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The classic 10-year population cycle of snowshoe hares ( Lepus americanus, Erxleben 1777) and Canada lynx ( Lynx canadensis, Kerr 1792) in the boreal forests of North America has drawn much attention from both population and community ecologists worldwide; however, the ecological mechanisms driving the 10-year cyclic dynamic pattern are not fully revealed yet. In this study, by the use of historic fur harvest data, we constructed a series of generalized additive models to study the effects of density dependence, predation, and climate (both global climate indices of North Atlantic Oscillation index ( NAO), Southern Oscillation index ( SOI) and northern hemispheric temperature ( NHT) and local weather data including...
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We measured stable carbon and nitrogen isotope ratios in guard hair of 81 populations of grizzly bears (Ursus arctos L., 1758) across North America and used mixing models to assign diet fractions of salmon, meat derived from terrestrial sources, kokanee (Oncorhynchus nerka (Walbaum in Artedi, 1792)), and plants. In addition, we examined the relationship between skull size and diet of bears killed by people in British Columbia. The majority of carbon and nitrogen assimilated by most coastal grizzly bear populations was derived from salmon, while interior populations usually derived a much smaller fraction of their nutrients from salmon, even in areas with relatively large salmon runs. Terrestrial prey was a large...
This article is a product from the project "Can Mammals Mediate Climatically-Induced Vegetation Transitions in Alpine Ecosystems of the Western United States?". Abstract: In ecological studies, it is useful to estimate the probability that a species occurs at given locations. The probability of presence can be modeled by traditional statistical methods, if both presence and absence data are available. However, the challenge is that most species records contain only presence data, without reliable absence data. Previous presence-only methods can estimate a relative index of habitat suitability, but cannot estimate the actual probability of presence. In this study, we develop a presence and background learning...
Abstract: Restoration of degraded wet meadows found on upland valley floors has been proposed to achieve a range of ecological benefits, including augmenting late‐season streamflow. There are, however, few field and modelling studies documenting hydrologic changes following restoration that can be used to validate this expectation, and published changes in groundwater levels and streamflow following restoration are inconclusive. Here, we assess the streamflow benefit that can be obtained by wet‐meadow restoration using a physically based quantitative analysis. This framework employs a 1‐dimensional linearized Boussinesq equation with a superimposed solution for changes in storage due to groundwater upwelling and...
Nutritional restrictions in winter may reduce the availability of protein for reproduction and survival in northern ungulates. We refined a technique that uses recently voided excreta on snow to assess protein status in wild caribou (Rangifer tarandus) in late winter. Our study was the first application of this non-invasive, isotopic approach to assess protein status of wild caribou by determining dietary and endogenous contributions of nitrogen (N) to urinary urea. We used isotopic ratios of N (?15N) in urine and fecal samples to estimate the proportion of urea N derived from body N (p-UN) in pregnant, adult females of the Chisana Herd, a small population that ranged across the Alaska-Yukon border. We took advantage...
Previous research on the relationship between spatial memory and adult hippocampal neurogenesis has been controversial. In the present study, neurogenesis was compared between two natural populations of the same species that differ in their reliance on spatial memory to cache and retrieve stored food. Western red squirrels store food in a single site whereas eastern red squirrels store food in multiple sites. Neurogenesis was assessed using endogenous markers of the number of proliferating cells (Ki-67) and the number of immature neurons (DCX), and neuronal recruitment was determined by measuring the area of the dentate gyrus of the hippocampus. The number of proliferating cells, immature neurons and neuronal recruitment...
This study explores relationships between the normalized difference vegetation index (NDVI) and structural characteristics associated with deciduous shrub dominance in arctic tundra. Our structural measures of shrub dominance are stature, branch abundance, aerial per cent woody stem cover (deciduous and evergreen species), and per cent deciduous shrub canopy cover. All measurements were taken across a suite of transects that together represent a gradient of deciduous shrub height. The transects include tussock tundra shrub and riparian shrub tundra communities located in the northern foothills of the Brooks Range, in northern Alaska. Plot-level NDVI measurements were made in 2010 during the snow-free period prior...
