Managing native predators: Evidence from a partial removal of raccoons (Procyon lotor) on the Outer Banks of North Carolina, USA

Raccoons (Procyon lotor) are important predators of ground-nesting species in coastal systems. They have been identified as a primary cause of nest failure for the American Oystercatcher (Haematopus palliatus) throughout its range. Concerns over the long-term effects of raccoon predation and increased nest success following a hurricane inspired a mark-resight study of the raccoon population on a barrier island off North Carolina, USA. Approximately half of the raccoons were experimentally removed in 2008. Nests (n = 700) were monitored on two adjacent barrier islands during 2004–2013. Daily nest survival estimates were highest for 2004 (0.974 ± 0.005) and lowest for 2007 and 2008 (0.925 ± 0.009 and 0.925 ± 0.010, respectively). The only model in our candidate set that received any support included island and time of season, along with a diminishing effect of the hurricane and a constant, 5-year effect of the raccoon removal. For both hurricane and raccoon removal, however, the support for island-specific effects was weak (β = -0.204 ± 0.116 and 0.146 ± 0.349, respectively). We conclude that either the raccoon reduction was inadequate, or factors other than predation cause more variation in nest success than previously recognized. A multi-faceted approach to management aimed at reducing nest losses to storm overwash, predation, and human disturbance is likely to yield the largest population level benefits.