Although little is known about the specific cues that predators use to locate turtle nests, there is much conjecture about the importance of visual and olfactory cues (see recent reviews by Bernstein et al. 2015; Geller 2015; Oddie et al. 2015). For example, several studies reported that soil disturbance was a major visual cue used by raccoons (Procyon lotor) and other predators to locate turtle nests (Burke et al. 2005; Strickland et al. 2010; Bernstein et al. 2015). Wirsing et al. (2012) suggested that both visual and soil- and egg-related olfactory cues were important for raccoon predation at snapping turtle (Chelydra serpentine) nests. Yet, Geller (2015) reported that broom sweeping at Ouachita map turtle (Graptemys ouachitensis) nests did not reduce raccoon predation rates, and he suggested that raccoons use olfactory cues to find newly constructed nests. Galois (1996) reported that captive raccoons used visual, olfactory, and tactile cues to find artificial nests. Further, he suggested that raccoons might use tactile cues more frequently when nests are close together whereas olfactory cues may play a more dominant role in nests that are spaced farther apart. Additionally, Oddie et al. (2015) reported that raccoons located snapping turtle nests using tactile, olfactory, and visual cues. Yet, they concluded that nests found by raccoons using olfactory and visual cues had a higher probability of nest predation where tactile cues were also present. Consequently, they suggested that nest screening was the most effective way of protecting turtle nests from raccoon predation because it removes the tactile cue of the loose, soft substrate surrounding nests while also protecting the nest from predation.

Although purely speculative, we suggest that the dramatic difference in the efficacy of habanero pepper powder for reducing nest predation rates between our 2 studies may be primarily due to the different predator species. Our study suggests that coyotes, compared with raccoons, may have increased sensitivity to the irritating effects of habanero pepper powder, possibly resulting from differing olfactory abilities. Secondly, we speculate that coyotes on Sand Island may use different search strategies (primarily olfactory) for turtle nests on a long (8 km) island compared with raccoons (primarily visual, olfactory, and tactile) on Ruler’s Bar, where terrapin nests are concentrated into a relatively small (1.5 ha) nesting area on a small dredge island.

Although probably minor, there were also small differences in the way each turtle nest was handled prior to treatment between the 2 studies. Burke et al. (2015) reported that each nest was fully excavated to collect egg weight and clutch size data. However, in our study on Sand Island, we only dug down to the top-most egg to confirm it was a nest and then immediately covered it back up and applied our treatments. At the same study site, Burke et al. (2005) reported that nest disturbance and fresh turtle scent at terrapin nests were associated with higher nest predation rates by raccoons. Is it possible that nest excavation dispersed the scent of the fresh nest while also further disturbing the soil, therefore increasing raccoon attraction? Additionally, Burke et al. (2015) reported mixing the pepper powder and sand prior to treatment, possibly reducing the concentration and irritant effects of the habanero pepper powder. Yet, we suspect it is highly unlikely that these small methodological differences explain the dramatic differences between our two studies.

We commend Burke et al. (2015) on their excellent study that suggests that the use of habanero pepper powder may be largely ineffective for reducing nest predation rates of turtle nests where raccoons are the dominant nest predator. However, we encourage further research into the efficacy of the combined effects of using screens in combination with pepper powder for reducing depredation of sea turtle nests, especially where coyotes are the primary predator. We also encourage additional research on the possible irritant effects of habanero pepper powder on turtle hatchlings.