Human-carnivore conflicts are complex and are influenced by: the spatial distribution of the conflict species; the organisation and intensity of management measures such as zoning; historical ...experience with wildlife; land use patterns; and local cultural traditions. We have used a geographically stratified sampling of social values and attitudes to provide a novel perspective to the human - wildlife conflict. We have focused on acceptance by and disagreements between residents (measured as Potential Conflict Index; PCI) towards illegal hunting of four species of large carnivores (bear, lynx, wolf, wolverine). The study is based on surveys of residents in every municipality in Sweden and Norway who were asked their opinion on illegal hunting. Our results show how certain social values are associated with acceptance of poaching, and how these values differ geographically independent of carnivore abundance. Our approach differs from traditional survey designs, which are often biased towards urban areas. Although these traditional designs intend to be representative of a region (i.e. a random sample from a country), they tend to receive relatively few respondents from rural areas that experience the majority of conflict with carnivores. Acceptance of poaching differed significantly between Norway (12.7-15.7% of respondents) and Sweden (3.3-4.1% of respondents). We found the highest acceptance of illegal hunting in rural areas with free-ranging sheep and strong hunting traditions. Disagreements between residents (as measured by PCI) were highest in areas with intermediate population density. There was no correlation between carnivore density and either acceptance of illegal hunting or PCI. A strong positive correlation between acceptance of illegal hunting and PCI showed that areas with high acceptance of illegal hunting are areas with high potential conflict between people. Our results show that spatially-stratified surveys are required to reveal the large scale patterns in social dynamics of human-wildlife conflicts.
Selective harvesting regimes are often implemented because age and sex classes contribute differently to population dynamics and hunters show preferences associated with body size and trophy value. ...We reviewed the literature on how such cropping regimes affect the demography of the remaining population (here termed demographic side effects ). First, we examined the implications of removing a large proportion of a specific age or sex class. Such harvesting strategies often bias the population sex ratio toward females and reduce the mean age of males, which may consequently delay birth dates, reduce birth synchrony, delay body mass development, and alter offspring sex ratios. Second, we reviewed the side effects associated with the selective removal of relatively few specific individuals, often large trophy males. Such selective harvesting can destabilize social structures and the dominance hierarchy and may cause loss of social knowledge, sexually selected infanticide, habitat changes among reproductive females, and changes in offspring sex ratio. A common feature of many of the reported mechanisms is that they ultimately depress recruitment and in some extreme cases even cause total reproductive collapse. These effects could act additively and destabilize the dynamics of populations, thus having a stronger effect on population growth rate than first anticipated. Although more experimental than observational studies reported demographic side effects, we argue that this may reflect the quite subtle mechanisms involved, which are unlikely to be detected in observational studies without rigorous monitoring regimes. We call for more detailed studies of hunted populations with marked individuals that address how the expression of these effects varies across mating systems, habitats, and with population density. Theoretical models investigating how strongly these effects influence population growth rates are also required.
Rodent population cycles have fascinated scientists for a long time. Among various hypotheses, an interaction of an extrinsic factor (predation) with intrinsic factors (e.g., sociality and dispersal) ...was suggested to lead to the generation of population cycles. Here, we tested this hypothesis with an individual‐based model fully parameterized with an exceptionally rich empirical database on vole life histories. We employed a full factorial design that included models with the following factors: predation only, predation and sociality, predation and dispersal, and predation and both sociality and dispersal. A comprehensive set of metrics was used to compare results of these four models with the long‐term population dynamics of natural vole populations. Only the full model, which included both intrinsic factors and predation, yielded cycle periods, amplitudes, and autumn population sizes closest to those observed in nature. Our approach allows to model, as emergent properties of individual life histories, the sort of nonlinear density‐ and phase‐dependence that is expected to destabilize population dynamics. We suggest that the individual‐based approach is useful for addressing the effects of other mechanisms on rodent populations that operate at finer temporal and spatial scales than have been explored with models so far.
The boreal forest is one of the largest terrestrial biomes on Earth. Conifers normally dominate the tree layer across the biome, but other aspects of ecosystem structure and dynamics vary ...geographically. The cause of the conspicuous differences in the understory vegetation and the herbivore–predator cycles between northwestern Europe and western North America presents an enigma. Ericaceous dwarf shrubs and 3– to 4-year vole–mustelid cycles characterize the European boreal forests, whereas tall deciduous shrubs and 10-year snowshoe hare–lynx cycles characterize the North American ones. We discuss plausible explanations for this difference and conclude that it is bottom-up: Winter climate is the key determinant of the dominant understory vegetation that then determines the herbivore–predator food-web interactions. The crucial unknown for the twenty-first century is how climate change and increasing instability will affect these forests, both with respect to the dynamics of individual plant and animal species and to their community interactions.
Vole population cycles are a major force driving boreal ecosystem dynamics in northwestern Eurasia. However, our understanding of the impact of winter on these cycles is increasingly uncertain, ...especially because climate change is affecting snow predictability, quality, and abundance. We examined the role of winter weather and snow conditions, the lack of suitable habitat structure during freeze‐thaw periods, and the lack of sufficient food as potential causes for winter population crashes. We live‐trapped bank voles Myodes glareolus on 26 plots (0.36 ha each) at two different elevations (representing different winter conditions) in southeast Norway in the winters 2013/2014 and 2014/2015. We carried out two manipulations: supplementing six plots with food to eliminate food limitation and six plots with straw to improve habitat structure and limit the effect of icing in the subnivean space. In the first winter, all bank voles survived well on all plots, whereas in the second winter voles on almost all plots went extinct except for those receiving supplemental food. Survival was highest on the feeding treatment in both winters, whereas improving habitat structure had no effect. We conclude that food limitation was a key factor in causing winter population crashes.
