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A South Swedish population of the vespertilionid bat Pipistrellus pipistrellus was studied by means of bat boxes from April to the beginning of October in 1984. The mating system of the pipistrelle bat is a “resource defence polygyny”. Three territorial males were studied to determine the relative importance of two potential resources, food and roost sites, for male reproductive success. The day roost was found to be the crucial resource for the male's chances to get access to females. A territorial male advertises the location of his day roost to the females by a songflight display. The male who spent most time in songflight display was visited by the greatest number of females.

Two populations of the pipistrelle bat Pipistrellus pipistrellus in southernmost Sweden were studied for eight consecutive breeding seasons using bat boxes. The population living in the vicinity of an industrial area had a declining population trend when compared to that form a rural area. Mass indices in September, when fat accumulation prior to hibernation has started, were also lower compared to those obtained in the rural area. The levels of organochlorine residues and of cadmium were also higher in the population living close to the industrial area. The proximate cause of the decline, however, is assumed to be deteriorating feeding conditions due to drainage and water pollution.

A pipistrelle bat (Pipistrellus pipistrellus) population in southernmost Sweden was studied for eight consecutive breeding seasons by means of bat boxes. Survival rates were calculated using Cormack's stochastic technique. The mean survival rate of adult females exceeded that of territorial males. Annual variations in survival rates were most evident in males, low rates being observed in years following wet autumns. Energy constraints imposed on territorial males by the mating system, a resource defence polygyny, were assumed to account for the differences obtained in survival rates between the sexes.

The relationships of faunal diversity and vegetation structure were studied in twenty deciduous forest plots in South Sweden, all of them managed. Following animal groups were censused: shrews (Soricidae), bats (Chiroptera), voles (Cricetidae), fieldmice (Muridae), birds (Aves), groundliving beetles (Coleoptera), spiders (Araneida), and harvestmen (Opilionidae). The analysis of the 22 vegetation variables was made by means of repeated and rotated PCA. Rarefaction was used to ordinate the bird species richness of the different forest plots. The multivariate vegetational analysis resulted in three distinct and readily interpretable components: horizontal and vertical spatial heterogeneity, and mean basal area. The number of small mammal species (except bats) was greatest in forests with great amount of understory while the number of bat species increased with increasing mean basal area. The number of bird species in a fixed number of territories was also highly correlated with the mean basal area. Hence, maximum bird species richness was obtained in mature forests but not in those with greatest vertical heterogeneity. The invertebrate communities showed very few distinct relationships to the vegetation structure. Dominance decreased as vegetation complexity increased. Dominance also decreased with increasing species richness in all faunal communities studied.

The social organization of the pipistrelle bat (Pipistrellus pipistrellus) was studied by means of bat boxes in southern Sweden. The males set up territories around a roosting site in the beginning of the summer at the same time as the females formed nursing colonies. After breeding, the females joined the single males in their day roosts establishing transient mating harems. Subsequently, immatures arrived at the mating grounds. The immature females, which probably attained sexual maturity during their first autumn, were admitted to the day roosts of the harem males, in contrast to the immature males. The size of the harem was dependent on the total number of females present on the mating grounds. The size, however, was also restricted by some factor, presumably the quantity of food resources in the surroundings of the specific roost site, or the capability of the harem male for mating. The mating system in the pipistrelle bat is best characterized as a resource defence polygyny. Available data on other related temperate species indicate a similar social organization in Pipistrellus nathusii and Nyctalus noctula.

Etude menee dans un archipel au large du sud de la Suede, en 1972-74. Les femelles de Somateria mollissima presentent deux strategies differentes de selection du site de nidification: celles qui commencent la reproduction tot choisissent les iles contenant des colonies de Larus argentatus; celles qui se reproduisent plus tardivement choisissent les iles ou vivent Larus canus. Ces deux strategies seraient des adaptations contre la predation

Home ranges of nine minks Mustela vison in southern Sweden were studied by telemetric techniques during eleven periods in 1968-69. Data obtained allowed accurate determinations of the boundaries of the ranges and quantitative descriptions of the distribution of use-intensity. Information on seasonal movements were obtained by trapping and marking. The adult male occupied the largest home range, twice as large as that of the juvenile male. Adult females kept within smaller ranges than the adult males. In winter the minks tended to concentrate their activity to restricted parts of the home ranges. The great irregularity found in intensity of use of the home range may be due to the availability of food. An adult female may temporarily hold a territory against an adult male. The balance, however, demands more attention from her at the common border. Unlike juvenile females, juvenile males did not seem to be allowed to stay within the ranges of adult males. The dispersal of juveniles started in the beginning of July and most of them left the study area. The extent of male movements during the mating season was greater than during the rest of the year.

The food habits of the mink in Sweden were studied in three different habitats by means of scat analyses. The entire material contained 4,738 scats. There were very marked seasonal variations due to changes in the relative availability of the prey. The principal food groups were mammals, mainly rodents, birds, fish, and crayfish. Crayfish occurred most frequently in the summer food, due to its higher activity in the warm months which increased its vulnerability. Fish was consumed preferentially in winter and spring. The great availability in these seasons was a result of increased vulnerability due to low water temperature. Frogs were secondary food and occurred most frequently in the diet at seasons when the mink changed its food habits. Birds occurred most frequently in the diet during migration and breeding seasons. Rodents constituted a very variable source of food due to the great fluctuations of their number. Their availability influenced the food habits in a conspicuous manner, particularly in the northern area investigated. The greatest changes in the food habits occurred in late spring and in the autumn. Differences between habitats with regard to food habits were most marked in summer. At other seasons the food habits were dominated by the great fish consumption. Pe3ioMe

Activities of six minks (Mustela vison) in southern Sweden were monitored during nine different periods in 1968-69 by radio-tracking techniques. Diel activity patterns were determined and related to availability of prey, reproduction cycle, and certain environmental factors. 1. All the wild male minks studied were mainly nocturnal at all seasons. The level of activity tended to increase with increasing length of night and with decreasing temperature. In general, the activity peaks of male mink corresponded to peaks in prey activity. 2. The female studied showed a very low activity during pregnancy. During the litter period when she was mainly diurnal her level of activity was considerably higher.