Thomas S. Jung

Fat dynamics and development of body condition indices for harvested populations of wolverine Gulo gulo

Sufficient energy reserves are crucial to the overwinter survival of northern non-hibernating mustelids. We sought a reliable index of body condition (fatness) in harvested populations of wolverine Gulo gulo, based on the relationship between fatness and the mass of distinct fat depots extractable by necropsy. Fatness did not differ significantly between genders or winter months, nor was it significantly related to body size or age. Using a first group of 18 males and 14 females, we developed predictive least-square linear regressions between fat depots (popliteal, sternal, omentum, mesenteric and perirenal) and fatness (g fat/100 g body mass) using skinned carcasses provided by fur trappers in the Yukon, Canada. Fatness was consistently better predicted in females than in males. Fatness was best predicted by the sternal fat depot (R2 = 0.73) in males and by the omentum as well as sternal fat depots in females (R2 = 0.94 and 0.87, respectively). We then compared known fatness and fatness predicted from regressions of the sternal fat depot using a second group of 14 males and nine females, and mean fatness did not differ significantly. We suggest that, due to its ease of extraction and predictive power, the sternal fat depot is a valid fat index with both sexes of wolverine, although it (or any other fat depot) should be used with caution with males, which seem more prone to obesity. This new index will help wildlife managers monitor changes in body condition of wolverines in response to changes in environmental conditions.

Extralimital movements of reintroduced bison (Bison bison): implications for potential range expansion and human-wildlife conflict

Extralimital movements are of interest to ecologists and wildlife managers alike because they can be used to understand the ecological process of range establishment and to determine if management interventions are necessary. I summarize available information of 17 observations of extralimital movements of 23 bison (Bison bison) from two reintroduced populations in northwestern Canada, during 2000–2016. Distances recorded from the release sites and the centre of their range were 125–260 and 70–285xa0km, respectively. All observations were of adult (≥5xa0years old) males, and most (11 of 17) were of lone animals. Most (13 of 17) observations of extralimital bison were made during summer, ≥10xa0years after reintroduction. Results were similar for both populations. Four extralimital bison were killed by wildlife officials because of conflicts with agricultural interests; the fate of the others was unknown. These data point to the exploratory nature of reintroduced adult male bison during the summer, which may be a precursor to range expansion. Wildlife managers can monitor extralimital movements of reintroduced bison to identify potential areas of future range expansion or human-bison conflict. More generally, these observations may be useful to inform planning efforts for future reintroductions of bison.

Performance of GPS collars on free-ranging bison (Bison bison) in north-western Canada

Abstract Context. Global positioning system (GPS) collars are increasingly used to study animal ecology. However, understanding their real-world performance is important so that biases in data collection can be addressed. These biases may be species specific. Few studies have examined the influence of sex or temporal variation on locational fix success rates (FSR), and none has assessed GPS-collar performance on bison (Bison bison). Aims. To test for sex- and temporal-based biases on the performance of GPS collars on free-ranging bison. Methods. Data from 59 deployments of 37 GPS collars on 27 female and seven male bison was used to test for temporal variation and differences between sexes on collar-deployment success rates and four fix acquisition metrics. Key results. Most (72.9%) of the 55 GPS collars retrieved malfunctioned before reaching their expected deployment schedule (2 years). We observed a significant difference in the performance of GPS collars deployed on male and females, with those on females functioning almost three times longer. All four fix metrics differed between sexes, with males having significantly better metrics. For females, nightly fix metrics were better than the daytime ones, whereas for males, there was no difference. We observed a significant difference in fix metrics between seasons for females, but not males. Conclusions. Although the data from GPS collars may be useful in understanding animal ecology, understanding associated biases can aid in the design of field studies using, and the interpretation of results stemming from, GPS collars. Temporal variation in our study was apparent for females, but not males, and likely related to differences in habitat use and movements. Overall, sex had a significant influence on the success of GPS-collar deployments on bison, and should be examined for other species as well. Implications. Bison damage to the collars was the main reason for collar failures. Researchers should plan for catastrophic failures and malfunctions when deploying GPS collars on bison, particularly adult males. Significant differences observed between daily and seasonal FSR for females were small (≤4.9%), and do not warrant post hoc treatment before analyses.

