USING 30 YEARS OF NESTING DATA TO INVESTIGATE CONSERVATION EFFORT SUCCESS ON BALD HEAD ISLAND, NORTH CAROLINA Introduction

•  Bald Head Island (BHI), North Carolina (33°52’2”N, 78°0’24”W; Fig 1a) is located within the northernmost range of the Northwest Atlantic Ocean Distinct Population Segment for loggerhead sea turtles

•  Bald Head Island Conservancy (BHI Conservancy), a 501(c)3 dedicated to barrier island conservation, education and preservation, initiated nightly patrols in 1983

Figure 1. Loggerhead critical habitat designation by US Fish and Wildlife Service. (a) Western Atlantic and Gulf designated areas (image credit: NMFS 2013) and (b) southeastern North Carolina including Bald Head Island, NC site LOGG-N-05 (image credit: NMFS 2013).

•  Long life spans and late sexual maturation of sea turtles make it difficult to gauge the status of populations and the effectiveness of conservation efforts

•  Data collected for over 30 years by BHI Conservancy scientists provide a unique opportunity to investigate nesting patterns of BHI’s loggerhead turtles

Methods•  BHI Conservancy maintains a saturation-tagging program, conducting nightly beach

patrols between 9pm and 6am (May through August), intercepting approximately 80% of all nesting mothers

•  BHI Conservancy began applying unique Inconel flipper tags in 1991 and injecting passive integrated transponder tags (PIT tags) in 2002

•  Morphometric measurements (e.g. curved carapace length and width) are taken from each nesting female and nests are protected with cages (Fig 2).

•  Relocations are conducted following NC WRC guidelines

Figure 2. Nests protected with metal Figure 3. Public excavation on BHI. caging. Plastic cages initiated in 2016. Conservancy scientific staff educate

attendees about sea turtle conservation. Data Analysis •  Analysis was conducted on data from 1986 to 2016 •  Linear regressions, Shapiro-Wilks and post-hoc Mann-Whitney U-tests were used

Results

Nests Per Year

Figure 4. BHI Nesting trends. (a) Significant decrease in BHI sea turtle nesting since 1986 (P<0.05, R2 = 0.1893) and (b) increasing nesting trend since 2007 (P<0.05, R2= 0.2692). •  Average of 64 ± 12% of nesting population are new (previously untagged) •  Average of 31 ± 11% identifiable individuals per season •  Stable hatching success over time and 70 ± 15% of incubated eggs produce

hatchlings

Incubation Times

Figure 5. Incubation times of BHI Nests. Average nest incubation times nest exhibit a decreasing trend from an average of 61.6 days (1986) to 52 days (2016).

Nest Relocations •  Average of 32.85% of nests are relocated; no significant trend in relocations Incubation Times •  Average is significantly shorter for relocated nests (58.3 days) than in-situ nests

(59.1 days; p<0.05) •  From 2007-2017, average incubation times decreased by 5.6 days for relocated

nests and 1.3 days for in-situ nests and are still significantly different (P<0.05) Emergence Success •  Average lower in relocated nests (66.0%) than in-situ nests (68.8%; P<0.05) •  From 2007 – 2017, average emergence success for relocated nests (66.0%) is

significantly higher than that of in-situ nests (64.9%; P<0.05) Hatching Success •  Average is lower in relocated nests (72.3%) than in-situ nests (73.8%; P<0.05) •  In last decade, no significant difference between hatching success of relocated

(74.9%) and in-situ nests (73.1%)

ConclusionsNests Per Year •  Mean age at maturation for female loggerhead turtles in this region ranges from 22.5

to 38 years2 •  Therefore, the increasing trend in sea turtle nests per year on BHI between 2007 and

2016 may suggest that conservation efforts initiated 30+ years ago are starting to have a positive effect on the Bald Head Island rookery

Incubation •  Incubation time has decreased significantly since 1986 (Fig 5) and the decline is

correlated to an increase in mean air temperature3

•  Sea turtle sex determination is temperature dependent, at 29°C the sex ratio is 1:14 •  Warmer nests produce more females while cooler nests produce more males

•  Shorter incubation times could increase the female bias of hatchlings on BHI beaches

•  With predicted climate change, air and sea temperatures will likely rise resulting in an increased female bias on BHI beaches

Nest Relocations •  Nest relocations are carried out immediately after nest laying and follow NC

Wildlife Resource Commission protocols •  From 2007 to 2016, incubation time of relocated nests is significantly shorter than

in-situ nests; however, there was no difference in hatching success •  This suggests that nest success may not be affected by incubation time but relocation

may still effect the population by unnaturally increasing the bias towards females •  Over the years relocation methods have improved and become more sophisticated

possibly increasing the success of relocated nests •  Further research is needed to elucidate the true cost of relocations to overall nest

success

SummaryThe combined influences of a high percentage of new nesting mothers each summer, a steady hatching success rate, and the relocation and protection of vulnerable nests by BHI Conservancy staff suggest that conservation efforts are postively affecting turtles nesting on BHI beaches. BHI’s coastal habitat will likely continue to support a healthy nesting loggerhead population.

Literature CitedImage Credit: National Marine Fisheries Service. 2013. Biological Report on the Designation of Marine Critical Habitat for the Loggerhead Sea Turtle, Caretta carretta 1. Endangered and Threatened Wildlife and Plants; Designation of Critical Habitat for the Northwest Atlantic Ocean Distinct Population Segment of the Loggerhead Sea Turtle, Final Rule. 79 Federal Register 132, 39756-39854 (July 10, 2014) 2. Avens L, Goshe LR, Coggins L, Snover ML, Pajuelo M, Bjorndal KA and Bolten AB. 2015. Age and Size at Maturation- and Adult-Stage Duration for Loggerhead Sea Turtles in the Western North Atlantic. Mar Biol. 162: 1749-1767 3. Reneker JL and Kamel, SJ. 2016. Climate Change Increases the Production of Female Hatchlings at a Northern Sea Turtle Rookery. Ecology 97(12): 3257-3264 4. Mrosovsky N. 1988. Pivotal temperatures for loggerhead turtles (Caretta caretta) from northern and southern nesting beaches. Can. J. Zool. 66: 661- 669.

AcknowledgmentsWe wish to thank the BHI Conservancy interns, nest monitors, volunteers and staff for their dedication to protecting and collecting data on our sea turtle population. This work is funded through private contributions; we would like to thank to Mrs. Kit Adcock for supporting travel to Las Vegas. The BHI Conservancy saturation-tagging program would not be possible without the support of Dr. Matthew Godfrey and the North Carolina Wildlife Resources Commission. All research was conducted under a NC WRC Endangered Species Permit.

Brooke K. Milligan, Emily E. Hardin & G. Christopher Shank Bald Head Island Conservancy, 700 Federal Road, Bald Head Island, NC 28461

R²=0.2692

0

40

80

120

160

2007 2010 2013 2016

Num

bero

fNests

SeaTurtlenestsperYear(2007-2016)

R²=0.1893

0

50

100

150

200

1986 1996 2006 2016

Num

bero

fNests

SeaTurtlenestsperYear

R²=0.4335

50

60

70

1986 1996 2006 2016

IncubaFo

nTime(Days)

AverageIncubaFonTimeperYear

a b

a b