First report of Taenia arctos (Cestoda: Taeniidae) from grizzly (Ursus arctos horribilis) and black bears (Ursus americanus) in North America

The cestode Taenia arctos was found at necropsy in the small intestine of a grizzly (Ursus arctos horribilis) and a black bear (Ursus americanus) from Kananaskis Country in southwestern Alberta, Canada. The autolysis of the tapeworm specimens precluded detailed morphological characterization of the parasites but molecular analysis based on mitochondrial DNA cytochrome c oxidase subunit 1 gene confirmed their identity as T. arctos. This is the first report of T. arctos from definitive hosts in North America. Its detection in Canadian grizzly and black bears further supports the Holarctic distribution of this tapeworm species and its specificity for ursids as final hosts. Previously, T. arctos was unambiguously described at its adult stage in brown bears (Ursus arctos arctos) from Finland, and as larval stages in Eurasian elk (Alces alces) from Finland and moose (Alces americanus) from Alaska, USA. Given the morphological similarity between T. arctos and other Taenia species, the present study underlines the potential for misidentification of tapeworm taxa in previous parasitological reports from bears and moose across North America. The biogeographical history of both definitive and intermediate hosts in the Holarctic suggests an ancient interaction between U. arctos, Alces spp., and T. arctos, and a relatively recent host-switching event in U. americanus.     

Cardiac function adaptations in hibernating grizzly bears (Ursus arctos horribilis)

Research on the cardiovascular physiology of hibernating mammals may provide insight into evolutionary adaptations; however, anesthesia used to handle wild animals may affect the cardiovascular parameters of interest. To overcome these potential biases, we investigated the functional cardiac phenotype of the hibernating grizzly bear (Ursus arctos horribilis) during the active, transitional and hibernating phases over a 4 year period in conscious rather than anesthetized bears. The bears were captive born and serially studied from the age of 5 months to 4 years. Heart rate was significantly different from active (82.6 ± 7.7 beats/min) to hibernating states (17.8 ± 2.8 beats/min). There was no difference from the active to the hibernating state in diastolic and stroke volume parameters or in left atrial area. Left ventricular volume:mass was significantly increased during hibernation indicating decreased ventricular mass. Ejection fraction of the left ventricle was not different between active and hibernating states. In contrast, total left atrial emptying fraction was significantly reduced during hibernation (17.8 ± 2.8%) as compared to the active state (40.8 ± 1.9%). Reduced atrial chamber function was also supported by reduced atrial contraction blood flow velocities and atrial contraction ejection fraction during hibernation; 7.1 ± 2.8% as compared to 20.7 ± 3% during the active state. Changes in the diastolic cardiac filling cycle, especially atrial chamber contribution to ventricular filling, appear to be the most prominent macroscopic functional change during hibernation. Thus, we propose that these changes in atrial chamber function constitute a major adaptation during hibernation which allows the myocardium to conserve energy, avoid chamber dilation and remain healthy during a period of extremely low heart rates. These findings will aid in rational approaches to identifying underlying molecular mechanisms.     

Prevalence of sarcocysts in Florida black bears (Ursus americanus floridanus)

Sections of muscle from Florida black bears (Ursus americanus floridanus) collected in the state of Florida were observed for the presence of Sarcocystis sp. sarcocysts. Two of 132 (1.5%) black bears had muscle sections containing sarcocysts. One sarcocyst was observed per muscle section. The sarcocysts averaged 181.5 x 99.0 microm by light microscopy of hematoxylin and eosin-stained sections.     

Dietary protein content alters energy expenditure and composition of the mass gain in grizzly bears (Ursus arctos horribilis)

Many fruits contain high levels of available energy but very low levels of protein and other nutrients. The discrepancy between available energy and protein creates a physiological paradox for many animals consuming high-fruit diets, as they will be protein deficient if they eat to meet their minimum energy requirement. We fed young grizzly bears both high-energy pelleted and fruit diets containing from 1.6% to 15.4% protein to examine the role of diet-induced thermogenesis and fat synthesis in dealing with high-energy-low-protein diets. Digestible energy intake at mass maintenance increased 2.1 times, and composition of the gain changed from primarily lean mass to entirely fat when the protein content of the diet decreased from 15.4% to 1.6%. Daily fat gain was up to three times higher in bears fed low-protein diets ad lib., compared with bears consuming the higher-protein diet and gaining mass at the same rate. Thus, bears eating fruit can either consume other foods to increase dietary protein content and reduce energy expenditure, intake, and potentially foraging time or overeat high-fruit diets and use diet-induced thermogenesis and fat synthesis to deal with their skewed energy-to-protein ratio. These are not discrete options but a continuum that creates numerous solutions for balancing energy expenditure, intake, foraging time, fat accumulation, and ultimately fitness, depending on food availability, foraging efficiency, bear size, and body condition.     

