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| 2. |
- 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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| 3. |
- 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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| 5. |
- Chapron, Guillaume, et al.
(författare)
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Unravelling the Scientific Debate on How to Address Wolf-Dog Hybridization in Europe
- 2019
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Ingår i: Frontiers in Ecology and Evolution. - : Frontiers Media SA. - 2296-701X. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- Anthropogenic hybridization is widely perceived as a threat to the conservation of biodiversity. Nevertheless, to date, relevant policy and management interventions are unresolved and highly convoluted. While this is due to the inherent complexity of the issue, we hereby hypothesize that a lack of agreement concerning management goals and approaches, within the scientific community, may explain the lack of social awareness on this phenomenon, and the absence of effective pressure on decision-makers. By focusing on wolf x dog hybridization in Europe, we hereby (a) assess the state of the art of issues on wolf x dog hybridization within the scientific community, (b) assess the conceptual bases for different viewpoints, and (c) provide a conceptual framework aiming at reducing the disagreements. We adopted the Delphi technique, involving a three-round iterative survey addressed to a selected sample of experts who published at Web of Science listed journals, in the last 10 years on wolf x dog hybridization and related topics. Consensus was reached that admixed individuals should always be defined according to their genetic profile, and that a reference threshold for admixture (i.e., q-value in assignment tests) should be formally adopted for their identification. Tomitigate hybridization, experts agreed on adopting preventive, proactive and, when concerning small and recovering wolf populations, reactive interventions. Overall, experts' consensus waned as the issues addressed became increasingly practical, including the adoption of lethal removal. We suggest three non-mutually exclusive explanations for this trend: (i) value-laden viewpoints increasingly emerge when addressing practical issues, and are particularly diverging between experts with different disciplinary backgrounds (e.g., ecologists, geneticists); (ii) some experts prefer avoiding the risk of potentially giving carte blanche to wolf opponents to (illegally) remove wolves, based on the wolf x dog hybridization issue; (iii) room for subjective interpretation and opinions result from the paucity of data on the effectiveness of different management interventions. These results have management implications and reveal gaps in the knowledge on a wide spectrum of issues related not only to the management of anthropogenic hybridization, but also to the role of ethical values and real-world management concerns in the scientific debate.
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| 6. |
- Jonzén, Niclas, et al.
(författare)
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Sharing the bounty-Adjusting harvest to predator return in the Scandinavian human-wolf-bear-moose system
- 2013
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Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800 .- 1872-7026. ; 265, s. 140-148
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Tidskriftsartikel (refereegranskat)abstract
- The increase and range extension of wolves (Canis lupus L) and brown bears ( Ursus arctos L) in Scandinavia inevitably impacts moose (Alces alces L.) populations and, as a consequence, the size and composition of the hunter harvest must be adjusted. We used a sex- and age-structured moose population model to delineate optimal harvest strategies under predation and to compare the resulting harvest composition with the strategy commonly implemented in practice. We examined how much moose density or adult sex ratio needs to change to fully compensate for losses to predation. We found a harvest allocation pattern in commonly used practical management across calves, bulls and cows that indicated a trade-off strategy between maximising the number of shot moose, the yield biomass and the number of shot prime bulls. This strategy performed quite well with respect to all yield measures and yielded an age structure most similar to the strategies maximising harvest biomass and prime bulls. Unless predation pressure was very high, the harvest loss could be completely compensated for by allowing a higher moose density. In other situations the current hunting strategy was not possible to implement and the moose density needed to sustain predation even without hunting increases dramatically. An alternative option to balance the predation loss was to accept a more female-biased sex ratio in the winter population. Hence, it may be possible to keep 50% calves in the harvest and still obtain the same total harvest if the proportion of bulls in the harvest is increased to compensate for predation. The increase of large carnivores competing with moose hunting creates conflicts and will inevitably reduce harvest yield unless hunting strategies change. We show how increased moose density and redistribution of the harvest towards bulls can mitigate this conflict and we provide a web-based tool, where stakeholders can compare the long-term effects of alternative management decisions and eventually adjust their hunting strategy accordingly. (C) 2013 Elsevier B.V. All rights reserved.
