This study characterizes population genetic structure among grey wolves (Canis lupus) in northwestern Canada, and discusses potential physical and biological determinants of this structure. Four hundred and ninety-one grey wolves, from nine regions in the Yukon, Northwest Territories and British Columbia, were genotyped using nine microsatellite loci. Results indicate that wolf gene flow is reduced significantly across the Mackenzie River, most likely due to the north-south migration patterns of the barren-ground caribou herds that flank it. Furthermore, although Banks and Victoria Island wolves are genetically similar, they are distinct from mainland wolf populations across the Amundsen Gulf. However, low-level island-mainland wolf migration may occur in conjunction with the movements of the Dolphin-Union caribou herd. Whereas previous authors have examined isolation-by-distance in wolves, this study is the first to demonstrate correlations between genetic structure of wolf populations and the presence of topographical barriers between them. Perhaps most interesting is the possibility that these barriers reflect prey specialization by wolves in different regions.
Diet and habitat selection of wood bison (Bison bison athabascae) were studied in the Mackenzie Bison Sanctuary, Northwest Territories, between February 1986 and April 1988. Wood bison showed pronounced seasonal changes in diet. Sedges constituted 96.1–98.8% of the winter diet. During summer, the diet became a more diverse mix of sedge (Carex spp.), grass (Graminae), and willow (Salix spp.). Lichen (Cladina mitis) became a major dietary component in fall. Summer browsing on willows increased when sedge standing crops were reduced. Forage availability was the main factor determining habitat selection. Wet sedge meadows provided the most available crude protein in winter and were the preferred winter habitat. Willow savannas provided the most available crude protein in summer and were the preferred summer habitat. Between June and October, all forages except lichen decreased in nitrogen content and increased in fibre content. The lack of distinct habitat preference in fall corresponded to dispersion of animals into forested habitats, increased use of lichen as forage, and more homogeneous availability of crude protein among habitats. Snow conditions were harsher in 1987–1988 than in 1986–1987, which affected forage availability and caused a noticeable shift in habitat use.
The Arctic is entering a new ecological state, with alarming consequences for humanity. Animal-borne sensors offer a window into these changes. Although substantial animal tracking data from the Arctic and subarctic exist, most are difficult to discover and access. Here, we present the new Arctic Animal Movement Archive (AAMA), a growing collection of more than 200 standardized terrestrial and marine animal tracking studies from 1991 to the present. The AAMA supports public data discovery, preserves fundamental baseline data for the future, and facilitates efficient, collaborative data analysis. With AAMA-based case studies, we document climatic influences on the migration phenology of eagles, geographic differences in the adaptive response of caribou reproductive phenology to climate change, and species-specific changes in terrestrial mammal movement rates in response to increasing temperature.
Effective management and conservation of species, subspecies, or ecotypes require an understanding of how populations are structured in space. We used satellite-tracking locations and hierarchical and fuzzy clustering to quantify subpopulations within the behaviorally different barren-ground caribou (Rangifer tarandus groenlandicus), Dolphin and Union island caribou (R. t. groenlandicus x pearyi), and boreal (R. t. caribou) caribou ecotypes in the Northwest Territories and Nunavut, Canada. Using a novel approach, we verified that the previously recognized Cape Bathurst, Bluenose-West, Bluenose-East, Bathurst, Beverly, Qamanirjuaq, and Lorillard barren-ground subpopulations were robust and that the Queen Maude Gulf and Wager Bay barren-ground subpopulations were organized as individuals. Dolphin and Union island and boreal caribou formed one and two distinct subpopulation, respectively, and were organized as individuals. Robust subpopulations were structured by strong annual spatial affiliation among females; subpopulations organized as individuals were structured by migratory connectivity, barriers to movement, and/or habitat discontinuity. One barren-ground subpopulation used two calving grounds, and one calving ground was used by two barren-ground subpopulations, indicating that these caribou cannot be reliably assigned to subpopulations solely by calving-ground use. They should be classified by annual spatial affiliation among females. Annual-range size and path lengths varied significantly among ecotypes, including mountain woodland caribou (R. t. caribou), and reflected behavioral differences. An east-west cline in annual-range sizes and path lengths among migratory barren-ground subpopulations likely reflected differences in subpopulation size and habitat conditions and further supported the subpopulation structure identified.
