ABSTRACT
Stress responses, which are mediated by the neurogenic system (NS) and hypothalamic–pituitary–adrenal (HPA) axis help vertebrates maintain physiological homeostasis. Fight‐or‐flight ...responses are activated by the NS, which releases norepinephrine/noradrenaline and epinephrine/adrenaline in response to immediate stressors, whilst the HPA axis releases glucocorticoid hormones (e.g. cortisol and corticosterone) to help mitigate allostatic load. There have been many studies on stress responses of captive animals, but they are not truly reflective of typical ranges or the types of stressors encountered by free‐ranging wildlife, such as responses and adaptation to environmental change, which are particularly important from a conservation perspective. As stress can influence the composition of age and sex classes of free‐ranging populations both directly and indirectly, ecological research must be prioritised towards more vulnerable taxa. Generally, large predators tend to be particularly at risk of anthropogenically driven population declines because they exhibit reduced behavioural plasticity required to adapt to changing landscapes and exist in reduced geographic ranges, have small population sizes, low fecundity rates, large spatial requirements and occupy high trophic positions. As a keystone species with a long history of coexistence with humans in highly anthropogenic landscapes, there has been growing concern about how humans influence bear behaviour and physiology, via numerous short‐ and long‐term stressors. In this review, we synthesise research on the stress response in free‐ranging bear populations and evaluate the effectiveness and limitations of current methodology in measuring stress in bears to identify the most effective metrics for future research. Particularly, we integrate research that utilised haematological variables, cardiac monitors and Global Positioning System (GPS) collars, serum/plasma and faecal glucocorticoid concentrations, hair cortisol levels, and morphological metrics (primarily skulls) to investigate the stress response in ursids in both short‐ and long‐term contexts. We found that in free‐ranging bears, food availability and consumption have the greatest influence on individual stress, with mixed responses to anthropogenic influences. Effects of sex and age on stress are also mixed, likely attributable to inconsistent methods. We recommend that methodology across all stress indicators used in free‐ranging bears should be standardised to improve interpretation of results and that a wider range of species should be incorporated in future studies.
► We analyze a change in public attitudes toward brown bears in Croatia. ► We discuss the effects of a more centralized bear management and an increase in the bear population. ► Findings show that ...value orientations and perceived threat did not change over time. ► Instead bear acceptance capacity was reduced. ► Public involvement, hunting and adaptive management are important conservation tools.
Successful carnivore conservation depends on public attitudes and acceptance levels of carnivores, and these are likely to change as circumstances change. Attitude studies repeated in time that can demonstrate such change are rare. Our study surveyed Croatian rural inhabitants in 2002 and in 2008 and analyzed their responses to detect a change in attitudes toward brown bears (Ursus arctos) over time. Important developments occurring in Croatia at the time of our research included a more centralized and more clearly defined bear management strategy, and an increase in the bear population. We constructed models to explain respondent’s value orientations, their level of perceived threat and their acceptance capacity for bears. Findings show that while value orientations and the overall level of perceived threat did not change over time, bear acceptance capacity was reduced. This suggests that the increase in the bear population and perhaps the more centralized bear management reduced respondents’ willingness to accept a larger bear population. We conclude that continuous public involvement in bear management is essential in order to maintain a feeling of control over the bear among the local population. Furthermore we argue that hunting is an important form of public involvement in the region, serving to reinforce existence and bequest values of the bear and increase its public acceptance.
The diet of free-ranging bears is an important dimension regarding their ecology, affecting their behavior, population structure, and relation with humans. In Croatia, there has been no recent study ...on the natural food habits of brown bears (Ursus arctos) or the influence of artificial feeding sites on their diet. During 2017, we collected 53 brown bear stomachs from bears in 2 regions of Croatia—Gorski Kotar and Lika—to assess their diet. Plants—Allium ursinum, the Poaceae family, Cornus mas, berries (i.e., Prunus avium, Rubus plicatus), beechnuts (Fagus spp.)—and various plant parts (i.e., dry leaves, buds, conifer needles, and twigs), as well as mushrooms, made up 80% of the percentage of the volume (%V) of all consumed items. Corn (Zea mays) from the feeding sites made up 37% of the bears' diet (%V), whereas 20% (%V) was meat and 14% (%V) was pome fruits. Scavenged or preyed animal species, such as wild boar (Sus scrofa), horse (Equus caballus), domestic pig (S. scrofa domesticus), cattle (Bos taurus), roe deer (Capreolus capreolus), and small mammals comprised >66% of %FO (frequency of occurrence), but only 20% of %V. Our results showed that food resources (i.e., livestock such as horses, cattle, and pigs, and corn) found at supplemental feeding sites were more frequently chosen by bears than natural food in 2017, a year characterized by almost no beechnut crop. The results showed that subadult bears obtained most food from feeding sites. These 2 patterns suggested that bears may focus on artificial feeding sites to find food in years when natural food sources are depleted, although this should be tested using diet and food availability data collected from several years.
