Martin-Hugues St-Laurent

Fine-scale habitat selection by female forest-dwelling caribou in managed boreal forest: Empirical evidence of a seasonal shift between foraging opportunities and antipredator strategies

Abstract: Forest harvesting is a major cause of habitat alteration negatively affecting forest-dwelling caribou (Rangifer tarandus caribou) in the boreal forest. In order to identify female caribou habitat requirements, we conducted a fine-scale habitat selection analysis in a managed forest of eastern Canada. Five land-cover types used by 8 female caribou during 2 periods (winter and snow-free) were considered to characterize structural attributes, ground cover, and lichen abundance at 320 GPS locations and at 200 random points within home ranges. Because caribou rely on a limited food supply in winter, we predicted that they would select sites of higher biomass of terrestrial and/or arboreal lichens. Since female caribou (especially those with calves) are more vulnerable to predation during the snow-free period, we predicted that they would select sites where predation would be reduced by a denser hiding cover (i.e., high basal area, shrub height, and/or lateral cover) or by a lower forage availability for alternative prey (i.e., low shrub density). Within each land-cover type, comparisons between used and random sites were conducted using an exploratory PCA analysis followed by conditional logistic regressions. Our results demonstrated that, in winter, female caribou selected sites with higher terrestrial lichen biomass or ericaceous shrub cover in old spruce stands and old cutovers. During the snow-free period, female caribou did not select sites of denser hiding cover. However, well-regenerated shrub layer was avoided during both periods, suggesting that caribou avoided sites containing abundant forage attractive to moose and, consequently, wolf. At a fine scale, forest management should focus on protecting sites or stands with a high biomass of terrestrial lichens. Silvicultural practices that prevent cutovers from regenerating into areas with abundant moose forage should also be favoured. Nomenclature: Marie-Victorin, 1995; Farrar, 1996; Brodo et al., 2001, Feldhamer et al., 2003.

Unifying Framework for Understanding Impacts of Human Developments on Wildlife

Natural resource professionals recognize the negative impacts of human developments on the distribution, abundance, and, in some cases, persistence of wildlife populations or species. Indeed, human activity in all its forms (Kerr and Currie 1995) is a primary cause of the global decline in biodiversity in general (Brooks et al.2002; Dudgeon et al. 2006; White and Kerr 2006) and wildlife in particular (Ceballos and Ehrlich 2002; Laliberte and Ripple 2004; Davies et al.2006). This recognition has led to a rapid increase in the number of studies designed to elucidate and document wildlife–human interactions (fig. 3.1).

The influence of landscape matrix on isolated patch use by wide-ranging animals: conservation lessons for woodland caribou.

For conservation purposes, it is important to design studies that explicitly quantify responses of focal species to different land management scenarios. Here, we propose an approach that combines the influence of landscape matrices with the intrinsic attributes of remaining habitat patches on the space use behavior of woodland caribou (Rangifer tarandus caribou), a threatened subspecies of Rangifer. We sought to link characteristics of forest remnants and their surrounding environment to caribou use (i.e., occurrence and intensity). We tracked 51 females using GPS telemetry north of the Saguenay River (Québec, Canada) between 2004 and 2010 and documented their use of mature forest remnants ranging between 30 and ∼170 000 ha in a highly managed landscape. Habitat proportion and anthropogenic feature density within incremental buffer zones (from 100 to 7500 m), together with intrinsic residual forest patch characteristics, were linked to caribou GPS location occurrence and density to establish the range of influence of the surrounding matrix. We found that patch size and composition influence caribou occurrence and intensity of use within a patch. Patch size had to reach approximately 270 km2 to attain 75% probability of use by caribou. We found that small patches (<100 km2) induced concentration of caribou activities that were shown to make them more vulnerable to predation and to act as ecological traps. Woodland caribou clearly need large residual forest patches, embedded in a relatively undisturbed matrix, to achieve low densities as an antipredator strategy. Our patch-based methodological approach, using GPS telemetry data, offers a new perspective of space use behavior of wide-ranging species inhabiting fragmented landscapes and allows us to highlight the impacts of large scale management. Furthermore, our study provides insights that might have important implications for effective caribou conservation and forest management.

