The effects of traffic on large carnivore populations in Croatia

Sheep and wolves: Is the occurrence of large predators a limiting factor for sheep grazing in the Czech Carpathians?

BackgroundOne of the classic approaches in environmental economics is the environmental Kuznets curve, which predicts that when a national economy grows from low to medium levels, threats to biodiversity conservation increase, but they decrease when the economy moves from medium to high. We evaluated this approach by examining how population densities of the brown bear (Ursus arctos), gray wolf (Canis lupus), and Eurasian lynx (Lynx lynx) were related to the national economy in 24 European countries.Methodology/Principal findingsWe used forest proportions, the existence of a compensation system, and country group (former socialist countries, Nordic countries, other countries) as covariates in a linear model with the first- and the second-order polynomial terms of per capita gross domestic product (GDP). Country group was treated as a random factor, but remained insignificant and was ignored. All models concerning brown bear and wolf provided evidence that population densities decreased with increasing GDP, but densities of lynx were virtually independent of GDP. Models for the wolf explained >80% of the variation in densities, without a difference between the models with all independent variables and the model with only GDP. For the bear, the model with GDP alone accounted for 10%, and all three variables 33%, of the variation in densities.ConclusionsWolves exhibit a higher capacity for dispersal and reproduction than bear or lynx, but still exists at the lowest densities in wealthy European countries. We are aware that several other factors, not available for our models, influenced large carnivore densities. Based on the pronounced differences among large carnivore species in their countrywide relationships between densities and GDP, and a strikingly high relationship for the gray wolf, we suggest that our results reflected differences in political history and public acceptance of these species among countries. The compensation paid for the damages caused by the carnivores is not a key to higher carnivore densities, but might be necessity for the presence of large carnivores to be accepted in countries with high GDP.

Through killing and instilling fear in their prey, large terrestrial carnivores shape the structure and function of ecosystems globally. Most large carnivore species have experienced severe range and population declines due to human activities, and many are now threatened with extinction. Consequently, the impacts of these predators on food webs have been diminished or lost completely from many ecosystems. Kill rates provide a fundamental metric for understanding large carnivore ecology and assessing and comparing predation within and across ecological communities. Our systematic review of large terrestrial mammalian carnivore kill rates reveals significant positive geographic (North America, Europe, and Africa) and taxonomic (grey wolf Canis lupus, puma Puma concolor, lion Panthera leo, and Eurasian lynx Lynx lynx) bias, with most studies apparently motivated by human-carnivore conflict over access to ungulate prey and wildlife management objectives. Our current understanding of the behaviour and functional roles of many large carnivore species and populations thus remains limited. By synthesising and comparing kill rates, we show that solitary carnivores (e.g. brown bears Ursus arctos and most felids) exhibit higher per capita kill rates than social carnivores. However, ungulate predation by bears is typically limited to predation of neonates during a short period. Lower per capita kill rates by social carnivores suggests group living significantly reduces energetic demands, or, alternatively, that group-living carnivores defend and consume a greater proportion of large prey carcasses, or may acquire more food through other means (e.g. scavenging, kleptoparasitism) than solitary hunters. Kill and consumption rates for Canidae - measured as kilograms of prey per kilogram of carnivore per day - are positively correlated with body mass, consistent with increasing energy costs associated with a cursorial hunting strategy. By contrast, ambush predators such as felids show an opposite trend, and thus the potential energetic advantage of an ambush hunting strategy for carnivores as body mass increases. Additionally, ungulate kill rates remain relatively constant across solitary felid body sizes, indicative of energetic constraints and optimal foraging. Kill rate estimates also reveal potential insights into trophic structuring within carnivore guilds, with subordinate carnivores often killing more than their larger counterparts, which may be indicative of having to cope with food losses to scavengers and dominant competitors. Subordinate carnivores may thus serve an important role in provisioning food to other trophic levels within their respective ecosystems. Importantly, kill rates also clarify misconceptions around the predatory behaviour of carnivores (e.g. spotted hyaenas Crocuta crocuta and wolverines Gulo gulo are often considered scavengers rather than the capable hunters that they are) and thus the potential impacts of various carnivore species on their ecological communities. Despite the importance of kill rates in understanding predator-prey interactions, their utility is not widely recognised, and insufficient research limits our ability to fully appreciate and predict the consequences of modified predation regimes, justify current management actions affecting carnivores, or inform effective conservation measures. Together with other important research on predator-prey interactions, robust kill rate studies that address the research deficiencies we highlight will provide a deeper understanding of the foraging behaviours and potential ecosystem impacts of many of the world's carnivores, thus aiding effective conservation and management actions.

