Variation in size of home range is among the most important parameters required for effective conservation and management of a species. However, the fact that home ranges can vary widely within a species makes data transfer between study areas difficult. Home ranges of Eurasian lynx Lynx lynx vary by a factor of 10 between different study areas in Europe. This study aims to try and explain this variation in terms of readily available indices of prey density and environmental productivity. On an individual scale we related the sizes of 52 home ranges, derived from 23 (9:14 male:female) individual resident lynx obtained from south-eastern Norway, with an index of density of roe deer Capreolus capreolus. This index was obtained from the density of harvested roe deer within the municipalities covered by the lynx home ranges. We found a significant negative relationship between harvest density and homerange size for both sexes. On a European level we related the sizes of 111 lynx (48:63 male: female) from 10 study sites to estimates derived from remote sensing of environmental productivity and seasonality. A multiple linear regression model indicated that productivity of the study site had a clear negative relationship with home-range size. At both scales, sex emerged as a significant explanatory variable with males having larger home ranges than females. In addition, the size of male home-ranges increased faster with decreasing prey density than for females. These analyses support widely held predictions that variation in home-range size is due to variation in prey density.

Abstract. Across the Arctic, heavy rain-on-snow (ROS) is an ''extreme'' climatic event that is expected to become increasingly frequent with global warming. This has potentially large ecosystem implications through changes in snowpack properties and ground-icing, which can block the access to herbivores' winter food and thereby suppress their population growth rates. However, the supporting empirical evidence for this is still limited. We monitored late winter snowpack properties to examine the causes and consequences of ground-icing in a Svalbard reindeer (Rangifer tarandus platyrhynchus) metapopulation. In this high-arctic area, heavy ROS occurred annually, and ground-ice covered from 25% to 96% of low-altitude habitat in the sampling period (2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010). The extent of ground-icing increased with the annual number of days with heavy ROS (!10 mm) and had a strong negative effect on reindeer population growth rates. Our results have important implications as a downscaled climate projection (2021-2050) suggests a substantial future increase in ROS and icing. The present study is the first to demonstrate empirically that warmer and wetter winter climate influences large herbivore population dynamics by generating ice-locked pastures. This may serve as an early warning of the importance of changes in winter climate and extreme weather events in arctic ecosystems.

Summary1. The loss, fragmentation and degradation of habitat everywhere on Earth prompts increasing attention to identifying landscape features that support animal movement (corridors) or impedes it (barriers). Most algorithms used to predict corridors assume that animals move through preferred habitat either optimally (e.g. least cost path) or as random walkers (e.g. current models), but neither extreme is realistic. 2. We propose that corridors and barriers are two sides of the same coin and that animals experience landscapes as spatiotemporally dynamic corridor-barrier continua connecting (separating) functional areas where individuals fulfil specific ecological processes. Based on this conceptual framework, we propose a novel methodological approach that uses high-resolution individual-based movement data to predict corridor-barrier continua with increased realism. 3. Our approach consists of two innovations. First, we use step selection functions (SSF) to predict friction maps quantifying corridor-barrier continua for tactical steps between consecutive locations. Secondly, we introduce to movement ecology the randomized shortest path algorithm (RSP) which operates on friction maps to predict the corridor-barrier continuum for strategic movements between functional areas. By modulating the parameter Ѳ, which controls the trade-off between exploration and optimal exploitation of the environment, RSP bridges the gap between algorithms assuming optimal movements (when Ѳ approaches infinity, RSP is equivalent to LCP) or random walk (when Ѳ ? 0, RSP ? current models). 4. Using this approach, we identify migration corridors for GPS-monitored wild reindeer (Rangifer t. tarandus) in Norway. We demonstrate that reindeer movement is best predicted by an intermediate value of Ѳ, indicative of a movement trade-off between optimization and exploration. Model calibration allows identification of a corridor-barrier continuum that closely fits empirical data and demonstrates that RSP outperforms models that assume either optimality or random walk. 5. The proposed approach models the multiscale cognitive maps by which animals likely navigate real landscapes and generalizes the most common algorithms for identifying corridors. Because suboptimal, but non-random, movement strategies are likely widespread, our approach has the potential to predict more realistic corridor-barrier continua for a wide range of species.

