Use of a population viability analysis to evaluate human-induced impacts and mitigation for the endangered Lower Keys marsh rabbit

Rapid development and urbanization of the lower Florida Keys in the last 30 years has fragmented the habitat of the Lower Keys marsh rabbit (Sylvilagus palustris hefneri), hereafter called marsh rabbit, and threatened it with extinction. On the Naval Air Station–Key West (NAS), Boca Chica Key, marsh rabbits exist as a meta-population of discrete habitat patches in a matrix of wetlands and airfield facilities. Airfield safety regulations require NAS to maintain vegetation below a minimum height on runway peripheries (clear zones). We developed a spatially-explicit, stage-structured, stochastic matrix model using the programs RAMAS-Metapop and ArcGIS. Model parameters were estimated using pellet counting (2001–2002), radio tracking (1991–1992 and 2001–2005, n = 75), and published literature. We compared a baseline no-action model to Alternative 1 that simulated impacts from the NAS airfield clearance project with no conservation measures for marsh rabbits and Alternative 2 that also simulated airfield clearance impacts. Alternative 2 included mitigation actions to offset impacts to marsh rabbits in the form of reduced mortality via free-roaming cat (Felis catus) control and creation of marsh rabbit habitat (e.g., salt marsh). Both alternatives increased the extinction risk (probability of extinction) from a baseline of 0.499 to 0.90 and 0.713 for Alternatives 1 and 2, respectively. Although airfield clearance with creation of marsh rabbit habitat (Alternative 2) increased extinction risk from the baseline scenario, reducing marsh rabbit mortality associated with control of free-roaming cats was an effective strategy to decrease this risk. Our research demonstrates the use of population viability analysis as a conservation planning tool for reducing human–wildlife conflicts.