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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: Temporal dynamics in animal community assembly during post-logging succession in boreal forest
Le Borgne, Hélène; Hébert, Christian; Dupuch, Angélique; Bichet, Orphé; Pinaud, David; Fortin, Daniel — 2019-09-13 Species assemblages can result from deterministic processes, such as niche differentiation and interspecific interactions, and from stochastic processes, such as random colonisation and extinction events. Although changes in animal communities following disturbances have been widely examined, few studies have investigated the mechanisms structuring communities during ecological succession. We assessed the impact of logging on small mammal and beetle assemblages in landscapes dominated by old-growth boreal forests. Our objectives were to 1) characterize variations in communities during the first 66 years of post-harvest forest succession, 2) determine if there are non-random patterns of species co-occurrence (i.e., deterministic processes), and if there are, 3) establish whether non-random co-occurrences are best explained by habitat attributes or by interspecific interactions. We captured small mammals and beetles along a gradient of forest succession (5-66 years) and in old-growth forest, and characterized key vegetation attributes. First, we tested whether community compositions in clear-cut stands became similar to those in natural stands after 66 years. We then used null models, which were either unconstrained or constrained by habitat attributes, to address the last two objectives and distinguish effects of vegetation attributes from interspecific interactions on community assembly. We showed that beetle assemblages differed in stands 21-30 years post-harvest compared to old-growth forests. In contrast, harvesting did not influence the composition of small mammal communities. Overall, our results suggest that community assembly during forest succession is driven by both stochastic and deterministic processes, the latter being linked to interspecific interactions more strongly than to vegetation attributes.
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Data for: Global change risks a threatened species due to alteration of predator-prey dynamics
Labadie, Guillemette; Hardy, Clément; Boulanger, Yan; Vanlandeghem, Virginie; Hebblewhite, Mark; Fortin, Daniel — 2023-03-01 <p>Datasets generated and analyzed within the study area located in the Côte-Nord region of Québec, Canada. To identify species-specific movement rules that were implemented in the IBM, we used empirical data collected for caribou, moose, and wolves over the study area.</p> <p>"DataFinal_SSF_Species_season.csv" (6 files) were used to develop Step Selection Functions for caribou, moose, and wolves to assess habitat selection. <span lang="EN-CA">SSFs</span><span lang="EN-CA"> were estimated from data for the real animals and provide the relative probability of selection among a set of options based on the comparison of observed and random steps (i.e., the linear segment between successive locations at 8-h interval) using conditional</span><span lang="EN-CA"> logistic regression </span><span lang="EN-CA">(Fortin et al. 2005). Details on GPS data and SSF models can be found in the article in Appendix S1: Section S2. </span></p> <p>SSFs compare resource characteristics of observed (scored 1) and random (scored 0) locations presented in column case. Habitat characteristics (columns conif_dense, conif_open, mixed, open, other, fire010, fire1020, fire20, cut010, cut1020, cut20) was extracted from the Canadian National Forest Inventory (NFI) forest cover maps. Land cover maps were updated every year by adding roads, recent (&lt;5 years), regenerating (6–20 years) and old (21–50 years) cutblocks/fires based on information provided annually by local forestry companies and from the Canadian National Fire Database (CNFDB).  Columns dist0_0.25, dist0.25_0.50, dist0.5_1.00, dist1.00_1.5, and dist1.5 are a set of 5 dichotomous covariables representing the classes of distance to the nearest road (i.e., 1) ≤250 m, 2) 251–500 m, 3) 501–1000 m, 4) 1001–1500 m and 5) &gt;1500 m as the reference category).</p> <p>"DataFinal_IBM_Caribou_Season.csv" (2 files) corresponded to the IBM outputs with the proportion of caribou agent killed (Prop.Caribou_killed, number of caribou killed/total number of caribou), in function of the different scenarios (CC,LUC,Year,Season,Scenario) and the response (Behavioral-Numerical responses or Behavioral response). The columns Prop.CutsRoads, Prop.Fire, Prop.Broadleaf, Homogenization, Isolation correspond to the different variable we tested to predict the cumulative impact of anthropogenic disturbance and climate change. To explore how changes in forest structure and composition impacted the proportion of caribou killed, we used the proportion of areas disturbed by cuts and roads (Prop.CutsRoads), burned areas (Prop.Fire), and landscape characteristics, such as the proportion of deciduous vegetation (Prop.Broadleaf), landscape homogenization (Homogenization) and isolation (Isolation) of mature conifer stands.</p> https://creativecommons.org/publicdomain/zero/1.0/
