Unfounded claims about productivity beyond density for reindeer pastoralism systems

We point out problems with the article Productivity beyond density: A critique of management models for reindeer pastoralism in Norway by Marin and co-workers published in Pastoralism in 2020. In our opinion, there are several misleading claims about the governance of the reindeer pastoralist system in Norway, the Røros model for herd management and density dependence in reindeer herds in their article. We point out the errors in their empirical re-evaluation of previous work on the relationship between reindeer densities and the productivity and slaughter weights in herds. These errors have a significant bearing on their conclusions. We agree that weather variability has a substantial impact on reindeer body mass growth, fecundity and survival, but disagree with Marin et al. when they argue that reindeer densities are of minor importance for reindeer productivity and animal welfare

The role of predation and food limitation on claims for compensation, reindeer demography and population dynamics

1.A major challenge in biodiversity conservation is to facilitate viable populations of large apex predators in ecosystems where they were recently driven to ecological extinction due to resource conflict with humans. 2. Monetary compensation for losses of livestock due to predation is currently a key instrument to encourage human–carnivore coexistence. However, a lack of quantitative estimates of livestock losses due to predation leads to disagreement over the practise of compensation payments. This disagreement sustains the human–carnivore conflict. 3. The level of depredation on year-round, free-ranging, semi-domestic reindeer by large carnivores in Fennoscandia has been widely debated over several decades. In Norway, the reindeer herders claim that lynx and wolverine cause losses of tens of thousands of animals annually and cause negative population growth in herds. Conversely, previous research has suggested that monetary predator compensation can result in positive population growth in the husbandry, with cascading negative effects of high grazer densities on the biodiversity in tundra ecosystems. 4. We utilized a long-term, large-scale dataset to estimate the relative importance of lynx and wolverine predation and density-dependent and climatic food limitation on claims for losses, recruitment and population growth rates in Norwegian reindeer husbandry. 5. Claims of losses increased with increasing predator densities, but with no detectable effect on population growth rates. Density-dependent and climatic effects on claims of losses, recruitment and population growth rates, were much stronger than the effects of variation in lynx and wolverine densities. 6. Synthesis and applications. Our analysis provides a quantitative basis for predator compensation and estimation of the costs of reintroducing lynx and wolverine in areas with free-ranging semidomestic reindeer. We outline a potential path for conflict management which involves adaptive monitoring programs, open access to data, herder involvement, and development of management strategy evaluation (MSE) models to disentangle complex responses including multiple stakeholders and individual harvester decisions. depredation, human–carnivore conflict, MODIS, onset of spring, plant productivity, predator compensation, Rangife

Retrospective growth analysis of the dwarf shrub Cassiope tetragona allows local estimation of vascular plant productivity in high arctic Svalbard

The work was supported financially by Research Council of Norway (POLARPROG grant 216051, “Reinclim”). AS was supported by the Norwegian Institute of Nature research.Peer reviewedPostprin

Environmental variation as a driver of predator-prey interactions

Animals often face the trade-off of optimizing foraging while limiting predation. In variable and seasonal environments the availability of resources changes spatially and temporally, forcing animals to adapt their spatial foraging patterns over time and, thus, to modify their exposure to predation. Previous research has mostly dealt with the causes and consequences of animal spatial patterns separately, with studies either examining how changes in the environment influence habitat selection, or determining the effects of habitat use on vulnerability to predation. Here we combine these aspects through an examination of how weather conditions affect predation risk by modifying the spatial behavior of the prey. We used reindeer calves (Rangifer tarandus) in Norway to investigate (1) the environmental causes and (2) the survival consequences of habitat use. We further examined how those relationships varied temporally and according to the body mass of calves. We found that deep snow and ice conditions led reindeer to shift from their usually preferred high-elevation pastures to lowland forested areas. This increase in forest use was associated with lower calf survival, mostly due to elevated lynx (Lynx lynx) predation rates. Golden eagles (Aquila chrysaetos) and wolverines (Gulo gulo) also preyed on calves but their effect was much smaller and not associated with a specific habitat type. The link between climatic conditions, habitat use, and predation changed over the winter season and depended on the body weights of the calves. The effect of harsh weather conditions on reindeer use of forested habitats was stronger towards the end of the winter, which coincides with more deteriorated body conditions and lower food availability on high-elevation pastures, and predation probabilities were higher for smaller individuals. Our study demonstrates that environmental variation importantly affects predator-prey interactions. Key words: ecological trade-off; habitat use; Norwegian semidomestic reindeer; predation rates; predator-prey dynamics; Rangifer tarandus; seasonal environments; ungulate foraging ecology; weather variability.publishedVersio

Climate variability and density-dependent population dynamics: Lessons from a simple High Arctic ecosystem

