IUCN / SSC Cat Specialist Group - Digital Cat Library |
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| Nilsson, T. | |
| Population viability analyses of the Scandinavian populations of bear (_Ursus arctos_), lynx _(Lynx lynx_) and wolverine (_Gulo gulo_) | |
| 2013 Full Book | |
Population viability analyses have been performed concerning populations of bear, lynx and wolverine. The main purpose of these analyses was to form part of the scientific basis for Sweden's reporting to the European Commission according to the Habitats Directive. Estimates of minimum viable population size (MVP) under the long-term viability criterion of a genetically effective population size (Ne) exceeding 500 were derived in two different ways: using empirical estimates of rates of loss of genetic variation, when such data were available, and otherwise using computer simulations with the program Vortex. The possibility of setting Favour-able Reference Population (FRP) values by partitioning these long-term MVP estimates between neighbouring countries is discussed, and the following tentative FRP values for Sweden are suggested: 800 lynx, 2 800 bears, and 500 wolverines. Population viability was also analyzed in relation to five different short-term viability criteria. Moderate uncertainty in the input parameters describing the ecology and genetics of a population may lead to very high uncertainty in the estimated extinction risk, and also in the resulting MVP values. A crucial challenge for conservation biologists is to make this uncertainty in MVP estimates clear and comprehensible to decision-makers and other non-experts. I developed a series of alter-native scenarios for each population, with slightly different input parameters, and estimated separate MVP values for each scenario. Under the MVP criterion of < 10 % extinction risk in 100 years, the MVP estimates derived from different scenarios ranged between 25 and 65 for bear, between 90 and 700 for wolverine, and between 30 and 1 500 for lynx. If one chooses to focus on estimates from the most likely scenarios, but with catastrophes included, and then among scenarios representing different geographical areas chooses the highest estimate for each species, those MVP estimates were 35 for bear, 210 for lynx and 150 for wolverine, under the < 10 % extinction risk criterion. Compared to the other four short-term viability criteria, < 10 % extinction risk in 100 years was the criterion giving the lowest MVP estimates. In most cases, short-term genetic MVP values were higher than the short-term extinction risk MVP values; hence, populations meeting the extinction risk criteria will often not fulfil the genetic MVP criteria. Under the short-term genetic MVP criterion of < 5 % loss of genetic variation in 100 years, the MVP estimates derived from different scenarios varied between 900 and 1 300 for bear, between 370 and 1 300 for wolverine, and between 280 and 1 700 for lynx. If one chooses to focus on estimates from the most likely scenarios, but with catastrophes included, and then among scenarios representing different geographical areas chooses the highest estimate for each species, those MVP estimates were 1 100 for bear, 700 for lynx and 500 for wolverine, under the criterion of < 5 % loss of genetic variation in 100 years. The author alone is responsible for the contents of the report; hence, the views and conclusions presented should not be taken as or referred to as the views or position of the Swedish Environmental Protection Agency. |
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