We test the role of winter climate and snow conditions, the lack of suitable habitat, and of insufficient food in causing winter population crashes in voles. We found a higher survival where voles were fed supplementary, whereas the improved habitat structure had no effect.
Most small rodent populations in the world have fascinating population dynamics. In the northern hemisphere, voles and lemmings tend to show population cycles with regular fluctuations in numbers. In ...the southern hemisphere, small rodents tend to have large amplitude outbreaks with less regular intervals. In the light of vast research and debate over almost a century, we here discuss the driving forces of these different rodent population dynamics. We highlight ten questions directly related to the various characteristics of relevant populations and ecosystems that still need to be answered. This overview is not intended as a complete list of questions but rather focuses on the most important issues that are essential for understanding the generality of small rodent population dynamics.
Seasonality has been suggested as a necessary factor for the initiation of vole population cycles in Fennoscandia. This has been well described for a latitudinal gradient. Here, we used an ...elevational gradient as a proxy for winter length to study how the length of the winter season correlates with the amplitude of bank vole Myodes glareolus population cycles. In addition, we studied whether the small mammalian generalist predator community present locally could explain any elevational effects. We estimated the population size of 30 local bank vole populations. We found a strong effect of elevation on the amplitude of the population cycle with local populations at around 800 m elevation having 1.5 times greater densities than populations in the valley (ca 300 m elevation). A univariate model with elevation as predictor for amplitude was twice as likely to be the best model than models including generalist predators. Our results fit well with the theories of a positive effect of winter length on the amplitude of vole population cycles in Fennoscandia, irrespective of whether the seasonal effect corresponds to a latitudinal or elevational gradient. The mechanisms may be limited resources during winter rather than generalist predators.
Based on evidence from a series of recent studies linking behaviour to demography in experimental vole populations we propose how intrinsic and extrinsic factors interact through the various phases ...of the multi-annual population cycles of voles and lemmings. We hypothesise that population growth in the increase phase of the cycle is enhanced by a high degree of space sharing (sociality) among reproductive females who share resource patches, especially during winter. These social females enjoy a high reproductive output due to good resource conditions, and facilitation provided by communal thermoregulation, breeding and defence of weanlings towards infanticidal conspecifics. We hypothesise on the other hand that the crash phase is initiated and enhanced by predation of adult males that leads to a series of cascading events involving infanticidal behaviour by immigrant males, increased mortality of adult social females, and inversely density-dependent and/or disturbance-induced dispersal. These events further enhance predation-induced mortality and thus a negative feed-back loop to the rate of the crash. In this framework we may explain how extrinsic factors such as predation and winter resource distribution contribute to transitions between docile and aggressive behaviours, and how this transition is spatially synchronised by inversely density-dependent dispersal that may act to mediate a rapidly spreading wave throughout the population. We propose that innate differences among rodent species in their propensities for different social organizations also determine their propensity for exhibiting multi-annual cycles as well as other cycle-related phenomena such as shape of the population cycles and spatial synchrony. We provide a set of testable predictions for further empirical evaluation.
Changes in winter climate is a possible explanation for dampened population cycles in voles. For voles living in the subnivean space for several months of the year, we may expect that winter ...conditions affect survival. We examined the effect of different winter climate descriptors (snow depth, subnivean temperature, snow crust) and different intrinsic factors (sex, age, physiology, behaviour estimated as the longest distance travelled between traps) on winter survival of bank voles Myodes glareolus in southeastern Norway by live-trapping voles monthly along elevation gradients. We tested whether winter conditions alone (winter hypothesis), intrinsic factors alone (intrinsic hypothesis), or winter conditions in combination with age and sex were more important for winter survival of voles (multiple factor hypothesis). Our results do not support the winter hypothesis as there were no relations between winter survival and snow depth, snow crust and subnivean temperature. We found strongest support for the intrinsic hypothesis, where the distance travelled was positively correlated with survival. We hypothesize that this behavioural descriptor is related to food resources and their importance during winter, where an increased activity range (distance travelled between traps) increase the access to food resources.
Species and ecosystems are under constant pressure from a rapidly-growing human population. Human tolerance of carnivores, including the willingness to live in areas with these predators, is key to ...the success of large carnivore conservation. In the Scandinavian Peninsula, large carnivore populations conflict with human activity; low tolerance among local people may lead to illegal hunting. A survey of 2521 Scandinavian respondents to measure environmental value orientation, using the new environmental paradigm (NEP) scale and attitudes toward large carnivores, revealed attitudes towards the presence of carnivores were not related to carnivore abundance. Nor was there a significant relationship between environmental value orientation and personal experiences with loss of domestic sheep or hunting dogs. Environmental values were mainly explained by country differences; Swedes had a more ecocentric value orientation than Norwegians. Significantly more Norwegians (45 %) than Swedes (19 %) responded that there were too many carnivores in their country. Historic differences in how government is perceived between Norway and Sweden may result in different attitudes towards illegal hunting and towards carnivores. Specifically, Norwegians may hold a more anthropocentric view, based on a suspicion of central authorities, whereas Swedes may hold a more ecocentric view.
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