Disentangling Woodland Caribou Movements in Response to Clearcuts and Roads across Temporal Scales

Although prey species typically respond to the most limiting factors at coarse spatiotemporal scales while addressing biological requirements at finer scales, such behaviour may become challenging for species inhabiting human altered landscapes. We investigated how woodland caribou, a threatened species inhabiting North-American boreal forests, modified their fine-scale movements when confronted with forest management features (i.e. clearcuts and roads). We used GPS telemetry data collected between 2004 and 2010 on 49 female caribou in a managed area in Québec, Canada. Movements were studied using a use – availability design contrasting observed steps (i.e. line connecting two consecutive locations) with random steps (i.e. proxy of immediate habitat availability). Although caribou mostly avoided disturbances, individuals nonetheless modulated their fine-scale response to disturbances on a daily and annual basis, potentially compromising between risk avoidance in periods of higher vulnerability (i.e. calving, early and late winter) during the day and foraging activities in periods of higher energy requirements (i.e. spring, summer and rut) during dusk/dawn and at night. The local context in which females moved was shown to influence their decision to cross clearcut edges and roads. Indeed, although females typically avoided crossing clearcut edges and roads at low densities, crossing rates were found to rapidly increase in greater disturbance densities. In some instance, however, females were less likely to cross edges and roads as densities increased. Females may then be trapped and forced to use disturbed habitats, known to be associated with higher predation risk. We believe that further increases in anthropogenic disturbances could exacerbate such behavioural responses and ultimately lead to population level consequences.

Age-Dependent Response of Migrant and Resident Aegolius Owl Species to Small Rodent Population Fluctuations in the Eastern Canadian Boreal Forest

ABSTRACT We investigated the relationship between late summer abundance of small rodents and fall migrant abundance of two nocturnal avian predators, the Boreal Owl (Aegolius funereus) and the Northern Saw-whet Owl (A. acadicus), during their fall movement/migration. In the eastern Canadian boreal forest, Boreal Owls are considered resident (with irruptive movements to the south thought to occur during periods of low prey availability), and Northern Saw-whet Owls migratory. Data on late summer abundance of small rodents collected between 1995 and 2004 were used to develop an index of prey availability. Data on the number and age of irrupting/migrating owls were collected between 1996–2004 (mid-September to late October) using audiolures and mist nets. Our study revealed strong evidence of (1) a negative relationship between the abundance of small rodents and movement of Boreal Owls and (2) a positive relationship between the abundance of small rodents and the number of migrating juveniles and second year Northern Saw-whet Owls. In the latter case, it suggests that prey availability can strongly influence breeding success of this species, which is at the northern limit of its breeding range.

The reintroduction of boreal caribou as a conservation strategy: A long-term assessment at the southern range limit

Boreal caribou were extirpated from the Charlevoix region (Quebec) in the 1920s because of hunting and poaching. In 1965, the Quebec government initiated a caribou reintroduction program in Charlevoix. During the winters of 1966 and 1967, a total of 48 boreal caribou were captured, translocated by plane, and released within enclosures; only their offspring (82 individuals) were released in the wild. Between 1967 and 1980, a wolf control program was applied to support caribou population growth. The caribou population, however, remained relatively stable at 45–55 individuals during this period. During the 1980s, the population grew slowly at a rate of approximately 5% each year to reach a peak of 126 individuals in 1992. At that time, Bergerud & Mercer (1989) reported that the Charlevoix experiment was the only successful attempt at caribou reintroduction in the presence of predators (in North America). Afterwards, the population declined and since then it has been relatively stable at about 80 individuals. Here we reviewed the literature regarding the ecology and population dynamics of the Charlevoix caribou herd since its reintroduction, in an attempt to critically assess the value of reintroduction as a conservation tool for this species. Indeed, the Charlevoix caribou herd is now considered at very high risk of extinction mostly because of its small size, its isolation from other caribou populations, and low recruitment. The Charlevoix region has been heavily impacted by forestry activities since the early 1980s. Recent studies have indicated that these habitat modifications may have benefited populations of wolves and black bears—two predators of caribou—and that caribou range fidelity may have exposed caribou to higher predation risk via maladaptive habitat selection. As females are ageing, and females and calves suffer high predation pressure from wolves and bears respectively, we suggest that the future of this reintroduced herd is in question and that they are facing a high probability of extinction in the near future if further action is not taken.

A spatial theory for characterizing predator–multiprey interactions in heterogeneous landscapes

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.