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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: Energy benefits and emergent space use patterns of an empirically parameterized model of memory-based patch selection
Merkle, Jerod A.; Potts, Jonathan R.; Fortin, Daniel — 2016-07-14 Many species frequently return to previously visited foraging sites. This bias towards familiar areas suggests that remembering information from past experience is beneficial. Such a memory-based foraging strategy has also been hypothesized to give rise to restricted space use (i.e. a home range). Nonetheless, the benefits of empirically derived memory-based foraging tactics and the extent to which they give rise to restricted space use patterns are still relatively unknown. Using a combination of stochastic agent-based simulations and deterministic integro-difference equations, we developed an adaptive link (based on energy gains as a foraging currency) between memory-based patch selection and its resulting spatial distribution. We used a memory-based foraging model developed and parameterized with patch selection data of free-ranging bison Bison bison in Prince Albert National Park, Canada. Relative to random use of food patches, simulated foragers using both spatial and attribute memory are more efficient, particularly in landscapes with clumped resources. However, a certain amount of random patch use is necessary to avoid frequent returns to relatively poor-quality patches, or avoid being caught in a relatively poor quality area of the landscape. Notably, in landscapes with clumped resources, simulated foragers that kept a reference point of the quality of recently visited patches, and returned to previously visited patches when local patch quality was poorer than the reference point, experienced higher energy gains compared to random patch use. Furthermore, the model of memory-based foraging resulted in restricted space use in simulated landscapes and replicated the restricted space use observed in free-ranging bison reasonably well. Our work demonstrates the adaptive value of spatial and attribute memory in heterogeneous landscapes, and how home ranges can be a byproduct of non-omniscient foragers using past experience to minimize temporal variation in energy gains.
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Data from: Equivalence between step selection functions and biased correlated random walks for statistical inference on animal movement
Duchesne, Thierry; Fortin, Daniel; Rivest, Louis-Paul — 2016-03-03 Animal movement has a fundamental impact on population and community structure and dynamics. Biased correlated random walks (BCRW) and step selection functions (SSF) are commonly used to study movements. Because no studies have contrasted the parameters and the statistical properties of their estimators for models constructed under these two Lagrangian approaches, it remains unclear whether or not they allow for similar inference. First, we used the Weak Law of Large Numbers to demonstrate that the log-likelihood function for estimating the parameters of BCRW models can be approximated by the log-likelihood of SSFs. Second, we illustrated the link between the two approaches by fitting BCRW with maximum likelihood and with SSF to simulated movement data in virtual environments and to the trajectory of bison (Bison bison L.) trails in natural landscapes. Using simulated and empirical data, we found that the parameters of a BCRW estimated directly from maximum likelihood and by fitting an SSF were remarkably similar. Movement analysis is increasingly used as a tool for understanding the influence of landscape properties on animal distribution. In the rapidly developing field of movement ecology, management and conservation biologists must decide which method they should implement to accurately assess the determinants of animal movement. We showed that BCRW and SSF can provide similar insights into the environmental features influencing animal movements. Both techniques have advantages. BCRW has already been extended to allow for multi-state modeling. Unlike BCRW, however, SSF can be estimated using most statistical packages, it can simultaneously evaluate habitat selection and movement biases, and can easily integrate a large number of movement taxes at multiple scales. SSF thus offers a simple, yet effective, statistical technique to identify movement taxis.
