By Emily Hardin, 2014 BHI Conservancy Intern

1. The Slope of Our Beaches and How
it Affects Sea Turtle Nesting
Emily Hardin
Jaymie Reneker

2. Introduction – Groins
} Installed in 1996
} Currently 15 groins
} Tubes made of geotextile materials and filled with sand
} Used to combat erosion

3. Longshore DriftLongshore Drift

4. Is this also changing the
slope of the beach?

5. Introduction – Beach Nourishment
} Section of South Beach is re-nourished
} 650,000 m3 of sand initially dredged and added
} Re-nourished every few years
} Thought to have negative effects on sea turtle nesting
Village of Bald Head Island
Slurry Systems Marine Pty Ltd

6. Introduction – Beach Nourishment and Sea
Turtles
} Increases the amount of nest-able beach
} Affects:
} Sand composition and temperature
} Slope
} Loggerheads nest more frequently in areas with less shells
(Garmestani, et al. 2000)
} Number of nests has been found to decrease after
nourishment (Rumbold, et al. 2001)

7. Introduction - Slope
} Slope is the most influential factor in nest site selection
(Wood & Bjorndal 2000)
} Slope preference can vary among species (Cuevas, et al. 2010)
} Hawksbill prefer less steep beaches
} Greens prefer more steep beaches
} Loggerheads prefer flatter slopes (Garmestani, et al. 2000)
} Different populations may have different preferences
(Cuevas, 2010)
Gnaraloo Turtle Conservation Program

8. Objectives
} Measure slope in four areas of Bald Head Island:
} South Beach – groin field and re-nourishment
} South Beach – natural
} East Beach – developed
} East Beach – undeveloped

9. Objectives
} Measure slope in four areas of Bald Head Island
} Measure the slope of sea turtle nests
} Determine if:
} Slope varies over the course of the summer
} Slope varies from location to location
} Sea turtles have a preferred slope
} Which beach is preferred by turtles

10. Methods
} Used slope profile poles
} Started at vegetation line, measured to water line
} Measurements taken at low tide (± 2 hrs)
} Measurements taken every 2 weeks

11. Methods
} Measure the slope of nests
} Caged nests: began halfway on
either side of cage
} Relocated nests: from center of
body pit at original site
} ANOVA test to determine if measurements differed
significantly
} p-value of 0.05

12. Results
} Did the slope change over time?
} All areas except the natural section of South Beach changed
significantly
} Groins, p=4.5x10-8
} East Developed, p=3.4x10-5
} East Undeveloped, p=0.04
} South Natural, p=0.30
} Second measurements
seemed to be the greatest

13. Results
} Does the slope vary from location to location?
} No significant difference in the average slope of each location
(p=0.77)
} Groins have steepest slope

14. Results
} Do our sea turtles have a preferred slope?
} No, the slopes of nests are not statistically similar
}

15. Results
} Which beaches do our turtles prefer?
} Average slope of nests = -2.38
} Most similar to South Natural and East Developed

16. Conclusions & Implications
} Slope changes over time
} Bald Head Island has a pretty uniform slope on all its
beaches
} Groins and beach re-nourishment are NOT affecting slope
} Our population does not have a preferred slope
} Since the slope changes frequently, this allows them to be able
to nest throughout the summer
} Average slope of ascents is similar to South Natural and
East Developed beach slope
} Majority of our nests
} Factors other than slope may be at play

17. Further Directions
} Year-long study to observe slope changes over multiple
seasons
} Measure the slope of false crawls
} Take measurements more frequently
} Look back at previous data and continue study over time
Amelia Island Sea Turtle Watch, Inc.

18. References
} Cuevas, E., Liceaga-Correa, M.A., Marino-Tapia, I. (2010). Influence of Beach
Slope and Width on Hawksbill (Eretmochelys imbricata) and Green Turtle
(Chelonia mydas) Nesting Activity in El Cuyo,Yucatan, Mexico.
Chelonian Conservation and Biology, 9(2), 262-267.
} Denison, P.S. (1998). Beach Nourishment/groin field construction project:
Bald Head Island, North Carolina. Shore and Beach, 66(1), 2-9.
} Garmestani,A.S., Percival, H.F., Portier, K.M., Rice, K.G. (2000). Nest-Site
Selection by the Loggerhead Sea Turtle in Florida’s Ten Thousand
Islands. Journal of Herpetology, 34(4), 504-510.
} Rumbold, D.G., Davis, P.W., Perretta, C. (2001). Estimating the Effect of
Beach Nourishment on Caretta caretta (Loggerhead Sea Turtle)
Nesting. Restoration Ecology, 9(3), 304-310.
} Wood, D.W., Bjorndal, K.A. (2000). Relation of Temperature, Moisture,
Salinity, and Slope to Nest Site Selection in Loggerhead Sea Turtles.
Copeia, 2000(1), 119-128.

19. Acknowledgements
} Thank you to everyone who helped me measure!
} Brandt Quirk-Royal (+ modeling)
} Matt Salinski
} Connor Hinton (+ modeling)
} Amy Eldredge
} Abbie Dwire
} Savannah Currens
} Colleen MacGilvray
} Sara Thompson
} Thank you to the one and only:
} Jaymie Reneker