INTRODUCTION Norway and Sweden share the Scandinavian Peninsula and the people have similar languages, customs and lifestyles. Nevertheless, the situation regarding large carnivores, their depredations and the schemes devised to deal with these problems differ greatly. We view these two countries almost as ‘replicates’ to give us insight into how different types of livestock husbandry affect depredation levels and to compare compensation schemes. We will concentrate on sheep ( Ovis aries ) and semi-domestic reindeer ( Rangifer tarandus ) and will not consider predation on wild large game. THE SPECIES OF LARGE CARNIVORES Sweden and Norway have four species of large carnivores: the grey wolf ( Canis lupus ), wolverine ( Gulo gulo ), brown bear ( Ursus arctos ) and Eurasian lynx ( Lynx lynx ). All have been subject to lethal control since the seventeenth and eighteenth centuries with high state-financed bounties. The official policy was extermination, and this occurred over large areas. After official policies changed, the bounties were removed, and populations of all four species increased in size and distribution. Present policies include maintaining or promoting viable populations, balanced with mitigating losses they cause to farm livestock (primarily sheep), semi-domestic reindeer, hunting dogs, and large game animals (primarily moose ( Alces alces ) and roe deer ( Capreolus capreolus )). The wolf originally occurred over all of Scandinavia. During the early nineteenth century about 500 were killed annually, but it was exterminated from Scandinavia in the late 1960s. In 1982 a few wolves were observed in south-central Sweden/Norway. They reproduced in 1983.

In the last decades, large carnivores – the grey wolf (Canis lupus), Eurasian lynx (Lynx lynx) and brown bear (Ursus arctos), and to a certain extent also the wildcat (Felis silvestris) – have increased their distribution ranges throughout Europe. Monitoring of their current distribution and population trends in the Czech Republic is crucial for the effective conservation and elimination of possible conflicts with humans in the future. In the last years, many projects focused on small-scale monitoring of large carnivores were implemented in the Czech Republic and the neighbouring mountain ranges of Slovakia. Using their results, we compiled the dataset from different regions and analysed the recent distribution of large carnivores and the wildcat. The distribution maps are based on verified data on the presence and reproduction in 2012–2016. This is consistent with the standardized methodology used across Europe. The Eurasian lynx was the most widespread of all large carnivore species in the Czech Republic, with the two trans-boundary populations (Carpathian and Bohemian-Bavarian-Austrian) occupying 94 out of 868 squares (10.8%) of the mapping grid of the Czech Republic. Reproduction was confirmed in 46.8% of the occupied squares. The grey wolf occupied 6.8% of the squares in the Czech Republic and its reproduction was confirmed in 10.2% of the occupied squares. Three reproducing packs belonging to the Central European lowland population were confirmed and the area occupied by the species increased three times within the study period. The brown bear occupied 2.8% of the squares of the Czech Republic – the area is restricted to the Carpathians – with no signs of reproduction; its distribution fluctuated heavily during the study period. The wildcat occupied the smallest range of the Czech Republic among the studied species (1.4% of the squares) but its reproduction was confirmed in a trans-boundary area (White Carpathians) at the Slovakian side of the border. The wildcat also significantly increased its range from one to six squares during the study period.

Wild carnivores may be important sources of emerging zoonotic pathogens worldwide, however, specific data concerning their presence in large carnivores are limited. The genus Trypanosoma (protozoan parasites) comprises numerous species adapted to all classes of vertebrates. This genus includes highly pathogenic species, such as T. brucei ssp., T. congolense or T. vivax. The aim of this study was to expand on the ecological or zoonotic significance of detecting Trypanosoma in large carnivores. Samples from free-living carnivores (n = 26) were collected. The diversity and occurrence of Trypanosoma species among wildlife in Europe were investigated through the analysis of 18S rRNA gene sequences. The phylogenetic analysis showed three new haplotypes of the 18S rRNA gene of Trypanosoma sp. isolated from two grey wolves (Canis lupus) and two brown bears (Ursus arctos). To the best of our knowledge, this this study represents the first detection of trypanosomes in large carnivores in Europe. The detection of Trypanosoma sp. was achieved through nested- PCR amplification. Furthermore, the identification of new haplotypes of these protozoan highlights variability within Trypanosoma sp., which could lead to the emergence of new, potentially more virulent variants of these parasites in wild animal populations, posing a potential threat to their health. Moreover, these findings underscore the need for further research to comprehensively understand the diversity, distribution, and potential impact of Trypanosoma species on the populations of large carnivores.