The dynamic environmental history of the Arctic makes it a natural experiment for the effects of climate change. Dramatic fluctuations in climate during the Pleistocene led to large ice sheets covering large expanses of the Arctic during glacial maxima, while ice-free areas such as the Beringian refugium persisted at high latitudes over multiple glacial cycles. Beringia roughly extended from the Kolyma River in Far East Russia through Alaska to the Mackenzie River in northwestern Canada. During glacial maxima, sea levels were lower and the Bering Land Bridge of central Beringia connected Eurasia and North America. I use a statistical phylogeographic approach, incorporating theory and new analytical techniques from...
The caribou (Rangifer tarandus ) has been the most valuable game species throughout circumpolar regions since ancient times. They have remained an important economic and cultural resource for northern communities. However, caribou are not always a dependable resource, due to marked population declines and range shifts that occur at unpredictable intervals. These fluctuations are often caused by harsh environmental conditions. In addition, since the early 19 th century, many caribou herds have experienced various levels of stress due to human encroachment on caribou ranges. Consequently, a number of populations and subspecies have recently been listed as threatened or endangered . As herd range conditions change...
This study investigated the effects of human land-use on grizzly bear (Ursus arctos L.) habitat and populations in the Kluane region of southwest Yukon, Canada. Previous studies in the region identify grizzlies as the species most at risk from cumulative impacts of human activity. The goals of this project were to: (1) identify the effects of cumulative human activities on grizzly habitat and populations; and (2) provide recommendations on human-use management with respect to the conservation of grizzlies and their habitat. Thus, I investigated three aspects of bear ecology and synthesized them to examine the influence of human-activities on bears. First, I examined the appropriateness of using Tasselled Cap Transformation...
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This data package contains digital images, survey location logs and a summary tabulation from carcass survey conducted at walrus haulouts in Alaska. A summary of image collection times is provided as a tabular file. The images are considered sensitive. They are archived at the U.S. Geological Survey, Alaska Science Center (a USGS Trusted Digital Repository). At this time, only this metadata record describing the data, an image inventory table, and a satellite (GNSS) log are publicly accessible.
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Mountain meadows in the western United States provide key habitats for many plant and wildlife species, many of which rely exclusively on these areas. Mountain meadows are also treasured by the public and provide beautiful areas to view wildflowers and wildlife on public lands such as national parks. However, mountain ecosystems are expected to be disproportionately affected by climate change. There is a limited understanding of how mountain meadows are changing, how temperature and precipitation may be driving those changes, and how this will impact sensitive species that inhabit these landscapes. Natural resource managers have an immediate need to understand these relationships to conserve or restore habitats...
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Climate change is already affecting species in many ways. Because individual species respond to climate change differently, some will be adversely affected by climate change whereas others may benefit. Successfully managing species in a changing climate will require an understanding of which species will be most and least impacted by climate change. Although several approaches have been proposed for assessing the vulnerability of species to climate change, it is unclear whether these approaches are likely to produce similar results. In this study, we compared the relative vulnerabilities to climate change of 76 species of birds, mammals, amphibians, and trees based on three different approaches to assessing vulnerability....
We developed high-resolution climate projections for the mid- and late 21st century across the Great Lakes region, including the Midwest and Northeast United States and southern Canada. We applied a regional climate model that addresses future changes in Great Lakes’ water temperatures, ice cover, and evaporation, which critically impact lake-effect snowfall. This new dataset is highly valuable, given that most global climate models applied in the reports of the Intergovernmental Panel on Climate Change and National Climate Assessment either completely lack the Great Lakes or largely under-represent their coverage and impacts. After quantifying projected changes in weather severity based on air temperature and snow...
map background search result map search result map Understanding Climate Change Vulnerability in the Pacific Northwest: A Comparison of Three Approaches Linking climate change to population cycles of hares and lynx Major components of grizzly bear diet across North America Spatial distribution of meadow jumping mice (Zapus hudsonius) in logged boreal forest of northwestern Canada From Water to Wildlife: Linking Water Timing and Availability to Meadows and Wildlife in a Changing Climate Pacific Walrus Coastal Haulout Images from Carcass Surveys Pacific Walrus Coastal Haulout Images from Carcass Surveys From Water to Wildlife: Linking Water Timing and Availability to Meadows and Wildlife in a Changing Climate Major components of grizzly bear diet across North America Understanding Climate Change Vulnerability in the Pacific Northwest: A Comparison of Three Approaches Linking climate change to population cycles of hares and lynx Spatial distribution of meadow jumping mice (Zapus hudsonius) in logged boreal forest of northwestern Canada