We explored the long-term accumulation of aluminium, strontium, cadmium and lead in the compact and trabecular bone of the femoral epiphysis, metaphysis and diaphysis in 41 brown bears (
Ursus arctos
...) from Croatia. Also, we assessed their influence on macro and trace elements (sodium, magnesium, phosphorus, potassium, calcium, manganese, iron, cobalt, copper, zinc and barium) in bears’ bone. There were no sex differences in element levels in general, while age was associated with bone length and levels of all elements, except for cadmium. Elements had different levels depending on the part of the bone sampled. More pronounced differences were observed between the compact and trabecular regions, with higher levels of majority of elements found in compact bone. Moderate to high associations (Spearman coefficient,
r
S
= 0.59–0.97) were confirmed between calcium and potassium, magnesium, phosphorus, manganese, cobalt, zinc, strontium and lead. Lead levels in the bone were below those known to cause adverse health effects, but in 4 of 41 animals they exceeded baseline levels for domestic animals. The femoral bone of the brown bear reflected the accumulative nature of lead and strontium well, as it did the impairment of bone-forming essential element levels associated with these two elements. However, the distribution pattern of elements along the bone was not uniform, so additional care should be taken when choosing on the part of the bone sampled.
The influence of reproductive and (early) life stages on toxic metal levels was investigated in the brown bear (
Ursus arctos
), the largest mammalian predator species in Croatia. The purpose was to ...examine critical clusters in a population that might be at a higher risk of adverse health effects caused by metals as environmental contaminants. Levels of cadmium, mercury and lead in muscle, liver and kidney cortex of 325 male and 139 female bears, quantified by inductively coupled plasma mass spectrometry, were analysed according to distinct bear life stages (young: cub, yearling, subadult; mature: adult). Metal levels did not differ among sexes in young animals (< 4 years), except for mercury in muscles (higher in females), and adult females had higher cadmium and mercury. A trend of renal cadmium accumulation with age in immature male animals disappeared once they reached maturity, whereas for females this trend has only slowly declined in mature compared to immature bears. In early life stage (< 1 year), bear cubs had lower cadmium, comparable mercury, and higher lead in the kidneys than the bears of the following age category (yearlings). Due to a higher proportion of renal lead transfer from the mother to the cub compared with cadmium, it may be that the high burden of cadmium found in kidneys of older females has lower toxicological concern for their cubs than the lead content. Sex, reproductive, and life stages of bears were confirmed as important in assessing toxic metal burden.
Abstract
A microwave-assisted digestion method for the determination of cadmium (Cd) and lead (Pb) by inductively coupled plasma mass spectrometry (ICP-MS) was optimised on certified reference ...material (CRM) (bovine liver, BCR-185R) and wolf liver samples. Different factors influencing digestion efficiency (temperature, time, composition of the digestion mixture, sample mass) were tested. Validation included linearity (up to 200 μg L
-1
for Cd and Pb), detection (0.003 μg L-1 for Cd and 0.035 μg L
-1
for Pb), and quantification (0.008 μg L
-1
for Cd and 0.081 μg L
-1
for Pb) limits. Good agreement between measured and certified values was achieved in all conditions, with recoveries ranging from 94 % to 111 % for Cd and from 95 % to 105 % for Pb. The precision of the method, expressed as relative standard deviation, was up to 3 % for Cd and 8 % for Pb. The best digestion parameters (260 °C, 30 min, 1 mL HNO
3
+4 mL H
2
O, 0.1 g of CRM) based on accuracy and precision were applied on two wolf liver samples to evaluate the need for the predigestion step (freeze-drying) and appropriate mass of the sample. Freeze-drying improved precision and minimising the tissue mass to 0.1 g reduced the matrix effect. Using these optimised digestion conditions, we determined Cd and Pb in 40 wolf livers collected in Croatia, and their medians (0.055 μg g
-1
and 0.107 μg g
-1
, respectively) were in the range of previously reported data for the grey wolf.