Temporal variation in the population characteristics of harvested wolverine (Gulo gulo) in northwestern Canada

Abstract Context. Wolverines (Gulo gulo) are harvested for fur in northern Canada; however, the impacts of harvest are poorly known. Additionally, wolverine population data are largely absent for much of their northern range. Demographic data collected from harvested wolverines provide information on the vulnerability and variability of different sex and age cohorts to harvest, which, in turn, may have implications for harvest sustainability. Aims. We examined the temporal variability of different sex and age cohorts in wolverine harvest among years, and within the harvest season, in Yukon, Canada. We also examined the pregnancy status of female wolverines in relation to the harvest date, so as to evaluate the impact of the harvest-season length on breeding wolverines. Methods. We determined the sex and age composition of harvested wolverines via dissections of 655 carcasses collected from 2005 to 2014. We determined the reproductive status and fetal measurements for female wolverines via dissections of reproductive tracts. Key results. The harvest consisted mostly of males, particularly of young individuals. The sex ratio of harvested animals did not fluctuate significantly, but we observed variation in the age structure among years. The age structure varied within the harvest season (November to March), with a greater proportion of adults being harvested in late winter. Active gestation was evident in females harvested after mid-January, and near-term or postpartum females were harvested during late February and March. Conclusions. Late winter harvest is likely to have a more significant impact on populations than is early winter harvest, because of increased harvest of adults and breeding females. Wolverine harvest season extends to the onset of the denning season in late February and March, indicating a concern for ethical harvest. Implications. Limiting the legal harvest season to early winter may contribute to improved harvest sustainability and protection of breeding wolverines in northern latitudes.

Snow depth does not affect recruitment in a low-density population of boreal woodland caribou ( Rangifer tarandus caribou )

Winter snow depth may be an important driver of annual variability in recruitment of ungulate calves, and low calf recruitment has been implicated as a factor in declining boreal caribou (Rangifer tarandus caribou) populations. We used 11 consecutive years (2006–2016) of aerial survey data to document calf recruitment in a low-density population of boreal woodland caribou in the Northwest Territories, Canada. We measured snow depth in winter and tested two hypotheses: (1) that calf recruitment was lower in winters with greater snow depth and (2) that calf recruitment was lower following winters with greater snow depth (1-year time lag). Recruitment, the number of calves/adult female in March, ranged twofold from 0.23 to 0.45, and snow depth also ranged twofold from 41 to 85xa0cm. Yet, we found no support for the hypothesis that late-winter snow depth in the current or previous year was inversely related to calf recruitment.

Evaluating camera traps as an alternative to live trapping for estimating the density of snowshoe hares ( Lepus americanus ) and red squirrels ( Tamiasciurus hudsonicus )

Live trapping is one of the methods typically used to estimate population densities of small mammals, but this is labor-intensive and can be stressful to individuals. We assess the use of camera trap hit (detection) rates as a noninvasive alternative to live trapping for estimating population densities of snowshoe hares (Lepus americanus (Erxleben, 1777)) and red squirrels (Tamiasciurus hudsonicus (Erxleben, 1777))—two common small (≤1.5xa0kg) mammal species in the boreal forests of northern North America. We compared hit rates from camera trapping to live trapping mark-recapture density estimates and asked if the hit window—the length of time used to group consecutive videos together as single detections or “hits”—has an effect on the correlation between hit rates and live trapping density estimates. The relationship between hit rate and population density was sensitive to hit window duration for red squirrels with R2 values ranging from 0.41 to 0.68, and a 5-min hit window generated the highest value. R2 values for snowshoe hares ranged from 0.70 to 0.90, and a 10-min hit window generated the highest value, but hares were live trapped and filmed only at very low densities. Our results indicate that camera trapping is a robust means for estimating the density of red squirrels, but the appropriate hit window duration must be determined empirically if camera trapping data are to be used to monitor populations of this species. Additional live trapping and filming of snowshoe hares is required to better assess camera trapping of this species.

Body Condition of a Free-Ranging Little Brown Bat (Myotis lucifugus) with a Broken Humerus

Abstract We captured a free-ranging adult female little brown bat (Myotis lucifugus) with a fractured humerus that was in an advanced stage of healing. Compared to seven other adult female little brown bats captured the same evening from the same colony, the body condition of the bat with the healing humerus was 5.4%–13.8% less than other colony members. Our observation suggests that even though free-ranging bats may survive the trauma associated with a broken wing bone, there may be latent effects on their ability to forage and maintain body condition. This may ultimately compromise their ability to build up sufficient energetic reserves to migrate and hibernate.

