Patterns of island fox habitat use in sand dune habitat on San Clemente Island

Identifying areas of high-quality habitat is often a critical first step for the recovery and management of species of conservation concern, yet patterns of high density in an area may not always correspond with high-quality habitat. On San Clemente Island (SCI), the island fox subspecies ( Urocyon littoralis clementae ) has been monitored annually since 1988 to track long-term population trends. Annual density estimates in most habitat types across the island range from 2–13 foxes/km 2 , yet unusually high estimates have repeatedly approached 50 foxes/km 2 in a unique sand dune habitat area. Although sand dune habitat is restricted to one small area on the island, these estimates suggest sand dune habitat supports one of the highest population densities of any fox species in the world, and it may support > 5% of the SCI fox population. This prompted our investigation to determine if SCI foxes captured in sand dune habitat maintained home ranges within this habitat type. We hypothesized that island foxes used sand dune habitat as an important foraging area while maintaining home ranges centralized in adjacent habitat types, which likely inflated density estimates for sand dune habitat. Between January–July 2018, we used Global Positioning System collars to track the movements of 12 island foxes captured in the sand dune habitat area. Contrary to our initial predictions, we found that island foxes captured in the sand dune habitat area do maintain home ranges and core areas centralized in sand dune habitat. All 12 island fox home ranges estimated contained >50% sand dune habitat in either their 50% or 95% fixed kernel density estimate (KDE) home range, and island foxes were 3.14 times more likely to use active sand dune habitat when compared to the second most abundant habitat type, maritime desert scrub (Adjusted β = 3.14, 95% CI = 3.07–3.12).