflected in changes in correlation structures corresponding to periods of isometric and allometric growth.

A study was made of the food preferences of heres (Lepus europueus Pallas, 1778) in relation to branches of 12 of the commonest genera (and species) of trees found in hunting areas, placed for the purposes of the experiment on the ground, assessing the degree to which the branches were bitten according to a 7-degree scale from 0 to 6; a total of 3456 such assessments were made. Calculation of the significance of differences between mean assessments of degree to which the species examined were bitten permitted of dividing them into the following groups: (1) most readily bitten -Malus domestica Borkh