Personne : Dussault, Christian
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Université Laval. Département de biologie
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- PublicationAccès libreDetecting changes in the annual movements of terrestrial migratory species : using the first-passage time to document the spring migration of caribou(BioMed Central Ltd., 2014-08-01) Dussault, Christian; Côté, Steeve D.; Le Corre, Mael René VincentBackground : Migratory species face numerous threats related to human encroachment and climate change. Several migratory populations are declining and individuals are losing their migratory behaviour. To understand how habitat loss or changes in the phenology of natural processes affect migrations, it is crucial to clearly identify the timing and the patterns of migration. We propose an objective method, based on the detection of changes in movement patterns, to identify departure and arrival dates of the migration. We tested the efficiency of our approach using simulated paths before applying it to spring migration of migratory caribou from the Rivière-George and Rivière-aux-Feuilles herds in northern Québec and Labrador. We applied the First-Passage Time analysis (FPT) to locations of 402 females collected between 1986 and 2012 to characterize their movements throughout the year. We then applied a signal segmentation process in order to segment the path of FPT values into homogeneous bouts to discriminate migration from seasonal range use. This segmentation process was used to detect the winter break and the calving ground use because spring migration is defined by the departure from the winter range and the arrival on the calving ground. Results : Segmentation of the simulated paths was successful in 96% of the cases, and had a high precision (96.4% of the locations assigned to the appropriate segment). Among the 813 winter breaks and 669 calving ground use expected to be detected on the FPT profiles, and assuming that individuals always reduced movements for each of the two periods, we detected 100% of the expected winter breaks and 89% of the expected calving ground use, and identified 648 complete spring migrations. Failures to segment winter breaks or calving ground use were related to individuals only slowing down or performing less pronounced pauses resulting in low mean FPT. Conclusion : We show that our approach, which relies only on the analysis of movement patterns, provides a suitable and easy-to-use tool to study species exhibiting variations in their migration patterns and seasonal range use.
- PublicationAccès libreTemporally dynamic habitat suitability predicts genetic relatedness among caribou(The Royal Society Publishing, 2014-08-13) Dussault, Christian; Pellissier, Loïc; Yannic, Glenn; Côté, Steeve D.; Le Corre, Mael René Vincent; Bernatchez, LouisLandscape heterogeneity plays a central role in shaping ecological and evolutionary processes. While species utilization of the landscape is usually viewed as constant within a year, the spatial distribution of individuals is likely to vary in time in relation to particular seasonal needs. Understanding temporal variation in landscape use and genetic connectivity has direct conservation implications. Here, we modelled the daily use of the landscape by caribou in Quebec and Labrador, Canada and tested its ability to explain the genetic relatedness among individuals. We assessed habitat selection using locations of collared individuals in migratory herds and static occurrences from sedentary groups. Connectivity models based on habitat use outperformed a baseline isolation-by-distance model in explaining genetic relatedness, suggesting that variations in landscape features such as snow, vegetation productivity and land use modulate connectivity among populations. Connectivity surfaces derived from habitat use were the best predictors of genetic relatedness. The relationship between connectivity surface and genetic relatedness varied in time and peaked during the rutting period. Landscape permeability in the period of mate searching is especially important to allow gene flow among populations. Our study highlights the importance of considering temporal variations in habitat selection for optimizing connectivity across heterogeneous landscape and counter habitat fragmentation.
