Seasonal migrations (i.e. seasonal round‐trips between disjunct areas) have been rarely documented for large carnivores. The Dinaric‐Pindos brown bear (Ursus arctos) population is the third largest ...in Europe, but little information is currently available on individual movement patterns. We studied movement patterns by 12 GPS‐collared adult and subadult bears in Croatia and Bosnia Herzegovina during 2004–2017, including migratory movements by some instrumented bears. To investigate environmental correlates of migrations, we first used the canonical Outlying Mean Index analysis, identifying habitat descriptors of summer and fall ranges, and then applied mixed‐effects logistic regression to quantify variation in habitat use between them. Thirty‐seven per cent 37% of the bears (7 bear‐years) migrated during hyperphagia (i.e. partial migration), and seasonal migration was also facultative, as it occurred only during mast (i.e. beechnut) poor years. Migrating bears entered migration during early fall (median = 25 Sept) and returned to their pre‐migratory ranges after about 7 weeks (median = 18 Nov). Net distances between pre‐migratory (summer) and post‐migratory (fall) averaged (±sd) 26.5 ± 9.7 km, with a maximum distance of 38.8 km, corresponding to actual distances travelled of 61.1 ± 21.5 km. Summer ranges from which bears migrated were best described by proximity to supplemental feeding sites and mixed forests, whereas fall ranges reached by migrants were differentiated by lower elevations, and a higher share of deciduous forest, grasslands, forest edges and shrublands. Relative to pre‐migratory ranges, bears in post‐migratory ones increased their distance to anthropogenic features and showed higher use of cover types expectedly richer in berries and other fleshy fruits. Although we lack any causative evidence, we speculate migration in this bear population is triggered during poor beechnut years by increased social despotic interference at supplemental feeding sites that elicits redistribution of subordinate bears.
Seasonal migrations have been rarely documented for large carnivores. We studied movement patterns in Dinaric‐Pindos brown bears, a large European population exposed to anthropogenic supplemental food. In 2004 – 2017, thirty‐seven per cent of the GPS‐collared bears showed a complex, flexible behavioural trait such as partial and facultative migration, involving seasonal movements between areas where they are likely to increase their foraging opportunities in years of poor beechnuts production. Migrating bears entered migration during early fall and returned to their pre‐migratory ranges after about 7 weeks. Relative to pre‐migratory ranges, bears in post‐migratory ones increased their distance to anthropogenic features and showed higher use of cover types expectedly richer in berries and other fleshy fruits. We speculate migration in this bear population is triggered during poor beechnut years by increased social despotic interference at supplemental feeding sites that elicits redistribution of subordinate bears.
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 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.
In September 2019, two gravid female brown bears (
) 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 km
and 7.5 km
(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.
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.
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.
Free-living game can be an important source of dietary cadmium and lead; the question is whether exposure to these two elements is such that it might cause adverse health effects in the consumers. ...The aim of this study was to estimate dietary exposure to cadmium, lead, and mercury from free-living big game (fallow deer, roe deer, red deer, wild boar, and brown bear), and to mercury from small game (pheasant and hare), hunted in Croatia from 1990 to 2012. The exposure assessment was based on available literature data and our own measurements of metal levels in the tissues of the game, by taking into account different consumption frequencies (four times a year, once a month and once a week). Exposure was expressed as percentage of (provisional) tolerable weekly intake (P)TWI values set by the European Food Safety Authority (EFSA). Consumption of game meat (0.002-0.5 % PTWI) and liver (0.005-6 % PTWI) assumed for the general population (four times a year) does not pose a health risk to consumers from the general population, nor does monthly (0.02-6 % PTWI) and weekly (0.1-24 % PTWI) consumption of game meat. However, because of the high percentage of free-living game liver and kidney samples exceeding the legislative limits for cadmium (2-99 %) and lead (1-82 %), people should keep the consumption of certain game species’ offal as low as possible. Children and pregnant and lactating women should avoid eating game offal altogether. Free-living game liver could be an important source of cadmium if consumed on a monthly basis (3-74 % TWI), and if consumed weekly (11-297 % TWI), it could even give rise to toxicological concern.