Brown bears have lost most of their range on the European continent. The remaining western populations are small, isolated and highly endangered. The Dinaric-Pindos brown bear population is the ...western-most stable population and the fourth largest in Europe. It has been recognized as a potential source for recolonization of populations whose survival is at risk. Indeed, several translocations of Dinaric bears to Italy, Austria and France have recently been made. Despite the importance of the Dinaric bear population, its genetic status remains poorly understood. Using tissue samples from 156 hunted or accidentally killed Dinaric bears in Croatia, this study analysed genetic diversity at 12 microsatellite loci, as well as population structure and past reductions in size. In addition, a subset of 59 samples was used to assess diversity of the mitochondrial DNA control region. The results indicate that Dinaric bears have high nuclear genetic diversity, as compared to other extant brown bear populations, despite genetic evidence of a bottleneck caused by past persecutions. However, haplotype diversity was low, probably as a result of male-biased dispersal and female philopatry. Not surprisingly, no evidence of population sub-structure was found using nuclear markers, as the bear habitat has remained continuous and the highway network has been built only recently. Management should focus on maintaining habitat connectivity and keeping the effective population size as large as possible. In addition, when removing individuals, care should be taken not to further deplete the population of rare haplotypes. A coordinated transboundary management of the entire Dinaric-Pindos brown bear population should be a priority for its long-term conservation.
Historical samples, like tanned hides and trophy skulls, can be extremely important for genetic studies of endangered or elusive species. Selection of a sampling protocol that is likely to provide ...sufficient amount and quality of DNA with a minimum damage to the original specimen is often critical for a success of the study. We investigated microsatellite genotyping success of DNA isolated from three different types of Eurasian lynx historical samples. We analysed a total of 20 microsatellite loci in 106 historical samples from the endangered Dinaric lynx population, established from re‐introduction of three pairs of lynx in 1973 from Slovakian Carpathians. Of the three tested sample types, turbinal bone and septum from the nasal cavity of the trophy skulls had the lowest percentage of samples successfully genotyped for all 20 microsatellite loci. Footpad samples, collected using a cork drill, exhibited better results in polymerase chain reaction amplification and genotyping than samples of footpad epidermis cut with a scalpel. We report simple and efficient sampling protocols, which could be widely applied for future studies utilizing historical samples.
Environmental contaminants like arsenic (As), cadmium (Cd), mercury (Hg) or lead (Pb) may disrupt hypothalamic–pituitary–adrenal (HPA) and hypothalamic-pituitary-gonadal (HPG) axes due to their ...endocrine toxicity potential. Resulting long-term physiological stress or adverse effects on wildlife reproduction and ontogeny may cause detrimental effects at the individual and population levels. However, data on environmental metal(loid)sʼ impact on reproductive and stress hormones in wildlife, especially large terrestrial carnivores, are scarce. Hair cortisol, progesterone and testosterone concentrations were quantified and modelled with hair As, Cd, total Hg, Pb, biological, environmental and sampling factors to test for potential effects in free-ranging brown bears (Ursus arctos) from Croatia (N = 46) and Poland (N = 27). Testosterone in males (N = 48) and females (N = 25) showed positive associations with Hg and an interaction between Cd and Pb, but a negative association with interaction between age and Pb. Higher testosterone was found in hair during its growth phase compared to quiescent phase. Body condition index was negatively associated with hair cortisol and positively associated with hair progesterone. Year and conditions of sampling were important for cortisol variation, while maturity stage for progesterone variation (lower concentrations in cubs and yearlings compared to subadult and adult bears). These findings suggest that environmental levels of Cd, Hg and Pb might influence the HPG axis in brown bears. Hair was shown to be a reliable non-invasive sample for investigating hormonal fluctuations in wildlife while addressing individual and sampling specificities.
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•First effect study on hormonal association with metal (loid)s in European brown bear.•Hair testosterone was associated with potentially toxic metal (loid) levels.•Year and conditions of sampling important for cortisol variation in hair.•Maturity stage important for progesterone variation (lowest in cubs & yearlings).
Abstract Integrating data across studies with traditional microsatellite genetic markers requires careful calibration and represents an obstacle for investigation of wide-ranging species where ...populations require transboundary management. We used the “yardstick” method to compare results published across Europe since 2002 and new wolf ( Canis lupus ) genetic profiles from the Carpathian Mountains in Central Europe and the Dinaric Mountains in Southeastern Europe, with the latter as our reference population. We compared each population with Dinaric wolves, considering only shared markers (range 4–17). For each population, we calculated standard genetic diversity indices plus calibrated heterozygosity ( Hec ) and allelic richness ( Ac ). Hec and Ac in Dinaric (0.704 and 9.394) and Carpathian wolves (0.695 and 7.023) were comparable to those observed in other large and mid-sized European populations, but smaller than those of northeastern Europe. Major discrepancies in marker choices among some studies made comparisons more difficult. However, the yardstick method, including the new measures of Hec and Ac , provided a direct comparison of genetic diversity values among wolf populations and an intuitive interpretation of the results. The yardstick method thus permitted the integration of diverse sources of publicly available microsatellite data for spatiotemporal genetic monitoring of evolutionary potential.
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