- PublicationRestreintInfluence of habitat features and hunter behaviour on white-tailed deer harvest(Washington Wildlife Society, 2012-04-05) Dussault, Christian; Massé, Ariane; Côté, Steeve D.; Lebel, FrançoisSport hunting may help in controlling cervid populations over large areas. As with natural predators, several environmental factors can influence sport harvest. A better understanding of the environmental variables that limit the efficiency of sport hunting could provide guidelines for more efficient wildlife management using hunting. We studied white-tailed deer (Odocoileus virginianus) hunting on a high deer density island where hunting was the sole form of predation. Our objective was to study the behavior of sport hunters and determine the habitat characteristics (e.g., abundance of deer forage, visibility of the deer from the hunter's point of view, and accessibility of the territory to hunters) that are associated with a successful harvest. We collected movements and harvest site location data from 477 hunters equipped with handheld Global Positioning System (GPS) units. Harvest sites were visited and characterized, along with a paired random site, to determine the environmental conditions associated with a successful hunt. We also developed a model to predict the daily number of deer seen by hunters considering weather conditions, hunter characteristics (e.g., age, experience), and date of hunting. We used the mean number of deer seen per hunter per day as a relative index of local density in each hunted territory. At both the site and landscape scales, the combination of visibility and access had a positive effect on the distribution of harvested deer. Habitat types with less visual obstruction from vegetation enabled hunters to see more deer in a given day. At the site scale, harvested deer were located in areas with a lower density of access routes compared to areas where hunters travelled throughout the day. Using an innovative approach of studying hunter behavior with GPS technology, digital maps, and questionnaires, we highlighted the factors associated with hunter success. Our study suggests that habitat characteristics could be modified to increase harvest by improving accessibility and visibility near roads. Creating openings in mature and regenerating forest near access roads could make sport hunting a more efficient management tool, but the potential impact of increased forage availability in forest openings should not be overlooked. © 2012 The Wildlife Society.
- PublicationAccès libreCaribou herd dynamics : impacts of climate change on traditional and sport harvesting(Université Laval, ArcticNet Inc., 2012-01-01) Tremblay, Jean-Pierre; Festa-Bianchet, Marco; Dussault, Christian; Brodeur, Vincent; Hins, Caroline; Côté, Steeve D.; Simard, M.; Le Corre, Mael René Vincent; Taillon, Joëlle; Sharma, SapnaCaribou (Rangifer tarandus) are a key species in Arctic ecosystems including northern Québec and Labrador. They play a central role in the ecology of predators and the structure of Arctic plant communities. In addition, caribou provide socioeconomic and cultural benefits from subsistence and sport hunting activities. Changes in the distribution and abundance of caribou due to global climate change would have serious biological, societal, and economic implications. Direct and indirect consequences of climate change on migratory caribou herds may include alteration in habitat use, migration patterns, foraging behaviour and demography. For example, caribou may experience a further northerly shift in distribution due to several factors including longer ice-free periods, increases in snowfall and extreme weather events, alterations in the fire regime, and changes in the distribution of insects and predators. Future research by Caribou Ungava, a research group interested in the ecology of migratory caribou in the context of climate change, will address the factors outlining variations in the population dynamics of caribou, implications for survival and reproduction, as well as the response of caribou habitat to different climate change scenarios. Management efforts focusing on mitigating greenhouse gases to reduce the potential effects of climate change, preserving high quality habitat, limiting anthropogenic landscape disturbances, and managing hunting in a sustainable manner, could alleviate stressors on migratory caribou of the QuébecLabrador peninsula.
- PublicationRestreintLong-term decline in white-tailed deer browse supply: can lichens and litterfall act as alternative food sources that preclude density-dependent feedbacks(Canadian Science Publishing, 2005-09-14) Tremblay, Jean-Pierre; Dussault, Christian; Thibault, Isabel.; Huot, Jean; Côté, Steeve D.Selective browsing by cervids has persistent impacts on forest ecosystems. On Anticosti Island, Quebec, Canada, introduced white-tailed deer (Odocoileus virginianus (Zimmermann, 1780)) have caused massive changes to the native boreal forest. Despite the apparent stability of the deer population over recent decades, we suspected that they were not at equilibrium with their browse supply and that further degradation of the habitat had occurred. A comparison of two browse surveys conducted 25 years apart showed a strong decline in browse availability. Although balsam fir (Abies balsamea (L.) P. Mill.) remained the most available browse species, it declined or disappeared from most stands (n = 13). Preferred deciduous species that were still available 25 years ago have almost disappeared. The continuous decline of the browse supply confirmed our hypothesis. This situation may be exacerbated by a subsidy from the winter litterfall, a significant and stable alternative food source. The abundance of litterfall from mature trees is independent of browsing over a long time period, which introduces a temporal uncoupling between the impact of deer browsing on balsam fir seedlings and the negative feedback from recruitment failure of mature balsam fir on the deer population. This means that the system is susceptible to being forced into an alternative regime.
