Klemen Jerina

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

Habitat suitability modelling for red deer (Cervus elaphus L.) in South-central Slovenia with classification trees

We study and assess the potential habitats of a population of red deer in South-central Slovenia. Using existing data on the deer population spatial distribution and size, as well as data on the landscape and ecological properties (GIS) of the area inhabited by this population, we develop a habitat suitability model by automated data analysis using machine learning of classification trees. We assume that the recorded observations of deer approximate the actual spatial distribution of the deer population reasonably well. The habitat suitability models for individual animals have the form of classification trees. The induced trees are interpreted by domain experts and a generic model is proposed. The generic habitat suitability models can help determine potential unoccupied habitats for the red deer population and develop guidelines for managing the development of the red deer population and its influence on the environment.

Long-term changes of structure and tree species composition in Dinaric uneven-aged forests: are red deer an important factor?

Uneven-aged silver fir-European beech forest stands were studied to (1) analyse the dynamics of diameter structure and tree species composition in the past two centuries and (2) determine the impact of red deer on the regeneration and recruitment of silver fir. The study used current data on forest stands, archival data from old forest management plans for the period 1789–2004, and red deer harvesting records for the period 1907–2006. During the observation period, the silver fir population aged and silver fir and European beech alternated in dominance. The study revealed a strong impact of red deer on the composition and recruitment of tree regeneration, especially on silver fir regeneration. The drastic changes in red deer density (from extermination up to 5.8 animals km−2) and past forest management practices were apparently the main factors driving the population dynamics of silver fir (regeneration, recruitment, and diameter structure) in the study area during the past two centuries.

Modeling the brown bear population in Slovenia: A tool in the conservation management of a threatened species

In this paper, we address three aspects of the brown bear population in Slovenia: its size (and its evolution over time), its spatial expansion out of the core area, and its potential habitat based on natural habitat suitability. Data collected through measurement/observation of the bear population and from the literature are used. A model is developed for each aspect. The results are estimates of population size, a picture of the spatial expansion of the population and maps of its optimal and maximal potential habitat (based on natural suitability). Overall, the brown bear population has been increasing since the establishment of a core protective area and has been expanding outside this area. The habitat suitability maps show that there is room for further expansion. Based on habitat suitability and bear population density, as well as human activity and current damage reports, we recommend that the Alps should be temporarily kept free of the bears, until the necessary mitigation measures regarding human–bear conflicts are carried out. On the other hand it is of crucial importance to adapt human activities and improve bear management in the optimal habitat, with which the goals of successful conservation of the species might be achieved.

Monitoring the effective population size of a brown bear (Ursus arctos) population using new single-sample approaches.

The effective population size (Ne) could be the ideal parameter for monitoring populations of conservation concern as it conveniently summarizes both the evolutionary potential of the population and its sensitivity to genetic stochasticity. However, tracing its change through time is difficult in natural populations. We applied four new methods for estimating Ne from a single sample of genotypes to trace temporal change in Ne for bears in the Northern Dinaric Mountains. We genotyped 510 bears using 20 microsatellite loci and determined their age. The samples were organized into cohorts with regard to the year when the animals were born and yearly samples with age categories for every year when they were alive. We used the Estimator by Parentage Assignment (EPA) to directly estimate both Ne and generation interval for each yearly sample. For cohorts, we estimated the effective number of breeders (Nb) using linkage disequilibrium, sibship assignment and approximate Bayesian computation methods and extrapolated these estimates to Ne using the generation interval. The Ne estimate by EPA is 276 (183–350 95% CI), meeting the inbreeding‐avoidance criterion of Ne > 50 but short of the long‐term minimum viable population goal of Ne > 500. The results obtained by the other methods are highly consistent with this result, and all indicate a rapid increase in Ne probably in the late 1990s and early 2000s. The new single‐sample approaches to the estimation of Ne provide efficient means for including Ne in monitoring frameworks and will be of great importance for future management and conservation.

