9.6 year cycle of lynx abundance

From Wikipedia, the free encyclopedia

The Canadian lynx lives in the northern parts of Canada and its population can be estimated from the records kept from the number caught each year for its fur. Records have been kept by the Hudson's Bay Company and Canadian government since the 1730s. A graph of its abundance is characterized by huge rises and falls with the peaks occurring at a level typically ten times higher than the troughs and about 5 years after them, and the process then reversing itself.

Because the lynx catches and eats snowshoe hares which also show the same average 9.6 year cycle of population, this has been described as a predator-prey cycle. There are reasons to believe that this is not the actual cause of population variations however.^{[citation needed]}

• Firstly, there is no time lag between the variations in the two species which would be expected if a predator-prey cycle was the cause.^{[citation needed]}
• Secondly, a number of other species that are unrelated to either, as far as food chains are concerned, show the same 9.6 year cycle.^{[citation needed]} These include abundance of atlantic salmons, chinch bugs in Illinois, tent caterpillars, coyote, hawk owl eggs, grouse, marten, mink, muskrat, fisher and hawks.

There are 9.6 year cycles found in a number of weather variables including barometric pressure, atmospheric ozone content, storm track shifts, U-magnetic value and weather generally.^{[citation needed]}

The 9.6 year cycle has also been reported in human heart disease, wheat acreage and prices, tree ring widths, international battles and trade peaks in Great Britain.^{[citation needed]}

Edward R. Dewey stated that the cause of the 9.6 year cycle is unknown, but whatever the cause it clearly has a wide spread effect. Variations in the atmospheric ozone content or other weather factors may play a part in determining the various animal population fluctuations. All the animal abundances come to peaks at the same time, a phenomenon that Dewey described as cycle synchrony. The rate of human heart disease peak occurs when animal populations are falling most rapidly, so humans are also synchronized with the other animals although the human population does not fluctuate markedly.

[edit] References

• Journal of Cycle Research, vol. 2 no. 1, An Index of Lynx Abundance, Dr Leonard W Wing
• Cycles Classic Library Collection, vol.1 pages 40-41, An Example of an Especially Dominant Cycle, Edward R Dewey
• The Case for Cycles, Edward R Dewey
• Hinterland Who's Who - Canadian Lynx