- PublicationAccès libreSimulated drilling noise affects the space use of a large terrestrial mammal(Nordic Council of Wildlife Research, 2016-11-01) Dussault, Christian; Drolet, Amélie; Côté, Steeve D.Wildlife is exposed to increasing anthropogenic disturbances related to shale oil and gas extraction in response to rising worldwide demands. As these disturbances increase in intensity and occurrence across the landscape, understanding their impacts is essential for management. On Anticosti Island (Québec, Canada), we equipped six white-tailed deer Odocoileus virginianus with GPS collars taking hourly locations. We then designed a playback experiment by simulating constant drilling noise emitted by generators to which half of the collared deer were exposed for a three-week period. Deer tolerated noise levels up to 70 dB(C). However, the number of locations recorded in areas where the noise was above 70 dB(C) was on average 73% (SE ± 18%) lower than before the disturbance, which suggests that deer experienced fine scale functional habitat loss. This loss of habitat occurred up to 200 m from the noise source. The size of home ranges and movement rates did not appear to be affected by the noise disturbance. In addition, during the experiment, deer were able to relocate in areas of their home range where food availability was similar to that of sites used before the disturbance. These results show that drilling noise can affect the habitat use of white-tailed deer. However, future research is needed to better understand the cumulative impacts of shale mining on large mammals, as this study isolated only one of the many disturbances present near mining sites and for a limited period.
- PublicationRestreintLandscape attributes explain migratory caribou vulnerability to sport hunting(Wildlife Society, 2016-12-04) Dussault, Christian; Côté, Steeve D.; Plante, SabrinaHuman disturbances are increasing in Arctic regions and have been suggested as one of the main factors explaining caribou (Rangifer tarandus) decline. The cumulative effects of disturbances may negatively affect caribou habitat use, survival, and population dynamics. Thus, there is a need to evaluate the impact of various human disturbances, especially those that cause direct mortality (e.g., sport hunting). We evaluated the relative importance of caribou and hunter habitat selection and landscape characteristics on caribou vulnerability to sport hunting in northern Québec, Canada. We used resource selection functions to describe habitat selection of 223 caribou and 87 hunters. We then characterized >169,000 caribou harvest sites recorded over 17 years according to the relative probability of co-occurrence of caribou and hunters, the relative probability of occurrence of hunters only, or the characteristics of the landscape (e.g., distance to human infrastructures, elevation, land cover type). Landscape characteristics better explained caribou vulnerability to sport hunting than habitat selection of caribou and hunters, or their co-occurrence. Caribou were more vulnerable in proximity to hunting infrastructures (e.g., roads, outfitter camps) than elsewhere, but caribou strongly avoided roads. Caribou were also more vulnerable on frozen lakes than in other land cover types. Lakes were, however, avoided by caribou and not selected by hunters. Harvest was more likely in smoother terrain, even if caribou and hunters did not select for this characteristic. We demonstrated caribou were more vulnerable in areas with good accessibility (near roads) or where caribou were easily detectable (lakes, smoother terrain), which also represents areas that were either avoided or not selected by caribou or hunters. This discrepancy between harvest distribution and behaviors of caribou and hunters suggests that harvest may be an opportunistic event where visibility and accessibility increased chances of success for hunters. Managers could use this information to manipulate hunting success according to population estimates and harvest quota by establishing minimal distance to risky areas within which hunting would be prohibited.