Roads and supplemental feeding affect home-range size of Slovenian red deer more than natural factors

Abstract Most studies on the relationship between home-range size and composition focus on natural factors, whereas effects of anthropogenic factors are poorly understood. I evaluated effects of multiple natural and anthropogenic habitat factors, population density, and sex on the annual home-range size of red deer (Cervus elaphus) in well-preserved forest areas in the Dinaric Mountains of Slovenia, Europe, based on >11,000 telemetry locations from 17 males and 25 females. Home ranges were 90–2,107 ha and averaged 460 ha. Using a mixed linear model, I estimated that home-range size decreased with increasing 1) red deer density, 2) supplemental feeding intensity, and 3) average annual temperature; 4) home-range size increased as the distance of main roads from the edge of the home range increased; and 5) males had a larger home range than females (580 ha versus 400 ha). These results were explained by effects of food availability (1, 2, and 3), energy expenditure of an individual (4 and 5), intraspecific interactions (1 and 5), and size of unfragmented habitat patches (4) on home-range size. To my knowledge, this is the 1st large mammal study to explicitly show that the density and spatial distribution of roads and supplemental feeding affect home-range size of red deer and that humans can have a greater impact on home-range size and shape than natural habitat factors. Ungulates are often supplementally fed to increase their value to hunters and to reduce forest damage, particularly in Europe; however, this practice can greatly reduce the home-range size, potentially leading to increased disease transmission and competition associated with the higher deer densities around feeding sites, which can result in just the opposite of what was intended.

Supplemental feeding with carrion is not reducing brown bear depredations on sheep in Slovenia

Abstract Supplemental feeding is often believed to be a successful tool for reducing human–bear (Ursus arctos) conflicts, especially in Europe. However, effectiveness of this measure is poorly understood and there is growing concern for potential negative side-effects. This is particularly true for supplemental feeding using livestock carrion. Carrion feeding is considered especially effective in reducing livestock depredations by diverting bears from pastures and meeting their protein needs. In Slovenia, year-round supplementary feeding of bears with livestock carrion and corn was intensive and in some areas practiced for over 100 years. However, in 2004 the use of livestock carrion was banned in accordance with European Union regulations. This provided an opportunity to study the effects of carrion feeding on livestock depredations by bears. We used sheep as they represented 97% of all depredation events by brown bears in Slovenia. We analyzed whether bears selectively used carrion feeding stations over corn feeding stations (i.e., indicating that carrion might be more effective in diverting bears from sheep pastures) during 1994–2011, and compared the annual frequency and seasonal distribution of sheep depredations 5 years before and after the ban on livestock carrion feeding during 1999–2009. We found no support that bears selected carrion feeding sites over feeding sites with corn. When controlled for changes in bear and sheep numbers, there was no indication that the ban on carrion feeding increased sheep depredations. Moreover, complementary data indicated that natural protein sources were considerably more important than livestock carrion and that use of carrion peaked in spring, when sheep are rarely outdoors and thus unavailable for depredation. Because of the observed lack of effectiveness, high costs, and potential negative side-effects, we discourage supplemental feeding with livestock carrion to reduce livestock depredations.

Demography and mortality patterns of removed brown bears in a heavily exploited population

Abstract Harvesting wild animals can affect demographic parameters and life history traits of surviving individuals. Most brown bear (Ursus arctos) populations currently experience low levels of hunting. We characterized mortality patterns in a heavily exploited transboundary brown bear population in Slovenia, Central Europe. Overall, 927 brown bears were reported removed from 1998 to 2008. Most (97%) removals were human caused including removals from hunting (59% of removals), management removals of problem individuals (18%), and vehicle collisions (16%). Median age of bears removed in Slovenia was 2.3 years, and 78% of bears removed were <4 years old. Removal was male-biased overall (59%), mainly due to the high percent (49%) of young (<4 years old) males removed during hunting, a possible consequence of sex-related differences in bear behavior and harvest regulations. However, the effect of sex-biased removal was less than expected based on removal data, and it appears a different harvest regimen in neighboring Croatia and sex-biased dispersal of young bears buffered the demographic effects of selective harvest in Slovenia. We also observed that annual proportion of females in harvests increased with harvest intensity. More males were removed among younger classes, whereas females started to dominate above the age of 8 years. About 20% of the brown bear population was removed annually by legal harvest; this is one of the highest harvest rates reported for this species.

