Olav Strand

Winter distribution of wild reindeer in relation to power lines, roads and resorts

Abstract Southern Norway holds the last remaining population of wild reindeer ( Rangifer tarandus tarandus ) in Europe. Roads, railroads, and power lines have fragmented the original population into 26 separate herds. The reindeer populations are regulated directly according to availability of winter forage. These winter ranges, generally at lower elevations, are however, often subjected to development. Effects of infrastructure and associated human activity on the distribution of wild reindeer during winter were investigated in the Nordfjella mountain region of western Norway. Systematic aerial surveys of the distribution of ca. 2500 reindeer were conducted during late winter 1986–1998. Areas within 2.5 km from power lines were used less than available in 6 of the 8 sampling years, and areas beyond this zone more than expected. Density of reindeer was 79% lower within 2.5 km from power lines compared with background areas, and increased with increasing distance from infrastructure for comparable habitat. Available forage in terms of lichen cover declined 15–30-fold with distance, and was lowest in the undisturbed areas with the highest density of grazing animals. Areas within 5 km from resorts or from roads and power lines in combination were avoided in all years. Continued construction of roads, power lines and cabin resorts endanger these available winter ranges, and hence the long term survival of the population.

Age-specific harvest mortality in a Norwegian moose Alces alces population.

The annual age- and sex-specific patterns of harvest mortality in a Norwegian moose Alces alces population during a period of 17 years for females and 24 years for males were estimated using cohort analysis. In males the harvest mortality increased with age, whereas in females the pattern was U-shaped with higher harvest mortality of less fecund young (1–3 year) and old (≥ 10 years) age classes, and lower harvest mortality of prime age (4–9 years old) females. In both sexes, the calf harvest mortality was low, although it increased with increasing calf quotas following a change from an indiscriminate to a sex- and age-specific hunting system during the study period. In adult males, the mortality pattern was opposite of what was expected based on the previously reported higher susceptibility to hunting of young than old males, indicating that hunter selectivity for large (old) males affected the pattern. Moreover, the selectivity of the hunters decreased as the hunting pressure increased, suggesting that the hunters became less selective when the mean time available per moose in the quota decreased. Among adult female age groups, the variation in harvest mortality increased with the proportion of calves per female in the population prior to hunting. This was mainly because of relatively higher mortality of post-prime females, supporting our expectation that hunters avoid shooting females with calves and thus increase the harvest of less fecund age groups during high recruitment years. The observed selectivity led to harvest mortality that differed significantly from patterns of natural mortality, even where the mortality is mainly due to wolves Canis lupus and bears Ursus arctos. This may have consequences for the life history evolution of both male and female moose. The potential ecological, evolutionary and management implications of the results are discussed.

EFFECTS OF INFRASTRUCTURE ON MIGRATION AND RANGE USE OF WILD REINDEER

Abstract We studied reindeer (Rangifer tarandus tarandus) distribution in relation to possible travel barriers (roads and power lines) in south-central Norway, 1997–2000, using lichen biomass as an indicator of reindeer use. We recorded lichen cover on both sides of potential barriers within comparable habitat in 42 sites for 3 different reindeer herds. We used cover–biomass regressions to assess the relationship between lichen cover and biomass. In 2 of the regions, lichen biomass was 5.3 times and 2.8 times higher in areas isolated by 2 parallel power lines and an adjacent winter-closed road compared to biomass on the other side of the potential barrier. In a third region, lichen biomass did not vary significantly between areas on either side of a single winter-closed road. Lichen biomass data suggested that wild reindeer used both sides of a closed road in winter, whereas 2 parallel power lines and a winter-closed road in combination reduced reindeer migration and resulted in very different grazing pressures on either side of the power lines, even 30 years after the power lines were constructed. Construction of power lines, and particularly parallel power lines, should thus be avoided in wild reindeer habitat. Fragmentation of wild reindeer ranges in Norway results in a substantial reduction in available ranges and traditional migration routes between important seasonal ranges, with a likely overall reduction in carrying capacity.