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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: Functional responses in animal movement explain spatial heterogeneity in animal-habitat relationships
Mason, Tom H.E.; Fortin, Daniel; Mason, Tom H. E. — 2018-04-05 1. Understanding why heterogeneity exists in animal-habitat spatial relationships is critical for identifying the drivers of animal distributions. Functional responses in habitat selection – whereby animals adjust their habitat selection depending on habitat availability – are useful for describing animal-habitat spatial heterogeneity. However, they could be yielded by different movement tactics, involving contrasting inter-specific interactions. 2. Identifying functional responses in animal movement, rather than in emergent spatial patterns like habitat selection, could disentangle the effects of different movement behaviours on spatial heterogeneity in animal-habitat relationships. This would clarify how functional responses in habitat selection emerge and provide a general tool for understanding the mechanistic drivers of animal distributions. 3. We tested this approach using data from GPS-collared woodland caribou (Rangifer tarandus), a prey species under top-down control. We tested how caribou selected and moved with respect to a key resource (lichen-conifer stands) as a function of the availability of surrounding refuge land-cover (closed-conifer stands), using step selection functions. 4. Caribou selected resource patches more strongly in areas richer in refuge land-cover – a functional response in habitat selection. However, adjustments in multiple movement behaviours could have generated this pattern: stronger directed movement towards resources patches and/or longer residency within resource patches, in areas richer in refuges. Different contributions of these behaviours would produce contrasting forager spatial dynamics. 5. We identified functional responses in both movement behaviours: caribou were more likely to move towards resource patches in areas richer in refuge land-cover, and to remain in these patches during movement steps. This tactic enables caribou to spend longer foraging in safer areas where they could rapidly seek refuge in dense cover when predators are detected. 6. Our study shows that functional responses in movement can expose the context-dependent movement decisions that generate heterogeneity in animal-habitat spatial relationships. We used these functional responses to characterise anti-predator movement tactics employed by a large herbivore, but they could be applied in many different scenarios. The movement rules from functional responses in movement are well-suited to integration in spatial explicit individual-based models for forecasting animal distributions in landscapes undergoing environmental change.
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Data from: Resampling method for applying density-dependent habitat selection theory to wildlife surveys
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Tardy, Olivia; Massé, Ariane; Pelletier, Fanie; Fortin, Daniel — 2016-05-07 Isodar theory can be used to evaluate fitness consequences of density-dependent habitat selection by animals. A typical habitat isodar is a regression curve plotting competitor densities in two adjacent habitats when individual fitness is equal. Despite the increasing use of habitat isodars, their application remains largely limited to areas composed of pairs of adjacent habitats that are defined a priori. We developed a resampling method that uses data from wildlife surveys to build isodars in heterogeneous landscapes without having to predefine habitat types. The method consists in randomly placing blocks over the survey area and dividing those blocks in two adjacent sub-blocks of the same size. Animal abundance is then estimated within the two sub-blocks. This process is done 100 times. Different functional forms of isodars can be investigated by relating animal abundance and differences in habitat features between sub-blocks. We applied this method to abundance data of raccoons and striped skunks, two of the main hosts of rabies virus in North America. Habitat selection by raccoons and striped skunks depended on both conspecific abundance and the difference in landscape composition and structure between sub-blocks. When conspecific abundance was low, raccoons and striped skunks favored areas with relatively high proportions of forests and anthropogenic features, respectively. Under high conspecific abundance, however, both species preferred areas with rather large corn-forest edge densities and corn field proportions. Based on random sampling techniques, we provide a robust method that is applicable to a broad range of species, including medium- to large-sized mammals with high mobility. The method is sufficiently flexible to incorporate multiple environmental covariates that can reflect key requirements of the focal species. We thus illustrate how isodar theory can be used with wildlife surveys to assess density-dependent habitat selection over large geographic extents.
