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A prime numbered cycle means that the cicada rarely meets a predator (since any predator would have to be synchronized to 17 years, for example) and mass emerge
by itistoday 17y ago
A prime numbered cycle means that the cicada rarely meets a predator (since any predator would have to be synchronized to 17 years, for example) and mass emergence would overwhelm any predator around.
I don't understand. That sentence doesn't explain why it can't be a non-prime number like every 16 years, or every 18 years. It looks like part of the argument is missing.
- itistoday 17y agoAh OK, the full explanation is in the linked paper: The present work is based on the hypothesis that the cycle length is a prime number in order to optimally escape predators. For example, a prey with a 12-year cycle will meet—every time it appears—properly synchronized preda- tors appearing every 1, 2, 3, 4, 6 or 12 years, whereas a mutant with a 13-year period has the advantage of being subject to fewer predators. So it has to do with the number of available (different) predators, because their populations also go through cycles. Link: http://www.cims.nyu.edu/~eve2/predprey.pdf http://www.cims.nyu.edu/~eve2/predprey.pdf
- jgrahamc 17y agoWell suppose it's not a prime number then if you have some predator whose cycle is a factor of the cicada cycle then it's going to meet up with the cicada every time. Suppose you have an 18 year cicada, it has factor of 2, 3, 6, 9 so any predator that peaks every 2, 3, 6 or 9 years can synchronize with the cicada and be around to eat it. But if the cicada has a prime numbered cycle then it greatly reduces the chance of synchronizing with a predator.