Theses and Dissertations Collection

The long-lived iteroparous animals are known to favor their own survival over current reproduction. Indeed, the tradeoff between future survival and investment in reproduction is central to life history theory. One means of managing this tradeoff involves the adjustment of reproductive investment post conception. We modeled one such strategy, using a series of life stage-specific equations (both deterministic and stochastic) derived either from our own empirical data or from previously published data for elk, in which a simulated population of female elk adjust the parturition date of their calves based on their body condition. We predicted that due to the reduced energetic costs of gestation relative to lactation, females would be able to enter winter in a better state and thus more likely to survive to attempt reproduction the following season. In addition, calves would be born larger and thus better able to survive through the summer. These two factors would lead to the simulated elk populations employing this state-dependent “bet-hedging” strategy to increase at a faster rate than populations for which timing of reproduction is independent of maternal condition. Our result supported the prediction that elk simulated using the bet-hedging strategy would have a higher rate of population increase. However, this was driven mostly by female over-winter survival rates. These results help provide a better understanding of the evolution of life-history traits and how they affect population dynamics.