Biology subjects

Kindberg, J.

Publications and source records attributed to Kindberg, J..

4 recordsLinked to original sources

bioRxiv2026

Forty-four years of change: Capercaillie and Black grouse responses to changes in forestry, climate and vole decline in icentral Sweden

Human land use has greatly affected the natural landscapes in most parts of the world, and Scandinavian industrial forestry has substantially altered the age structure of the boreal forest over the last 75 years. In this study, we analyzed 44 years of line transect counts of Capercaillie and Black grouse collected in an industrial forest landscape in central Sweden between 1980 and 2024. The area was heavily logged in the 1960s and 1970s, followed by large-scale replanting. A hierarchical Gompertz state-space model to assess long-term population dynamics of both species. The adult state model included a brood production submodel, and forest age structure, snow depth, vole abundance, and spring frost were covariates. Our results reveal strong density dependence and temporally variable environmental effects. Capercaillie and Black grouse exhibited contrasting decadal trends: Capercaillie increased markedly during the early study years, whereas Black grouse declined steeply before recovering later in the series. Increasing proportions of forest aged 21-40 years had a clearly positive effect on Capercaillie, whereas snow depth in the previous winter negatively influenced Capercaillie but not Black grouse. Brood production exhibited substantial interannual unexplained variation, although late spring frost reduced brood size in Capercaillie. Toward the end of the study, the two species reached similar levels of latent adult abundance, demonstrating that both can persist at sustainable densities across a broader range of forest structures than suggested in earlier studies.

ecology↗

bioRxiv2026

Using activity data to estimate brown bear den exit and entry dates

BackgroundIn hibernating mammals, the timing of den entry and exit reflects complex interactions among environment, physiology, and energetic constraints, with consequences for fitness. Consequently, shifts in denning phenology can affect population dynamics, particularly under climate change. Reliable estimation of denning timing is therefore critical, yet current methods often rely on GPS-derived movement data, limited by coarse sampling intervals, detection issues, and the inability to distinguish true inactivity from active presence at the den site. In this study, we developed and apply a method to estimate denning phenology in a brown bear population in south-central Sweden using accelerometer-derived activity data. Our approach employs adaptive, individual-specific thresholds to account for variation in baseline activity across bears, focusing on day-to-day changes to identify the start and end of inactivity periods. This method allows flexible and reproducible detection of den entry and exit dates, overcoming limitations associated with fixed thresholds and small sample sizes. ResultsWe compared activity-based estimates with GPS-derived den occupancy and examined variation in denning behavior across demographic groups. Analyzing 388 bear-winters, the method successfully identified inactivity periods in 360 cases. The method failed to identify clear start and end dates of hibernation for 28 (7%) bear-winters, which were characterized by unusually high or low daily activity levels at the boundaries of the inactivity period. Den site occupancy ranged from September 5 to June 2, with durations of 112-260 days, whereas inactivity periods detected from activity data extended from September 6 to May 13, lasting 83-217 days. Our comparison of activity-based and GPS-based methods indicates that bears may arrive at the den site several weeks before the onset of inactivity, with timing varying among demographic groups. ConclusionWe show that activity-based analysis provides a robust framework for estimating denning phenology, distinguishing actual inactivity from site presence, and improving understanding of the timing and variability of bear denning behavior. Applying an individual-level activity-based method improves accuracy in assessing ecological mechanisms underlying hibernation in bears and other hibernators, while also enhancing interpretation of environmental drivers and providing a reliable tool to monitor phenological shifts in response to climate change.

animal behavior and cognition↗

bioRxiv2024

Human footprint and forest disturbance reduce space use of brown bears across Europe.

Three-quarters of the planets land surface has been altered by humans, with consequences for animal ecology, movements and related ecosystem functioning. Species often occupy wide geographical ranges with contrasting human disturbance and environmental conditions, yet, limited data availability across species ranges has constrained our understanding of how human impact and resource availability jointly shape intraspecific variation of animal space use. Leveraging a unique dataset of 752 annual GPS movement trajectories from 370 brown bears (Ursus arctos) across the species range in Europe, we investigated the effects of human impact (i.e., human footprint index), resource availability, forest cover and disturbance, and area-based conservation measures on brown bear space use. We quantified space use at different spatio-temporal scales during the growing season (May - September): home range size; representing general space requirements, 10-day long-distance displacement distances, and routine 1-day displacement distances. We found large intraspecific variation in brown bear space use across all scales, which was profoundly affected by human footprint index, vegetation productivity, and recent forest disturbances creating opportunity for resource pulses. Bears occupied smaller home ranges and moved less in more anthropized landscapes and in areas of higher resource availability. Forest disturbances reduced space use while contiguous forest cover promoted longer daily movements. The amount of strictly protected and roadless areas within bear home ranges were too small to affect space use. Anthropized landscapes may hinder the expansion of small and isolated populations, such as the Apennine and Pyrenean, and obstruct population connectivity, for example between the Alpine or Carpathian with the Dinaric Pindos populations. Our findings call for actions to maintain bear movements across landscapes with high human footprint, for example by maintaining forest integrity, to support viable bear populations and their ecosystem functions.

ecology↗

bioRxiv2023

The ontogeny of individual specialization

Individual dietary specialization, where individuals occupy a subset of a populations wider dietary niche, is a key factor determining a species resilience against environmental change. However, the ontogeny of individual specialization, as well as associated underlying social learning, genetic, and environmental drivers, remain poorly understood. Using a multigenerational dataset of female European brown bears (Ursus arctos) followed since birth, we discerned the relative contributions of environmental similarity, genetic heritability, maternal effects, and offspring social learning from the mother to individual specialization. Individual specialization accounted for 43% of phenotypic variation and spanned half a trophic position, with individual diets ranging from omnivorous to carnivorous. The main determinants of dietary specialization were social learning during rearing (13%), environmental similarity (9%), maternal effects (11%), and permanent between-individual effects (8%), whereas the contribution of genetic heritability was negligible. The trophic position of offspring closely resembled the trophic position of their mothers during the first 3-4 years of independence, but this relationship ceased with increasing time since separation. Our study shows that social learning and maternal effects are as important for individual dietary specialization as environmental composition. We propose a tighter integration of social effects into future studies of range expansion and habitat selection under global change that, to date, are mostly explained by environmental drivers.

ecology↗