Petter Wabakken

Recovery of large carnivores in Europe’s modern human-dominated landscapes

The conservation of large carnivores is a formidable challenge for biodiversity conservation. Using a data set on the past and current status of brown bears (Ursus arctos), Eurasian lynx (Lynx lynx), gray wolves (Canis lupus), and wolverines (Gulo gulo) in European countries, we show that roughly one-third of mainland Europe hosts at least one large carnivore species, with stable or increasing abundance in most cases in 21st-century records. The reasons for this overall conservation success include protective legislation, supportive public opinion, and a variety of practices making coexistence between large carnivores and people possible. The European situation reveals that large carnivores and people can share the same landscape. Many populations of brown bears, lynx, grey wolves, and wolverines persist successfully outside protected areas in Europe. Success for Europes large carnivores? Despite pessimistic forecasts, Europes large carnivores are making a comeback. Chapron et al. report that sustainable populations of brown bear, Eurasian lynx, gray wolf, and wolverine persist in one-third of mainland Europe. Moreover, many individuals and populations are surviving and increasing outside protected areas set aside for wildlife conservation. Coexistence alongside humans has become possible, argue the authors, because of improved public opinion and protective legislation. Science, this issue p. 1517

Rescue of a severely bottlenecked wolf (Canis lupus) population by a single immigrant.

The fragmentation of populations is an increasingly important problem in the conservation of endangered species. Under these conditions, rare migration events may have important effects for the rescue of small and inbred populations. However, the relevance of such migration events to genetically depauperate natural populations is not supported by empirical data. We show here that the genetic diversity of the severely bottlenecked and geographically isolated Scandinavian population of grey wolves (Canis lupus), founded by only two individuals, was recovered by the arrival of a single immigrant. Before the arrival of this immigrant, for several generations the population comprised only a single breeding pack, necessarily involving matings between close relatives and resulting in a subsequent decline in individual heterozygosity. With the arrival of just a single immigrant, there is evidence of increased heterozygosity, significant outbreeding (inbreeding avoidance), a rapid spread of new alleles and exponential population growth. Our results imply that even rare interpopulation migration can lead to the rescue and recovery of isolated and endangered natural populations.

Severe inbreeding depression in a wild wolf Canis lupus population

The difficulty of obtaining pedigrees for wild populations has hampered the possibility of demonstrating inbreeding depression in nature. In a small, naturally restored, wild population of grey wolves in Scandinavia, founded in 1983, we constructed a pedigree for 24 of the 28 breeding pairs established in the period 1983–2002. Ancestry for the breeding animals was determined through a combination of field data (snow tracking and radio telemetry) and DNA microsatellite analysis. The population was founded by only three individuals. The inbreeding coefficient F varied between 0.00 and 0.41 for wolves born during the study period. The number of surviving pups per litter during their first winter after birth was strongly correlated with inbreeding coefficients of pups (R2=0.39, p<0.001). This inbreeding depression was recalculated to match standard estimates of lethal equivalents (2B), corresponding to 6.04 (2.58–9.48, 95% CI) litter-size-reducing equivalents in this wolf population.

Shoot, shovel and shut up: cryptic poaching slows restoration of a large carnivore in Europe

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.

The near extinction and recovery of brown bears in Scandinavia in relation to the bear management policies of Norway and Sweden

Records of bountied brown bears Ursus arctos in Norway and Sweden were analysed to estimate population size in the mid-1800s, and changes in population size and distribution in relation to the bear management policies of both countries. In the mid-1800s about 65% of the bears in Scandinavia were in Norway (perhaps 3,100 in Norway and 1,650 in Sweden). Both countries tried to eliminate the bear in the 1800s; Sweden was more effective. By the turn of the century, the numbers of bears were low in both countries. The lowest population level in the population remnants that have subsequently survived occurred around 1930 and was estimated at 130 bears. Swedens policy was changed at the turn of the century to save the bear from extinction. This policy was successful, and the population is now large and expanding. Norway did not change its policy and bears were virtually eliminated by 1920–30. Since 1975, bear observations increased in Norway. This coincided temporally with an abrupt increase in the Swedish bear population, and bears reappeared sooner in areas closer to the remnant Swedish populations. Both conditions support our conclusion that the bear was virtually exterminated in Norway and suggest that bears observed now are primarily immigrants from Sweden, except for far northern Norway, which was recolonised from Russia and Finland. Today, we estimate that the Scandinavian bear population numbers about 700, with about 2% in Norway (on average about 14 in Norway, 650–700 in Sweden). This is a drastic reduction in the estimate of bears in Norway, compared with earlier studies. The trends in bear numbers responded to the policies in effect. The most effective measures used in Scandinavia to conserve bears were those that reduced or eliminated the economic incentive for people to kill them. Our analysis also suggests that population estimates based on reports from observations made by the general public can be greatly inflated.

