First data on polybrominated diphenyl ethers and temporal trend of polychlorinated biphenyls in European brown bear as a bioindicator species

The contamination status on persistent organic pollutants (POPs) in the Croatian terrestrial ecosystem was investigated by analyzing two classes of contaminants in adipose tissue of male European brown bear (Ursus arctos, N = 27) collected in 2021 and 2022. In addition to seven indicator polychlorinated biphenyls (PCBs), for the first time seven polybrominated diphenyl ethers (PBDEs) were analyzed in terrestrial species from this region. Sum of mass fractions detected in adipose tissue ranged from 0.011 to 0.463 ng g-1 lipid weight (lw) for the PBDEs, and from 0.652 to 30.17 ng g-1 lw for PCBs, with two orders of magnitude difference in the median value for these two groups of POPs (PBDEs: 0.022 ng g-1 lw; PCBs: 2.307 ng g-1 lw). PCBs dominated over PBDEs with a share of over 94 % of the total mass fractions of both groups of analyzed POPs. Results of the comparison of the PCB levels in the adipose tissue of brown bears reported here and in previous investigation from this region showed decrease in PCB-28, but increase of PCB-118 and PCB-180, while other congeners seemed to have reached a steady-state level in the environment over a ten-year period. Among the compounds analyzed in this study, BDE-47, PCB-153 and PCB-180 were the dominant congeners. Somewhat higher sum of PCBs was measured in April compared to October, although not statistically significant, indicating possible impact of winter hibernation causing concentration of lipophilic compounds due to body fat loss. Revealed POP levels in brown bears are consistent with the data on the low contamination of the Croatian terrestrial ecosystem in general.

90Sr and stable element levels in bones of brown bears: long-term trends in bear populations from Croatia and Poland

The aim of this study was to investigate the temporal trends and geographical differences in ⁹⁰Sr and stable element (Ba, Ca, Mn, Sr, Pb, Zn) levels in the bones of Croatian and Polish brown bear (Ursus arctos) populations. Experimental data suggest that in the decades after nuclear weapon tests and the Chernobyl accident, ⁹⁰Sr bone activity concentrations decreased from 352 to 11 Bq kg^-1 in the Croatian bear population (period 1982-2015) and from 831 to 27 Bq kg^-1 in Polish bears (period 1962-2020). Calculated effective and ecological half-lives were 9 and 13 years for Croatian bears, and 15 and 31 years for Polish bears, respectively. Different temporal trends were noted in levels of Ba, Mn, Pb and Zn between the two countries with majority of bones having lower Pb, Sr and Zn in Croatian than in Polish bears. Estimated values for the soil-to-bear transfer of ⁹⁰Sr were the same order of magnitude in the studied populations. Contrary to this, the estimated transfer of stable Sr was an order of magnitude lower for the Croatian bear population compared to Polish bears. The observed differences in soil-to-bear transfer between stable Sr and ⁹⁰Sr found for Croatian bears might suggest the need for careful consideration on the use of stable Sr data as an analogue for ⁹⁰Sr. To our knowledge, this is the first study that analysed ⁹⁰Sr activity in tissue of brown bears. As such, it provides insight into the fate and behaviour of one of the most relevant anthropogenic radionuclides at the top of the food chain.

Comparison of behaviors of black bears with and without habituation to humans and supplemental research feeding

Humans interact with wildlife regularly, mostly without conflict. Interactions between humans and bears, however, have a history of conflict. Using data from female black bears in two populations, we compared behaviors related to a series of hypotheses about habituation and food supplementation via research feeding. We livetrapped bears in the southern boreal forests and cove forests of the Pisgah National Forest, North Carolina, in barrel traps or modified leg-hold snares and outfitted them with very high frequency (VHF) transmitters, for 95 bear-years of data. In the southern boreal forests of Superior National Forest, Minnesota, we habituated bears and outfitted them with VHF collars supplemented with GPS units, for 42 bear-years. Some human residents of the Superior study area fed local black bears and we established a research feeding site. Bears in both populations avoided roads and habituated: Superior bears avoided houses where they were not fed; the study site for Pisgah bears (no habituation or feeding) had too few houses to test for avoidance. Bears in both populations gained weight faster during their active seasons when wild foods were abundant. Habituated, supplemented Superior bears averaged a smaller proportion of a day active, longer activity bouts, and less sinuous movements than did not-habituated or supplemented Pisgah bears. The bears in the two populations did not differ with respect to distances traveled per 2 h or mean lengths of activity bouts. The abundance of wild foods affected time active, distance traveled, and sinuosity of travel by not-habituated or supplemented Pisgah bears. Females in breeding condition in both populations were more active, had longer activity bouts, traveled further, and had more linear travel in spring and early summer while females with cubs pushed these activities into late summer and autumn. This timing pattern for bout length, distance moved, and sinuosity was less pronounced for habituated and research-fed Superior bears than for not-habituated or supplemented Pisgah bears. Thus, habituation to a small number of researchers appeared to not affect many behaviors of bears in our habituated and research-fed Superior population; research feeding appeared to affect some behaviors in a manner consistent with a food supply that had low annual variance. Because we have samples of one for each treatment (one site with habituation and feeding, one site without), our results do not establish that differences documented between the populations were caused by the differences in habituation and feeding. The effects of habituation, research feeding, or other forms of food supplementation on backcountry behaviors of black bears need broader testing across the range of black bears.

