What factors determine cyclic amplitude in the snowshoe hare (Lepusamericanus) cycle?

Charles Krebs, John Bryant, Knut Kielland, Mark O'Donoghue, Frank Doyle, Suzanne Carriere, Donna DiFolco, Nathan Berg, Rudy Boonstra, Stan Boutin, Alice Kenney, Donald Reid, Karin Bodony, Judy Putera, Henry Timm, Toby Burke, Julie Maier, Howard Golden

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

Snowshoe hares (Lepus americanus Erxleben, 1777) fluctuate in 9–10 year cycles throughout much of their North American range. These cycles show large variations in cyclic amplitude and we ask what factors could cause amplitude variation. We gathered data from 1976 to 2012 on hare numbers in the boreal forest of Alaska, Yukon, Northwest Territories, and northern British Columbia to describe the amplitude of hare fluctuations and to evaluate four possible causes. First, weather could cause variation in amplitude via hare reproduction or survival, but this mechanism does not fit our data. Second, bottom-up processes involving forest succession could explain amplitude variation through changes in winter forage availability, but succession is too slow a variable in our study areas. Third, plant defenses entrained by hare over-browsing in one cycle can produce variation in plant quality and quantity in subsequent cycles. A mathematical model suggests this is a possible explanation. Fourth, predator recovery following the cyclic low is inversely related to hare cyclic amplitude, and the existing data are consistent with this mechanism. A standardized regional monitoring program is needed to improve our understanding of cyclic amplitude variation in hares and the possible role of predators and winter foods in affecting amplitude.
Original languageEnglish
Pages (from-to)1039-1048
Number of pages10
JournalCanadian Journal of Zoology
Volume92
Issue number12
DOIs
Publication statusPublished - 2014
Externally publishedYes

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Lepus americanus
hares
predators
Northwest Territories
forest succession
Yukon Territory
winter
browsing
predator
boreal forests
British Columbia
plant defense
mathematical models
weather
forage
boreal forest
monitoring
food

Cite this

Krebs, C., Bryant, J., Kielland, K., O'Donoghue, M., Doyle, F., Carriere, S., ... Golden, H. (2014). What factors determine cyclic amplitude in the snowshoe hare (Lepusamericanus) cycle? Canadian Journal of Zoology, 92(12), 1039-1048. https://doi.org/10.1139/cjz-2014-0159
Krebs, Charles ; Bryant, John ; Kielland, Knut ; O'Donoghue, Mark ; Doyle, Frank ; Carriere, Suzanne ; DiFolco, Donna ; Berg, Nathan ; Boonstra, Rudy ; Boutin, Stan ; Kenney, Alice ; Reid, Donald ; Bodony, Karin ; Putera, Judy ; Timm, Henry ; Burke, Toby ; Maier, Julie ; Golden, Howard. / What factors determine cyclic amplitude in the snowshoe hare (Lepusamericanus) cycle?. In: Canadian Journal of Zoology. 2014 ; Vol. 92, No. 12. pp. 1039-1048.
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abstract = "Snowshoe hares (Lepus americanus Erxleben, 1777) fluctuate in 9–10 year cycles throughout much of their North American range. These cycles show large variations in cyclic amplitude and we ask what factors could cause amplitude variation. We gathered data from 1976 to 2012 on hare numbers in the boreal forest of Alaska, Yukon, Northwest Territories, and northern British Columbia to describe the amplitude of hare fluctuations and to evaluate four possible causes. First, weather could cause variation in amplitude via hare reproduction or survival, but this mechanism does not fit our data. Second, bottom-up processes involving forest succession could explain amplitude variation through changes in winter forage availability, but succession is too slow a variable in our study areas. Third, plant defenses entrained by hare over-browsing in one cycle can produce variation in plant quality and quantity in subsequent cycles. A mathematical model suggests this is a possible explanation. Fourth, predator recovery following the cyclic low is inversely related to hare cyclic amplitude, and the existing data are consistent with this mechanism. A standardized regional monitoring program is needed to improve our understanding of cyclic amplitude variation in hares and the possible role of predators and winter foods in affecting amplitude.",
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Krebs, C, Bryant, J, Kielland, K, O'Donoghue, M, Doyle, F, Carriere, S, DiFolco, D, Berg, N, Boonstra, R, Boutin, S, Kenney, A, Reid, D, Bodony, K, Putera, J, Timm, H, Burke, T, Maier, J & Golden, H 2014, 'What factors determine cyclic amplitude in the snowshoe hare (Lepusamericanus) cycle?', Canadian Journal of Zoology, vol. 92, no. 12, pp. 1039-1048. https://doi.org/10.1139/cjz-2014-0159

