Broadcast Predator Vocalizations Reduce Predation by Raccoons (Procyon lotor) on Artificial Nests of Diamondback Terrapins (Malaclemys terrapin)

Procyon lotor (Raccoon) are a dominant predator on eggs of Malaclemys terrapin (Diamondback Terrapin), an estuarine specialist turtle endemic to saltmarshes of the eastern and gulf coasts of the United States. The purpose of this study was to determine if broadcast predator vocalizations could potentially deter Raccoons from foraging on Diamondback Terrapin eggs. We used artificial nests arrays to test 2 hypotheses: (1) predator vocalization playbacks (barking Canis lupus familiaris [Domestic Dog]) reduce number of artificial nests depredated by Raccoons compared to non-predator vocalization playbacks (Urocyon cinereoargenteus [Gray Fox]) or control treatments (no playbacks), and (2) predator vocalization playbacks reduce frequency of visits by Raccoons and overall foraging time compared to non-predator playbacks and control treatments. We randomly assigned sound treatments to each night of a 3-day trial, with 3 trials conducted at 4 experimental sites. We counted the number of depredated artificial nests and used trail cameras to document number of Raccoon visits and Raccoon foraging time following each sound treatment. On average, 51% of artificial nests were depredated in the predator vocalization treatments, 66% in the non-predator-vocalization treatments, and 81% of nests in the control treatments. Average number of Raccoon visits was about 3 times higher in the control treatment compared to the predator treatment but auditory treatment did not affect time spent foraging. Response to predator vocalization was attenuated by repeated exposure to recorded predator playbacks. Variation in type of predator vocalization, length, and frequency of playbacks may increase effectiveness of auditory deterrents on predators of Diamondback Terrapin nests.

Automated summary

The study found that playing predator vocalizations can effectively reduce the number of raccoons foraging on diamondback terrapin eggs, but does not affect their foraging time. Raccoon response to the vocalizations is attenuated by repeated exposure, and variations in type, length, and frequency of the vocalizations may increase their effectiveness as deterrents.