Peary caribou (Rangifer tarandus pearyi) and muskoxen {Ovibos moschatus) on Banks Island had considerable similarity in their annual diets, with monthly similarities ranging from 17.8-73.3%. Diet similarity was more pronounced in areas of high muskox density {ca. 1.65/km 2 ) than in areas of low muskox density {ca. 0.4/km 2 ). Willow (Salix arctka) and sedge (Carex aquatilis and Eriophorum spp.) represented >80% of the monthly diet of muskoxen. The caribou diet was more diverse, and was dominated by sedge, willow, Dryas integrifolia, and Oxytropis maydelliana, Lichen use was rare, likely as a consequence of low availability on Banks Island. Lichen standing crop was estimated at 2.96 g/m 2 . The differences in muskox diet between high and low density areas could not be explained by differences in forage distribution or standing crop. We discuss diet similarities of caribou and muskoxen and potential consequences for the current Peary caribou population in relation to winter weather conditions and increasing muskox density.
Changes in primary productivity have the potential to substantially alter food webs, with positive outcomes for some species and negative outcomes for others. Understanding the environmental context and species traits that give rise to these divergent outcomes is a major challenge to the generality of both theoretical and applied ecology. In aquatic systems, nutrient-mediated eutrophication has led to major declines in species diversity, motivating us to seek terrestrial analogues using a large-mammal system across 598 000 km 2 of the Canadian boreal forest. These forests are undergoing some of the most rapid rates of land-use change on Earth and are home to declining caribou ( Rangifer tarandus caribou ) populations. Using satellite-derived estimates of primary productivity, coupled with estimates of moose ( Alces alces ) and wolf ( Canis lupus ) abundance, we used path analyses to discriminate among hypotheses explaining how habitat alteration can affect caribou population growth. Hypotheses included food limitation, resource dominance by moose over caribou, and apparent competition with predators shared between moose and caribou. Results support apparent competition and yield estimates of wolf densities (1.8 individuals 1000 km −2 ) above which caribou populations decline. Our multi-trophic analysis provides insight into the cascading effects of habitat alteration from forest cutting that destabilize terrestrial predator–prey dynamics. Finally, the path analysis highlights why conservation actions directed at the proximate cause of caribou decline have been more successful in the near term than those directed further along the trophic chain.
The conservation of species requires preservation of natural habitats. Where the integrity of natural habitats has been upset, species go extinct. All natural habitats are continuing to decline, both inside and outside of reserves. Habitat change is partly a natural process (e.g., succession), but human activities have accelerated the process of decay so that natural rates of renewal are insufficient to maintain natural habitats. We argue that our only recourse, in light of these scenarios, is to adopt a new conservation strategy that considers the importance of habitat renewal in addition to habitat preservation. Accordingly, in our management decisions we must not only choose the size of area to preserve but also the size of area that balances habitat loss with habitat renewal. We also suggest that this habitat equilibrium point, H*, needs to be decided upon urgently, otherwise many species will become extinct in the next 50 yr according to numerous predictions. There are two ways to achieve H*. The first is to set habitats aside in protected areas in perpetuity. There are two reasons why this protection alone is insufficient: (1) protected areas continue to decline, albeit at a slower rate than outside of their boundaries, and (2) achieving H* simply by setting aside protected areas is no longer an option in many areas where severe habitat degradation or fragmentation has already occurred. The other way to achieve H* is to promote the reestablishment of natural habitats, or "habitat renewal." This concept is illustrated using a simple trade‐off model that balances habitat decay and habitat renewal. We then provide examples of habitat loss outside and inside of protected areas and discuss the potential for habitat renewal to offset these losses. We conclude that continued emphasis needs to be placed on setting aside natural habitat in protected areas. However, our examples of habitat loss show that this policy alone is most likely doomed to failure, so a policy of habitat renewal is also required.
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