SOCIAL ORGANIZATION AND PARENTAL BEHAVIOR IN THE ARCTIC FOX

Abstract We studied social organization and behavior of arctic foxes (Alopex lagopus) in 3 adjacent territories from 1988 to 1995 in central Norway, where the major rodent prey were cyclic. Twenty-five foxes were equipped with radiotransmitters and several other individuals could be recognized visually. Paired adult foxes and their cubs had home ranges that overlapped more with each other than with neighboring foxes (37% versus 2.9%) and therefore seemed to be territorial. Family composition varied from monogamous pairs, to pairs with additional adults, to an example with 2 reproducing females and 1 male in the same den. Presence of additional family members was independent of the state of the rodent cycle and the reproductive state of the breeding pair. Additional family members contributed only 2% of the food provided to young pups and were therefore not regarded as true helpers. Breeding adults remained resident within the same territory even in years with low abundance of rodents, when they did not breed. All pups left their natal territory by 6 months of age, although some subsequently returned to their natal range or one of the adjacent dens.

Population structure in a critically endangered arctic fox population: does genetics matter?

The arctic fox (Alopex lagopus) in Scandinavia is classified as critically endangered after having gone through a severe decline in population size in the beginning of the 20th century, from which it has failed to recover despite more than 65 years of protection. Arctic foxes have a high dispersal rate and often disperse over long distances, suggesting that there was probably little population differentiation within Scandinavia prior to the bottleneck. It is, however, possible that the recent decline in population size has led to a decrease in dispersal and an increase in population fragmentation. To examine this, we used 10 microsatellite loci to analyse genetic variation in 150 arctic foxes from Scandinavia and Russia. The results showed that the arctic fox in Scandinavia presently is subdivided into four populations, and that the Kola Peninsula and northwest Russia together form a large fifth population. Current dispersal between the populations seemed to be very low, but genetic variation within them was relatively high. This and the relative FST values among the populations are consistent with a model of recent fragmentation within Scandinavia. Since the amount of genetic variation is high within the populations, but the populations are small and isolated, demographic stochasticity seems to pose a higher threat to the populations’ persistence than inbreeding depression and low genetic variation.

Use of dens by red Vulpes vulpes and arctic Alopex lagopus foxes in alpine environments: Can inter-specific competition explain the non-recovery of Norwegian arctic fox populations?

Following over-harvest in the early decades of the 20th century, the arctic fox Alopex lagopus has declined and failed to recover in Norway. Competition with the red fox Vulpes vulpes has frequently been suggested as a possible factor hindering arctic fox recovery. Between 1988 and 1997, a total of 213 former arctic fox dens in four alpine regions of Norway, i.e. Hardangervidda, Dovrefjell, Børgefjell and Dividalen, were checked at least once for occupation by red or arctic foxes. Of these 213 former arctic fox dens, 138 were unoccupied, and 32 and 43 were occupied by arctic and red foxes, respectively. In general, red foxes occupied dens situated at significantly lower altitudes than those occupied by arctic foxes, which supports present ideas of red fox/arctic fox coexistence. As arctic foxes tended to avoid dens at the lowest altitudes, it is possible that arctic foxes to some degree avoid the areas where red foxes are most abundant. This may have disproportionate effects, as the probability of reproduction in arctic fox dens was highest in dens at lower altitudes. Despite this, the large number of unoccupied dens indicates that dens are unlikely to be in limited supply. Therefore, neither our data, nor a review of published data and trapping records, support the hypothesis that inter-specific competition with the red fox is currently preventing arctic fox recovery in the Norwegian alpine environment.