What factors determine cyclic amplitude in the snowshoe hare (Lepusamericanus) cycle? / Krebs, Charles; Bryant, John; Kielland, Knut; O'Donoghue, Mark; Doyle, Frank; Carriere, Suzanne; DiFolco, Donna; Berg, Nathan; Boonstra, Rudy; Boutin, Stan; Kenney, Alice; Reid, Donald; Bodony, Karin; Putera, Judy; Timm, Henry; Burke, Toby; Maier, Julie; Golden, Howard.

In: Canadian Journal of Zoology, Vol. 92, No. 12, 2014, p. 1039-1048.

Research output: Contribution to journalArticle

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T1 - What factors determine cyclic amplitude in the snowshoe hare (Lepusamericanus) cycle?

AU - Krebs, Charles

AU - Bryant, John

AU - Kielland, Knut

AU - O'Donoghue, Mark

AU - Doyle, Frank

AU - Carriere, Suzanne

AU - DiFolco, Donna

AU - Berg, Nathan

AU - Boonstra, Rudy

AU - Boutin, Stan

AU - Kenney, Alice

AU - Reid, Donald

AU - Bodony, Karin

AU - Putera, Judy

AU - Timm, Henry

AU - Burke, Toby

AU - Maier, Julie

AU - Golden, Howard

PY - 2014

Y1 - 2014

N2 - Snowshoe hares (Lepus americanus Erxleben, 1777) fluctuate in 9–10 year cycles throughout much of their North American range. These cycles show large variations in cyclic amplitude and we ask what factors could cause amplitude variation. We gathered data from 1976 to 2012 on hare numbers in the boreal forest of Alaska, Yukon, Northwest Territories, and northern British Columbia to describe the amplitude of hare fluctuations and to evaluate four possible causes. First, weather could cause variation in amplitude via hare reproduction or survival, but this mechanism does not fit our data. Second, bottom-up processes involving forest succession could explain amplitude variation through changes in winter forage availability, but succession is too slow a variable in our study areas. Third, plant defenses entrained by hare over-browsing in one cycle can produce variation in plant quality and quantity in subsequent cycles. A mathematical model suggests this is a possible explanation. Fourth, predator recovery following the cyclic low is inversely related to hare cyclic amplitude, and the existing data are consistent with this mechanism. A standardized regional monitoring program is needed to improve our understanding of cyclic amplitude variation in hares and the possible role of predators and winter foods in affecting amplitude.

AB - Snowshoe hares (Lepus americanus Erxleben, 1777) fluctuate in 9–10 year cycles throughout much of their North American range. These cycles show large variations in cyclic amplitude and we ask what factors could cause amplitude variation. We gathered data from 1976 to 2012 on hare numbers in the boreal forest of Alaska, Yukon, Northwest Territories, and northern British Columbia to describe the amplitude of hare fluctuations and to evaluate four possible causes. First, weather could cause variation in amplitude via hare reproduction or survival, but this mechanism does not fit our data. Second, bottom-up processes involving forest succession could explain amplitude variation through changes in winter forage availability, but succession is too slow a variable in our study areas. Third, plant defenses entrained by hare over-browsing in one cycle can produce variation in plant quality and quantity in subsequent cycles. A mathematical model suggests this is a possible explanation. Fourth, predator recovery following the cyclic low is inversely related to hare cyclic amplitude, and the existing data are consistent with this mechanism. A standardized regional monitoring program is needed to improve our understanding of cyclic amplitude variation in hares and the possible role of predators and winter foods in affecting amplitude.

KW - snowshoe hare

KW - Lepus americanus

KW - 10 year cycle

KW - boreal forest

KW - predation

KW - Canada lynx

KW - Lynx canadensis

KW - succession

KW - secondary chemicals

KW - weather.

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DO - 10.1139/cjz-2014-0159

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