Jean-François Robitaille

Otter, Lutra lutra , occurrence in Europe and in France in relation to landscape characteristics

In recent decades, the abundance of otter, Lutra lutra, decreased in many European countries. This study aimed at determining if varying occurrence of otters is related to land features and if this occurs at many spatial scales. Values of landscape features were compared among three categories of otter occurrence, i.e. absent, sporadic and common, for 25 European countries, for 19 regions and 22‐40 departments in France. At all scales, significantly higher human and road densities were detected in areas where otters are absent, which illustrates the pervasive impact of human presence on otter population fragmentation. Moreover, particular natural features (‘percentage other use’ defined as nonagricultural and non-forested) may also limit otter populations at the scale of Europe. Our study failed to detect significant differences in landscapes occupied by common or sporadic otter populations, probably owing to a limited sample size, or to the resilience of otters. The conservation of the European otter in Europe would benefit from an improved list of common large-scale land descriptors, the recognition of large gaps of naturally unsuitable habitats, and the development of international large-scale conservation studies to support existing regional otter conservation efforts.

Winter habitat use of American martens Martes americana within second-growth forest in Ontario, Canada

A combination of discriminant function analysis and multiple regression was used to develop a linear model of American marten Martes americana winter habitat use within second-growth boreal forest in northeastern Ontario, Canada. Four structural variables significantly discriminated between sites that were used or not used by martens: the percentage of spruce or fir trees, tree height, the number of downed logs, and canopy closure. The model was tested against a second data set and was not invalidated. The results demonstrated that martens were using second-growth forests in Ontario, and that their response to structural characteristics was similar to responses described previously in uncut forests.

Rapid Homogenization of Multiple Sources: Genetic Structure of a Recolonizing Population of Fishers

Abstract Fishers (Martes pennanti) were extirpated from much of southern Ontario, Canada, prior to the 1950s. We hypothesised that the recent recolonization of this area originated from an expansion of the population in Algonquin Provincial Park, which historically served as a refuge for fishers. To test this hypothesis, we created a sampling lattice to encompass Algonquin and the surrounding area, and we collected contemporaneous DNA samples. We sampled fishers from each of 35 sites and genotyped them at 16 microsatellite loci. Using a Bayesian assignment approach, with no a priori geographic information, we inferred 5 discrete genetic populations and used genetic population assignment as a means to cluster sites together. We concluded that the Algonquin Park fisher population has not been a substantial source for recolonization and expansion, which has instead occurred from a number of remnant populations within Ontario, Quebec, and most recently from the Adirondacks in New York, USA. The genetic structure among sampling sites across the entire area revealed a pattern of isolation-by-distance (IBD). However, an examination of the distribution of genetic structure (FST/1−FST) at different distances showed higher rates of gene flow than predicted under a strict IBD model at small distances (40 km) within clusters and at larger distances up to 100 km among clusters. This pattern of genetic structure suggests increased migration and gene flow among expanding reproductive fronts.

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.

Additional indices to estimate fat contents in fisher Martes pennanti populations

Abstract In order to develop more practical indices of fat contents in fisher Martes pennanti populations at a large scale, the relationship between individual discernable fat depots (popliteal, sternal, omental, mesenteric and perirenal) and fat percentage (PFAT) was examined in male and female skinned carcasses obtained from trappers in northeastern Ontario from the 1998/99 and 1999/2000 fur harvest seasons. PFAT differed significantly between sex/age classes (F = 10.17, P < 0.0001). In a development group (86 males and 86 females), PFAT was well predicted by each of the five potential fat indices common to both males and females. During the test phase (87 males, 93 females), estimated fat contents (%) based on either fat depot did not differ from observed PFAT neither in males nor in females (0.05 < paired t < 1.33, 0.19 < P < 0.71). All models detected animals with lower fat levels, a useful feature for conservation applications. The accuracy of almost any of the five depots appears adequate to detect changes in fat levels in harvested fisher populations. This contrasts with other mustelids such as martens Martes americana where lower fat levels restrict the availability of discernable fat depots.

Indices to estimate fat depots in American marten Martes americana

The relationships between fat depots and body fat content and between protein content and protein indices were examined in American marten Martes americana carcasses obtained from trappers in northeastern Ontario during the 1995/96 fur harvest season. Percent fat and percent protein did not differ significantly between sexes (t = 0.45 and 0.55, P = 0.66 and 0.58, respectively). Protein contents did not vary much among 42 individuals (range: 14–19%), and therefore we found no significant index of percent protein (0.01 < r < 0.23, P > 0.05, N = 42). In the development phase, percent fat (PFAT) was better predicted by six of the eight potential fat indices, and better predicted in females than in males (N = 17 and 18, respectively), but the omentum dry mass (ODM) performed best with both sexes (r2 = 0.69 and 0.80 males and females, respectively). During the test phase (N = 18 males, 22 females), estimated PFAT based on ODM (per sex) did not differ from observed percent fat in either males or in females (paired t = 0.01 and 1.28; P = 0.99 and 0.22, respectively). The models slightly overestimated the number of males and females of below average condition, which indicates that the models were conservative. The accuracy of the omentum dry mass fat depot appears adequate to detect changes of physical condition in harvested marten populations. The lack of variation in protein contents 1) indicates that most animals were near average protein level, possibly due to suitable habitat conditions and 2) prevented us from finding a protein index. We encourage the development of models where conditions (e.g. temperature regime, level of disturbance, carrying capacity) may be harsher for marten.

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.