Jean-Pierre Tremblay

The range distribution of ticks is mainly governed by climatic conditions and their impact on habitat structure, host populations, and human activities. Winter ticks (Dermacentor albipictus) are particularly exposed because they do not take shelter in nests or burrows like nidicolous species. Winter ticks are mainly associated with ungulates, especially moose (Alces alces) for which they were reported to induce mass mortality events in northeastern North America. Although winter ticks have been studied since the 1930’s, their patterns of distribution within the landscape remain unclear. We used the flagging technique to sample ticks in five regions across Québec and New-Brunswick (Canada) during the falls of 2022 and 2023 to characterise environments suitable for them. We conducted flagging surveys in spatial core areas of moose during the tick drop-off period. We built two field-based models of presence and abundance and a remote-sensing-based model of presence to predict winter tick distribution at the landscape scale. Both meso- and micro-habitat (i.e. canopy height, solar exposure, elevation, habitat openness, and litter depth) and weather conditions (i.e. proportion of days at or above 28°C), determined tick distribution. Remote sensing variables predicted tick presence more accurately than field measurements, likely because they captured weather conditions across the entire off-host period. Inversely, field measurements represented the conditions on sampling days and at a very fine scale. Remote sensing data therefore offer a more efficient means for investigating temporal and spatial variations in winter tick distribution compared to field measurements, which can be challenging and costly to obtain.

Wild animals are infected with a large diversity and abundance of parasites that can affect their behavior, growth, body condition, and ultimately their survival. Although the adverse effects of parasites and the mechanisms involved in the interactions between a host and its parasites are generally well studied, much less is known about the additive or synergistic effects of multiple parasite species on a host. Moose populations in eastern Canada are infected by several species of endoparasites. In the last decades, the intensity of infestations by winter ticks, an ectoparasite, on moose have increased as a result of increased moose densities and favorable weather conditions that benefit winter tick survival. We aimed to document the diversity, intensity, prevalence, and distribution of different parasite species of moose in southern Quebec, Canada. We then evaluated the potential interaction between winter tick and endoparasites of moose, and we evaluated the effect of the simultaneous presence of ticks and endoparasites on moose body condition. To do so, we collected organs to identify and count endoparasite species, estimate winter tick abundance, and measure subcutaneous fat thickness from 174 hunted moose in fall 2019 in 8 regions of Quebec. Our results showed that the prevalence and intensity of winter tick and gastrointestinal parasites differed among regions, as well as the prevalence of the heart parasite Taenia krabbei and the intensity of lung parasite Echinoccocus granulosus. Moose body condition, however, was not influenced by the simultaneous presence of winter tick and endoparasites. The documentation of the interactive effects of multiple parasite species on a host is fundamental given that future environmental conditions in temperate climate will favor the reproduction, development, and survival of several parasite species, which could affect parasite diversity and abundance in the environment and modify host–parasite dynamics.

For many mammals living at higher latitudes, food scarcity and snow-hindered movements associated with their first winter are synonymous of trying months. In addition, most wild animals have to cope with parasites. Many studies have been conducted on captive animals to assess consequences parasitism on health over winter, but comparable studies on wild populations are scarce for large mammals. Here, we performed winter tick ( Dermacentor albipictus Packard, 1869) counts and collected body condition data (mass and hematological parameters) on 15 moose ( Alces alces (Linnaeus, 1758)) calves from two distinct climatic regions in northern and southern New Brunswick (Canada) in January. The same calves were recaptured 3 months later to observe variation in body condition parameters. Higher tick loads and more drastic changes of hematological parameters, such as hematocrit and creatinine in southern individuals, suggested that this population might be suffering more from the consequences of winter tick infestation than the northernmost population. However, other parameters that were not measured in our study, such as quantity and quality of food, could influence moose calves body condition at the southeastern limit of their range.

Gap dynamics facilitate recruitment of late-successional species such as northern white-cedar (Thuja occidentalis L.). For this reason, harvests that result in partial rather than complete canopy removal have been suggested for cedar. However, success of regenerating cedar following partial harvests is uncertain, especially where there is heavy browsing by white-tailed deer (Odocoileus virginianus Zimmerman) or snowshoe hare (Lepus americanus). Efforts to understand how partial harvests and browsing interact to affect natural regeneration of cedar have been limited. We inventoried partially harvested stands along a gradient of 1–11 years since harvest in New Brunswick, Canada, in an area where deer frequently overwinter. Cedar regeneration was negatively influenced by browsing, but positively influenced by years since harvest and sapling basal area. Cedar seedling survival was assessed over a 2-year period and found to be primarily a function of height at initial measurement, with little influence of browsing. Annual vertical gain of cedar seedlings (a surrogate for height growth) decreased with increasing years since harvest and was influenced by distance from gap edge. In gaps, vertical gain increased with distance to gap edge, while distance to gap edge had a negative influence on vertical gain of seedlings in the matrix (between-gap areas). Many tagged cedar seedlings disappeared prior to remeasurement. These were likely completely consumed by browsers, limiting our ability to determine relative influences of partial harvest and browsing on cedar regeneration. We conclude that partial harvests, as applied in this study, increase cedar abundance and vertical gain, but browsing may necessitate seedling protection. We suggest monitoring to confirm sufficient cedar regeneration in partially harvested stands, using exclosures where browsing is a concern, and retaining or at least delaying removal of seed-bearing cedar overstory trees until regeneration has reached heights safe from browsing.