Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - Noise and determinism in synchronized sheep dynamics
AU - Grenfell, B. T.
AU - Wilson, K.
AU - Finkenstädt, B. F.
AU - Coulson, T. N.
AU - Murray, S.
AU - Albon, S. D.
AU - Pemberton, J. M.
AU - Clutton-Brock, T. H.
AU - Crawley, M. J.
PY - 1998/8/13
Y1 - 1998/8/13
N2 - A major debate in ecology concerns the relative importance of intrinsic factors and extrinsic environmental variations in determining population size fluctuations1-6. Spatial correlation of fluctuations in different populations caused by synchronous environmental shocks2,7,8 is a powerful tool for quantifying the impact of environmental variations on population dynamics8,9. However, interpretation of synchrony is often complicated by migration between populations8,10. Here we address this issue by using time series from sheep populations on two island in the St Kilda archipelago11-13. Fluctuations in the sizes of the two populations are remarkably synchronized over a 40-year period. A nonlinear time-series model shows that a high and frequent degree of environmental correlation is required to achieve this level of synchrony. The model indicates that if there were less environmental correlation, population dynamics would be much less synchronous than is observed. This is because of a threshold effect that is dependent on population size; the threshold magnifies random differences between populations. A refined model shows that part of the required environmental synchronicity can be accounted for by large-scale weather variations. These results underline the importance of understanding the interaction between intrinsic and extrinsic influences on population dynamics14.
AB - A major debate in ecology concerns the relative importance of intrinsic factors and extrinsic environmental variations in determining population size fluctuations1-6. Spatial correlation of fluctuations in different populations caused by synchronous environmental shocks2,7,8 is a powerful tool for quantifying the impact of environmental variations on population dynamics8,9. However, interpretation of synchrony is often complicated by migration between populations8,10. Here we address this issue by using time series from sheep populations on two island in the St Kilda archipelago11-13. Fluctuations in the sizes of the two populations are remarkably synchronized over a 40-year period. A nonlinear time-series model shows that a high and frequent degree of environmental correlation is required to achieve this level of synchrony. The model indicates that if there were less environmental correlation, population dynamics would be much less synchronous than is observed. This is because of a threshold effect that is dependent on population size; the threshold magnifies random differences between populations. A refined model shows that part of the required environmental synchronicity can be accounted for by large-scale weather variations. These results underline the importance of understanding the interaction between intrinsic and extrinsic influences on population dynamics14.
U2 - 10.1038/29291
DO - 10.1038/29291
M3 - Journal article
AN - SCOPUS:0032514553
VL - 394
SP - 674
EP - 677
JO - Nature
JF - Nature
SN - 0028-0836
IS - 6694
ER -