Interactions between predators are typically either antagonistic, which benefit shared prey, or synergistic, which are detrimental to prey. Raccoons (Procyon lotor) and ghost crabs (Ocypode quadrata) are the two most important predators of marine turtle eggs on high density nesting beaches in Florida, USA. Intraguild predation by raccoons may limit ghost crab populations and their predation pressure on marine turtle eggs. However, previous research suggested ghost crab burrows into nests may release chemical cues that improve nest detection by raccoons. To determine whether ghost crabs facilitate nest predation by raccoons we constructed 40 pairs of artificial nests at Canaveral National Seashore, one of which was impregnated by a simulated ghost crab burrow, and monitored nightly raccoon activity around each nest using tracking plots.

Results/Conclusions

Raccoons visited significantly more treatment nests with simulated burrows than paired control nests, indicating raccoons are attracted to cues from nests released by ghost crabs. Thus, ghost crabs appear to facilitate secondary nest predation by raccoons. Our results support the presence of a predator‑predator interaction not previously described, which combines intraguild predation (one predator limits predation by the other predator) and facilitated predation (one predator increases the prey's susceptibility to the other predator). Determining the net effect of these antagonistic and synergistic interactions will have important conservation implications for marine turtle reproduction.