Abstract
The Lower Keys marsh rabbit (Sylvilagus palustris hefneri) is one of many endangered endemic species of the Florida Keys. The main threats are habitat loss and fragmentation from sea‐level rise, development, and habitat succession. Exotic predators such as free‐ranging domestic cats (Felis catus) pose an additional threat to these endangered small mammals. Management strategies have focused on habitat restoration and exotic predator control. However, the effectiveness of predator removal and the effects of anthropogenic habitat modifications and restoration have not been evaluated. Between 2013 and 2015, we used camera traps to survey marsh rabbits and free‐ranging cats at 84 sites in the National Key Deer Refuge, Big Pine Key, Florida, USA. We used dynamic occupancy models to determine factors associated with marsh rabbit occurrence, colonization, extinction, and the co‐occurrence of marsh rabbits and cats during a period of predator removal. Rabbit occurrence was positively related to freshwater habitat and patch size, but was negatively related to the number of individual cats detected at each site. Furthermore, marsh rabbit colonization was negatively associated with relative increases in the number of individual cats at each site between survey years. Cat occurrence was negatively associated with increasing distance from human developments. The probability of cat site extinction was positively related to a 2‐year trapping effort, indicating that predator removal reduced the cat population. Dynamic co‐occurrence models suggested that cats and marsh rabbits co‐occur less frequently than expected under random conditions, whereas co‐detections were site and survey‐specific. Rabbit site extinction and colonization were not strongly conditional on cat presence, but corresponded with a negative association. Our results suggest that while rabbits can colonize and persist at sites where cats occur, it is the number of individual cats at a site that more strongly influences rabbit occupancy and colonization. These findings indicate that continued predator management would likely benefit endangered small mammals as they recolonize restored habitats.
Highlights
Eighty percent of historically recorded extinctions have occurred on islands (Ricketts et al, 2005)
The Florida Keys are no exception to this pattern with 29 federally protected species affected by sea- level rise, habitat loss, and invasive species
We used a multiphase approach to model marsh rabbit occupancy and dynamic parameters, in which we modeled each parameter with the most supported covariate set for the previous parameter starting with detection, occupancy, colonization, and extinction
Summary
Eighty percent of historically recorded extinctions have occurred on islands (Ricketts et al, 2005). Abundant across the Lower Keys, marsh rabbit distribution is currently limited to remnant patches of marshes and coastal transition zones These patches often are fragmented due to development and habitat succession (Eaton, Hughes, Hines, & Nichols, 2014; Schmidt, McCleery, Lopez, Silvy, & Schmidt, 2010). Concurrent with expanding anthropogenic development, exotic predators such as large constrictor snakes (e.g., Python and Boa spp.), tegus (Salvator merianae), and feral and free-ranging domestic cats (Felis catus) are established throughout south Florida and are potential threats to endangered endemic species such as the marsh rabbit in the Keys (Cove, Gardner, Simons, Kays, & O’Connell, 2018; Dorcas et al, 2012; Engeman, Jacobson, Avery, & Meshaka, 2011). We hypothesized a negative relationship between marsh rabbit occupancy and cat occurrence, and a positive relationship between cat removal and rabbit site colonization rates
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