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Côté, Steeve D.

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Steeve D.
Université Laval. Département de biologie
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Voici les éléments 1 - 10 sur 109
  • Publication
    Accès libre
    Species indicators of ecosystem recovery after reducing large herbivore density : comparing taxa and testing species combinations
    (Elsevier Science Ireland, 2014-03-01) Brousseau, Pierre-Marc; Cloutier, Conrad; Poulin, Monique; Moretti, Marco; Cardinal, Étienne; De Cáceres, Miquel; Bachand, Marianne; Pellerin, Stéphanie; Côté, Steeve D.; Hébert, Christian; Martin, Jean-Louis
    Indicator species have been used successfully for estimating ecosystem integrity, but comparative studies for defining optimal taxonomic group remain scarce. Furthermore, species combinations may constitute more integrative tools than single species indicators, but case studies are needed to test their efficiency. We used Indicator Species Analysis, which statistically determines the association of species to one or several groups of sites, to obtain indicators of ecosystem recovery after various deer density reductions. We used five taxonomic groups: plants, carabid beetles, bees, moths and songbirds. To test whether species combinations could complement single indicator species, we used plants as a model taxon and examined the indicator value of joint occurrence of two or three plant species. Our study relies on experimental controlled browsing enclosures established for six years on Anticosti Island (Quebec). Four levels of deer density (0, 7.5 and 15 deer km-2 and natural densities between 27 and 56 deer km-2) were studied in two vegetation cover types (uncut forests and cut-over areas), in a full factorial design for a total of eight experimental treatments. For all taxa but bees, we tested 54 treatment groups consisting in one specific density or in a sequence of two or more consecutive deer densities in one or both cover types (ten groups for bees, sampled only in cut-over areas). We found 12 plants, 11 moths and one songbird to be single species indicators of ecosystem conditions obtained under 12 different treatment groups. Six treatment groups were indicated by plants and six different ones by moths, of which one group was also identified by a songbird species. Moths were thus worth the extra sampling effort, especially since the groups they indicated were more treatment-specific (mainly one or two deer density treatments). We tested the same 54 treatment groups for plant species combinations represented by two or three co-occurring species. Plant combinations efficiently complemented plant singletons for detecting ecosystem conditions obtained under various deer densities. In fact, although singletons were highly predictive, 17 additional treatment groups were identified exclusively with two- and three-species combinations, some being more treatment-specific. Our findings show that plants and moths provide complementary indicators of ecosystem conditions under various deer densities, and that computing species combinations increases our capacity to monitor ecosystem recovery after reducing herbivore densities.
  • Publication
    Accès libre
    Compositional and functional trajectories of herbaceous communities after deer density control in clear-cut boreal forests
    (Conseil national de recherches du Canada, 2015-02-17) Tremblay, Jean-Pierre; Poulin, Monique; Bachand, Marianne; Pellerin, Stéphanie; Côté, Steeve D.
    Overabundant populations of large herbivores have strong persistent effects on forest composition, structure, and function. However, the mechanism through which plant communities recover their original composition and function after herbivore management remains poorly understood. We assessed the temporal trajectories of the herbaceous communities in Abies balsamea (L.) Mill. and Picea glauca (Moench) Voss stands on Anticosti Island (Quebec, Canada) over 8 years following clear-cutting and deer management. The impact of deer exclusion or reduction to 7.5 and 15 deer·km–2 was compared with benchmark in situ deer densities (27 and 56 deer·km–2). Effects of deer management treatments on plant species and functional trait assemblages over time were assessed using principal response curves. Although complete deer exclusion seemed necessary to modify species composition from that occurring under intense browsing, a reduced density of 7.5 deer·km–2 was sufficient to induce significant changes in functional trait assemblages of regenerating stands. For instance, reduced deer densities favored plants with brightly colored flowers and compound inflorescences pollinated by animals and producing large seeds and fleshy fruits dispersed by animals. We conclude that the boreal forest's herbaceous communities are resilient to chronic browsing when deer population reduction and forest clearcutting are applied in synergy.
  • Publication
    Accès libre
    Are feeding preferences of white-tailed deer related to plant constituents?
    (Bioone, 2011-05-25) Dostaler, Simon; Therrien, Jean-François; Ouellet, Jean-Pierre; Côté, Steeve D.