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Data from: Logging-induced changes in habitat network connectivity shape behavioral interactions in the wolf-caribou-moose system
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Courbin, Nicolas; Fortin, Daniel; Dussault, Christian; Courtois, R. — 2014-12-09 Habitat connectivity influences the distribution dynamics of animals. Connectivity can therefore shape trophic interactions, but little empirical evidence is available, especially for large mammals. In forest ecosystems, logging alters functional connectivity among habitat patches, and such activities can affect the spatial game between large herbivores and their predators. We used graph theory to evaluate how harvesting-induced changes in habitat connectivity influence patch choice and residency time of GPS-collared caribou (Rangifer tarandus caribou) and moose (Alces alces) in winter in the boreal forest. We then investigated the predator–prey game by assessing how GPS-collared wolves (Canis lupus) adjusted their movements to changes in landscape properties and in the networks of their prey species. We built prey habitat networks using minimum planar graphs organized around species-specific, highly selected habitat patches (i.e., network nodes). We found that spatial dynamics of large herbivores were influenced not only by the intrinsic quality of habitat patches, but also by the connectivity of those network nodes. Caribou and moose selected nodes that were connected by a high number of links, and moose also spent relatively more time in those nodes. By limiting node accessibility, human disturbances influenced travel decisions. Caribou and moose avoided nodes that were surrounded by a high proportion of cuts and roads, but once within these nodes, moose stayed longer than in other nodes. Caribou selectively moved among nodes with low distance costs, and their residency time increased with distance costs required to reach the nodes. Wolves selected their prey's nodes, where vegetation consumed by caribou and moose was highly abundant. Furthermore, wolves discriminated among those nodes by selecting the most connected ones. In fact, selection by wolves was stronger for their prey's nodes than for the prey's utilization distribution per se, a difference that increased with the level of human disturbance. Considering the difficulty of keeping track of highly mobile prey, predators may benefit by targeting not only their prey's resource patches, but also the most highly connected patches. Matrix quality and connectivity are therefore key elements shaping the predator–prey spatial game in human-altered landscapes because of their impact on the spatial dynamics of the interacting species.
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The umbrella value of caribou management strategies for biodiversity conservation in boreal forests under global change
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Labadie, Guillemette; Bouderbala, Ilhem; Boulanger, Yan; Béland, Jean-Michel; Hébert, Christian; Allard, Antoine; Hebblewhite, Mark; Fortin, Daniel — 2023-11-15 <p><span lang="EN-CA">Single-species conservation management is often proposed to preserve biodiversity in human-disturbed landscapes. How global change will impact the umbrella value of single-species management strategies remains an open question of critical conservation importance. We assessed the effectiveness of threatened boreal caribou as an umbrella for bird and beetle conservation under global change. We combined mechanistic, spatially explicit models of forest dynamics and predator-prey interactions to forecast the impact of management strategies on the survival of boreal caribou in boreal forest. We then used predictive models of species occupancy to characterize concurrent impacts on bird and beetle diversity. Landscapes were simulated based on three scenarios of climate change and four of forest management. We found that strategies that best mitigate human impact on boreal caribou were an effective umbrella for maintaining bird and beetle assemblages. While we detected a stronger effect of land-use change compared to climate change, the umbrella value of management strategies for caribou habitat conservation were still impacted by the severity of climate change. Our results showed an interplay among changes in forest attributes, boreal caribou mortality, as well as bird and beetle species assemblages. The conservation status of some species mandates the development of recovery strategies, highlighting the importance of our study which shows that single-species conservation can have important umbrella benefits despite global change.</span></p>
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Insect-mediated apparent competition between mammals in a boreal food web
