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Abstract Unspoiled wildlands of boreal landscapes provide critical habitats for wildlife. With the increase in resource development across Canada's boreal zone, woodland caribou (Rangifer tarandus caribou) and grizzly bears (Ursus arctos) are at risk of population declines. We used 4 planning scenarios with variants of these in decision-support software Marxan to allocate potential conservation priority areas for caribou and grizzly bears in boreal wildlands of the Muskwa-Kechika Management Area in northeast British Columbia, Canada. For caribou and grizzly bears across their seasonal habitats, priority areas allocated to preserve connectivity of habitat patches maintained more intact high-value habitats, with moderate opportunity cost for resource development, than those allocated under other scenarios. In winter when high-value habitats of caribou tend to coincide with resource-rich areas, priority areas allocated to preserve areas that are more vulnerable to development maintained more intact high-value habitats with higher opportunity cost (therefore greater adverse economic consequences) than those allocated in areas with lower resource potential. In growing-season (non-winter) habitats of caribou and grizzly bears, allocating priority areas toward either more vulnerable or less vulnerable areas did not substantially affect patch and landscape characteristics of conserved habitats. Priority areas intended to avoid predation risk for caribou were not effective in maintaining intact high-value habitats for caribou in these undeveloped wildlands. Conserving connectivity would best maintain most intact habitats for both species across seasons; conserving habitats most vulnerable to development also would discourage future development outside of the conserved areas in winter habitats of caribou. Findings from these conservation planning scenarios have implications globally to other areas where sensitive species are threatened by pending resource developments. Highlights • Maintain connectivity to preserve high-value habitats of caribou and grizzly bears. • Avoiding predation risk does not always maintain intact habitat for caribou. • Conserving most vulnerable winter caribou habitat helps ensure spatial integrity. • Conservation priority areas may necessitate lost opportunities for resource development. [ABSTRACT FROM AUTHOR]

Helicopter- and snowcat-supported backcountry skiing is a unique industry that is widespread throughout southern mountain caribou habitat in British Columbia (BC). We analyzed records of helicopter and skier encounters with caribou collected by tourism operators under an agreement between the BC government and HeliCat Canada. Average reported encounter rates were low for helicopters (0.6%) and skiing groups (0.1%); however, encounters were likely underreported due to factors that affect caribou sightability. Helicopters encountered caribou more frequently than skiing groups, caribou were detected from helicopters at greater distances than by skiers. We used Bayesian network models to assess the independent contribution of different factors to the behavioural response of caribou to encounters. Encounter distance was the most important factor in both helicopter and skiing models. Larger groups of caribou responded strongly to skiers but not to helicopters, although the independent effect of this factor was small in both models. Larger helicopters elicited stronger reactions from caribou than smaller machines and were responsible for 25% of the modelled variation in caribou response. Encounters with helicopters at distances of 100-500m had a 78% probability of eliciting a concerned-to-very-alarmed response from caribou, while skiers at a similar distance had a 60% probability of eliciting the same response. The probability of concerned-to-very-alarmed responses dropped to <20% at encounter distances of >1000 m. These results indicate that initial encounter distance is the key variable to manage risk to caribou of helicopter and skiing encounters. Ongoing feedback on the effectiveness of management practices is critical to ensure the continued viability of industries operating in caribou habitat. [ABSTRACT FROM AUTHOR]

Populations that are fragmented in space may persist because of metapopulation function that relies on dispersal among subpopulations. Assuming that a fragmented distribution means that the species operates as a metapopulation can lead to erroneous conclusions about population structure, unless the dispersal traits of the organism are understood. A wide-ranging large mammal with an increasingly fragmented distribution is the mountain caribou, found in the interior rain forests of British Columbia, Canada. These caribou are an endangered ecotype of woodland caribou Rangifer tarandus caribou, and, based on movements of adult caribou, their population has been divided into 18 subpopulations. Their numbers have declined over at least the last 25 years, and it is unknown if their fragmented distribution operates as a metapopulation linked by juvenile dispersal or is simply a step towards extinction. From a database of radio-locations collected over a 23-year period (1984-2007) from 358 caribou, we used a spatial index to define summer/fall composite ranges (breeding ranges) across their distribution. The 18 previously recognized subpopulations were fragmented further into 41 summer/fall composite ranges. Young animals (<1 year of age) were not observed to disperse among subpopulations (0/26 opportunities) or even among summer/fall composite ranges (0/7). Similar results were found for animals 2 and 3 years of age. Breeding dispersal by adult caribou occurred in 1.4% of the observed opportunities (8/587). These dispersal rates are insufficient to rescue the smaller and declining subpopulations. We conclude that the distribution of these mountain caribou is more fragmented than thought previously and is not functioning as a classic metapopulation due to a lack of dispersal; rather, it is better described as an extreme non-equilibrium metapopulation. Mountain caribou and other wide-ranging species fragmented into subpopulations by human actions may appear to be in a metapopulation but unless they have the innate ability to disperse among subpopulations, the distribution is more likely the geographic pattern of the extinction process. [ABSTRACT FROM AUTHOR]