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| 7. |
- 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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| 9. |
- Liberg, Olof, et al.
(författare)
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Shoot, shovel and shut up: cryptic poaching slows restoration of a large carnivore in Europe
- 2012
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Ingår i: Proceedings of the Royal Society B: Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 279, s. 910-915
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Tidskriftsartikel (refereegranskat)abstract
- Poaching is a widespread and well-appreciated problem for the conservation of many threatened species. Because poaching is illegal, there is strong incentive for poachers to conceal their activities, and consequently, little data on the effects of poaching on population dynamics are available. Quantifying poaching mortality should be a required knowledge when developing conservation plans for endangered species but is hampered by methodological challenges. We show that rigorous estimates of the effects of poaching relative to other sources of mortality can be obtained with a hierarchical state space model combined with multiple sources of data. Using the Scandinavian wolf (Canis lupus) population as an illustrative example, we show that poaching accounted for approximately half of total mortality and more than two-thirds of total poaching remained undetected by conventional methods, a source of mortality we term as 'cryptic poaching'. Our simulations suggest that without poaching during the past decade, the population would have been almost four times as large in 2009. Such a severe impact of poaching on population recovery may be widespread among large carnivores. We believe that conservation strategies for large carnivores considering only observed data may not be adequate and should be revised by including and quantifying cryptic poaching.
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| 10. |
- Sand, Håkan, et al.
(författare)
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Beräkningar av beskattning av den svenska vargpopulationen 2017
- 2016
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Sammanfattning Tre olika modeller har använts för att beräkna sambandet mellan jaktuttag och populationens storlek efter en eventuell jakt under perioden 1/5 2016 till 30/4 2017. Beräkningarna visar sambandet mellan storleken på jaktuttaget under denna period och storleken på den kvarvarande populationen jämfört med populationens nivå efter jakten vintern 2016 (312, vargar, 95% CI = 241 - 414). Samtliga modeller visar på relativt god överensstämmelse i resultaten av det beräknade uttaget. Modell 1 använder data från de senaste 10 åren för att beräkna medeltillväxten i populationen inklusive det antal djur som har fällts under olika former av legal jakt. Modell 2 är en åldersstrukturerad s.k. Leslie matrix där medelvärden och standardavikelser på reproduktion och dödlighet är inlagda. Data på dödlighet i modellen erhålls från radiomärkta vargar och data på kullstorlek tas från snöspårningsdata vid vinterns början. Modell 3 som bygger på s.k. bayesisk statistik visar att föregående års prognos inte kunde förutsäga förändringen i populationens numerär. Gemensamt för resultaten från samtliga tre modeller är att det finns en betydande osäkerhet i kommande års tillväxt och därmed för utfallet av ett eventuellt jaktuttag på populationen storlek. Det betyder att om tillväxten för 2016/17 ligger inom den lägre delen av det beräknade intervallet finns det inget utrymme för jakt alls medan man kan ha en relativt hög beskattning om tillväxten uppgår till den högre delen av detta intervall. En genomgång av förändringar i populationens sammansättning under de fem senaste åren uppvisar inga tydliga samband med populationstillväxten för samma år. Materialet visar dock på en sjunkande trend av antalet nybildade revirmarkerande par i populationen fram till 2014/15. Det senaste året har det dock skett en liten uppgång för antal nybildade par vilket troligen kommer att få en positiv effekt på antalet familjegrupper till kommande säsong. En genomgång av jaktuttaget på enskilda kategorier av djur under 2015/2016 visar att vuxna reproducerande djur i jaktuttaget utgjorde en lägre andel än deras förekomst i populationen och kan inte förklara den relativt sett låga tillväxten för det senaste året. Det finns heller inga tecken på att det har genomförts en lägre inventeringsinsats under det senaste året eller att inavelsgraden har ökat i populationen. En ovanligt hög tillväxt i Norge under det sista året antyder att det inte rör sig om någon övergripande faktor som inverkar negativt på populationen som helhet. Nedgången i den svenska delen av populationen under det sista året är därför troligen en kombination av faktorer såsom legal jakt, illegal jakt samt demografiska slumpeffekter.
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