A modeling methodology to evaluate the efficacy of predator exclosures versus predator control

Abstract

Predation is seen as the most important source of mortality for many endangered species, including the piping plover. However, predation can be managed through lethal methods, birth control or by excluding predators from nests. Nevertheless, managing a predator population in order to protect a threatened prey population has uncertain outcomes making the monetary expenditures required to manage predators less appealing. We developed a methodology that utilizes a stochastic coupled predator–prey population viability analysis to determine the efficacy of using predator exclosures to protect piping plover nests versus using lethal or birth control measures for one of its principal predators, the red fox. We found that implementing predator exclosures led to slightly higher final abundances of plovers compared with the lethal or birth control of foxes. Moreover, the joint effort of predator control and predator exclosures resulted in considerably higher final plover abundance compared with either option alone. Additionally, there may be situations where certain demographic data about a predator population, such as the population size and age distribution, is not known to the manager. We evaluated the effect these demographics had on the predator control management option chosen. We found that the efficacy of different management options change depending on the starting demographics of the fox population. We emphasize the implementation of this type of model when managing a predator for the sake of prey in order to make informed management decisions that could save money while ensuring better protection of endangered species.