Allee effects can have significant consequences for small populations and understanding the causal mechanisms for such effects is important for guiding conservation actions. One proposed mechanism is through predation, in which a type II functional response leads to increasing predation rates as prey numbers decline. However, models to support this mechanism have incorporated only a single declining prey species in the functional response, which is probably an oversimplification. We reevaluated the potential for predator-mediated Allee effects in a multi-prey system using Holling's disc equation. We also used empirical data on a large herbivore to examine how grouping behavior may influence the potential for predation-mediated Allee effects. Results based on a multi-prey expression of the functional response predict that Allee effects caused by predation on relatively rare secondary prey may not occur because handling time of the abundant prey dominates the functional response such that secondary prey are largely "bycatch." However, a predator-mediated Allee effect can occur if secondary prey live in groups and if, as the population declines, their average group size declines (a relationship seen in several species). In such a case, the rate at which the number of groups declines is less than the rate at which the population declines. Thus the rate at which a predator encounters a group remains relatively stable, but when a predator kills one animal from smaller groups, the predation rate increases. These results highlight the need to evaluate risks associated with potential changes in group size as populations decline. [ABSTRACT FROM AUTHOR]

Mountain caribou (Rangifer tarandus caribou) populations in south-eastern British Columbia are declining over most of their range and are listed as Threatened. Predation has been documented as the major cause of declining caribou numbers. Excessive predation by wolves (Canis lupus) has been related to increased moose (Alces alces) numbers. The increase in moose appears to be the result of a natural colonization process that has been enhanced by human-caused habitat change. Options to reduce the rate of predation include reducing wolves, reducing moose, and reducing the amount of early seral habitat that supports moose. Current management includes population control of moose and wolves. Monitoring and assessment of these approaches will guide the future management strategy used to maintain mountain caribou in south-eastern British Columbia. [ABSTRACT FROM AUTHOR]

Conservation strategies for populations of woodland caribou Rangifer tarandus caribou frequently emphasize the importance of predator–prey relationships and the availability of lichen-rich late seral forests, yet the importance of summer diet and forage availability to woodland caribou survival is poorly understood. In a recent article, Wittmer et al. ( Can J Zool 83:407–418, ) concluded that woodland caribou in British Columbia were declining as a consequence of increased predation that was facilitated by habitat alteration. Their conclusion is consistent with the findings of other authors who have suggested that predation is the most important proximal factor limiting woodland caribou populations (Bergerud and Elliot in Can J Zool 64:1515–1529, ; Edmonds in Can J Zool 66:817–826, ; Rettie and Messier in Can J Zool 76:251–259, ; Hayes et al. in Wildl Monogr 152:1–35, ). Wittmer et al. ( Can J Zool 83:407–418, ) presented three alternative, contrasting hypotheses for caribou decline that differed in terms of predicted differences in instantaneous rates of increase, pregnancy rates, causes of mortality, and seasonal vulnerability to mortality (Table 1, p 258). These authors rejected the hypotheses that food or an interaction between food and predation was responsible for observed declines in caribou populations; however, the use of pregnancy rate, mortality season and cause of mortality to contrast the alternative hypotheses is problematic. We argue here that the data employed in their study were insufficient to properly evaluate a predation-sensitive foraging hypothesis for caribou decline. Empirical data on seasonal forage availability and quality and plane of nutrition of caribou would be required to test the competing hypotheses. We suggest that methodological limitations in studies of woodland caribou population dynamics prohibit proper evaluation of the mechanism of caribou population declines and fail to elucidate potential interactions between top-down and bottom-up effects on populations. [ABSTRACT FROM AUTHOR]