: Animal locations estimated by Global Positioning System (GPS) inherently contain errors. Screening procedures used to remove large positional errors often trade data accuracy for data loss. We developed a simple screening method that identifies locations arising from unrealistic movement patterns. When applied to a large data set of moose (Alces alces) locations, our method identified virtually all known errors with minimal loss of data. Thus, our method for screening GPS data improves the quality of data sets and increases the value of such data for research and management.

No abstract

Habitat alteration by humans may change the supply of food and cover for wild ungulates, but few studies have examined how these resources are utilised over time by individuals of different sex and reproductive status. We examined circadian and seasonal variation in habitat utilisation within a moose Alces alces population in central Norway. Our study area covers forests and open habitats, both influenced by human alterations (e.g. forestry and agriculture). We expected moose to select habitats with good forage and cover in all seasons, but to select open foraging habitats mainly during night-time. Moose selected good foraging habitats, such as young forest stands and cultivated land during night, whereas the utilisation of older forest stands providing cover increased during daytime. This circadian pattern changed throughout the year, seemingly related to variation in hours of daylight and provision of forage. Young forest stands provided higher density of preferred food plants compared to older stands and were highly selected from spring until autumn. Relative to young forest, the selection for older forest stands increased towards winter, likely due to provision of higher plant quality late in the growing season, and to reduced accumulation of movement-impeding snow during winter. Selection of cultivated land varied among seasons, being highest when crop biomass was high. We also found some indications of state-dependent habitat selection as reproducing females avoided open, food rich areas in the first months after their calves were born, whereas males and females without young selected these areas in spring and summer. Our results clearly show that moose exploit the variations in cover and food caused by forestry and agriculture. This is particularly relevant for moose in Norway as current changes in forestry practice lead to a reduction in young, food-rich forest stands, possibly aggravating the already declining body conditions and recruitment rates of moose.

In the multi-use landscape of southern Norway, the distribution of lynx is likely to be determined both by the abundance of their favoured prey Á the roe deer Á and the risk associated with the presence of humans because most lynx mortalities are caused by humans (recreational harvest, poaching, vehicle collisions). We described the distribution of the reproductive portion of the lynx population based on snow-track observations of females with dependent kittens collected over 10 yr (1997Á2006) in southern Norway. We used the ecological-niche factor analysis to examine how lynx distribution was influenced by roe deer, human activity, habitat type, environmental productivity and elevation. Our first prediction that lynx should be found in areas of relatively high roe deer abundance was supported. However, our second prediction that lynx should avoid human activity was rejected, and lynx instead occupied areas more disturbed in average than those available (with the exception of the most densely occupied areas). Lynx, however, avoided the most disturbed areas and our third prediction of a trade-off between abundance of prey and avoidance of human activity was supported. On the one hand, roe deer in the most disturbed areas benefit to a large extent from current human land use practices, potentially allowing them to escape predation from lynx. On the other hand, the situation is not so favourable for the predators who are restricted in competition refuges with medium to low prey densities. The consequence is that lynx conservation will have to be achieved in a human modifed environment where the potential for a range of conflicts and high human-caused mortality will remain a constant threat.

Identifying factors shaping variation in resource selection is central for our understanding of the behaviour and distribution of animals. We examined summer habitat selection and space use by 108 Global Positioning System (GPS)-collared moose in Norway in relation to sex, reproductive status, habitat quality, and availability. Moose selected habitat types based on a combination of forage quality and availability of suitable habitat types. Selection of protective cover was strongest for reproducing females, likely reflecting the need to protect young. Males showed strong selection for habitat types with high quality forage, possibly due to higher energy requirements. Selection for preferred habitat types providing food and cover was a positive function of their availability within home ranges (i.e. not proportional use) indicating functional response in habitat selection. This relationship was not found for unproductive habitat types. Moreover, home ranges with high cover of unproductive habitat types were larger, and smaller home ranges contained higher proportions of the most preferred habitat type. The distribution of moose within the study area was partly related to the distribution of different habitat types. Our study shows how distribution and availability of habitat types providing cover and high-quality food shape ungulate habitat selection and space use.Electronic supplementary materialThe online version of this article (doi:10.1007/s00442-011-2072-3) contains supplementary material, which is available to authorised users.