Using GPS technology and GIS cluster analyses to estimate kill rates in wolf‐ungulate ecosystems

Abstract Predatory behavior of wolves (Canis lupus) was studied in 2 wolf territories in Scandinavia. We used hourly data from Global Positioning System (GPS)-collared adult wolves in combination with Geographic Information System (GIS) for detailed analyses of movement patterns. We tested the hypothesis that wolves spend 1–2 days close to larger prey such as moose (Alces alces) and reasoned that 1–2 locations per day would be enough to find all larger prey killed by the wolves. In total, the study period comprised 287 days and yielded 6,140 hourly GPS positions, with an average of 21.4±2.4 (SD) daily positions. Depending on the radius used to define clusters, 4,045–5,023 (65.9–81.8%) positions were included in 622–741 GPS-clusters. We investigated all positions within clusters in the field, and 244 (22%) single positions. In total, we found 68 moose and 4 roe deer (Capreolus capreolus) and classified them as wolf-killed within the study period. Another 10–15 moose may have been killed but not found. The GIS analyses indicated the proportion of wolf-killed ungulates included in GPS clusters to be strongly dependent on both number of positions per day and the radius used for defining a set of spatially aggregated GPS positions as a cluster. A higher proportion (78%) of killed prey in clusters based on nighttime (2000–0700) than those based on daytime (0800–1900) positions (41%). Simulation of aerial search during daylight hours for killed moose resulted in a serious underestimation (>60%) as compared to the number of wolf-killed moose found during the study. The average kill rate, corrected for 14% nondetected moose, in the territories was 3.6–4.0 days per killed moose. We concluded that the feeding behavior of wolves in Scandinavia was either different from wolves preying on moose and living at the same latitude in North America, or that estimates of wolf kill rates on moose may have been seriously underestimated in previous North American studies.

Size, trend, distribution and conservation of the brown bear Ursus arctos population in Sweden

Abstract The density of adult (≥3 years) female brown bears Ursus arctos was estimated in two areas of Sweden from ratios of radio-marked and unmarked females consorting with radio-marked adult males during the breeding season. The resulting densities were 1·2 ± 0·81 (95% confidence interval) adult females/1000 km2 in a northern study area and 1·06 ± 3·44 adult females/1000 km2 in a southern area. These estimates were extrapolated to obtain a population estimate for Sweden using relative densities throughout the range of the species in Sweden, based on hunter-kill statistics, and observed rates of reproduction and juvenile and subadult survival. The total population in spring 1991 was estimated to be about 620 bears, with almost all females confined to four geographically separated areas, termed female core areas. A supplementary estimate, based on estimated kill rates of adult females in the study areas, was about 660 bears. Estimates based on hunter kill rates of marked bears gave minimum and maximum estimates of about 300 and 900 bears, respectively. Although these are not confidence intervals of the total population estimate, we believe that the true population size is included within these limits. Densities within the female core areas varied from 50 to 100% of those in similar habitats in European Russia. The bear population in Sweden appeared to have increased at a stable rate of about 1·5% annually during the past 50 years. Mean annual rate of legal harvest during 1943–1991 was estimated to be 5·5% (±2·1% SD), suggesting a maximum sustainable rate of 7·0% for this population. The harvest increased at a rate of 9·6% annually during 1981–1991, and apparently was at the maximum sustainable level during 1987–1991.

Biomedical Protocols for Free-ranging Brown Bears, Gray Wolves, Wolverines and Lynx Editors

PREFACE Compilation of this document was initiated by the Norwegian Directorate for Nature Management in order to establish recommended protocols for capture, chemical immobilization, anesthesia and radiotagging of free-ranging brown bears (Ursus arctos), gray wolves (Canis lupus), wolverines (Gulo gulo) and Eurasian lynx (Lynx lynx). In addition, procedures to ensure proper sampling of biological materials for management, research and banking purposes have been included. The current protocols are based on nearly 3,000 captures of free-ranging brown bears, wolves, wolverines and lynx carried out from 1984 through 2012 in Scandinavia. Some of the results have been published as peer reviewed papers, conference presentations, theses, and reports. However, a large amount of data are still on file and will be published in the future. In addition, comprehensive reviews of the global literature on brown bears, wolves, wolverines and lynx have been carried out in order to include pertinent information from other sources. These protocols have been approved by all ongoing research projects on brown bears, wolves, wolverines and lynx in Scandinavia. We thank the contributors for their cooperative efforts. We also thank the Norwegian Directorate for Nature Management for their support.

Selection for Heterozygosity Gives Hope to a Wild Population of Inbred Wolves

Recent analyses have questioned the usefulness of heterozygosity estimates as measures of the inbreeding coefficient (f), a finding that may have dramatic consequences for the management of endangered populations. We confirm that f and heterozygosity is poorly correlated in a wild and highly inbred wolf population. Yet, our data show that for each level of f, it was the most heterozygous wolves that established themselves as breeders, a selection process that seems to have decelerated the loss of heterozygosity in the population despite a steady increase of f. The markers contributing to the positive relationship between heterozygosity and breeding success were found to be located on different chromosomes, but there was a substantial amount of linkage disequilibrium in the population, indicating that the markers are reflecting heterozygosity over relatively wide genomic regions. Following our results we recommend that management programs of endangered populations include estimates of both f and heterozygosity, as they may contribute with complementary information about population viability.

Effects of hunting group size, snow depth and age on the success of wolves hunting moose

To study factors important to the success of wolves, Canis lupus, hunting moose, Alces alces, we analysed data from more than 4000 km of snow tracking of wolves during 1998e2003 in Scandinavia. We used two methods to estimate hunting success for 17 wolf territories from 185 observations of wolf attacks on moose. On average, hunting success was estimated at 45 and 64% for the two methods, respectively. We used a smaller data set (N ¼ 142) to examine the effect of age of breeding wolves, hunting group size, snow depth and moose density on hunting success. Multiple logistic regression showed that age of breeding males was the only variable significantly related to hunting success, with maximum hunting success at 4.5e5.5þ years of age. We also studied prey selection of radiocollared adult wolves over successive winters in two wolf packs that lost one of the breeding wolves. Whereas the surviving adult female switched to prey on roe deer, Capreolus capreolus, the surviving adult male continued mainly to select moose. Our results suggest that the positive effect of male age on hunting success reflects both increased experience of attacking prey and possibly the greater size of adult male wolves (25e30%) compared to adult female wolves.