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Labadie, Guillemette; McLoughlin, Philip D.; Hebblewhite, Mark; Fortin, Daniel — 2021-06-21 <p>Datasets generated and analyzed within the study area located in the Côte-Nord region of Québec, Canada. "DataFinal_Vegetation.csv" was used to evaluate the availability of deciduous vegetation (column <em>Cover_Deciduous</em>) in stands impacted by the spruce budworm (SBW, severity index values presented in column <em>SBW_SevCum</em>) outbreak and test our prediction that the reduction in canopy cover caused by SBW in coniferous stands would result in greater deciduous vegetation. We determined the percentage cover of deciduous vegetation for two height strata ([0-1m] and [1-3m] classes, column <em>Stratum</em>).</p> <p>"DataFinal_Moose_density.csv" was used to assess the influence of SBW outbreak (<em>SBW_SevCum</em>) on moose abundance by comparing moose densities (<em>Density</em>) before (<em>year </em>= 2006) and during SBW outbreak (<em>year </em>= 2018). We also determined the effect of the percentage cover of deciduous vegetation (<em>Broadleaf</em>) and the percentage cover of salvage-logged forest stands (<em>SBW_cut_2018Factor</em>) on moose densities.</p> <p>"DataFinal_RSF_Caribou.csv" and "DataFinal_RSF_Wolves.csv" were used to develop Resource Selection Functions for caribou and wolves to assess habitat selection. RSFs compare resource characteristics of observed (scored 1) and random (scored 0) locations presented in column <em>case</em>. Habitat characteristics (<em>columns conif_dense, conif_open, mixed, open, other, burned0_5, burned6_20, burned21_, cut0_5, cut6_20, cut21_</em>) was extracted from the Canadian National Forest Inventory (NFI) forest cover maps. Land cover maps were updated every year by adding roads, recent (&lt;5 years), regenerating (6–20 years) and old (21–50 years) cutblocks/fires based on information provided annually by local forestry companies and from the Canadian National Fire Database (CNFDB). SBW outbreak was characterized by its cumulative severity (<em>SBW_SevCum</em>), and also if infested stands were logged (<em>SBW_Cut</em>). As our study focused on the survival of boreal caribou, we added the mortality status for each individual  (<em>DeadStatus, </em>remained alive throughout the study = 0, died = 1<em>) </em>and interaction terms (i.e. the multiplication of two columns) <em>Dead_SBW_SevCum </em>and <em>Dead_SBW_Cut. </em></p> <p>Finally, we used "DataFinal_SurvivalAnalysis.csv" to evaluate whether the proportion of natural (<em>Prop_burned</em>) and anthropogenic (<em>Prop_Cut0_5, Prop_Cut6_20, Prop_SBW_cut</em>) disturbances within winter home range had an effect on the mortality risk of caribou (determined with the mortality status column <em>Dead : </em>remained alive throughout the study = 0, died = 1). For this analysis, we determined the individual ID (<em>ID</em>), the years during they were monitored (<em>Year</em>), and the time was defined as the total period of monitoring for that individual (<em>Time</em>). </p>
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Data from: Maintaining animal assemblages through single-species management: the case of threatened caribou in boreal forest
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Bichet, Orphé M.; Dupuch, Angélique; Hébert, Christian; Le Borgne, Hélène; Fortin, Daniel — 2015-09-15 With the intensification of human activities, preserving animal populations is a contemporary challenge of critical importance. In this context, the umbrella species concept is appealing because preserving a single species should result in the protection of multiple co-occurring species. Practitioners, though, face the task of having to find suitable umbrellas to develop single-species management guidelines. In North America, boreal forests must be managed to facilitate the recovery of the threatened boreal caribou (Rangifer tarandus). Yet, the effect of caribou conservation on co-occurring animal species remains poorly documented. We tested if boreal caribou can constitute an effective umbrella for boreal fauna. Birds, small mammals, and insects were sampled along gradients of post-harvest and post-fire forest succession. Predictive models of occupancy were developed from the responses of 95 species to characteristics of forest stands and their surroundings. We then assessed the similarity of species occupancy expected between simulated harvested landscapes and a 90 000-km2 uncut landscape. Managed landscapes were simulated based on three levels of disturbance, two timber-harvest rotation cycles, and dispersed or aggregated cut-blocks. We found that management guidelines that were more likely to maintain caribou populations should also better preserve animal assemblages. Relative to fragmentation or harvest cycle, we detected a stronger effect of habitat loss on species assemblages. Disturbing 22%, 35%, and 45% of the landscape should result, respectively, in 80%, 60%, and 40% probability for caribou populations to be sustainable; in turn, this should result in regional species assemblages with Jaccard similarity indices of 0.86, 0.79, and 0.74, respectively, relative to the uncut landscape. Our study thus demonstrates the value of single-species management for animal conservation. Our quantitative approach allows for the evaluation of management guidelines prior to implementation, thereby providing a tool for establishing suitable compromises between economic and environmental sustainability of human activities.
