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Krebs CJ, Kenney AJ, Gilbert BS, Boonstra R. Long-term monitoring of cycles in Clethrionomys rutilus in the Yukon boreal forest. Integr Zool 2024; 19:27-36. [PMID: 36892189 DOI: 10.1111/1749-4877.12718] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/10/2023]
Abstract
Baseline studies of small rodent populations in undisturbed ecosystems are rare. We report here 50 years of monitoring 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.
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Affiliation(s)
- Charles J Krebs
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Alice J Kenney
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | - B Scott Gilbert
- Renewable Resources Management Program, Yukon University, Whitehorse, Yukon, Canada
| | - Rudy Boonstra
- Department of Biological Sciences, University of Toronto Scarborough, Toronto, Ontario, Canada
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Oli MK, Kenney AJ, Boonstra R, Boutin S, Murray DL, Peers MJL, Gilbert BS, Jung TS, Chaudhary V, Hines JE, Krebs CJ. Does coat colour influence survival? A test in a cyclic population of snowshoe hares. Proc Biol Sci 2023; 290:20221421. [PMID: 37015272 PMCID: PMC10072933 DOI: 10.1098/rspb.2022.1421] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/06/2023] Open
Abstract
Some mammal species inhabiting high-latitude biomes have evolved a seasonal moulting pattern that improves camouflage via white coats in winter and brown coats in summer. In many high-latitude and high-altitude areas, the duration and depth of snow cover has been substantially reduced in the last five decades. This reduction in depth and duration of snow cover may create a mismatch between coat colour and colour of the background environment, and potentially reduce the survival rate of species that depend on crypsis. We used long-term (1977-2020) field data and capture-mark-recapture models to test the hypothesis that whiteness of the coat influences winter apparent survival in a cyclic population of snowshoe hares (Lepus americanus) at Kluane, Yukon, Canada. Whiteness of the snowshoe hare coat in autumn declined during this study, and snowshoe hares with a greater proportion of whiteness in their coats in autumn survived better during winter. However, whiteness of the coat in spring did not affect subsequent summer survival. These results are consistent with the hypothesis that the timing of coat colour change in autumn can reduce overwinter survival. Because declines in cyclic snowshoe hare populations are strongly affected by low winter survival, the timing of coat colour change may adversely affect snowshoe hare population dynamics as climate change continues.
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Affiliation(s)
- Madan K Oli
- Department of Wildlife Ecology and Conservation, University of Florida, Gainesville, FL 32611, USA
- School of Biological Sciences, Zoology Building, Tillydrone Avenue, University of Aberdeen, AB24 2TZ, UK
| | - Alice J Kenney
- Department of Zoology, University of British Columbia, Vancouver, Canada V6T 1Z4
| | - Rudy Boonstra
- Department of Biological Sciences, University of Toronto Scarborough, Toronto, Canada M1C 1A4
| | | | - Dennis L Murray
- Department of Biology, Trent University, Peterborough, ON, Canada K9L 1Z8
| | | | - B Scott Gilbert
- Renewable Resources Management Program, Yukon University, Whitehorse, Yukon, Canada Y1A 5K4
| | - Thomas S Jung
- Department of Renewable Resources, University of Alberta, Edmonton, Alberta, Canada T6G 2E9
- Department of Environment, Government of Yukon, Whitehorse, Yukon, Canada Y1A 2C6
| | - Vratika Chaudhary
- Department of Wildlife Ecology and Conservation, University of Florida, Gainesville, FL 32611, USA
| | - James E Hines
- U.S. Geological Survey Eastern Ecological Science Center, Laurel, MD 20708, USA
| | - Charles J Krebs
- Department of Zoology, University of British Columbia, Vancouver, Canada V6T 1Z4
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Abstract
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.
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Affiliation(s)
- Charles J Krebs
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Rudy Boonstra
- Department of Biological Sciences, University of Toronto Scarborough, Toronto, Ontario, Canada
| | - B Scott Gilbert
- Renewable Resources Management Program, Yukon College, Whitehorse, Yukon, Canada
| | - Alice J Kenney
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Stan Boutin
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
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Reid DG, Bilodeau F, Krebs CJ, Gauthier G, Kenney AJ, Gilbert BS, Leung MCY, Duchesne D, Hofer E. Lemming winter habitat choice: a snow-fencing experiment. Oecologia 2011; 168:935-46. [PMID: 22042523 DOI: 10.1007/s00442-011-2167-x] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2011] [Accepted: 10/03/2011] [Indexed: 11/28/2022]
Abstract
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 in spring. At all three sites, the density of winter nests increased in treated areas compared to control areas after the treatment, and remained higher on treated areas during the treatment. The treatment was relaxed at one site, and winter nest density returned to pre-treatment levels. The rodents' proportional use of treated areas compared to adjacent control areas increased and remained higher during the treatment. At two of three sites, lemmings and voles showed significant attraction to the areas of deepest snow accumulation closest to the fences. The strength of the treatment effect appeared to depend on how quickly the ground level temperature regime became stable in autumn, coincident with snow depths near the hiemal threshold. Our results provide strong support for the hypothesis that snow depth is a primary determinant of winter habitat choice by tundra lemmings and voles.
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Affiliation(s)
- Donald G Reid
- Wildlife Conservation Society Canada, 39 Harbottle Road, Whitehorse, YT, Y1A 5T2, Canada
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Gilbert BS. Use of winter feeding craters by snowshoe hares. CAN J ZOOL 1990. [DOI: 10.1139/z90-237] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Snowshoe hares (Lepus americanus) in the southwest Yukon foraged in winter on ground vegetation by digging feeding craters in snow. Hares utilized at least three species: Dryas drummondii, Hedysarum mackenzii, and Lupinus arcticus. Hares dug feeding craters to reach these plants in snow up to 36 cm deep, and the area of these craters ranged from 140 to 2600 cm2. I recorded few craters after midwinter when snow depths reached 40 cm; the few craters dug at this time were in areas of shallow snow either beneath trees or in windswept areas. When hares had stopped digging craters, I established 11 small plots (1 × 1 or 1 × 2 m) where I removed snow to ground level. Hares moved in and used these areas to feed on D. drummondii and L. arcticus. I conclude that the vegetation was suitable for hares and speculate that hares stopped digging feeding craters because snow depth or snow density made it energetically uneconomical. The food value of these plants and their importance in the winter diet of hares needs further study.
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Abstract
We counted the number of snowshoe hare (Lepus americanus) fecal pellets on 50 quadrats of 0.155 m2 on each of six areas near Kluane Lake, Yukon Territory, once a year from 1977 to 1983. On four of these areas we livetrapped hares once a month and estimated population density from the Jolly–Seber model. Average hare density for the year was linearly related to fecal pellet counts (r = 0.94) over the range 0–10 hares/ha. Mean turd counts also are related to the variance of these counts by Taylor's power law with exponent 1.30, indicating a clumped pattern in turd deposition. Fecal pellet counts provide a quick and accurate method for snowshoe hare censuses on an extensive scale.
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Abstract
Sixty patients were treated for pain by transcutaneous electric nerve stimulation in a general practice. The treatment resulted in a complete pain relief in 40%, a significant pain relief in 28.3%, and little or no pain relief in 31.7% of patients. These results are similar to those reported in several hospital series.
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Gilbert BS. Metatarsal stress fracture: the use of a posterior plaster of Paris splint. A case report. J Am Podiatry Assoc 1968; 58:438-40. [PMID: 5681631 DOI: 10.7547/87507315-58-10-438] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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