Use of Residual Forest by Snowshoe Hare in a Clear-cut Boreal Landscape

Abstract The short-term negative impacts on Lepus americanus (Snowshoe Hare) of logging activities in boreal forest are widely recognized, and conservation efforts are being taken now in designing residual forest stands to maintain use of logged landscapes by hares. This study evaluated the effectiveness of three types of residual stands in maintaining hares during the high phase of hare density cycle in Picea mariana (Black Spruce) forest of eastern Canada. Residual forest stands sampled were upland strips (60 m wide, 250–950 m long, mesic conditions), riparian strips (100 m wide, 250–950 m long, along a permanent stream), and residual blocks (200–300 m wide, 20–50 ha). Control stands were undisturbed forest. All stands were considered mature (56–97 years old). Pellet and browse surveys were conducted during spring 1998 and 1999. Hare abundance indices were significantly lower (1999), or tended to be lower (1998), in strips than in blocks, although habitat composition and structure of the treatments did not differ from control stands. Pellet presence was positively related to vertical cover. In 1998, foraging activity (browsing) was significantly higher in control and block landscapes than in strip landscapes; browsing was positively related to availability of ericaceous and deciduous twigs. In 1998, twenty Snowshoe Hares were radio-tracked in residual stands to monitor their summer home ranges, fidelity to capture sites and to type of residual stand, use of clear-cuts and uncut forest, and daily movements. There was a clear trend towards lower fidelity to strips than to blocks, and summer home ranges and daily movements (>330 m) tended to be larger in strips compared to those in blocks. Our study suggests that up to 5 years after logging, residual forest blocks appeared to be more suitable habitat in summer for Snowshoe Hare than were 60-m-wide strips.

Conservation status of caribou in the western mountains of Canada: Protections under the species at risk act, 2002-2014

In April 2014, the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) reviewed the status of caribou in the western mountains of Canada, in keeping with the ten-year reassessment mandate under the Species at Risk Act. Assessed as two ‘nationally significant’ populations in 2002, COSEWIC revised the conservation units for all caribou in Canada, recognising eleven extant Designatable Units (DUs), three of which -- Northern Mountain, Central Mountain, and Southern Mountain -- are found only in western Canada. The 2014 assessment concluded that the condition of many subpopulations in all three DUs had deteriorated. As a result of small and declining population sizes, the Central Mountain and Southern Mountain DUs are now recognised as endangered. Recent declines in a number of Northern Mountain DU subpopulations did not meet thresholds for endangered or threatened, and were assessed as of special concern. Since the passage of the federal Species at Risk Act in 2002, considerable areas of habitat were managed or conserved for caribou, although disturbance from cumulative human development activities has increased during the same period. Government agencies and local First Nations are attempting to arrest the steep decline of some subpopulations by using predator control, maternal penning, population augmentation, and captive breeding. Based on declines, future developments and current recovery effects, we offer the following recommendations: 1) where recovery actions are necessary, commit to simultaneously reducing human intrusion into caribou ranges, restoring habitat over the long term, and conducting short-term predator control, 2) carefully consider COSEWIC’s new DU structure for management and recovery actions, especially regarding translocations, 3) carry out regular surveys to monitor the condition of Northern Mountain caribou subpopulations and immediately implement preventative measures where necessary, and 4) undertake a proactive, planned approach coordinated across jurisdictions to conserve landscape processes important to caribou conservation.

Integrating ecological and genetic structure to define management units for caribou in Eastern Canada

Genetic diversity is a key parameter to delineate management units, but many organisms also display ecological characteristics that may reflect potential local adaptations. Here, we used ecological and genetic information to delineate management units for a complex system involving several ecotypes of caribou (Rangifer tarandus) from Québec and Labrador, eastern Canada. We genotyped 560 caribou at 16 microsatellite loci and used three Bayesian clustering methods to spatially delineate and characterize genetic structure across the landscape. The different approaches employed did not converge on the same solution, and differed in the number of inferred genetic clusters that best fit the dataset but also in the spatial distribution of genetic variation. We reconciled variability among the methods using a synthetic approach that considers the sum of the partitions obtained by each of them and retrieved six genetically distinct groups that differ in their spatial extent across the range of caribou in the study area. These genetic groups are not consistent with the presently defined ecological designations for this species. Combining both genetic and ecological criteria, we distinguished eight independent management units. Overall, the management units we propose should be the focus of conservation and management actions aimed to maximize genetic and ecological diversity and ensure the persistence of caribou populations inhabiting increasingly disturbed landscapes.