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- Chapron, Guillaume, et al.
(författare)
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Estimating wolf (Canis lupus) population size from number of packs and an individual based model
- 2016
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Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800 .- 1872-7026. ; 339, s. 33-44
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Tidskriftsartikel (refereegranskat)abstract
- Estimating wildlife population-size is fundamental for wildlife management and conservation. However, making monitoring of population size less resource demanding while still keeping a high monitoring accuracy and precision remains a recurrent challenge. One proposed alternative to count individuals is to instead focus on counting a segment of the population that is easier to monitor but at the same time well informative on total population size. We show how total population size can be estimated from group counts by using an individual-based population model in a social living species. We developed a wolf (Canis lupus) specific Individual Based Model and used Approximate Bayesian Computation (ABC) to fit this population model to the time series of annual number of packs, reproductions and pairs obtained from Scandinavian monitoring data. Model informative priors were obtained with data from collared individuals by the Scandinavian wolf research project. The fitted model was then used to estimate a conversion factor from number of packs to total number of individuals and to number of reproductions. There was a good fit between the retained simulations by ABC and the observed Scandinavian wolf population trajectory. The fitted simulations returned a conversion factor of 8.0 (95% CI = 6.62-10.07) from number of packs to total population size and of 1.0 (95% CI = 0.93-1.12) to number of reproductions in December. A sensitivity analysis revealed that the conversion factor from packs to total population size was positively correlated with pup survival and litter size and negatively correlated with subadult, vagrant and adult survivals. Using an individual based model allowed us to model the full complexity of demographic traits of a social-living species such as the wolf. The flexibility of the model also meant that the conversion factor could be estimated for any month during the year. Our approach to estimate total population size from counts of groups requires having a population model where both individuals and groups are explicitly described and can be applied to other wolf populations and group-living species where counting all individuals over a large area is unfeasible.
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| 2. |
- Chapron, Guillaume, et al.
(författare)
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Habitat segregation between brown bears and gray wolves in a human-dominated landscape
- 2018
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Ingår i: Ecology and Evolution. - : Wiley. - 2045-7758. ; 8, s. 11450-11466
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Tidskriftsartikel (refereegranskat)abstract
- Identifying how sympatric species belonging to the same guild coexist is a major question of community ecology and conservation. Habitat segregation between two species might help reduce the effects of interspecific competition and apex predators are of special interest in this context, because their interactions can have consequences for lower trophic levels. However, habitat segregation between sympatric large carnivores has seldom been studied. Based on monitoring of 53 brown bears (Ursus arctos) and seven sympatric adult gray wolves (Canis lupus) equipped with GPS collars in Sweden, we analyzed the degree of interspecific segregation in habitat selection within their home ranges in both late winter and spring, when their diets overlap the most. We used the K-select method, a multivariate approach that relies on the concept of ecological niche, and randomization methods to quantify habitat segregation between bears and wolves. Habitat segregation between bears and wolves was greater than expected by chance. Wolves tended to select for moose occurrence, young forests, and rugged terrain more than bears, which likely reflects the different requirements of an omnivore (bear) and an obligate carnivore (wolf). However, both species generally avoided human-related habitats during daytime. Disentangling the mechanisms that can drive interspecific interactions at different spatial scales is essential for understanding how sympatric large carnivores occur and coexist in human-dominated landscapes, and how coexistence may affect lower trophic levels. The individual variation in habitat selection detected in our study may be a relevant mechanism to overcome intraguild competition and facilitate coexistence.
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| 3. |
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| 4. |
- Liberg, Olof, et al.
(författare)
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An updated synthesis on appropriate science-based criteria for "favourable reference population" of the Scandinavian wolf (Canis lupus) population : Assignment from the Swedish Environmental Protection Agency (SEPA)
- 2015
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This report provides an updated synthesis on appropriate science-based criteria for "favourable reference population" FRP for the Scandinavian wolf (Canis lupus) population and present quantitative values on FRP. The assignment was given by the Swedish Environmental Protection Agency to the SKANDULV research group at Grimsö, SLU, Sweden. A thorough review of the ecology and genetics of the wolf population is provided, including measurements of inbreeding depression in the population. Results from earlier MVP analyses of the Scandinavian wolf population are presented, as are former suggestions of FRP or other management goals for the population. A consensus was not possible to achieve among all involved scientist, the results are therefore presented in two different parts. OL, CW, øF, PW and HS suggest that the population value for FRP should be 340 for Scandinavia, and 300 for Sweden. They argue that this Scandinavian sub-population should be connected to a larger meta-population with the minimum size of Ne=500, corresponding to approximately 1700 wolves, and the connection should be minimum one immigrant from the large meta-population to the Scandinavian wolf population per generation. They acknowledge a meta-population that includes also wolves living outside of EU territory, as long as there is the stipulated connectivity. GC evaluated FCS based on a strict interpretation of Habitats Directive informed by previous rulings by the European Court of Justice and documents from the European Commission. He finds that if Sweden cannot include wolves from outside its national territory to fulfill its obligations under the Habitats Directive, FCS will be achieved at 1700 wolves (Ne=500) or at the country carrying capacity. If on the contrary Sweden can include wolves living in a separate population from another country to fulfill its obligations under the Habitats Directive, FCS will be achieved at half the country carrying capacity (preliminarily estimated at 1200/2=600 wolves) or more according to the connectivity naturally achieved. Non EU Member States cannot contribute to this meta-population. There was consensus between all researchers that the target for the population inbreeding coefficient should be 0.2 or lower.
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| 5. |
- Wikenros, Camilla, et al.
(författare)
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Response of Moose Hunters to Predation following Wolf Return in Sweden
- 2015
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundPredation and hunter harvest constitute the main mortality factors affecting the size and dynamics of many exploited populations. The re-colonization by wolves (Canis lupus) of the Scandinavian Peninsula may therefore substantially reduce hunter harvest of moose (Alces alces), the main prey of wolves.Methodology/Principal findingsWe examined possible effects of wolf presence on hunter harvest in areas where we had data before and after wolf establishment (n = 25), and in additional areas that had been continuously exposed to wolf predation during at least ten years (n = 43). There was a general reduction in the total number of moose harvested (n = 31,827) during the ten year study period in all areas irrespective of presence of wolves or not. However, the reduction in hunter harvest was stronger within wolf territories compared to control areas without wolves. The reduction in harvest was larger in small (500-800 km(2)) compared to large (1,200-1,800 km(2)) wolf territories. In areas with newly established wolf territories moose management appeared to be adaptive with regard to both managers (hunting quotas) and to hunters (actual harvest). In these areas an instant reduction in moose harvest over-compensated the estimated number of moose killed annually by wolves and the composition of the hunted animals changed towards a lower proportion of adult females.Conclusions/SignificanceWe show that the re-colonization of wolves may result in an almost instant functional response by another large predator-humans-that reduced the potential for a direct numerical effect on the density of wolves' main prey, the moose. Because most of the worlds' habitat that will be available for future colonization by large predators are likely to be strongly influenced by humans, human behavioural responses may constitute a key trait that govern the impact of large predators on their prey.
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