Methods

Our study was conducted on the island of Ruler’s Bar in Jamaica Bay Wildlife Refuge, Queens, New York, from 26 June to 30 July 2014 in an area where 1000–2000 diamondback terrapins nest annually and where raccoons depredate 95%–100% of freshly laid nests, generally in the first 24 hrs after oviposition (Feinberg and Burke 2003; R.L.B. and A.K., unpubl. data, 2009–2015). The density of raccoons in this area is 0.27 to 0.34 raccoons/ha (Rulison 2009), which is relatively low for an urban area. We located freshly laid terrapin nests by observing nesting females. We selected terrapin nests that were widely distributed over the 1.5-ha nesting area. We first excavated each nest within 24 hrs of oviposition to collect egg weight and clutch size data. The eggs were returned to the nest cavities and covered entirely. We made no attempt to make the nests inconspicuous because raccoons find nearly all of these nests anyway (Feinberg and Burke 2003; R.L.B. and A.K., unpubl. data, 2009–2015). Pure habanero pepper powder (~ 200,000 Scoville heat units, My Spice Sage, Yonkers, NY) was applied in 10- or 20-g doses, equivalent to 67% and 133% of the doses used by Lamarre-DeJesus and Griffin (2013) for much larger sea turtle nests, following their protocol for “surface” treatment. We applied the powder over an area of ~ 0.3 m² centered on the nest. We used a stick to mix the pepper and sand until it was only slightly visible. In some cases we added sand to the measured pepper vials to prevent dosage inaccuracies when applying in windy conditions. We applied 10 g of pepper to each of 2 nests we subsequently caged with predator excluders (“low pepper caged”), 10 g of pepper to each of 15 uncaged nests (“low pepper uncaged”) and 20 g to each of 15 uncaged nests (“high pepper uncaged”). The predator excluders were metal mesh, square hardware cloth boxes approximately 0.3 m on each side; the open side was buried about 15 cm deep. A small hole was cut in the side of the cages at the ground level to allow hatchlings to escape. These caged nests were monitored until 16 November and then excavated to determine hatching and emergence success. All nests (caged and uncaged) were checked daily for depredation as indicated by excavation and empty egg shells. Two uncaged treated nests only exhibited the former; therefore, we excavated these nests to determine whether they had been depredated (they had not).

Eighteen additional nests without cages or pepper (“no pepper uncaged”) served as controls to measure background predation rates. These were monitored for at least 7 d postoviposition because nests that survive this long are nearly always safe from depredation (Feinberg and Burke 2003; R.L.B. and A.K., unpubl. data, 2009–2015). We used 9 additional caged nests without pepper (“no pepper caged”) to serve as controls to measure background hatching success and emergence rates, in the presence of cages but without pepper. The caged control nests were excavated 16 November 2014 as described above.

Results

We observed terrapin nesting on Ruler’s Bar from 14 June to 28 July 2014. Eighty-three percent (15/18) of uncaged, no pepper nests (no pepper uncaged) were depredated; mean days to depredation of those depredated was 1.4 d (range, 1–3 d). One hundred percent (15/15) of uncaged, 10-g pepper nests (low pepper uncaged) were depredated; mean days to depredation was 1.3 d (range, 1–5 d). Ninety-three percent (14/15) of uncaged, 20-g pepper nests (high pepper uncaged) were depredated; mean days to depredation of those depredated was 1.8 d (range, 1–7 d). Days to predation were not significantly different between controls (no pepper uncaged) and the 10-g treatment (low pepper uncaged) (t = 0.45, df = 28, 2-tailed p = 0.66) or between controls and the 20-g treatment (high pepper uncaged) (t = 0.81, df = 27, 2-tailed p = 0.43). All 9 caged control nests (no pepper caged) had some egg failure; successful hatch/emergence rates ranged from 55% to 93% (x¯ = 75%). The 2 caged and peppered nests (low pepper caged) had similar successful hatch/emergence rates (78%, 83%, x¯ = 81%). We found no dead or injured hatchlings in either caged control nests or caged peppered nests.

Discussion

Using nests laid by diamondback terrapins at Ruler’s Bar, New York, where the primary nest predators are raccoons, we found no evidence that habanero pepper powder reduced predation rates, despite following the protocol described by Lamarre-DeJesus and Griffin (2013) closely. Thus our results differ dramatically from those of Lamarre-DeJesus and Griffin, perhaps because the primary nest predators in their study were coyotes, which might be more sensitive to pepper. Similarly, Burke et al. (2005) found that marking nests did not increase depredation on diamondback terrapin nests by raccoons whereas Rollinson and Brooks (2007) found that the reverse was true regarding painted turtles (Chrysemys picta), where eggs were depredated by corvids (common ravens [Corvus corax] and American crows [C. brachyrhynchos]). Similar site-to-site variation in predator behavior may be common, and researchers should avoid generalizing predation patterns from one site to another.

We were also concerned that even if habanero pepper powder reduced depredation, it might affect hatching and emergence rates because pepper powder this hot is quite caustic (Culinary Farms 2014) and potentially a risk to neonate turtles. However, sensitivity to capsaicin, the active component of pepper powder, may be much higher in mammals than in birds (Tewksbury and Nabhan 2001; Jordt and Julius 2002) and perhaps also in turtles. Alternatively, the powder might degrade over the incubation period. We could not find any information on this point and Lamarre-DeJesus and Griffin (2013) did not report emergence data. We found that terrapin nests treated with 10 g of relatively caustic pepper powder (measured in Scoville heat units) appeared to undergo incubation, hatching, and emergence about as successfully as did control nests.

Finally, we urge caution to researchers attempting similar work. Our study area was often windy, and working with a caustic fine powder in such conditions can be dangerous, with a high risk of pepper blowing into our eyes or being transferred to our hands and later elsewhere. It is important to take appropriate safety precautions, especially in fairly remote locations. Also, if turtles excavate nests at a site where pepper powder had been used previously, those turtles might be harmed.