Patterns of Human–Brown Bear Conflict in the Urban Area of Brașov, Romania

Human–bear conflicts are increasing in number due to deforestation, urban expansion, tourism, and habitat invasion by humans. Our study was conducted in Brașov, a picturesque city in central Romania. Brașov is surrounded by forests and has significant tourist traffic, but also much uncollected garbage and many garbage containers, which attract brown bears. We recorded human–bear conflicts in four districts (Răcădău, the Historic Centre, Noua, and Gară) between 2004 and 2018, finding 55 cases in total, of which in 19 cases involving people, 4 people were killed and 32 were injured. In 36 cases, there were no human victims. We mapped the locations of human–bear conflicts and garbage containers, then analysed their space–time location and human victims in terms of behavioural factors. The altitudes at which brown bears were identified ranged from 580 to 790 m, whereas bears were found in the city at distances of between 100 and 2600 m from the forest. The highest frequency of human–bear conflicts occurred during summer and autumn, and the most common behavioural factor was human outdoor activities. This study provides an important background for understanding human–bear conflicts and will help local authorities develop effective strategies to reduce human–bear conflicts and mitigate risk.

Reintroductions of the Corsican Red Deer (Cervus elaphus corsicanus): Conservation Projects and Sanitary Risk

The Corsican red deer is an endangered subspecies that needs artificial translocation projects to gain its complete recovery with the formation of viable, interconnected populations. Between 2007 and 2017, we performed two reintroduction projects in four sites in central–eastern Sardinia via tracking 32 deer by means of GPS/GSM radiotelemetry. On the basis of the obtained results, we built a species distribution model (SDM) using MaxEnt software, selecting 200 random points from the merged deer core areas as presence data. Furthermore, to evaluate the sanitary risk linked to artificial translocations, we analyzed deer positivity to Bluetongue virus (BTV) in the founder populations. The SDM showed a high deer capability to colonize central–eastern Sardinia, but it also showed the possibility of spreading BTV to domestic sheep because sanitary analyses confirmed the virus’ presence in the founder populations. Our main conclusion was that reintroductions are effective tools for the long-term conservation of the Corsican red deer, as long as sanitary risks are minimized by means of sanitary monitoring of translocated deer.

Understanding Species–Habitat Associations: A Case Study with the World’s Bears

Habitat modeling is one of the most common practices in ecology today, aimed at understanding complex associations between species and an array of environmental, bioclimatic, and anthropogenic factors. This review of studies of seven species of terrestrial bears (Ursidae) occupying four continents examines how habitat models have been employed, and the functionality of their predictions for management and conservation. Bear occurrence data have been obtained at the population level, as presence points (e.g., sign surveys or camera trapping), or as locations of individual radio-collared animals. Radio-collars provide greater insights into how bears interact with their environment and variability within populations; they are more commonly used in North America and Europe than in South America and Asia. Salient problematic issues apparent from this review included: biases in presence data; predictor variables being poor surrogates of actual behavioral drivers; predictor variables applied at a biologically inappropriate scale; and over-use of data repositories that tend to detach investigators from the species. In several cases, multiple models in the same area yielded different predictions; new presence data occurred outside the range of predicted suitable habitat; and future range projections, based on where bears presently exist, underestimated their adaptability. Findings here are likely relevant to other taxa.

Very Small Home Ranges of Two Gravid European Brown Bears during Hyperphagia

Simple Summary

Paklenica National Park is home to the European brown bear while it is also frequently visited by tourists and home to permanent and semi-permanent residents. The aim of our study was to analyze the use of space of the National Park in autumn. Therefore, we have live captured two brown bears in September 2019 and equipped them with GPS/GSM collars to track their movement pattern and then estimate their home range. We captured two females that were both gravid. We found out that these individuals used very small seasonal home ranges in autumn before denning. Additionally, they almost exclusively showed solitary use of their home range. They nevertheless spent a considerable amount of time close to feeding sites and approached human settlements as close as 4 m while they were mostly active during the night. During the pre-denning stage, most human–bear encounters occur, which is why it is important to offer refugia for the animals from human disturbance.

Abstract

In September 2019, two gravid female brown bears (Ursus arctos) were captured and equipped with GPS/GSM collars in Paklenica National Park (Croatia). Home ranges during hyperphagia were analyzed to describe the spatiotemporal requirements. Mean seasonal home ranges were very small with 9.2 km² and 7.5 km² (Brownian Bridge Movement Model 95%). During the tracking period, both bears used different territories and showed little to no use of overlapping area. The bears in our study spent a considerable time in proximity of artificial feeding sites, indicating a probable use of these structures as a food resource (mean 15.7% and 30.7%). Furthermore, the bears approached very close to human structures such as 8.9 m and 4.4 m. As most encounters between humans and bears occur during hyperphagia, it is important to offer refugia from human disturbance, especially as the National Park is not only used by residents, but also by tourists. To adapt management according to the animal’s needs, further studies should include more individuals from different age and sex classes. Both females were gravid. It remains unclear whether gravidity has an effect on the home range and should be further investigated.