Seroprevalence of Toxoplasma gondii from free-ranging black bears ( Ursus americanus ) from Florida

Toxoplasma gondii is a significant worldwide parasitic protozoan. In the present study, prevalence of antibodies of T. gondii was examined from 29 free-ranging black bears ( Ursus americanus ) from south-central Florida where the host species was listed as state threatened during this project. Overall T. gondii prevalence was found to be 44.8%, specifically 46.2% in male and 43.8% in female U. americanus , using a modified agglutination test (1:25 titer). Seroprevalence differences between sexes were not significant (P > 0.05). Results of the present study add supportive data to the growing body of evidence suggesting that U. americanus has one of the highest T. gondii seroprevalences among all known intermediate hosts. In addition, our data emphasize the importance of understanding parasitic disease dynamics from a conservation perspective.     

Annual changes in serum sex steroids in male and female black (Ursus americanus) and polar (Ursus maritimus) bears

The adaptation of black and polar bears to their environments is proportional to the severity of climate and food restriction. Both black and polar bears mate during the spring, despite differences in their recent metabolic state. Reproductive activity in black bears follows 4 mo of torpor, whereas reproduction in polar bears occurs prior to torpor. The goals of this study were to measure the annual changes in serum sex steroids in male and female black and polar bears, and to determine if changes in serum levels of these steroids were associated with metabolic condition or photoperiod. Serum testosterone (T) concentrations were elevated during spring in black and polar bears. Moreover, this increase in serum T in polar bears during spring was correlated with age and testis size. Serum progesterone (P4) concentrations increased in pregnant polar bears in fall coincident with the time of expected implantation. No increases in serum P4 were observed in nonpregnant black and polar bears. Serum estradiol (E2) was elevated in nonpregnant and pregnant polar bears 2 mo prior to the time of expected implantation. We found that serum sex steroids measured in black and polar bears change independent of torpor. Therefore, our results suggest that photoperiod may be a more important regulator of serum steroid levels and reproduction than metabolic condition.     

Serologic survey for infectious canine hepatitis virus in grizzly bears (Ursus arctos) from Alaska, 1973 to 1987

Serum antibody prevalence of infectious canine hepatitis virus was 12% (90 of 725) for grizzly bears (Ursus arctos) from Alaska (USA) during the period 1973 to 1987. Prevalence was highest on Kodiak Island at 29% (37 of 127). Prevalence of exposure at individual collection areas did not change significantly over time. There were no significant sex-specific differences in prevalence. Prevalence was directly related to age, but it was 0% for bears less than 2-yr-old. Young bears which are exposed to the virus may develop clinical disease and die as a result of the infection. This disease may be a factor affecting grizzly bear population dynamics.     

Activity patterns of brown bears (Ursus arctos) in Slovenia and Croatia

In most of Europe, true wilderness areas do not exist and brown bears Ursus arctos generally have to cope with human disturbance and infrastructure. The few studies in Europe that have investigated brown bear activity have demonstrated a predominantly nocturnal and 'shy' behaviour in bears. There is still quite a debate on whether the shy, nocturnal bears of Europe are the result of centuries of persecution by men (genetically fixed trait) or whether hunting and the high disturbance potential in the multi-use landscapes are the driving force (individually learnt trait). We analysed the activity pattern of 16 individual bears monitored for 3372 h between May and October 1982–1998 in the Dinaric Mountains of Slovenia and Croatia. The data were collected via time sampling and basically analysed using two approaches: a general linear model with seasonal component to delineate the most important variables influencing the activity pattern and level and cluster analysis to group bears according to their 24-h activity pattern. Time of day and age were the most important variables predicting activity. Although individual variation in the activity pattern was high among individual bears, in general, yearlings were more diurnal and had a less distinct difference between day- and night-time activity levels than adult bears. Subadults were somewhat intermediate to adults and yearlings. We believe that nocturnal behaviour is most likely driven through negative experiences with humans, giving space for much individual variation. More research is needed to prove the causal relationship of nocturnal behaviour and the degree of disturbance that an individual bear is exposed to.     

Exertional myopathy in a grizzly bear (Ursus arctos) captured by leghold snare

We diagnosed exertional myopathy (EM) in a grizzly bear (Ursus arctos) that died approximately 10 days after capture by leghold snare in west-central Alberta, Canada, in June 2003. The diagnosis was based on history, post-capture movement data, gross necropsy, histopathology, and serum enzyme levels. We were unable to determine whether EM was the primary cause of death because autolysis precluded accurate evaluation of all tissues. Nevertheless, comparison of serum aspartate aminotransferase and creatine kinase concentrations and survival between the affected bear and other grizzly bears captured by leghold snare in the same research project suggests EM also occurred in other bears, but that it is not generally a cause of mortality. We propose, however, occurrence of nonfatal EM in grizzly bears after capture by leghold snare has potential implications for use of this capture method, including negative effects on wildlife welfare and research data.     