Conservation of biodiversity is rapidly changing as a result of increased impact of human activity on the natural world. At the beginning of a new epoch - the Anthropocene - the cumulative effect of population growth and natural resource consumption has left no corner of the planet unaffected by humans. Impacts can be observed on a global scale, such as climate change, ocean acidification, and nitrification and also on a local scale including habitat destruction, community composition, and pollution. These impacts are restructuring ecosystems into novel systems that require creative approaches to conserve ecosystem processes and maintain biodiversity. Large mammalian carnivores represent a clade of organisms that has a varied ability to survive in human dominated landscapes. For my dissertation, I examined community structure, movement, and abundance of brown bears (Ursus arctos arctos), gray wolves (Canis lupus), and Caucasian lynx (Lynx lynx dinniki) in a human dominated landscape in eastern Turkey. From 2013-2016, I surveyed for all medium-large mammal species using remote cameras deployed in a fragmented forest patch near Sarikamis, Turkey. Occupancy estimates reveal a mammal community dominated by large carnivores, humans and livestock, and lacking a natural prey base. During 2011-2016, I collared 28 bears, 11 wolves and 2 lynx and used species-specific seasonal resource selection functions to assess habitat selection patterns. I found that all three species use of habitat varies between seasons and is strongly linked to elevation and slope. By identifying critical habitat for all three species, I have prioritized a specific area for conservation efforts in the future. To estimate the minimum population size of brown bears in my main study area, during 2013-2015, I used scat detection dogs to collect 1,520 bear scat samples for genetic analysis, and using 8 polymorphic microsatellite loci, I identified 27 unique multilocus genotypes and expected heterozygosity of 0.70 as a proxy of genetic diversity. I also conducted opinion surveys in 2014 and combined results with surveys conducted 2006 and 2010 to understand the perspective of the local community about large carnivores. Lastly, I propose a prioritized list of future conservation plans for large carnivore conservation in the human-dominated landscape of Sarikamis Forest, eastern Anatolia.

The highway from Zagreb to Rijeka stretches 68.5 km through a wildlife core area in Gorski kotar (Croatia). It has 43 viaducts and tunnels, and one specifically constructed (100 m wide) green bridge (Dedin). One quarter of the total highway length consists of possible crossing structures. At Dedin green bridge, a total of 12,519 crossings have been recorded during 793 different days of active infrared monitors being in operation, or 15.8 crossings per day. Two monitored tunnel overpasses had 11.2 and 37.0 crossings per day, respectively, whilst 4.3 crossings occurred per day under one monitored viaduct. Of those crossings, 83.2% were by ungulates and 14.6% by large carnivores. Radio-tracked large carnivores, brown bear (Ursus arctos), grey wolf (Canis lupus) and Eurasian lynx (Lynx lynx), expressed strong positive selection for tunnels and viaducts, whilst avoiding small underpasses or bridges. Selection for the use of Dedin green bridge was equal to its availability. We conclude that this green bridge, constructed as a measure to mitigate the negative effects of the studied highway, served its purpose acceptably. Territorial and dispersing radio-tracked large carnivores crossed the highway 41 times, using both sides of the highway as parts of their home ranges. Overall, the highway in Gorski kotar does not seem to be a barrier. This demonstrates that it is possible to maintain habitat connectivity during the process of planning the highway route.