    Controlled feeding experiments can provide valuable insights into food selection of herbivores. We conducted cafeteria trials on captive yearling white-tailed deer (Odocoileus virginianus) during 2 years to determine feeding preferences in relation to plant chemical constituents, i.e., nitrogen and fibers. We simultaneously offered 8 species of cultivated and wild plants in monthly foraging trials conducted from June to October. We predicted that species preferences would be positively related to protein content from June to August and to digestible energy in September and October. As predicted, crude protein (CP) was positively related to feeding preferences, particularly as summer progressed. Feeding preferences were also negatively related to fiber content, especially in early summer. Our results indicate high protein needs over the complete growing season for yearling deer but a decrease in overall plant selectivity as summer progresses. Our results also suggest that deer browsing on cultivated plants might be due to higher CP content of cultivated plants than wild plants. To prevent deer impact on crops, managers should favor regeneration of plants rich in CP content in forests.
  • Publication
    The role of previous social encounters and body mass in determining social rank : an experiment with white-tailed deer
    (Baillière Tindall, 2006-09-20) Côté, Steeve D.; Taillon, Joëlle
    The social organization of many vertebrates is based on dominance behaviours occurring between pairs of individuals. Initial encounters between any two individuals can be crucial in determining the dominance relationship that will prevail between them throughout their lifetime. Achieving a high dominance status can be critical when competition for limited resources such as foraging sites is intense. The mechanisms that prevail for the establishment and stability of dominance relationships between individuals are, however, poorly understood. Our study aims to identify factors influencing the establishment of dominance relationships between young individuals, using white-tailed deer, Odocoileus virginianus, fawns as a model species, and to evaluate the possibility of long-term individual recognition after temporal separation. We used an experimental approach to test the alternative hypotheses that dominance relationships after temporal separation are explained by (1) the outcome of the previous encounters between opponents or (2) the body mass difference between individuals independently of the outcome of initial encounters. Social rank was established during the first encounters between individuals based on differences in body mass and was maintained afterwards even when the differences in mass between individuals were reversed. Our results suggest that individual long-term recognition may influence the outcome and the stability of dominance relationships after temporal separation of individuals. Dyadic dominance relationships seem to be established early in life and may then endure into adulthood.
  • Publication
    Habitat selection of a large herbivore at high density and without predation : trade-off between forage and cover?
    (American Society of Mammalogists., 2009-08-14) Massé, Ariane; Côté, Steeve D.
    Although herbivores are generally known to trade off forage in open habitat patches and cover in forested habitat patches, it remains unclear if high population density and low predation risk can modulate the trade-off between forage and cover. We studied a population of white-tailed deer (Odocoileus virginianus) that was at high density and on a large island free of predators to assess the influence of forage and cover on habitat selection under harsh environmental conditions. We fitted 19 female white-tailed deer with global positioning system collars and delineated summer home ranges and core areas. We sampled vegetation in the core areas and in the rest of the home ranges to determine abundance of forage and forest cover within habitat patches, and assessed habitat selection between open and forested habitat patches. At a coarse scale, white-tailed deer preferred open habitat patches over forested ones, suggesting that they adopted a foraging strategy favoring energy intake. At a fine scale, habitat selection was influenced positively by the percentage of ground cover of forbs and deciduous shrubs, but negatively by conifer density. The biomass of preferred plant species, lateral cover, fir regeneration, and distance to the nearest open-forest edge were not strong predictors of habitat selection by deer. We conclude that fine-scale habitat selection by white-tailed deer at high population density and in the absence of predation is mainly determined by forage abundance. These patterns of habitat selection demonstrate that herbivores can adjust their behavior to other limiting factors when predation risk is relaxed.
  • Publication
    Body-condition dynamics in a northern ungulate gaining fat in winter
    (Canadian Science Publishing, 2008-04-07) Couturier, Serge; Côté, Steeve D.; Huot, Jean; Otto, Robert D.
    Individual condition generally depends on density and is partly determined by habitat quality and climate. Westudied long-term trends in the condition and productivity of female caribou (Rangifer tarandus(L., 1758)) in two largemigratory herds in the Quebec–Labrador peninsula (Canada), the George and the Feuilles herds. Females from the Georgeherd were in better summer condition than those from the more abundant Feuilles herd in 2001–2002, while it was the op-posite in 1988 when the Feuilles herd was less abundant than the George herd. Summer nutrition followed the same pat-tern between herds through time. Spring body condition of females in the George herd declined from 1976 to the mid-1980s during early population growth. Fall condition, however, did not change from 1983 to 2002 when caribou numbersfirst peaked and later declined. Pregnancy rates were inversely related to herd size in both herds. Vegetation quality(NDVI) in June was significantly related to body proteins in the fall. Albeit unusual for a northern ungulate, body fat in-creased from fall to spring in the George herd. We conclude that a relatively small and highly grazed summer range, aswell as density-dependent effects, affected summer nutrition and the need to continue lipogenesis during winter.