Serologic evidence of West Nile virus infection in black bears (Ursus americanus) from New Jersey

Serum samples obtained from 51 free-ranging black bears (Ursus americanus) in northwestern New Jersey in February and March 2002 were analyzed for neutralizing antibodies to West Nile virus (WNV) and St. Louis encephalitis virus. Three (6%) of the black bears tested positive for WNV-neutralizing antibodies. One additional sample was positive for flavivirus-neutralizing antibodies but could not be differentiated for a specific virus type. This is the first report of WNV infection in black bears.     

Prevalence of Trichinella spiralis in black bears (Ursus americanus) from Newfoundland and Labrador, Canada.

Tongue and diaphragm samples from 158 black bears (Ursus americanus) from Newfoundland and Labrador were examined for Trichinella spiralis. No larvae were detected in samples from the island of Newfoundland but one animal from the Labrador samples was infected. The results of this and other studies suggest a lack of involvement of the black bear in a sylvatic cycle of T. spiralis in eastern Canada.     

Use of Ketamine hydrochloride and xylazine hydrochloride to immobilize black bears (Ursus americanus).

Ketamine hydrochloride (KH) and xylazine hydrochloride (XH) used in combination (KH-XH) were effective immobilants for captive and wild black bears (Ursus americanus). Single intramuscular injections of 1.5-17.1 mg of KH per kg body weight combined in an approximate ratio of 2:1 with 0.9-10.0 mg of XH per kg body weight immobilized bears for 1.5-197 min. Dosages most frequently used were 4.5-9 mg KH/kg with 2-4.5 mg XH kg. Supplemental administrations maintained tractability for up to 31 h. Immobilization was characterized by smooth induction, relaxed muscles, occasional groaning and vomition, no eye closure, no defecation, and a smooth recovery phase of variable length. Male and female bears responded similarly to KH-XH. Induction times for small bears (less than or equal to 25 kg) were shorter than for larger bears.     

Immobilization of black bears (Ursus americanus) with a combination of butorphanol, azaperone, and medetomidine

Sixteen captive and five free-ranging black bears (Ursus americanus) were immobilized with a combination of butorphanol, azaperone, and medetomidine (BAM). The BAM drug combination was premixed using 0.5 ml butorphanol (30 mg/ml), 0.25 ml azaperone (50 mg/ml), and 0.25 ml medetomidine (20 mg/ml) per milliliter to yield a final mix of (15 mg butorphanol+12.5 mg azaperone+5 mg medetomidine)/ml. This combination, dosed at 0.4 ml BAM/approximately 23 kg estimated body weight, provided a mean induction time of 10 min (95% confidence interval [CI]=2 min), consistent anesthesia without apparent adverse effects, and smooth recovery (mean=15 min, 95% CI=4 min) after antagonism with atipamezole (5 mg/mg medetomidine) alone or in combination with naltrexone (5 mg/mg butorphanol). Based on our initial observations, BAM appears to be a reversible and accessible drug combination for immobilizing black bears that merits further evaluation for field use.     

Pityrosporum pachydermatis in a black bear (Ursus americanus)

Pityrosporum pachydermatis was repeatedly isolated from portions of alopecic tissue from the throax and ears of a black bear cub (Ursus americanus). Yeastlike cells morphologically identical with those of P. pachydermatis were observed in stained tissue sections. This is the first reported association of this yeast with a member of the family Ursidae.     

Factors associated with fecal glucocorticoids in Alaskan brown bears (Ursus arctos horribilis)

The aims of this study were to validate a radioimmunoassay (RIA) for quantifying glucocorticoid metabolite concentrations in the feces of Alaskan brown bears (Ursus arctos horribilis) and to investigate whether any of the following factors are associated with those concentrations: the presence of humans or other bears, fishing difficulty, sex-age class, diet, and season. We tested an established corticosterone RIA for assay sensitivity, similarity, precision, and sample matrix effects of brown bear feces, and it proved satisfactory. We collected fecal samples from brown bears along salmon-spawning streams and assessed fecal glucocorticoid (FG) concentrations. We observed that the factors explaining the most variation in measured concentrations were date and diet type and that there was a significant interaction between the two. We did not observe a significant effect of human and bear activities or sex-age class on FG concentrations. This study demonstrates that although FG concentrations may be assessed in brown bears, complex dietary patterns and seasonal variations must be taken into consideration in the study design in order to make inferences regarding stress.