In order to estimate age at natal dispersal and dispersal distance, wild boars Sus scrofa were studied in Sweden by use of mark-recapture and telemetry. To de scribe the average natal dispersal in the population, we applied a sigmoid re gression model to analyse the age specific distance to the natal site. We used the first and second order derivatives of the model to determine at which ave rage age dispersal begins, reaches its maximum rate and ceases. The average dispersal distance was estimated by the maximum value of the model. Using this method, we reached the conclusion that male wild boars begin to disperse at the age of 10 months, reach their maximum dispersal rate at the age of 13 months, and that dispersal ceases at the age of 16 months. At that age, they have dispersed 16.6 km from their natal sites. For females, the corresponding ages were 7 ,9 and 11 months, with a dispersal distance of 4.5 km. The results fol low the prevalent opinion on natal dispersal in polygynous mammals. Dispersal distances are generally short with a negative exponential probability distribu tion. Dispersal reaches its maximum rate during the age at which sexual matu rity is occurring, and males disperse longer distances than females.

The present wild boar Sus scrofa population in Sweden mainly originates from animals that have escaped from enclosures. At some locations wild boars have evidently been released deliberately. Whatever their origin, rapid increases in both number and distribution of free-ranging wild boars have occurred. As wild boars are considered exotic in the Swedish fauna, sportsmen very often provide supplemental food in varying degrees, partly to facilitate and secure hunting possibilities, partly to keep wild boars out of farmed crops. In this paper we describe wild boar activity behaviour and intend to show how wild boar adjust their activity behaviour under different ambient conditions. The aim of our study was to increase the knowledge of managers to improve hunting effectivity and risk assessment concerning crop damage. The wild boars were, al most without exceptions, active during night. The mean time for an activity bout was 7.2 hours and the wild boars in the study area were only to a minor de gree adjusting their activity bout to the prevailing night length. However, the hour of sunset seemed to be the cue which triggered the onset of activity bouts. The mean distance that the wild boars travelled during activity bouts was 7.2 km and the estimated mean activity range was 104.4 ha. The mean effort when roaming the activity range was 110.9 m/ha. A substantial variance was typical for all activity variables. For activity distance, 72% of the variation was explained by adding wind speed, season, minimum temperature and snow cov er to our model. Significant effects of minimum temperature, snow cover and an interaction between activity time and minimum temperature explained 42% of the variation in activity range. The variation in relative air humidity explained 41% of the time active during an activity bout.

Ecosystem budgets of matter contribute to the assessment of transport and accumulation of bioavailable contaminants in a landscape, since flows of matter and energy ultimately determine the rates at which contaminants will be partitioned in the environment. This study compares ecosystem properties, such as net primary production (NPP), sequestration of matter and fluxes to food sources for humans, which are of potential interest to describe fluxes and accumulation of bioavailable radionuclides in 14 catchments within a larger catchment area in southeast Sweden. The carbon budgets, used as a proxy for organic matter, are mainly based on local estimates of pools and fluxes, which have been distributed across a landscape mosaic of different vegetation types and management regimes using a geographical information system (GIS). NPP varied by a factor close to two (432 - 709 g x Cx m(-2)x y(-1)), while net ecosystem production ranged between -124 and 159 gx C x m(-2) x y (-1) for the different catchments. Carbon sequestration mainly occurred in the vegetation while the soil organic carbon pool was mainly a source of carbon. Large herbivores consumed on average 4.5 % of the above-ground green tissue production. When arable land was present in the catchment, the flux of carbon to humans was highest from crops and, in decreasing order, milk and beef, followed by the flux from hunting and berry/fungus picking. The results can be used to estimate the potential assimilation of radionuclides in vegetation and the potential exposure to humans of bioavailable radionuclides.