Bet-hedging theory and eigenelasticity: a comparison of the life histories of loggerhead sea turtles (Caretta caretta) and snapping turtles (Chelydra serpentina)

Abstract

The life table for snapping turtles (Chelydra serpentina) generated from a 16-year study in Algonquin Park, Ontario, suggests that the population is declining. We use a stage-based matrix model based on this life table to simulate population management options. In addition we analyze the demographic sensitivities of the Algonquin Park population life table and a life table recently published for a population of snapping turtles at the E.S. George Reserve in Michigan. The results are compared with a similar study of loggerhead sea turtles (Caretta caretta). We use these inter- and intra-specific comparisons to test bet-hedging life-history theory. Bet-hedging theory predicts that the long lives and low annual reproductive effort of turtles reduces the effect of low, stochastic juvenile survival on an individual's reproductive success. We test this prediction using proportional sensitivity of the intrinsic rate of increase to variation in life-table parameters (eigenelasticity) to compare the two populations of snapping turtles with each other and with loggerhead sea turtles. Annual adult survival is shown to be the variable most predictive of sensitivity to variation in first-year survival.