Magicicada - Predator Satiation Survival Strategy

Predator Satiation Survival Strategy

The nymphs emerge in large numbers at about the same time, sometimes more than 1.5 million individuals per acre (>370/m²). Their mass-emergence is a survival trait called predator satiation: for the first week after emergence, the periodic cicadas are an easy prey for reptiles, birds, squirrels, cats, and other small and large mammals. Early ideas maintained that the cicadas' overall survival mechanism was simply to overwhelm predators by their sheer numbers, ensuring the survival of most of the individuals. It was hypothesized that the emergence period of large prime numbers (13 and 17 years) was a predatory avoidance strategy adopted to eliminate the possibility of potential predators receiving periodic population boosts by synchronizing their own generations to divisors of the cicada emergence period. A more parsimonious viewpoint holds that the prime numbered developmental times represent an adaptation to colder soil temperatures during Pleistocene glacial stadia, and that predator satiation is a short term maintenance strategy. This hypothesis was subsequently supported through a series of mathematical models, and stands as the most widely accepted explanation of the unusually lengthy and mathematically precise immature period of these bizarre insects. The length of the cycle appears to be controlled by a single gene locus, with the 13-year cycle dominant to the 17-year one.