AimThe recent recovery of large carnivores in Europe has been explained as resulting from a decrease in human persecution driven by widespread rural land abandonment, paralleled by forest cover increase and the consequent increase in availability of shelter and prey. We investigated whether land cover and human population density changes are related to the relative probability of occurrence of three European large carnivores: the grey wolf (Canis lupus), the Eurasian lynx (Lynx lynx) and the brown bear (Ursus arctos).LocationEurope, west of 64° longitude.MethodsWe fitted multi‐temporal species distribution models using >50,000 occurrence points with time series of land cover, landscape configuration, protected areas, hunting regulations and human population density covering a 24‐year period (1992–2015). Within the temporal window considered, we then predicted changes in habitat suitability for large carnivores throughout Europe.ResultsBetween 1992 and 2015, the habitat suitability for the three species increased in Eastern Europe, the Balkans, North‐West Iberian Peninsula and Northern Scandinavia, but showed mixed trends in Western and Southern Europe. These trends were primarily associated with increases in forest cover and decreases in human population density, and, additionally, with decreases in the cover of mosaics of cropland and natural vegetation.Main conclusionsRecent land cover and human population changes appear to have altered the habitat suitability pattern for large carnivores in Europe, whereas protection level did not play a role. While projected changes largely match the observed recovery of large carnivore populations, we found mismatches with the recent expansion of wolves in Central and Southern Europe, where factors not included in our models may have played a dominant role. This suggests that large carnivores’ co‐existence with humans in European landscapes is not limited by habitat availability, but other factors such as favourable human tolerance and policy.

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.

The possibilities for assessing the impact of human activity on mammals using camera traps are demonstrated in Russia for the first time, three species of large carnivores taken as examples: the brown bear (Ursus arctos), the Eurasian lynx (Lynx lynx), and the grey wolf (Canis lupus). To do this, a single-season species-level occupancy analysis and an analysis of daily activity were utilized. The study was carried out in 2022 in the territory of the Southern Forestry of the Central Forest Nature Reserve, western European Russia during the period of maximum human activity (July–August). The relative abundance indices of pedestrians, all-terrain vehicles, as well as the distance to villages were used as variables. The maximum predicted occupancy was found for the lynx (ψ = 0.97), vs the minimum for the wolf (ψ = 0.78). The detection probability was the highest for the brown bear (p = 0.18), in contrast to both lynx and wolf (0.08 each). For the lynx and the brown bear, large degrees of overlap of daily activities with pedestrians (\({{\hat {\Delta }}_{4}}\) = 0.57 and \({{\hat {\Delta }}_{4}}\) = 0.47) and all-terrain vehicles (\({{\hat {\Delta }}_{4}}\) = 0.51 and \({{\hat {\Delta }}_{4}}\) = 0.41) were noted, in contrast to those for the wolf (\({{\hat {\Delta }}_{1}}\) = 0.37 and \({{\hat {\Delta }}_{1}}\) = 0.35, respectively). Human activity had no noticeable effect on either the spatial or temporal distribution patterns of the brown bear and lynx. In contrast, the wolf showed a shift in both patterns away from human activity. The combined use of occupancy and daily activity analyses based on data from camera traps is the optimal method for assessing and regulating the human activity in particularly strictly protected natural areas.

Europe is currently being re‐colonized by large carnivore species such as brown bear Ursus arctos, Eurasian lynx Lynx lynx and grey wolf Canis lupus. Approximately one‐third of Europe currently hosts at least one of these large carnivore species: they show permanent occurrence in some regions and sporadic occurrence without reproduction in others. We investigated potential future range expansions of these three large carnivores using three different analyses. First, we compared niche overlap between the historical, current permanent and current sporadic occurrences using n‐dimensional hypervolumes. Second, we identified the environmental variables that best explain differences between current sporadic and permanent occurrences through multi‐model inference. Third, we projected permanent occurrences into the future across a range of land‐use change scenarios. We also determined future refuges (i.e. sub‐optimal habitat in the environmental model, good habitat in the human disturbance model) and ecological traps (i.e. good habitat in the environmental model, sub‐optimal habitat in the human disturbance model). In the three large carnivore species, ecological niche overlap was higher between historical and current permanent occurrences than between historical and current sporadic occurrences, and we also found low ecological niche overlap between current permanent and sporadic occurrences. Between 20 and 24% (corresponding to 86 800 to 173 200 km2) of the current sporadic occurrences could result in permanent settlement of large carnivores in the year 2040, while 17–24% (corresponding to 122 200 to 104 100 km2) and 2.7–4.6% (corresponding to 11 800 to 28 400 km2) of the current sporadic occurrences are likely to become refuges and ecological traps, respectively. Factors affecting range expansion are human activities, which were negatively related to permanent occurrences of all three species. In light of our results, human‐dominated European landscapes provide ample space for the future recolonization of large carnivores.

