Human activities are rapidly and significantly transforming environments, altering historic ecosystem disturbance regimes. While the effects of disturbance frequency and magnitude on species diversity and competitive communities have been studied, their effects on predator-prey interactions have not been investigated. Furthermore, since disturbance could exert either direct effects, indirect effects, or both, it is likely those effects would differ depending on the relative magnitude or frequency of disturbance. The objective of this study is to investigate the effects of varying disturbance frequency and magnitude on predator-prey populations, and examine how timing and intensity of disturbance affect prey population persistence. In order to accomplish this objective, we developed a series of simple dynamic models to compare the effects of disturbance on predator-prey populations. Using these models, we ran simulations applying varying disturbance frequencies and magnitudes to predator attack rate and mortality parameters, as well as predator-prey abundance. The population response was assessed by examining the probability of prey extinction under the various disturbance regimes. Model parameter importance under different disturbance regimes were investigated through global sensitivity analysis using random forests.
Results/Conclusions
The results reveal that the frequency and magnitude of disturbance are not interchangeable. Increasing the magnitude of disturbance increases the probability of prey population extinction more than increasing frequency. Additionally, the effect of increasing frequency and magnitude on prey population persistence also depends on the behavior of the system. Predator-prey populations in coexistence require an unrealistic amount of disturbance to decrease prey population persistence. Prey population extinction is more likely in systems with cyclic dynamics when facing disturbances of increasing frequency and magnitude. Furthermore, in cyclic systems there is a synergistic effect of frequency and magnitude on prey population persistence. Lastly, there is a differential response in prey population persistence depending on whether the disturbance affects population abundance or demographic rates. These results have important implications for management efforts of wild interacting populations, particularly of harvest species, which encounter both natural and anthropogenic disturbances. Effective management necessitates further understanding of the effect of various disturbances on interacting populations in order to improve long-term population outcomes.