Ecologists are still puzzled by the diverse population dynamics of herbivorous small mammals that range from high-amplitude, multiannual cycles to stable dynamics. Theory predicts that this diversity results from combinations of climatic seasonality, weather stochasticity, and density-dependent food web interactions. The almost ubiquitous 3- to 5-y cycles in boreal and arctic climates may theoretically result from bottom-up (plant–herbivore) and top-down (predator–prey) interactions. Assessing, empirically, the roles of such interactions and how they are influenced by environmental stochasticity has been hampered by food web complexity. Here, we take advantage of a uniquely simple High Arctic food web, which allowed us to analyze the dynamics of a graminivorous vole population not subjected to top-down regulation. This population exhibited high-amplitude, noncyclic fluctuations—partly driven by weather stochasticity. However, the predominant driver of the dynamics was overcompensatory density dependence in winter that caused the population to frequently crash. Model simulations showed that the seasonal pattern of density dependence would yield regular 2-y cycles in the absence of stochasticity. While such short cycles have not yet been observed in mammals, they are theoretically plausible if graminivorous vole populations are deterministically bottom-up regulated. When incorporating weather stochasticity in the model simulations, cyclicity became disrupted and the amplitude was increased—akin to the observed dynamics. Our findings contrast with the 3- to 5-y population cycles that are typical of graminivorous small mammals in more complex food webs, suggesting that top-down regulation is normally an important component of such dynamics

Berettiget kritikk av NMBU sin reindriftsforskning

Source at https://forskersonen.no/akademia-debattinnlegg-dyrevelferd/berettiget-kritikk-av-nmbu-sin-reindriftsforskning/1956081Det er flere elementer i artikkelen til NMBU-forskerne som fremstår som uforenlig med god vitenskapelig praksis

Rangifer management controls a climate-sensitive tundra state transition

Source at https://doi.org/10.1002/eap.1618 .Rangifer (caribou/reindeer) management has been suggested to mitigate the temperature- driven transition of Arctic tundra into a shrubland state, yet how this happens is uncertain. Here we study this much focused ecosystem state transition in riparian areas, where palatable willows (Salix) are dominant tall shrubs and highly responsive to climate change. For the state transition to take place, small life stages must become tall and abundant. Therefore we predicted that the performance of small life stages (potential recruits) of the tall shrubs were instrumental to the focal transition, where Rangifer managed at high population density would keep the small-stage shrubs in a “browse trap” independent of summer temperature. We used a large-scale quasi-experimental study design that included real management units that spanned a wide range of Rangifer population densities and summer temperatures in order to assess the relative importance of these two driving variables. Ground surveys provided data on density and height of the small shrub life stages, while the distributional limit (shrubline) of established shrublands (the tall shrub life stage) was derived from aerial photographs. Where Rangifer densities were above a threshold of approximately 5 animals/km2, we found, in accordance with the expectation of a “browse trap,” that the small life stages of shrubs in grasslands were at low height and low abundance. At Rangifer densities below this threshold, the small life stages of shrubs were taller and more abundant indicating Rangifer were no longer in control of the grassland state. For the established shrubland state, we found that the shrubline was at a 100- m lower elevation in the management units where Rangifer had been browsing in summer as opposed to the migratory ranges with no browsing in summer. In both seasonal ranges, the shrubline increased 100 m per 1°C increment in temperature. Our study supports the proposal that Rangifer management within a sustainable range of animal densities can mitigate the much-focused transition from grassland to shrubland in a warming Arctic. browse trap; browsing; climate change; life history stage; plant–herbivore interactions; Salix; shrub growth; shrubline; summer temperature

Disturbance, recovery and tundra vegetation change : Final report project 17/92 - to Svalbard Environmental Protection Fund

Preprin

Effect of scavenging on predation in a food web

The fasting endurance hypothesis (FEH) predicts strong selection for large body size in mammals living in environments where food supply is interrupted over prolonged periods of time. The Arctic is a highly seasonal and food-restricted environment, but contrary to predictions from the FEH, empirical evidence shows that Arctic mammals are often smaller than their temperate conspecifics. Intraspecific studies integrating physiology and behaviour of different-sized individuals may shed light on this paradox. We tested the FEH in free-living Svalbard reindeer Rangifer tarandus platyrhynchus. We measured daily energy expenditure (DEE), subcutaneous body temperature (Tsc) and activity levels during the late winter in 14 adult females with body masses ranging from 46.3 to 57.8 kg. Winter energy expenditure (WEE) and fasting endurance (FE) were modelled dynamically by combining these data with body composition measurements of culled individuals at the onset of winter (14 years, n = 140) and variation in activity level throughout winter (10 years, n = 70). Mean DEE was 6.3 ± 0.7 MJ/day. Lean mass, Tsc and activity had significantly positive effects on DEE. Across all 140 individuals, mean FE was 85 ± 17 days (range 48–137 days). In contrast to the predictions of the FEH, the dominant factor affecting FE was initial fat mass, while body mass and FE were not correlated. Furthermore, lean mass and fat mass were not correlated. FE was on average 80% (45 days) longer in fat than lean individuals of the same size. Reducing activity levels by ~16% or Tsc by ~5% increased FE by 7% and 4% respectively. Our results fail to support the FEH. Rather, we demonstrate that (a) the size of fat reserves can be independent of lean mass and body size within a species, (b) ecological and environmental variation influence FE via their effects on body composition and (c) physiological and behavioural adjustments can improve FE within individuals. Altogether, our results suggest that there is a selection in Svalbard reindeer to accumulate body fat, rather than to grow structurally large. </ol

Effekter på økosystemer og biologisk mangfold : klimaendringer i norsk Arktis : NorACIA delutredning 3

The Norwegian Polar Institute is Norway’s main institution for research, monitoring and topographic mapping in Norwegian polar regions.The institute also advises Norwegian authorities on matters concerning polar environmental management