Baseline studies of small rodent populations in undisturbed ecosystems are rare.We report here 50 years of mon-itoring and experimentation in Yukon of a dominant rodent species in the North American boreal forest,the ...Baseline studies of small rodent populations in undisturbed ecosystems are rare.We report here 50 years of mon-itoring and experimentation in Yukon of a dominant rodent species in the North American boreal forest,the red-backed vole Clethrionomys rutilus.These voles breed in summer,weigh 20–25 g,and reach a maximum density of 20 to 25 per ha.Their populations have shown consistent 3–4-year cycles for the last 50 years with the only change being that peak densities averaged 8/ha until 2000 and 18/ha since that year.During the last 25 years,we have measured food resources,predator numbers,and winter weather,and for 1-year social interactions,to estimate their contribution to changes in the rate of summer increase and the rate of overwinter decline.All these potential limiting factors could contribute to changes in density,and we measured their relative contributions statistically with multiple regressions.The rate of winter decline in density was related to both food supply and winter severity.The rate of summer increase was related to summer berry crops and white spruce cone production.No measure of predator numbers was related to winter or summer changes in vole abundance.There was a large signal of climate change effects in these populations.There is no density dependence in summer population growth and only a weak one in winter population declines.None of our results provide a clear understanding of what generates 3–4-year cycles in these voles,and the major missing piece may be an understanding of social interactions at high density.展开更多
Long-term monitoring is critical to determine the stability and sustainability of wildlife populations,and if change has occurred,why.We have followed population density changes in the small mammal community in the bo...Long-term monitoring is critical to determine the stability and sustainability of wildlife populations,and if change has occurred,why.We have followed population density changes in the small mammal community in the boreal forest of the southern Yukon for 46 years with density estimates by live trapping on 3-5 unmanipulated grids in spring and autumn.This community consists of 10 species and was responsible for 9%of the energy flow in the herbivore component of this ecosystem from 1986 to 1996,but this increased to 38%from 2003 to 2014.Small mammals,although small in size,are large in the transfer of energy from plants to predators and decomposers.Four species form the bulk of the biomass.There was a shift in the dominant species from the 1970s to the 2000s,with Myodes rutilus increasing in relative abundance by 22%and Peromyscus maniculatus decreasing by 22%.From 2007 to 2018,Myodes comprised 63%of the catch,Peromyscus 20%,and Microtus species 17%.Possible causes of these changes involve climate change,which is increasing primary production in this boreal forest,and an associated increase in the abundance of 3 rodent predators,marten(Martes americana),ermine(Mustela ermine)and coyotes(Canis latrans).Following and understanding these and potential future changes will require long-term monitoring studies on a large scale to measure metapopulation dynamics.The small mammal community in northern Canada is being affected by climate change and cannot remain stable.Changes will be critically dependent on food-web interactions that are species-specific.展开更多
文摘Baseline studies of small rodent populations in undisturbed ecosystems are rare.We report here 50 years of mon-itoring and experimentation in Yukon of a dominant rodent species in the North American boreal forest,the red-backed vole Clethrionomys rutilus.These voles breed in summer,weigh 20–25 g,and reach a maximum density of 20 to 25 per ha.Their populations have shown consistent 3–4-year cycles for the last 50 years with the only change being that peak densities averaged 8/ha until 2000 and 18/ha since that year.During the last 25 years,we have measured food resources,predator numbers,and winter weather,and for 1-year social interactions,to estimate their contribution to changes in the rate of summer increase and the rate of overwinter decline.All these potential limiting factors could contribute to changes in density,and we measured their relative contributions statistically with multiple regressions.The rate of winter decline in density was related to both food supply and winter severity.The rate of summer increase was related to summer berry crops and white spruce cone production.No measure of predator numbers was related to winter or summer changes in vole abundance.There was a large signal of climate change effects in these populations.There is no density dependence in summer population growth and only a weak one in winter population declines.None of our results provide a clear understanding of what generates 3–4-year cycles in these voles,and the major missing piece may be an understanding of social interactions at high density.
文摘Long-term monitoring is critical to determine the stability and sustainability of wildlife populations,and if change has occurred,why.We have followed population density changes in the small mammal community in the boreal forest of the southern Yukon for 46 years with density estimates by live trapping on 3-5 unmanipulated grids in spring and autumn.This community consists of 10 species and was responsible for 9%of the energy flow in the herbivore component of this ecosystem from 1986 to 1996,but this increased to 38%from 2003 to 2014.Small mammals,although small in size,are large in the transfer of energy from plants to predators and decomposers.Four species form the bulk of the biomass.There was a shift in the dominant species from the 1970s to the 2000s,with Myodes rutilus increasing in relative abundance by 22%and Peromyscus maniculatus decreasing by 22%.From 2007 to 2018,Myodes comprised 63%of the catch,Peromyscus 20%,and Microtus species 17%.Possible causes of these changes involve climate change,which is increasing primary production in this boreal forest,and an associated increase in the abundance of 3 rodent predators,marten(Martes americana),ermine(Mustela ermine)and coyotes(Canis latrans).Following and understanding these and potential future changes will require long-term monitoring studies on a large scale to measure metapopulation dynamics.The small mammal community in northern Canada is being affected by climate change and cannot remain stable.Changes will be critically dependent on food-web interactions that are species-specific.
