Biology subjects

Sergiel, A.

Publications and source records attributed to Sergiel, A..

4 recordsLinked to original sources

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↗

bioRxiv2024

Trophic adaptation of large terrestrial omnivores to global change

Large omnivores at the top of food webs play a key role in ecosystems, as their ability to feed on multiple trophic levels stabilizes food-web dynamics and impacts ecosystem functioning. However, it is largely unexplored how large omnivores adapt their trophic interactions to altered resource availability under global change, particularly in terrestrial ecosystems. Here, we combine macroecological and paleoecological approaches and reveal that extant bears, the largest terrestrial omnivores, adapt their trophic position in food webs dynamically to net primary productivity and growing season length. Throughout their geographic ranges, extant bears occupy higher trophic positions in unproductive ecosystems with short growing seasons than in productive ecosystems with long growing seasons. Consistent with this geographic pattern, the trophic position of the brown bear sharply decreased at the transition from the Late Pleistocene to the Holocene, coinciding with an increase in net primary productivity and growing season length. These findings demonstrate that trophic interactions of omnivores are not static but change dynamically in response to environmental change. Our findings suggest that global change impacts on primary production and vegetation seasonality may trigger shifts in the functional role of omnivores, with consequences for food webs and ecosystem functions. Significance statementLarge omnivores play a key role in ecosystems, as they stabilize food-web dynamics and impact ecosystem functioning. However, how omnivores adapt their trophic interactions to changes in resource availability under global change remains unexplored. Combining macroecological and paleoecological approaches, we show that extant bears, the largest terrestrial omnivores, occupy lower trophic positions in food webs as net primary productivity and growing season length increase. This trophic adaptation is evident across the geographic ranges of all extant terrestrial bear species and for brown bears at the transition from the Late Pleistocene to the Holocene. Therefore, impacts of global change on primary production and vegetation seasonality may trigger shifts in the functional role of omnivores, with consequences for food webs and ecosystems. One sentence summaryGlobal changes in primary productivity and vegetation seasonality alter the functional role of large omnivores in terrestrial ecosystems.

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↗

bioRxiv2022

Clarifying space use concepts in ecology: range vs. occurrence distributions

Quantifying animal movements is necessary for answering a wide array of research questions in ecology and conservation biology. Consequently, ecologists have made considerable efforts to identify the best way to estimate an animals home range, and many methods of estimating home ranges have arisen over the past half century. Most of these methods fall into two distinct categories of estimators that have only recently been described in statistical detail: those that measure range distributions (methods such as Kernel Density Estimation that quantify the long-run behavior of a movement process that features restricted space use) and those that measure occurrence distributions (methods such as Brownian Bridge Movement Models and the Correlated Random Walk Library that quantify uncertainty in an animal movement path during a specific period of observation). In this paper, we use theory, simulations, and empirical analysis to demonstrate the importance of applying these two classes of space use estimators appropriately and distinctly. Conflating range and occurrence distributions can have serious consequences for ecological inference and conservation practice. For example, in most situations, home-range estimates quantified using occurrence estimators are too small, and this problem is exacerbated by ongoing improvements in tracking technology that enable more frequent and more accurate data on animal movements. We encourage researchers to use range estimators to estimate the area of home ranges and occurrence estimators to answer other questions in movement ecology, such as when and where an animal crosses a linear feature, visits a location of interest, or interacts with other animals. Open Research StatementTracking data on Aepyceros melampus, Beatragus hunteri, Bycanistes bucinator, Cerdocyon thous, Eulemur rufifrons, Glyptemys insculpta, Gyps coprotheres, Madoqua guentheri, Ovis canadensis, Propithecus verreauxi, Sus scrofa, and Ursus arctos are publicly archived in the Dryad repository (Noonan et al. 2018; https://doi.org/10.5061/dryad.v5051j2), as are data from Procapra gutturosa (Fleming et al. 2014a; https://doi.org/10.5061/dryad.45157). Data on Panthera onca were taken from (Morato et al. 2018). Additional data are publicly archived in the Movebank repository under the following identifiers: Canis latrans, 8159699; Canis lupus, 8159399; Chrysocyon brachyurus, 18156143; Felis silvestris, 40386102; Gyps africanus, 2919708; Lepus europaeus, 25727477; Martes pennanti, 2964494; Panthera leo, 220229; Papio cynocephalus, 222027; Syncerus caffer, 1764627; Tapirus terrestris, 443607536; Torgos tracheliotus, 2919708; and Ursus americanus, 8170674.

ecology↗