Mating-related movements of male brown bears on the periphery of an expanding population

Abstract Use of habitat and resources of large carnivores living at the expansion front of a population can differ considerably from those living in core areas. Using GPS (global positioning system) telemetry, we studied movements of male brown bears living in the northwest edge of the Alpine–Dinaric–Pindos population in Slovenia and Italy, 2005–08. Because there was a steep gradient of female densities in the periphery of the population and females occurred only in a small portion of the area used by males, we could test how the distribution of breeding females affected the spatial distribution and movements of male brown bears. The home-range size of the males in our study was inversely related to female densities. During the mating season we observed directed movement from the periphery of the population with low female densities toward the core area with higher female densities. Our observations suggest that this strategy allows even males living at the periphery of the population, where no females were know to occur, to take part in reproduction.

Does despotic behavior or food search explain the occurrence of problem brown bears in Europe

Bears foraging near human developments are often presumed to be responding to food shortage, but this explanation ignores social factors, in particular despotism in bears. We analyzed the age distribution and body condition index (BCI) of shot brown bears in relation to densities of bears and people, and whether the shot bears were killed by managers (i.e., problem bears; n = 149), in self-defense (n = 51), or were hunter-killed nonproblem bears (n = 1,896) during 1990–2010. We compared patterns between areas with (Slovenia) and without supplemental feeding (Sweden) of bears relative to 2 hypotheses. The food-search/food-competition hypothesis predicts that problem bears should have a higher BCI (e.g., exploiting easily accessible and/or nutritious human-derived foods) or lower BCI (e.g., because of food shortage) than nonproblem bears, that BCI and human density should have a positive correlation, and problem bear occurrence and seasonal mean BCI of nonproblem bears should have a negative correlation (i.e., more problem bears during years of low food availability). Food competition among bears additionally predicts an inverse relationship between BCI and bear density. The safety-search/naivety hypothesis (i.e., avoiding other bears or lack of human experience) predicts no relationship between BCI and human density, provided no dietary differences due to spatiotemporal habitat use among bears, no relationship between problem bear occurrence and seasonal mean BCI of nonproblem bears, and does not necessarily predict a difference between BCI for problem/nonproblem bears. If food competition or predation avoidance explained bear occurrence near settlements, we predicted younger problem than nonproblem bears and a negative correlation between age and human density. However, if only food search explained bear occurrence near settlements, we predicted no relation between age and problem or nonproblem bear status, or between age and human density. We found no difference in BCI or its variability between problem and nonproblem bears, no relation between BCI and human density, and no correlation between numbers of problem bears shot and seasonal mean BCI for either country. The peak of shot problem bears occurred from April to June in Slovenia and in June in Sweden (i.e., during the mating period when most intraspecific predation occurs and before fall hyperphagia). Problem bears were younger than nonproblem bears, and both problem and nonproblem bears were younger in areas of higher human density. These age differences, in combination with similarities in BCI between problem and nonproblem bears and lack of correlation between BCI and human density, suggested safety-search and naïve dispersal to be the primary mechanisms responsible for bear occurrence near settlements. Younger bears are less competitive, more vulnerable to intraspecific predation, and lack human experience, compared to adults. Body condition was inversely related to the bear density index in Sweden, whereas we found no correlation in Slovenia, suggesting that supplemental feeding may have reduced food competition, in combination with high bear harvest rates. Bears shot in self-defense were older and their BCI did not differ from that of nonproblem bears. Reasons other than food shortage apparently explained why most bears were involved in encounters with people or viewed as problematic near settlements in our study.