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Data from: Adjustments in habitat selection to changing availability induce fitness costs for a threatened ungulate
Losier, Chrystel L.; Couturier, Serge; St-Laurent, Martin-Hugues; Drapeau, Pierre; Dussault, Claude; Rudolph, Tyler; Brodeur, Vincent; Merkle, Jerod A.; Fortin, Daniel — 2016-01-21 1. Functional responses in habitat selection occur when individuals adjust their selection of habitat features as a function of the availability of those features. Functional responses in habitat selection are generally assumed to be fitness-rewarding tactics and are used to guide conservation actions. Fitness consequences of functional responses, however, have rarely been evaluated. 2. Eighty-three caribou were followed with GPS collars to establish the link between functional responses in habitat selection and adult female survival, a strong fitness correlate for caribou. We measured how caribou avoidance of mixed/deciduous stands and 6–20-year-old clearcuts varied with the proportion of 6–20-year-old clearcuts within their 100% minimal convex polygon (MCP), and if these functional responses were linked to survival. Mixed/deciduous stands and 6–20-year-old clearcuts are risky for caribou because they are selected by moose, thereby attracting wolves and increasing predation risk for caribou. 3. Caribou avoided mixed/deciduous stands, especially when 6–20-year-old clearcuts comprised a large proportion of their MCP, but this functional response did not differ between caribou that died and those that survived. When the proportion of 6–20-year-old clearcuts in the MCP was low, caribou generally had low odds of occurring near 6–20-year-old clearcuts. However, when the proportion of clearcuts in the MCP was relatively high, caribou that strongly increased their odds of being near 6–20-year-old clearcuts were generally those that died. 4. Synthesis and applications. Assessing the fitness consequences of how animals respond to habitat disturbances is central to wildlife conservation. We demonstrate that distinct functional responses in habitat selection involve different mortality risks and that population dynamics should depend on the frequency of the different tactics observed within populations. Individuals that persistently select riskier areas should be important drivers of population decline. Caribou mortality could be reduced by decreasing the appeal of 6–20-year-old clearcuts for moose by removing deciduous vegetation through cleaning, which should reduce the selection of wolves for these stands. Removing deciduous vegetation should be especially effective in areas where those clearcuts comprise a large proportion of the landscape, because this is where a subset of the caribou population experiences high mortality rates by selecting 6–20-year-old clearcuts.
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Data from: A spatial theory for characterizing predator–multiprey interactions in heterogeneous landscapes
Fortin, Daniel; Buono, Pietro-Luciano; Schmitz, Oswald J.; Courbin, Nicolas; Losier, Chrystel; St-Laurent, Martin-Hugues; Drapeau, Pierre; Heppell, Sandra; Dussault, Claude; Brodeur, Vincent; Mainguy, Julien — 2015-07-14 Trophic interactions in multiprey systems can be largely determined by prey distributions. Yet, classic predator–prey models assume spatially homogeneous interactions between predators and prey. We developed a spatially informed theory that predicts how habitat heterogeneity alters the landscape-scale distribution of mortality risk of prey from predation, and hence the nature of predator interactions in multiprey systems. The theoretical model is a spatially explicit, multiprey functional response in which species-specific advection–diffusion models account for the response of individual prey to habitat edges. The model demonstrates that distinct responses of alternative prey species can alter the consequences of conspecific aggregation, from increasing safety to increasing predation risk. Observations of threatened boreal caribou, moose and grey wolf interacting over 378 181 km2 of human-managed boreal forest support this principle. This empirically supported theory demonstrates how distinct responses of apparent competitors to landscape heterogeneity, including to human disturbances, can reverse density dependence in fitness correlates.
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Data from: Forest productivity mitigates human disturbance effects on late-seral prey exposed to apparent competitors and predators
Fortin, Daniel; Barnier, Florian; Drapeau, Pierre; Duchesne, Thierry; Dussault, Claude; Heppell, Sandra; Prima, Marie-Caroline; St-Laurent, Martin-Hugues; Szor, Guillaume — 2020-02-20 Primary production can determine the outcome of management actions on ecosystem properties, thereby defining sustainable management. Yet human agencies commonly overlook spatio-temporal variations in productivity by recommending fixed resource extraction thresholds. We studied the influence of forest productivity on habitat disturbance levels that boreal caribou – a threatened, late-seral ungulate under top-down control – should be able to withstand. Based on 10 years of boreal caribou monitoring, we found that adult survival and recruitment to populations decreased with landscape disturbance, but increased with forest productivity. This benefit of productivity reflected the net outcome of an increase in resources for apparent competitors and predators of caribou, and a more rapid return to the safety of mature conifer forests. We estimated 3-fold differences in forest harvesting levels that caribou populations could withstand due to variations in forest productivity. The adjustment of ecosystem provisioning services to local forest productivity should provide strong conservation and socio-economic advantages.
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Data from: Linking GPS telemetry surveys and scat analyses helps explain variability in black bear foraging strategies
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Lesmerises, Rémi; Rebouillat, Lucie; Dussault, Claude; St-Laurent, Martin-Hugues — 2016-05-22 Studying diet is fundamental to animal ecology and scat analysis, a widespread approach, is considered a reliable dietary proxy. Nonetheless, this method has weaknesses such as non-random sampling of habitats and individuals, inaccurate evaluation of excretion date, and lack of assessment of inter-individual dietary variability. We coupled GPS telemetry and scat analyses of black bears Ursus americanus Pallas to relate diet to individual characteristics and habitat use patterns while foraging. We captured 20 black bears (6 males and 14 females) and fitted them with GPS/Argos collars. We then surveyed GPS locations shortly after individual bear visits and collected 139 feces in 71 different locations. Fecal content (relative dry matter biomass of ingested items) was subsequently linked to individual characteristics (sex, age, reproductive status) and to habitats visited during foraging bouts using Brownian bridges based on GPS locations prior to feces excretion. At the population level, diet composition was similar to what was previously described in studies on black bears. However, our individual-based method allowed us to highlight different intra-population patterns, showing that sex and female reproductive status had significant influence on individual diet. For example, in the same habitats, females with cubs did not use the same food sources as lone bears. Linking fecal content (i.e., food sources) to habitat previously visited by different individuals, we demonstrated a potential differential use of similar habitats dependent on individual characteristics. Females with cubs-of-the-year tended to use old forest clearcuts (6–20 years old) to feed on bunchberry, whereas females with yearling foraged for blueberry and lone bears for ants. Coupling GPS telemetry and scat analyses allows for efficient detection of inter-individual or inter-group variations in foraging strategies and of linkages between previous habitat use and food consumption, even for cryptic species. This approach could have interesting ecological implications, such as supporting the identification of habitats types abundant in important food sources for endangered species targeted by conservation measures or for management actions for depredating animals.

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(Author: Dussault, Claude)

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