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Data from: Many places called home: the adaptive value of seasonal adjustments in range fidelity
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Lafontaine, Alexandre; Drapeau, Pierre; Fortin, Daniel; St-Laurent, Martin-Hugues — 2018-01-19 1. The vast majority of animal species display range fidelity, a space-use behaviour enhancing familiarity with local habitat features. While the fitness benefits of this behaviour have been demonstrated in a variety of taxa, some species or populations rather display infidelity, displacing their home range over time. Others, such as many ungulate species, show seasonal adjustments in their range fidelity to accommodate changes in the dominance of limiting factors or in the distribution of resources. 2. Few empirical studies have explored the adaptive value of seasonal adjustments in range fidelity. Using boreal populations of woodland caribou (Rangifer tarandus caribou) as a biological model, we evaluated how range fidelity impacted individual performance during two seasons where juvenile and adult survival are limited by different predation pressures. 3. Between 2004 and 2013, we monitored the survival, reproductive success, habitat selection and range fidelity of female caribou in the boreal forest of eastern Canada. Using resource selection functions, we assessed how seasonal range fidelity was linked to two fitness correlates: calf survival in summer and adult female survival in winter. 4. Females displayed season-specific space use tactics: they selected previously used areas during calving and summer, but tended to shift their winter range from one year to the next. During calving and summer, range fidelity yielded relatively high fitness benefits, as females that did not lose their calf displayed stronger fidelity than females that did. In winter, however, adult survival was negatively linked to range fidelity, as females that survived selected areas further away from their seasonal range of the previous year than females that died. 5. We provide one of the first evidences that making seasonal adjustments in range fidelity can be an adaptive behaviour influencing the spatial distribution of a threatened species. Assessing the seasonal nature of range fidelity tactics may improve our predictions of space use and associated fitness implications for species displaying this behaviour.
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Data from: Spatial heterogeneity in the strength of plant-herbivore interactions under predation risk: the tale of bison foraging in wolf country
Harvey, Léa; Fortin, Daniel — 2013-09-12 Spatial heterogeneity in the strength of trophic interactions is a fundamental property of food web spatial dynamics. The feeding effort of herbivores should reflect adaptive decisions that only become rewarding when foraging gains exceed 1) the metabolic costs, 2) the missed opportunity costs of not foraging elsewhere, and 3) the foraging costs of anti-predator behaviour. Two aspects of these costs remain largely unexplored: the link between the strength of plant-herbivore interactions and the spatial scale of food-quality assessment, and the predator-prey spatial game. We modeled the foraging effort of free-ranging plains bison (Bison bison bison) in winter, within a mosaic of discrete meadows. Spatial patterns of bison herbivory were largely driven by a search for high net energy gains and, to a lesser degree, by the spatial game with grey wolves (Canis lupus). Bison decreased local feeding effort with increasing metabolic and missed opportunity costs. Bison herbivory was most consistent with a broad-scale assessment of food patch quality, i.e., bison grazed more intensively in patches with a low missed opportunity cost relative to other patches available in the landscape. Bison and wolves had a higher probability of using the same meadows than expected randomly. This co-occurrence indicates wolves are ahead in the spatial game they play with bison. Wolves influenced bison foraging at fine scale, as bison tended to consume less biomass at each feeding station when in meadows where the risk of a wolf's arrival was relatively high. Also, bison left more high-quality vegetation in large than small meadows. This behavior does not maximize their energy intake rate, but is consistent with bison playing a shell game with wolves. Our assessment of bison foraging in a natural setting clarifies the complex nature of plant-herbivore interactions under predation risk, and reveals how spatial patterns in herbivory emerge from multi-scale landscape heterogeneity.

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