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Filters: Tags: Monitoring 1-Changes in Plant and Animal Distribution: Fauna (X) > partyWithName: Krebs, Charles J. (X)

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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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Two population oscillations dominate terrestrial community dynamics in northern Canada. In the boreal forest, the snowshoe hare (Lepus americanus) fluctuates in cycles with an 8–10 year periodicity and in tundra regions lemmings typically fluctuate in cycles with a 3–4 year periodicity. I review 60 years of research that has uncovered many of the causes of these population cycles, outline areas of controversy that remain and suggest key questions to address. Lemmings are keystone herbivores in tundra ecosystems because they are a key food resource for many avian and mammalian predators and are a major consumer of plant production. There remains much controversy over the role of predation, food shortage and social...
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Small mammals in boreal forest ecosystems fluctuate dramatically in abundance and 1 possible mechanism to explain these changes is the bottom-up hypothesis of variation in food supplies. Here we ask if variation in berry crops produced by 6 major species of dwarf shrubs and herbs, epigeous mushroom crops, and white spruce seeds allow us to predict changes in the abundance of the red-backed vole (Myodes [= Clethrionomys] rutilus), the deer mouse (Peromyscus maniculatus), and field voles (Microtus oeconomus and M. pennsylvanicus combined) over 13 years (1997-2009) in the Kluane Lake region of the southwestern Yukon, Canada. M. rutilus is the dominant rodent in these forests, comprising 64% of the catch. Overwinter...
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We review the population dynamics of red-backed voles (Myodes species) in North America, the main deciduous and coniferous forest-dwelling microtines on this continent, and compare and contrast their pattern with that of the same or similar species in Eurasia. We identify 7 long-term studies of population changes in Myodes in North America. Using autoregressive and spectral analysis, we found that only 2 of the 7 show 3- to 5-year cycles like those found in some Eurasian populations. There was no relationship between latitude and cycling. The general lack of cyclicity is associated with two key aspects of their demography that act in tandem: first, poor overwinter survival in most years; second, chronically low...
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The insulative value of early and deep winter snow is thought to enhance winter reproduction and survival by arctic lemmings (Lemmus and Dicrostonyx spp). This leads to the general hypothesis that landscapes with persistently low lemming population densities, or low amplitude population fluctuations, have a low proportion of the land base with deep snow. We experimentally tested a component of this hypothesis, that snow depth influences habitat choice, at three Canadian Arctic sites: Bylot Island, Nunavut; Herschel Island, Yukon; Komakuk Beach, Yukon. We used snow fencing to enhance snow depth on 9-ha tundra habitats, and measured the intensity of winter use of these and control areas by counting rodent winter nests...
Estimating population densities of small mammals (< 100 g) has typically been carried out by intensive livetrapping, but this technique may be stressful to animals and the effort required is considerable. Here, we used camera traps to detect small mammal presence and assessed if this provided a feasible alternative to livetrapping for density estimation. During 2010-2012, we used camera trapping in conjunction with mark-recapture livetrapping to estimate the density of northern red-backed voles (Myodes rutilus) and deer mice (Peromyscus maniculatus) in the boreal forest of Yukon, Canada. Densities for these 2 species ranged from 0.29 to 9.21 animals/ha and 0 to 5.90 animals/ha, respectively, over the course of this...
map background search result map search result map Do changes in berry crops drive population fluctuations in small rodents in the southwestern Yukon? Density estimation for small mammals from livetrapping grids: rodents in northern Canada Population dynamics of red-backed voles (Myodes) in North America Lemming winter habitat choice: a snow-fencing experiment Linking climate change to population cycles of hares and lynx Population limitation of the northern red-backed vole in the boreal forests of northern Canada Of lemmings and snowshoe hares: the ecology of northern Canada Cyclic dynamics of snowshoe hares on a small island in the Yukon What factors determine cyclic amplitude in the snowshoe hare (Lepus americanus) cycle? Estimating snowshoe hare population density from pellet plots: a further evaluation The role of red squirrels and arctic ground squirrels Herbivores - Forest grouse and ptarmigan Is the relationship between predator and prey abundances related to climate for lynx and snowshoe hares? Evidence for source–sink dynamics in a regional population of arctic ground squirrels (Urocitellus parryii plesius) Arctic ground squirrel population collapse in the boreal forests of the Southern Yukon Ecosystem Dynamics of the Boreal Forest: the Kluane Project Voles and mice The impact of rewilding, species introductions and climate change on the structure and function of the Yukon boreal forest ecosystem Cyclic dynamics of snowshoe hares on a small island in the Yukon Density estimation for small mammals from livetrapping grids: rodents in northern Canada Lemming winter habitat choice: a snow-fencing experiment Herbivores - Forest grouse and ptarmigan Is the relationship between predator and prey abundances related to climate for lynx and snowshoe hares? The role of red squirrels and arctic ground squirrels Voles and mice Evidence for source–sink dynamics in a regional population of arctic ground squirrels (Urocitellus parryii plesius) Arctic ground squirrel population collapse in the boreal forests of the Southern Yukon Do changes in berry crops drive population fluctuations in small rodents in the southwestern Yukon? Estimating snowshoe hare population density from pellet plots: a further evaluation Ecosystem Dynamics of the Boreal Forest: the Kluane Project The impact of rewilding, species introductions and climate change on the structure and function of the Yukon boreal forest ecosystem Population dynamics of red-backed voles (Myodes) in North America What factors determine cyclic amplitude in the snowshoe hare (Lepus americanus) cycle? Linking climate change to population cycles of hares and lynx Population limitation of the northern red-backed vole in the boreal forests of northern Canada Of lemmings and snowshoe hares: the ecology of northern Canada