The Effectiveness of BHIC's Sea Turtle Nest Relcation Practices
Post on 20-Jul-2015
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Overview
Ê The Bald Head Island Conservancy’s efforts since 1983
Ê The sea turtle monitoring program involved nightly monitoring of nesting sea turtles Ê Involving tagging, implementing conservation techniques of
caging and relocation, and recording nests’ location, hatching and emergence success rates, and incubation period
Ê Study’s Objective: To examine the relocation practice as a sea turtle nest management tool on the Bald Head Island beaches
Ê Study’s Findings: The BHIC’s use of relocation is an important nest management tool
Background & Significance
Ê There are seven species of sea turtle of which three have nested on Bald Head Island:
Loggerhead Green Leatherback
Ê It is difficult to find population numbers for sea turtles
Ê Observing hatchlings and females that leave the water to lay eggs is key
Nesting Behavior
Ê Sea turtles tend to build nests in the general region where they were born. Cues that influence this behavior include: • scent • surf noise • magnetic fields • offshore currents • reefs and rocks • beach slope and width • sand texture • dune vegetation • lighting
Nesting Behavior (continued)
Ê When females come to the shore they dig out a nest in the ground with their back flippers, bury their clutch of eggs and return to the ocean
Ê Sea turtle eggs’ incubation period: 50-‐70 days
Ê Hatch at night to reduce the risk of predation
Major Population Declines
Ê Overall reduction in all sea turtle populations
Ê All seven species of sea turtles are endangered and several factors have contributed to their decline Ê Heavy predation on young Ê Poaching of eggs and adults Ê Pollution Ê Unsound fishing practices
Conservation Efforts
Ê Conservation efforts focused on sea turtle reproduction since hatchlings are vulnerable and nests are accessible
Ê Three most common conservation techniques: Ê Fencing Ê Screening/caging Ê Relocating
Ê All significantly increase hatchling success rate – Georgia Study
Background on Relocation Practices
Ê Relocating involves excavating the nest that is at risk of: Ê Tidal inundation Ê Erosion
Ê Eggs are carefully placed into a cooler for transport
Ê An egg chamber is then dug out using a cockle shell
Ê Eggs are placed into a new/safe nest and covered up
Risks with Relocation Practices
Ê Intense patrolling allows nests to be found and relocated within the six hour window before development starts
Ê Risks: Ê Embryo mortality Ê Sex ratio Ê Hatchling fitness
Relocation’s Effect on Nest’s Temperature Ê Relocations generally occur further
from the water
Ê Sand temperature increases with distance from the water
Ê Temperature impacts sea turtle eggs
Ê Affects sex ratio
Ê Incubation periods decreases with increasing temperature
Ê Hatching success may decrease for nests in which sand temperatures exceed 33C
Hypotheses & Predictions
Ê H: The application of the relocation technique would affect the hatching success rate, emergence success rate and the incubation period in comparison to in situ nests.
Ê P1: Relocated nests will have a lower hatching success rate
Ê P2: Relocated nests will have a lower emergence success rate
Ê P3: Relocated nests will have a shorter incubation period
Methods
Ê Sea turtle nesting data collected from the nesting and hatching seasons for 2003-‐2013 were analyzed
Ê A comparison between the in situ and relocated nests for: Ê Hatching Success Rate HS = # Hatched / Total # Eggs Ê Emergence Success Rate ES = (# Hatched – (# Live + # Dead)) / Total # Eggs Ê Incubation Period # of Days between Date Laid & Date Hatched
Statistical Analysis
Ê Comparison between In Situ and Relocated Nests
Ê Normality Test (Kolmogorov–Smirnov test: p<0.05)
Ê Nonparametric version of Independent T-‐Test
Ê Mann-‐Whitney U Test
Results: Hatching Success Not Significant
Ê Mann-‐Whitney U Test: U=44083.500, df=603, df=154, p=0.33
Results: Emergence Success Not Significant
Ê Mann-‐Whitney U Test: U=45621.500, df=603, df=154, p=0.737
Results: Incubation Period Significant
Ê Mann-‐Whitney U Test: U=16868.000, df=438, df=130, p<0.001
Discussion
Ê For Relocated vs. In Situ Nests: Ê Hatching Success did not change Ê Emergence Success did not change Ê Incubation Period was shortened
Ê For Hatching & Emergence Success this is good news!
Ê Consider implications of a shorter incubation period:
Ê Used to predict sex ratio Ê Area of future research
Relocation Study in St. Croix Ê Sandy Point National Wildlife Refuge, St Croix, US Virgin Islands
Ê Natural beach erosion: Ê loss of 45–60% leatherback sea turtle eggs per year
Ê 31·∙4–68·∙1% of the nests were relocated
Ê Overall hatch success of relocated clutches compared to in situ clutches decreased (53·∙7% vs 64·∙1%)
Ê Relocation of “doomed eggs” resulted in a net gain of 6650 hatchlings over 4 years
Conclusion
Ê Relocation is a successful tool to continue to use!
Ê Bald Head Island seeing better results Ê Compare to study of 1997-‐2001 data
Ê Still be cautious
Ê Strive to improve technique
Ê Continue research and investigate consequences of a short incubation period period
Future Research
Ê Expand analysis to include earlier years of data collection
Ê Next Questions: Why do we need to relocate? Ê Do we have bad beaches or bad mothers?
Ê Examine where relocation more frequently occurs Ê Per individual, how has the percentage of relocations
changed over time?
References Ê Baskale, E., Kaska, Y. (2005) Sea turtle nest conservation techniques on
southwestern beaches in Turkey. Israel Journal of Zoology. 51:13–26.
Ê Broderick, A. C., Glen, F., Godley, B. J., Hays, G. C. (2002) Estimating the size of nesting populations of green and loggerhead turtles in the Mediterranean. Oryx. 36: 227–236.
Ê Davenport, J., Davenport, J.L. (2006) The impact of tourism and personal leisure transport on coastal environments: A review. Estuarine, Coastal and Shelf Science. 67(1-‐2):280-‐292.
Ê Davidson, O. G. (1998) The Enchanted Braid. John Wiley & Sons, Inc: New York.
Ê Eckert, K.L., Eckert, S.A. (1990) Embryo mortality and hatch success in In Situ and translocated leatherback sea turtle Dermochelys coriacea eggs. Biological conservation. 53(1):37-‐46.
References (continued) Ê Matsuzawa, Y., Sato, K., Sakamoto, W., Bjorndal, K. (2002) Seasonal fluctuations in
sand temperature: effects on the incubation period and mortality of loggerhead sea turtle (Caretta caretta) pre-‐emergent hatchings in Minabe,Japan. Marine Biology. 140 (3):639-‐646.
Ê Pike, D.A. (2008) Environmental correlates of nesting in loggerhead turtles, Caretta caretta. Animal Behaviour. 76: 603-‐610.
Ê Pinedo, M.C., Polacheck. T. (2004) Sea turtle bycatch in pelagic longline sets off southern Brazil. Biological Conservation. 119: 335–339.
Ê Weishampel, J.F., Bagley, D.A., Ehrhart, L.M., Rodenbeack, B.L. (2003) Spatiotemporal patterns of annual sea turtle nesting behaviors along an East Central Florida beach. Biological Conservation. 110(2):295-‐303.
Ê Wyneken, J., Burke, T. J., Salmon, M., Pedersn, D. K. (1988) Egg Failure in Natural and Relocated Sea Turtle Nests. Journal of Herpetology. 22(1):88-‐96.
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