- PublicationRestreintWeather conditions and variation in timing of spring and fall migrations of migratory caribou(American Society of Mammalogist, 2016-11-10) Dussault, Christian; Côté, Steeve D.; Le Corre, Mael René VincentSpecies that make long-distance migrations face changes in the phenology of natural processes linked to global climate changes. Mismatch between the onset of resources and arrival on breeding grounds or changes in the conditions faced during migration such as early snowmelt in northern environments could have severe impacts on migrant populations. We investigated the impact of local weather and broad-scale climate and of the availability of forage resources on timing of spring and fall migrations of migratory caribou (Rangifer tarandus) from the Rivière-George and Rivière-aux-Feuilles herds in northern Québec and Labrador, Canada. We tested the effect of local weather using data provided by the Canadian Regional Climate Model, a large-scale climate index, snow and ice cover, and the Normalized Difference Vegetation Index on departure and arrival dates of 377 spring migrations and 499 fall migrations of female caribou. Since 2000, except for the spring arrival, migrations tended to occur earlier. Spring arrival was delayed when caribou encountered mild temperatures and abundant precipitation during migration, as early snowmelt may increase cost of movements. At greater population sizes, caribou seemed to limit the time spent on summer range by arriving later and departing earlier, possibly to limit competition for summer forage. During fall, caribou adjusted their migration to conditions en route because they arrived earlier if November was snowy and mild, possibly to limit the costs of moving through deep snow. Like numerous migrant species, most caribou herds are declining, and it is crucial to assess which environmental factors affect migrant populations. Our study contributes to the understanding of the impact of local weather conditions and climate change on migratory land mammals.
- PublicationRestreintEcological impacts of deer overabundance(Annual Reviews Inc., 2004-06-10) Tremblay, Jean-Pierre; Rooney, Thomas P.; Dussault, Christian; Côté, Steeve D.; Waller, Donald M.Deer have expanded their range and increased dramatically in abundance worldwide in recent decades. They inflict major economic losses in forestry, agriculture, and transportation and contribute to the transmission of several animal and human diseases. Their impact on natural ecosystems is also dramatic but less quantified. By foraging selectively, deer affect the growth and survival of many herb, shrub, and tree species, modifying patterns of relative abundance and vegetation dynamics. Cascading effects on other species extend to insects, birds, and other mammals. In forests, sustained overbrowsing reduces plant cover and diversity, alters nutrient and carbon cycling, and redirects succession to shift future overstory composition. Many of these simplified alternative states appear to be stable and difficult to reverse. Given the influence of deer on other organisms and natural processes, ecologists should actively participate in efforts to understand, monitor, and reduce the impact of deer on ecosystems.
- PublicationRestreintCoping with strong variations in winter severity : plastic habitat selection of deer at high density(International Society for Behavioral Ecology, 2017-04-20) Veillette, Alexandre; Dussault, Christian; Giroux, Marie-Andrée; Courbin, Nicolas; Côté, Steeve D.Few empirical studies on large herbivores considered how behavioral plasticity could enhance their capacity to cope with rapid and extreme changes in weather conditions at several spatiotemporal scales. During winter, large herbivores living under low predation pressure mainly trade-off benefits of forage acquisition with the costs of exposure to harsh weather conditions. We assessed the changes in this trade-off for white-tailed deer adult females on Anticosti Island (Canada) at different scales during 2 contrasted winters (i.e., a harsher and a milder winter). We hypothesized that deer should adjust their foraging decisions to avoid cold wind-chill temperatures and high locomotion costs in deep snow as winter severity increased. We compared habitat selection at the home-range scale, habitat selection relative to thermal conditions within the home range, and selection for foraging sites relative to snow conditions along the foraging tracks between winters. Home-range selection of deer was similar between winters. Deer adjusted their within-home-range selection relative to thermal conditions: they selected thermal cover during cold-stress periods while their selection for open areas increased during the warmer periods. Deer showed high behavioral plasticity along their foraging tracks: they selected tracks with different forage resources between winters and traded-off the locomotion costs in deep snow cover with the benefits of forage availability as winter severity increased. We discuss how behavioral plasticity of deer in their thermoregulatory behavior and foraging site selection allows them to cope with varying winter conditions, in a system where their short-term behavioral adaptations were already strongly constrained by intraspecific competition.