The proximate role of predation in limiting caribou (Rangifer tarandus) populations is well documented, but the long-term effects of predation pressure on selection of calving areas and the subsequent impacts to calving success remain unclear. We examined the relationships among calf survival, predation risk, and vegetation characteristics among 3 calving areas and across spatial scales in the Besa-Prophet River drainage of northern British Columbia. Fifty woodland caribou (R. t. caribou) neonates were collared and monitored twice daily for the first month and once weekly (luring the next month of life in 2 summer field seasons (2002 and 2003). Predation risk was estimated using resource selection functions (RSFs) from Global Positioning System (GPS) locations of 15 grizzly bears (Ursus arctos) and 5 gray wolf (Canis lupus) packs. The Normalized Difference Vegetation Index (NDVI) derived from Landsat Thematic Mapper (TM) and Enhanced Thematic Mapper (ETM) data were used to quantify large-scale characteristics of vegetation (indices of biomass and quality). We incorporated small- and large-scale characteristics (i.e., predation risk, vegetation, and movement of woodland caribou calves) of neonatal calving sites into logistic regression models to predict survival for the calving (25 May-14 Jun) and summer (15 Jun-31 Jul) seasons. Predation risk and vegetation characteristics were highly variable among calving areas and calving sites, and parturient woodland caribou responded to these characteristics at different scales. Minimizing gray wolf risk and selecting against areas of high vegetation biomass were important at large scales; areas with high biomass were likely associated with increased predation risk. Calving in areas high in vegetation quality was important across scales, as parturient woodland caribou took higher levels of predation risk to access areas of high vegetative change. Models using small-scale characteristics of calving sites to predict survival performed better in the calving season than in summer. Large-scale characteristics predicted survival of woodland caribou neonates better in summer than in the calving season, probably in part because of the unexpected role of wolverines (Gulo gulo) as the main predator of woodland caribou calves during calving. Gray wolves were the main cause of mortality during the summer. Movement away from calving sites corresponded to higher calf survival and appeared to be in response to increased access to forage during the peak demands of lactation and/or minimizing gray wolf risk in the summer. High variation in predation risk and vegetation attributes among calving areas and at calving sites within calving areas, with no differences in calf mortality related to that variation, illustrates the importance of behavioral plasticity as a life-history strategy for woodland caribou. [ABSTRACT FROM AUTHOR]

We used census results and radiotelemetry locations of >380 collared individuals sampled over the entire distribution of the endangered mountain ecotype of woodland caribou (Rangifer tarandus caribou (Gmelin, 1788)) in British Columbia, Canada, to delineate population structure and document the size and trend of the identified populations. We also describe the spatial pattern of decline and the causes and timing of adult mortality and provide estimates of vital rates necessary to develop a population viability analysis. Our results indicate that the abundance of mountain caribou in British Columbia is declining. We found adult female annual survival rates below annual survival rates commonly reported for large ungulates. The major proximate cause of population decline appears to be predation on adult caribou. Spatial patterns of population dynamics revealed a continuous range contraction and an increasing fragmentation of mountain caribou into smaller, isolated subpopulations. The population fragmentation process predominantly occurs at the outer boundaries of the current distribution. Our results indicate that recovery strategies for mountain caribou should be directed at factors contributing to the fragmentation and isolation of mountain caribou populations as well as management strategies aimed at increasing adult survival. [ABSTRACT FROM AUTHOR]

Summary 1. During winter, mountain caribou Rangifer tarandus caribou live in late successional and old-growth coniferous forests, where they feed almost exclusively on arboreal lichens. Because some of these forests are also valuable to the forest industry, caribou ecology and forest management remains a central conservation issue in British Columbia. To improve our understanding of caribou habitat use in relation to forest management, we investigated the winter habitat selection patterns of mountain caribou at a range of spatial scales between 1988 and 1993 in the northern Cariboo Mountains, British Columbia. 2. Within winter ranges, caribou selected forest stands dominated by subalpine fir (> 80% Abies lasiocarpa ) and with moderate slopes (16–30%) during early winter (November–December). Although stands with moderately high timber volumes (201–300 m3 ha-1 ) were used the most during early winter, caribou used these stands in proportion to their availability. Caribou primarily used open-canopy subalpine fir stands (i.e. parkland) later in the winter (January–March), where low stocking and inoperable timber volumes (< 100 m3 ha-1 ) reduced direct conflicts with forest harvesting. 3. Characteristics of subalpine forests at early winter caribou foraging areas did not differ significantly from random sites for most variables measured. However, a multivariate analysis indicated that sites used by caribou had slightly less total basal area, more moderate slopes and slightly heavier lichen loads than unused sites. 4. Within early winter foraging areas, caribou chose foraging paths with more trees and greater accessible lichen biomass per standing tree compared with random paths. Although windthrown trees and lichen litterfall were encountered infrequently, caribou rarely rejected these sources of lichen when encountered. 5. The relatively low basal area (27 m2 ha-1 ) and... [ABSTRACT FROM AUTHOR]