  • Publication
    Spring normalized difference vegetation index (NDVI) predicts annual variation in timing of peak faecal crude protein in mountain ungulates
    (British Ecological Society, 2009-04-28) Hamel, Sandra; Garel, Mathieu; Festa-Bianchet, Marco; Côté, Steeve D.; Gaillard, Jean-Michel
    1 In recent years, the Normalized Difference Vegetation Index (NDVI) has been used to assess the relationships between habitat quality and animal life-history traits. Since numerous ecological studies now use NDVI rather than perform direct vegetation assessments, field validations are essential to provide confidence in the biological significance of NDVI estimates. While some studies have compared NDVI with plant biomass, very few examined the relationship between NDVI and changes in vegetation quality. 2 Using data from two long-term studies of alpine ungulates, we assessed the relationship between two NDVI indices and the date of peak in faecal crude protein (FCP), which represents temporal variability in the availability of high-quality vegetation. We also evaluated if NDVI data could predict annual variation in the timing of spring green-up. 3 In both populations, integrated NDVI in June was negatively correlated with the date of the peak in FCP, indicating that high integrated NDVI values corresponded to early springs in alpine habitats. Maximum NDVI increase during spring green-up was positively correlated with the timing of peak FCP, illustrating that rapid increases in NDVI represented delayed springs. 4 Predicted values of date of peak FCP estimated each year from NDVI data satisfactorily fitted observed values, and prediction intervals included all observed values. These results suggest that NDVI can reliably predict variation over years in the timing of spring. 5 Synthesis and applications. Our long-term studies demonstrate that a multi-year time series of Normalized Difference Vegetation Index (NDVI) can reliably measure yearly changes in the timing of the availability of high-quality vegetation for temperate herbivores. This finding therefore supports the use of NDVI as a proxy for vegetation attributes in population ecology and wildlife management studies.
  • Publication
    Is territory defence related to plumage ornaments in the king penguin Aptenodytes patagonicus?
    (Blackwell, 2008-01-14) Viera, Vanessa; Nolan, Paul M.; Côté, Steeve D.; Jouventin, Pierre; Groscolas, René
    Colourful ornaments in monogamous birds may be directed at potential mates or other conspecifics to signal individual condition, reproductive status or fighting ability, especially in monogamous and territorial species. We investigated whether the size of the orange auricular patch may be an indicator of aggressiveness in the king penguin Aptenodytes patagonicus, a monogamous and territorial seabird. The relationship between auricular patch size and defence behaviour was explored relative to territory location (centre vs. periphery of the colony), period of reproduction (early vs. late), state of reproduction (incubation vs. brooding) and sex. The proportion of time spent in territorial defence and the rate of aggressive behaviours were positively correlated with auricular patch size, mainly because central birds were more aggressive than peripheral birds and also had larger patch sizes. The period of reproduction, state of reproduction and sex did not interact with patch size to affect aggressiveness. Our results suggest that the size of the auricular patch in king penguins may be a reliable signal allowing individuals to evaluate the quality of mates or competitors in terms of aggressiveness. Whether aggressiveness is directly linked to patch size or indirectly through body condition, however, remains to be determined. In any event, birds with larger patches seem to gain central territories in the colony, thereby increasing their reproductive success. Finally, our study adds to the growing evidence that the evolution of sexually monomorphic ornaments may stem from mutual sexual selection.
  • Publication
    Equus kiang (Perissodactyla : Equidae)
    (American Society of Mammalogists, 2009-05-27) St-Louis, Antoine; Côté, Steeve D.
    Equus kiang Moorcroft, 1841, is an equid commonly called the kiang or Tibetan wild ass and is the only equid living on the Tibetan Plateau. It is the largest of the wild asses, with a distinct dark-brown coat on the back, and 1 of the 7 species of Equus. It is endemic to the high-elevation rangelands of China (Tibet, Xinjiang, Qinghai, and Gansu), India (Ladakh and Sikkim), Pakistan (Khunjerab National Park), and Nepal (Mustang). It inhabits open steppes and rolling hills sparsely vegetated with grasses and sedges. E. kiang is vulnerable to illegal poaching and competition with domestic livestock, and data are insufficient to accurately estimate its total abundance.
  • Publication
    Coping 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.