Wolf Population Dynamics

ABSTRACT
Background

Understanding mortality is crucial to predict the dynamics of animal populations, especially for long-lived species subjected to widespread human pressure. This is the case for the grey wolf (Canis lupus), yet local studies provide an incomplete view of the patterns and determinants of this process.
Aims and Methods

We conducted a systematic review of the existing literature on grey wolf mortality across the species’ distribution range (i.e., most of the Northern Hemisphere) to identify global patterns and potential differences across continents. Studies were analysed based on the type of information provided, including mortality rates, proportion of dead individuals by cause, and natural and human-related determinants of mortality.
Results and Discussion

We found high global minimum annual mortality rates in wolves (0.31 ± 0.18), compared to those reported under low human persecution (< 0.2). Most deaths were linked to human activities, primarily deliberate (legal and illegal) killing (60% ± 25%). Europe reported a higher percentage of human-related deaths (86% ± 14%) than North America (66% ± 24%). This is likely due to higher anthropogenic pressures in Europe and differences in carcass detection methods between continents (opportunistic recovery in Europe vs. tracking of collared wolves in North America). However, the lack of data from areas with low human influence (e.g., the Arctic and deserts) limits our understanding of the natural dynamics of mortality in the species. We found that many individual, social and environmental variables determine mortality values, and our global perspective allowed us to disentangle long-standing debates in large carnivore ecology, including support for the hypothesis that human-caused and natural mortality are additive.

Abstract

The brown bear Ursus arctos, Eurasian lynx Lynx lynx, and gray wolf Canis lupus are Europe’s threatened large carnivores. The analyses were conducted using data on the abundance of these species in Poland, collected by the Polish Central Statistical Office (bear 1965–2023, wolf 1995–2023, and lynx 1996–2023). For the years 2000–2023, data were also available by region. We subjected these data to statistical analysis: chi-square tests, segmented regression, and principal component analysis. Biplots, charts of population dynamics, and distribution maps were created to visualize the results. In Poland in the analyzed time period, an increase in the population of all three studied carnivores was observed along with the westward expansion of the territorial range of lynx and wolf, while bear range remained unchanged. The most mean population increase was exhibited by the gray wolf (7.01%), followed by the brown bear (4.78%) and, finally, the Eurasian lynx (2.94%). The population dynamics of the carnivores showed trends over time, with a notable increase in the last decade. The use of multi-year data in modelling enables a better understanding of the mechanisms governing the abundance and distribution of populations of endangered species. This, in turn, facilitates the planning of more effective conservation measures.

Abstract

Death is an inherently spatial process. It happens to someone, somewhere, but often remains undetected in nature. Death is also the primary means by which humans regulate wildlife populations. Using a novel analytical method that accounts for the cryptic nature of the fate of individuals and one of the world’s most comprehensive non-invasive genetic monitoring datasets, we were able to map cause-specific mortality of the entire Scandinavian grey wolf (Canis lupus) population despite the fact that most mortality events (mean = 65%; [95% CrI: 50.3–76.8%]) remained undetected. Our analysis revealed strong spatial variation in mortality with, for example, areas with a high risk of mortality linked with the current wolf management policies. Furthermore, we showed that the risk of legal mortality increased, while the risk of mortality due to causes other than legal mortality decreased with local wolf population density. This illustrates the complex interactions between spatial determinants and cause-specific mortality and therefore the importance of considering spatial variation when estimating mortality. Maps of mortality can inform wildlife management and conservation by capturing an elusive process in population dynamics as it unfolds in time and space.

Abstract
The ongoing wolf’s recolonization of continental Europe at the beginning of the 21st century recently reached many regions where wolves were absent for centuries, including several areas on the Czechia’s borders. We observed the process of wolf recolonization across the Bohemian Forest Ecosystem from 2015 until April 2023. We adopted a multifaceted approach, based on systematic tracking surveys, camera traps, telemetry, and provoked howling. The first breeding pair with permanent occupation was detected in 2016, connecting two major European wolf populations – Alpine and Central European. We observed increasing amounts of confirmed wolf occurrence data from 2015 to April 2023, with camera trap pictures and scats being the most abundant data sources. The implications of intensive population expansion were confirmed by locating six activity centres in the wolf year 2022/2023, reflecting six existing packs in the Bohemian Forest Ecosystem. Although those wolf packs spread practically across the whole study area in eight wolf years, the intense phase of recolonization is probably finished, and only continuous small changes in population density are expected. Further observations on the population dynamics are essential, focusing on the transitions between existing packs and the establishment of new territories within the existing social structure.

Abstract

Grey wolves have been recovering throughout Europe over the last decades, widely portrayed as a conservation success story. We evaluated the trends and demography of two wolf populations that recolonised the Czech Republic between 2011/2012 and 2022/2023, integrating a variety of fieldwork and laboratory methods including snow tracking, camera trapping, telemetry and non-invasive genetics, with some of these methods being carried out within a citizen science framework. We then compared these demographic trends with the frequency of wolf attacks on livestock. Wolf territories grew annually by λ = 1.25 ± 0.18 (0.92–1.68) in the Carpathian and λ = 1.39 ± 0.08 (1.22–1.57) in the Central European population. Over the same period, the growth rate of wolf attacks on livestock exceeded the growth rate of territories. Wolf pack sizes averaged 5.7 ± 0.24 individuals in autumn and winter, but packs in their first and second year were significantly smaller than those occupying a territory for at least three years. The wolf density in areas occupied by a wolf pack reached, on average, 4.19±0.49 individuals per 100 km². Overall, the recovery of the Central European wolf population in Czechia was delayed compared with neighbouring Germany and western Poland, and the Carpathian population recovered even six years later. We discuss that this delayed recovery may have been influenced by hunting pressure in neighbouring Slovakia prior 2021 or by other undetected sources of mortality, making the population vulnerable in the long term.