Effect of temporal variation in reproduction on models of population viability : a case study for remnant arctic fox (Alopex lagopus) populations in Scandinavia

Despite more than 69 years of protection populations of arctic fox (Alopex lagopus) in Scandinavia has not recovered their former numbers or distribution following over-hunting at the turn of the century. We aimed to evaluate the possible fate of arctic fox populations using discrete-time models including both demographic and environmental variability. Because the reproduction of arctic fox in Scandinavia is dependent on the abundance of small rodents, which is cyclic, we included the temporal variability of reproductive performances in our viability analysis based on time series available for three Scandinavian populations. Whatever the modelling of the reproductive performances and the range of adult survival rates considered, the risks of extinction were high. They were very sensitive to adult survival rates and variability in reproductive performances. Populations with the longest duration between two successful reproductions were at the greatest risks of extinction. The time elapsed between two successful reproductions may depend on failure to respond to rodent peaks. The cyclicity of food availability for arctic fox may have been the main selective force for their large litter size, but may also be the cause of a fine-tuned, and fragile dynamic system.

Predicting the continuum between corridors and barriers to animal movements using Step Selection Functions and Randomized Shortest Paths.

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. 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. 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). 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. 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.

Placental Scars and Estimation of Litter Size: An Experimental Test in the Arctic Fox

The assumptions required to estimate litter size at birth from counts of placental scars were experimentally tested in the Arctic fox ( Alopex lagopus ). Effects of abortions were tested by examination of uteri from females caused to abort at 20 and 40 days pregnancy. The reliability of estimated litter sizes was tested by comparing litter size at 2–3 days postpartum with counts of placental scars. Placental scars were categorized according to their visibility, with pale and hardly detectable scars designated as category 1 and dark and fully pigmented scars as category 6. The results showed that scars from abortions and scars that persisted for 80 weeks postpartum were paler and less visible than scars from full-term fetuses at 20–35 weeks postpartum. Pale scars from abortions and scars sustained from earlier pregnancies, therefore, should be excluded when estimating litter size at birth. Litter size at 2–3 days postpartum was not significantly different from estimated litter size when pale scars were excluded from the estimates. Our results confirmed that breeding females might be distinguished from nonbreeders by the visibility of placental scars. The accuracy of this approach, however, depends on the frequency of late abortions in the population.

A road in the middle of one of the last wild reindeer migration routes in Norway: crossing behaviour and threats to conservation

The development of roads and associated infrastructure has interrupted several traditional migrations of wild reindeer (Rangifer tarandus tarandus) in Norway. The population in the Setesdal Austhei wild reindeer area still migrates from winter to calving grounds by semi-annually crossing a cabin-lined road through a narrow corridor, in which further anthropogenic development is planned. To understand if and how infrastructure affected reindeer migration patterns we studied the movements of 10 female reindeer equipped with GPS collars between 2002 and 2010. First, we identified the start and end of the migration period, and then we compared trajectory parameters (net displacement, step length and turning angles) recorded during migration with those recorded in proximity of the road. The analysis of the net displacement indicated that during spring migration reindeer moved at a constant pace towards the calving ground covering a net linear distance of 25 km in 40 days. In the middle of migration, reindeer changed travel direction and roamed parallel to the road for ca. 5 days without approaching further, possibly searching for an undisturbed place and time to cross. Reindeer finally crossed the road before daylight with highly directed movements, increasing their travel speed up to the highest values recorded during migration (4 km/3 hrs vs. 0.5 km/3 hrs). After crossing, reindeer moved quickly toward their calving ground covering the remaining 25 km net distance in less than a week. Migration patterns were markedly affected by disturbance during spring, as the road crossings occurred in the period characterized by the high traffic volume and intense human activities related to Easter holidays; during autumn, on the contrary, the hampering effect of the road was minimal. The results suggest that the current disturbance associated to the road hampers spring migration and might delay the arrival to the calving ground. The planned construction of a large number of recreational cabins in the migration corridor has the potential to threaten the migration and obstruct the access to the calving ground. Normal 0 21 false false false SV X-NONE X-NONE Normal 0 21 false false false EN-US X-NONE X-NONE