Hepatozoon spp. are tick-borne parasites causing subclinical to clinical disease in wild and domestic animals. Aim of this study was to determine Hepatozoon prevalence and species distribution among ...wild mammals and ticks in Europe.
Samples of wild mammals and ticks, originating from Austria, Bosnia and Herzegovina, Croatia, Belgium and the Netherlands, were tested with PCR to amplify a ~ 670-bp fragment of the small subunit ribosomal RNA gene.
Of the 2801 mammal samples that were used for this study, 370 (13.2%) tested positive. Hepatozoon canis was detected in samples of 178 animals (3 Artiodactyla, 173 Carnivora, 1 Eulipotyphia, 1 Lagomorpha), H. martis in 125 (3 Artiodactyla, 122 Carnivora), H. sciuri in 13 (all Rodentia), Hepatozoon sp. in 47 (among which Hepatozoon sp. Vole isolate, all Rodentia) and H. ayorgbor in 4 (all Rodentia). Regarding origin, 2.9% (6/208) tested positive from Austria, 2.8% (1/36) from Bosnia and Herzegovina, 14.6% (173/1186) from Croatia and 13.9% (190/1371) from Belgium/the Netherlands. Of the 754 ticks collected, 0.0% (0/35) Hyalomma sp., 16.0% (4/25) Dermacentor spp., 0.0% (0/23) Haemaphysalis spp., 5.3% (24/50) Ixodes and 1.4% (3/221) Rhipicephalus spp. tested positive for Hepatozoon (4.2%; 32/754), most often H. canis (n = 22).
Hepatozoon canis is most present in mammals (especially in Carnivora such as gray wolves and golden jackals) and ticks, followed by H. martis, which was found merely in stone martens and pine martens. None of the rodent-associated Hepatozoon spp. were detected in the ticks, suggesting the possible implication of other arthropod species or non-vectorial routes in the transmission cycle of the hemoprotozoans in rodents. Our findings of H. canis in ticks other than R. sanguineus add to the observation that other ticks are also involved in the life cycle of Hepatozoon. Now that presence of Hepatozoon has been demonstrated in red foxes, gray wolves, mustelids and rodents from the Netherlands and/or Belgium, veterinary clinicians should be aware of the possibility of spill-over to domestic animals, such as dogs.
Wolf diet and prey selection in Croatia Octenjak, Daria; Pađen, Lana; Šilić, Valentina ...
Mammal research,
10/2020, Letnik:
65, Številka:
4
Journal Article
Recenzirano
Tensions between humans and wolves have led to intensive worldwide studies of wolf feeding habits and their relative preference for domestic and wild ungulates. The aim of this study was to provide ...further insight into the diet composition of wolves in Croatia, based on stomach contents of dead wolves. We examined spatial variation in wolf diet and prey selection relative to availability of wild and domestic animals. Furthermore, we aimed to determine selectivity in feeding habits in relation to wolf gender and age. The study was conducted on the stomach contents of 42 gray wolves (18 females, 24 males). Samples were collected from three regions of Croatia with different ratios of domestic and wild prey availability. The density ratio of domestic to wild ungulates increased gradually from north-west (5.8), through central (11.6) to south-east (134) Croatia. Wolf diet followed this pattern with the ratio of domestic animals increasing from 0.7 to 1.3 and 5.3, respectively. The relative share of wild ungulates in wolf diet was significantly higher in all three regions of wolf range in Croatia, even where livestock availability was high. Female wolves ate birds, rodents, and dogs more than males and in the south, where wild ungulates were scarce. This study showed wolves’ selectivity for wild ungulate, rather than for abundant, but well-guarded livestock. The European idea of coexistence of humans and wolves in human-dominated landscape seems possible with some effort and understanding from humans’ side.
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