Invading white-tailed deer change wolf-caribou dynamics in northeastern Alberta (original) (raw)
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Ecography, 2013
Population increases of primary prey can negatively impact alternate prey populations via demographic and behavioural responses of a shared predator through apparent competition. Seasonal variation in prey selection patterns by predators also can aff ect secondary and incidental prey by reducing spatial separation. Global warming and landscape changes in Alberta ' s bitumen sands have resulted in prey enrichment, which is changing the large mammal predator -prey system and causing declines in woodland caribou Rangifer tarandus caribou populations. We assessed seasonal patterns of prey use and spatial selection by wolves Canis lupus in two woodland caribou ranges in northeastern Alberta, Canada, that have undergone prey enrichment following recent white-tailed deer Odocoileus virginianus invasion. We determined whether risk of predation for caribou (incidental prey) and the proportion of wolf-caused-caribou mortalities varied with season. We found that wolves showed seasonal variation in primary prey use, with deer and beaver Castor canadensis being the most common prey items in wolf diet in winter and summer, respectively. Th ese seasonal dietary patterns were refl ected in seasonal wolf spatial resource selection and resulted in contrasting spatial relationships between wolves and caribou. During winter, wolf selection for areas used by deer maintained strong spatial separation between wolves and caribou, whereas wolf selection for areas used by beaver in summer increased the overlap with caribou. Changing patterns in wolf resource selection were refl ected by caribou mortality patterns, with 76.2% of 42 adult female caribou mortalities occurring in summer. Understanding seasonal patterns of predation following prey enrichment in a multiprey system is essential when assessing the eff ect of predation on an incidental prey species. Our results support the conclusion that wolves are proximately responsible for woodland caribou population declines throughout much of their range.
Wolf predation in the Burwash caribou herd, southwest Yukon
Rangifer, 1986
The role of wolf predation as a proximate mortality factor influencing caribou herd growth was assessed in the Burwash herd (400 animals) in the southwest Yukon between 1980 - 1982. Ten to 14 wolves in two packs preyed primarily on caribou (Rangifer tarandus caribou) and moose (Alces alces) with disproportionate consumption of caribou (relative to available biomass) in the rut and winter periods. Wolf predation was responsible for 72% of total annual mortality in 1980 - 1981 and 46% in 1981 - 1982. Losses due to human harvest varied between 7 to 13%. Additional limited data on climatic factors and winter forage indicated forage-climate were not major proximate mortality factors in 1980 - 1981, but that early-calving climate may have been a factor in increased calf mortality in 1982.
How Best to Proceed with Western North American Woodland Caribou: Get Back to Basics? - JULY 2023
Maintaining an umbilical link between wildlife management and research is essential to ensure that applied research fills critical knowledge gaps to foster the development, advancement, testing and modification of socially acceptable and effective management actions. A detailed review of contemporary literature for threatened and endangered (Species at Risk Act, Environment Canada) boreal, mountain and northern woodland caribou (Rangifer tarandus caribou) in western North America, places them as victims of persistent, landscape scale, anthropogenic disturbances that tend to increase the extent of early successional forest areas favoured by moose (Alces alces), elk (Cervus canadensis), and/or deer (Odocoileus spp.) expensed against the mature forest communities and peatlands they have specialized to exploit for over a million years. The resulting range overlap of these caribou with their interspecific competitors, including their primary predators, wolves, (Canis lupus) and bears (Ursus spp.) has exposed adult and/or neonate caribou to higher rates of incidental depredation that has resulted in critical declines, and in some cases, extirpation of a number of caribou populations. This relationship is referred to as an example of the theory of Apparent Competition (AC), the existence of which has dominated the human approach to both research and the management treatment of woodland caribou across their range of distribution in Canada. The powerful and progressive emerging role and influence of GPS (Global Positioning Systems), GIS (Global Information Systems), neck-mounted video cameras, and SSAP (sophisticated statistical analysis package) technologies to effecting paradigm shifts in the ways in which scientists perceive nature cannot be overstated. Wolves, moose, elk, deer and caribou have proven to be excellent candidates for geospatial research given the relative speed to locate (aerial tracking), capture and place battery-powered GPS digital signal transmitter collars on animals during winter months where high resolution spatially referenced locational datasets can be downloaded in real time on demand. These data can then be analyzed to extract statistically important habitat relationships, and when combined with archived locational data, provide a compelling spatial-temporal story. The results of remote digital locational analysis efforts do not in themselves present documentary-level evidence of the predator/prey dynamic, but they do enhance insights into species’ seasonal habitat preferences including distance from features analyses. The recent application of neck-mounted video cameras placed on predators however, have been particularly revealing respecting the nature of the predator-prey dynamic. Radio-tagged subjects also provide researchers the timely opportunity to track mortalities and undertake forensic level investigations regarding causes of mortalities increasing the confidence of estimates of adult survival and recruitment. There has been however, an obvious tendency of field investigators to focus their data sampling efforts on caribou and their interspecific competitors (ICs) cohabiting ranges in western Canada and wolves regardless of the presence of other predators (brown bears, black bears, coyotes, wolverines, lynx, cougars, and/or eagles). This narrow focus essentially introduced a strong bias in which wolves, regardless of the degree of background effects (i.e., range disturbance, other predators), were broadly incriminated as the proximate direct cause of most caribou population failures. This manuscript tracks the emergence of such biases since the early 1970’s that continue to dominate management strategies to this day. The alternative would be the transparent pursuit of data, information and knowledge systems that would decrease the predictive uncertainty of management strategies and openly address the multi-predator/multi-prey dynamic that has evolved out of a broad range of anthropogenic landscape-level disturbances within which caribou struggle to find refuge and productivity. There also exists a strong tendency in recent years for ecologists to overlook the pervasive role of ‘bottom-up’ processes (i.e., variability in seasonal weather trends, patterns of plant phenology, and/or extreme ambient conditions), in shaping their perceptions of the relative well-being of each of the predator and prey at the local, range, and landscape levels, notwithstanding the inarguable mystery of the existence of synchronous temporal trends in population metrics observed across extremely broad bio-geoclimatic zones. This manuscript provides an attempt to explore a comprehensive review of the 50+ year investigative record for a threatened species in context of the diverse ecological, economic, political, social, cultural and academic interests that have forged a range of approaches to their management across Canada, while keeping in mind that wildlife are a public trust resource implying some role for the public in decision-making. Thus, while both federal, provincial and territorial governments are ultimately charged as the custodians of this public resource, their most important role should be to prepare and maintain fertile ground for meaningful public participation in the decision processes, and to incentivize the development and testing of novel solutions that meet the ethical standards of all participants. Adaptive Resource Management (ARM) approaches bolstered by applied research, logically offers the best paths forward but requires that government provide the leadership to reach out to the public. This document reviews and weighs the impacts of government decisions of the past, including evaluations of i) wolf culling ii) fertility control iii) diversionary and supplemental feeding iv) maternity enclosures v) inter-specific prey reductions vi) vegetation management vii) access reduction and, viii) wild to wild translocations.
