Using a coupled predator-prey PVA to direct efforts of controlling predation on at-risk populations

Background/Question/Methods

Population viability analysis has been used to guide management decisions by analyzing growth rates of populations of concern.  As part of PVAs sensitivity analyses help determine the effectiveness of management action by identifying important life stages or demographic processes most important for population growth.  Recent work has suggested that PVAs for species of concern should be expanded to include their interaction with other species rather than in isolation.  In this way, PVA can be extended to explore management options for one species (e.g., predators) for the benefit of another (e.g., their prey).  While sensitivity analysis will reveal which life stages are the most critical for controlling the predator population, focusing action on those life stages may not be the most effective way to manage the prey species, which is the conservation target.  We demonstrate this paradox using a matrix population model for an invasive predator and native prey, coupled by a classical predator-prey model.  Both direct perturbation analysis and PVA sensitivity analysis were conducted on the predator matrix in order to determine and contrast the management recommendations that resulted in the largest population increase of the targeted prey species.

Results/Conclusions

Our results show how standard sensitivity analysis does not always give the most effective management strategy when multiple species and their interactions are considered.  While sensitivity analysis may give the most effective management strategy to decrease the invasive predator population, situations exist where this method does not give the best immediate increase in the prey population.  When considering a PVA with two or more interacting species, one must consider the interactions of the various age classes within each population before making management suggestions.