Dental anomalies suggest an evolutionary trend in the dentition of wolverine (Gulo gulo)

In mammals, congenital dental anomalies likely represent an evolutionary trend in the reduction of teeth (oligodonty) from the primitive dental formula. We quantified variation in the number of teeth from 421 wolverine (Gulo gulo) from northwestern Canada, focusing on polydonty (additional teeth), congenital oligodonty, and tooth rotation (misalignment). We predicted that oligodonty may be an evolutionary consequence of a previously reported increase in size of carnassial teeth since the Pleistocene. We also predicted that wolverine with missing or rotated teeth had smaller dental arcades than those without these anomalies. Oligodonty was observed in 42 wolverines (10xa0%), with the most cases involving the P1 or P1 (56xa0%) and P2 or P2 (32xa0%). We observed rotated teeth in 43xa0% of wolverines; virtually all of the rotated teeth we observed were P2 or P2. The frequency of oligodonty or rotated teeth was strikingly similar between the sexes. Both oligodonty and rotated teeth were observed more frequently in the mandibular than the maxillary toothrows. Most wolverine (67xa0%) with oligodonty were missing teeth unilaterally; in contrast, most animals with rotated teeth exhibited bilateralism (86xa0%). Condylobasal length and most measures of the dental arcade did not differ between wolverine with or without missing or rotated teeth; however, we found that skulls with missing or rotated teeth had narrower palate breadth ratios. Our data suggest that there may be an evolutionary trend in the loss of teeth at the anterior of the toothrows of wolverines, which may be a result of narrower dental arcades and larger carnassial teeth. Wolverine have a hypercarnivorous diet, and selection may be toward optimizing those teeth that contribute to securing and processing food (i.e., canine and carnassial teeth), and against those that likely do not contribute substantially to increasing fitness and survival, such as the P1/P1 and P2/P2.

Efficacy of a Butorphanol, Azaperone, and Medetomidine Combination for Helicopter-Based Immobilization of Bison (Bison bison)

Abstract Decreased access to potent narcotics for wildlife applications has stimulated the need to explore alternative drug combinations for ungulate immobilizations. A combination of butorphanol, azaperone, and medetomidine (BAM) has been used for some ungulate species, but information on its use in bison (Bison bison) is limited. We conducted field trials using BAM, in conjunction with atipamezole and naltrexone as antagonists, for reversible field immobilization of bison during ground- and helicopter-based operations. We compared times to induction and recovery, vital rates (rectal temperature and respiration rate), and the quality of induction, immobilization, and recovery between ground- and helicopter-based immobilizations of bison. Overall, 15 of 21 bison were induced with the volume we used (mean±SD=3.4±0.6 mL); two other animals darted from a helicopter required a full second dose, and four others (two darted from the ground and two from a helicopter) required a supplemental partial dose to achieve induction. All immobilizations achieved a sufficient plane of anesthesia to permit minor invasive procedures (e.g., skin biopsy and blood sampling). All animals recovered, and most (17 of 21) were reversed in ≤5 min. The mean time to induction was 10.8±7.3 min while that for recovery was 5.0±2.1 min. We found few differences in vital rates or the quality of immobilizations between ground- and helicopter-based captures. The drug combination provided good immobilization and was reliably reversed; however, inconsistent inductions at the doses we used may limit its use in field immobilizations of bison, particularly those animals being darted from a helicopter.

Health Status of Reintroduced Wood Bison (Bison bison athabascae): Assessing the Conservation Value of an Isolated Population in Northwestern Canada

Abstract A central goal for reintroduced populations of threatened wood bison (Bison bison athabascae) is to maintain them free of diseases of concern, particularly bovine tuberculosis (caused by Mycobacterium bovis) and brucellosis (caused by Brucella abortus). A wood bison population in southwestern Yukon, Canada was reintroduced into the wild in 1988, but no health assessment has been done since then. To provide an initial assessment of the health status and, hence, the conservation value of this population, we serologically tested 31 wood bison (approximately 3% of the population) for pathogens of interest and obtained histopathology results for select tissues. We found no evidence of exposure to M. bovis or Brucella spp., but antibodies were present to bovine parainfluenza virus 3, bovine coronavirus, Leptospira interrogans, and Neospora caninum, with seroprevalences of 87, 7, 61, and 7% of the tested animals, respectively. Reintroduced wood bison in southwestern Yukon may be of high value for wood bison recovery because it is a large and geographically isolated population with no bacteriologic, histopathologic, or serologic evidence of exposure to Brucella spp. or M. bovis.