Resource separation analysis with moose indicates threats to caribou in human altered landscapes
Ecography, 2013
Species recovery is often impeded by inadequate knowledge on mechanisms of community interactions that cause and exacerbate species endangerment. Caribou and wild reindeer Rangifer tarandus are declining in many regions of their circumpolar range likely because of human-induced landscape changes. In general, their niche specialization enables Rangifer to survive in nutrient-poor habitats spatially separated from other ungulates and their shared predators. Research has indicated that shifts in primary prey distribution following human landscape alteration may result in spatial overlap with Rangifer. We studied overlap relationships of woodland caribou R. t. caribou and moose Alces alces, quantified by their differential use of environmental resources, and evaluated the role of human landscape alteration in spatial separation in south-western Canada. Anthropogenic conversion of old-growth forests to early seral stands is hypothesized to decrease the spatial separation between caribou and moose, the dominant prey for wolves Canis lupus, contributing to increased caribou mortality. Redundancy analysis (RDA) was first used to examine coarse scale resource separation across our study area. Second, at a finer spatial scale, we used logistic regression to compare resource-and spatial separation of sympatric pairs of 17 moose and 17 caribou. Finally, we tested if the frequency of predator-caused caribou mortalities was higher in regions with higher moose resource use. Although environmental resource separation was strong at the coarser scale, we observed substantial spatial overlap ( 50%) at the finer scale. In summer we reported a significant positive relationship between spatial overlap of moose and caribou and the degree of human landscape alteration. Most importantly, locations of caribou mortalities corresponded with areas of high resource use by moose in summer. Thus, consistent with the spatial separation hypothesis, our research suggests that early successional forest stages may decrease spatial separation between caribou and moose, resulting in increased mortality risk for threatened caribou.
Winter Survey of Bathurst Caribou and Associated Wolf Distribution and Abundance
With the current rate of decline for the Bathurst barren-ground caribou herd (Rangifer tarandus groenlandicus) estimated at 5% per year and with causes of the decline unknown, research on the winter dynamics of the herd and its main predator, the wolf (Canis lupus) is a priority. During February through March 2006, we conducted a stratified random survey of the Bathurst caribou winter range, a total area of 494,000 km 2 . Survey cells were stratified as high or low caribou density, based on the current distribution of satellite-collared caribou.
The role of predation in the decline and extirpation of woodland caribou
Oecologia, 2005
To select appropriate recovery strategies for endangered populations, we must understand the dynamics of small populations and distinguish between the possible causes that drive such populations to low numbers. It has been suggested that the pattern of population decline may be inversely density-dependent with population growth rates decreasing as populations become very small; however, empirical evidence of such accelerated declines at low densities is rare. Here we analyzed the pattern of decline of a threatened population of woodland caribou (Rangifer tarandus caribou) in British Columbia, Canada. Using information on the instantaneous rate of increase relative to caribou density in suitable winter foraging habitat, as well as on pregnancy rates and on causes and temporal distribution of mortalities from a sample of 349 radiocollared animals from 15 subpopulations, we tested 3 hypothesized causes of decline: (a) food regulation caused by loss of suitable winter foraging habitat, (b) predation-sensitive foraging caused by loss of suitable winter foraging habitat and (c) predation with caribou being secondary prey. Population sizes of caribou subpopulations ranged from <5 to >500 individuals. Our results showed that the rates of increase of these subpopulations varied from À0.1871 to 0.0496 with smaller subpopulations declining faster than larger subpopulations. Rates of increase were positively related to the density of caribou in suitable winter foraging habitat. Pregnancy rates averaged 92.4% ±2.24 and did not differ among subpopulations. In addition, we found predation to be the primary cause of mortality in 11 of 13 subpopulations with known causes of mortality and predation predominantly occurred during summer. These results are consistent with predictions that caribou subpopulations are declining as a consequence of increased predation. Recovery of these woodland caribou will thus require a multispecies perspective and an appreciation for the influence of inverse density dependence on population trajectories.