Université de Sherbrooke
M.Sc. candidate
Supervisor: Fanie Pelletier
Patrick Bergeron
Start: 2026-08-30
Personal page

Project

Individual and Environmental Drivers of Tick Prevalence and Infestation Intensity in Bighorn Sheep (Ovis canadensis)
Climate change is driving shifts in species’ geographic ranges toward higher latitudes, thereby altering the composition and structure of local ecological communities. These range shifts can generate novel interactions between resident species and newly established or expanding species. Among these interactions, changes in parasite transmission dynamics may have important consequences for host populations that are less adapted to newly occurring parasites. In addition, increasing temperatures and changes in seasonal duration may extend the transmission period of infectious stages and accelerate parasite development, thereby contributing to an increase in parasite load, prevalence, and infection intensity. Parasite transmission can also be influenced by other ecological factors, including host density and opportunities for intra- and interspecific transmission. Ticks are an important group of ectoparasites that inhabit the external surfaces of their hosts and obtain nutrients primarily through blood feeding. In addition, ticks serve as vectors for a wide range of pathogens and may therefore have consequences for host health, physiological condition, and reproductive performance. Tick infestation may also contribute to increasing host vulnerability following periods of energetic stress, such as winter. Climate-driven increases in precipitation and temperatures—which occur earlier in the spring and become more frequent in the summer— may create environmental conditions conducive to tick development, survival, and proliferation. However, parasite load is also determined by host-specific characteristics, including physiology, immune function, behavior, and social status, which may contribute to differences in infestation patterns among sexes and age classes. Although tick parasitism has been documented in several cervids, notably moose (Alces alces) and elk (Cervus canadensis), its effects on the condition and population dynamics of alpine ungulates remain poorly understood. Ram Mountain hosts the longest-running individual-based study of a bighorn sheep population. Since 2011, data on tick abundance has been collected at this site but remains unexploited, and the tick species present in the population remain unidentified. This long-term dataset provides a unique opportunity to investigate temporal variation in tick infestation and its potential associations with environmental and host-related factors in the context of ongoing climate change. The objective of my project is to characterize interannual and interindividual variation in the prevalence and intensity of tick infestation in bighorn sheep in relation to environmental variables, including winter duration and temperature, as well as host characteristics such as sex and age. In addition, my study will identify the tick species present at this study site. Consequently, this project will provide a better understanding of the factors shaping parasite–host interactions in alpine ungulates. More broadly, the results will thus help to better characterize this parasitic pressure and its implications for the conservation and management of this alpine population.

Keywords

Parasitologie, changements climatiques, Tiques, Mouflon d'Amérique (Ovis canadensis), Prévalence parasitaire, Intensité d'infestation

Publications

1- Nature-based coastal restoration: Development of an early-rearing production protocol of sugar kelp (Saccharina latissima Linnaeus) for bottom planting activities in the Gulf of St-Lawrence (Québec, Canada)
Le François, Nathalie R., Anne Tremblay-Gratton, Charles Drouin-Johnson, Jasmine Prégent, Marie-Pomme Presne-Poissant, Jean-Christophe Boussin, Florence Piché-Lebel, Isabelle Gendron-Lemieux
2023 Frontiers in Marine Science