The daily activity patterns of animals are modulated by external factors such as habitat selection, temporal niche selection, prey availability and predation risk. Furthermore, different species show a variety of responses to human disturbance; therefore, to understand the effects of human activities on wildlife, it is crucial to consider the disturbance characteristics (e.g. type, frequency, timing and location of human activity). Our objective was to evaluate whether vehicles on forest roads altered the daily temporal activity patterns of three apex predators; Eurasian lynx (Lynx lynx), the grey wolf (Canis lupus) and brown bear (Ursus arctos), using an extensive camera trap data set collected across a gradient of forest roads and wildlife trails in the Croatian part of the Dinaric mountains. We expected a low temporal overlap between humans and apex predators but predicted this even lower at sites where vehicles are present. Consistent with our expectations, the general overlap in temporal activity of all three apex predators and humans was low, the former being primarily active at night/dawn/dusk hours and the latter during daylight hours. In contrast, our results showed similarity in the temporal activity of all three predators on wildlife trails and forest roads where human activity was more frequent and diverse.

Large carnivore populations are recovering in many parts of the world and this generates conflicts with humans, notably in terms of livestock depredation. Governmental programs of mitigation measures and compensation for losses are often implemented to reduce conflicts, but the factors affecting losses are poorly understood. We used 11 years of data on domestic sheep (Ovis aries) claimed, and confirmed, to have been killed by predators in Norway to evaluate how predator density, flock management, and other environmental or habitat‐related variables are related to losses. The percentage of animals claimed as lost that was found and confirmed to have been killed by large predators (i.e., the detection rate) was low, especially for sheep claimed as killed by Eurasian lynx (Lynx lynx), wolverine (Gulo gulo) and golden eagle (Aquila chrysaetos). Still, we generally found that similar factors predicted the number of claims and number of carcasses found across predator species. Predator density was strongly associated with losses, especially for sheep claimed as killed by brown bears (Ursus arctos), lynx and wolverines. Percentage of forest in the pastures, average slaughter weight of the lambs (an indicator of the forage conditions during summer) and vegetation characteristics in the spring also predicted the number of sheep claimed and found killed by lynx, wolverines and eagles. Factors related to losses due to wolves (Canis lupus) were harder to ascertain, possibly because of the severity of mitigation measures (e.g., electric fences) taken to protect sheep in wolf territories, a factor we were not able to include in our large scale analyses. Patrolling of the grazing area and early gathering of sheep in the autumn were not associated with a substantial reduction in losses. However, our dataset was not well suited to evaluate the efficiency of those mitigation strategies. Our findings could help develop new mitigation strategies as alternatives to predator removal where large carnivore conservation is a concern.

Terrestrial ecosystems are shaped by interacting top‐down and bottom‐up processes, with the magnitude of top‐down control by large carnivores largely depending on environmental productivity. While carnivore‐induced numerical effects on ungulate prey populations have been demonstrated in large, relatively undisturbed ecosystems, whether large carnivores can play a similar role in more human‐dominated systems is a clear knowledge gap. As humans influence both predator and prey in a variety of ways, the ecological impacts of large carnivores can be largely modified. We quantified the interactive effects of human activities and large carnivore presence on red deer (Cervus elaphus) population density and how their impacts interacted and varied with environmental productivity. Data on red deer density were collected based on a literature survey encompassing 492 study sites across 28 European countries. Variation in density across study sites was analysed using a generalized additive model in which productivity, carnivore presence (grey wolf, European lynx, Brown bear), human activities (hunting, intensity of human land‐use activity), site protection status and climatic variables served as predictors. The results showed that a reduction in deer density only occurred when wolf, lynx and bear co‐occurred within the same site. In the absence of large carnivores, red deer density varied along a productivity gradient without a clear pattern. Although a linear relationship with productivity in the presence of all three large carnivore species was found, this was not statistically significant. Moreover, hunting by humans had a stronger effect than the presence of all large carnivores in reducing red deer density and red deer density increased with increasing intensity of human land use, with stronger large carnivore effects (all three carnivore species present) at sites with low human land‐use activities. Synthesis and applications. This study provides evidence for the dominant role played by humans (i.e. hunting, land‐use activities) relative to large carnivores in reducing red deer density across European human‐dominated landscapes. These findings suggest that when we would like large carnivores to exert numeric effects, we should focus on minimizing human impacts to allow the ecological impacts of large carnivores on ecosystem functioning.