Eglin Air Force Base and Sea Turtle Nesting: A Success Story

By: Andrea Helmstetter and Debby Atencio

Along with many other military installations, Eglin Air Force Base (AFB), Florida shares the responsibility of being a large, undeveloped area (463,000 acres) that supports numerous threatened and endangered species and critical habitats. Eglin is unique because it has both terrestrial and marine species under its supervision and the base has developed an aggressive natural resources plan to manage them (Hardesty and Kindell 1997). One critical habitat they have successfully managed is Santa Rosa Island (SRI). Historically, SRI has been used as a testing and training site, and currently the Air Force facilities provide essential electronics support for nearly all air operations on Eglin's land and water ranges. However, the island is also an important nesting site for the threatened loggerhead sea turtle (Caretta caretta), and, more recently, the Atlantic green sea turtle (Chelonia mydas). Breeding populations of green sea turtles are endangered in Florida and the Pacific coast of Mexico; elsewhere they are threatened (Meylan et al. 1995). The endangered leatherback sea turtle (Dermochelys coriacea) has been documented in waters adjacent to the island but there has been no known nesting on Eglin AFB property.

Santa Rosa Island is a barrier island approximately 80 kilometers (km) long and 0.8 km wide. It is separated from the mainland by Choctawhatchee Bay and Santa Rosa Sound to the north and is bordered by the Gulf of Mexico to the south. Eglin AFB owns and manages two stretches of beach on Santa Rosa Island: a 6.4 km section which receives limited public usage and is known as "Okaloosa Island," and a 21 km section of federal beach on which access is restricted.

For turtles on SRI, biotic and abiotic stresses on nesting, hatching success and hatchling survival include tropical storms, hurricanes, and predation. For example, hurricanes Erin and Opal (August 1995 and October 1995, respectively) transformed three well-developed dune ridges, with slopes of nine to ten degrees and heights up to 9.5 meters, to relatively flat barren areas. Loss in dune height has allowed more artificial lighting to illuminate the coastal beaches at night, which in the past had been fairly dark. The primary sea-finding mechanism for hatchling sea turtles is an orientation towards light. On darkened beaches, the reflection of the moon or scattered starlight off the ocean's surface generally guides hatchlings in a direction towards the water. Artificial lighting, however, is known to cause major disorientation and can subsequently lead to increased mortality. Artificial lighting may also cause confusion or misorientation in females attempting to nest and can lead to an increase in the number of false crawls (emergence with no deposition of eggs) (Mortimer 1981; Verheijen 1985; Salmon 1990).

Historically, predators on SRI have included fire ants, ghost crabs and raccoons. These smaller predators will take a few eggs and newly hatched turtles, but usually not cause a major decline in overall hatching success. On the other hand, larger mammals, such as coyotes and fox, can decimate a whole nest rapidly and have potential to train their young to do the same. The presence of large predators has increased on SRI, further decreasing hatching success.

After realizing the extent of nesting on federal property, a comprehensive sea turtle program at Eglin AFB was initiated in 1987 due to requirements of the Endangered Species Act (ESA). Under Section 7 of the ESA, Eglin has to undergo consultation with the U.S. Fish and Wildlife Service when proposing new military testing or training that may impact turtles. The objective of the sea turtle program is to document and protect nests while maintaining Eglin's primary mission of national defense. This is being done in several ways. With a Geographical Information System (GIS), nesting locations have been recorded spatially and temporally. With this information, military testing and training can be managed, as required by the National Environmental Policy Act, to ensure there are no negative impacts on nesting success, hatching success or species survival. For example, nighttime defense missions which require lighting are carefully managed to prevent misorientation of nesting females or disorientation of emergent hatchlings. Other management measures include locating activities in areas having lower nesting densities, and scheduling activities to occur outside the nesting season.

Southern Florida sees a greater number of nestings and subsequently receives more attention from the public. Santa Rosa and Okaloosa Counties are areas of large-scale tourism, but tourists generally do not have knowledge of indigenous natural resources. Eglin is providing the educational tools to remedy this problem by working within a network of public nonprofit groups, the U.S. Fish and Wildlife Service, and the Florida Department of Environmental Protection to protect nesting sites and educate the public about the sea turtles that are present. By fostering an open communication between all parties, more information is gained further solidifying common conservation goals.

On Eglin AFB, sea turtle activity is monitored seven days a week throughout the nesting season­mid-May until mid-September. The 27 km of shoreline are surveyed beginning before sunrise via an all-terrain vehicle. When a sea turtle crawl is found, a visual determination is made as to whether it is a true nesting emergence or a false crawl. Species identification is possible from a visual inspection of the crawl as each species has unique characteristics. For example, loggerhead turtles have tracks that show alternating flipper movements with no tail drag marks and the tracks are generally 65 cm in width, whereas green sea turtles show simultaneous flipper movements with a center tail drag mark and tracks generally 80 cm in width. All nests are marked for visual identification and protection, using wooden stakes surrounded with surveyor's flagging. If a nest is dug at or below the mean high water mark, relocation is necessary to alleviate the threat of water inundation. Nests are monitored throughout the incubation period for storm damage, hatching activity and predation. Nest success evaluations are conducted for all nests subsequent to hatching, predation, or 100 days post-deposition.

Between 1989 and 1996, there were 211 loggerhead nesting occurrences and 219 false crawls on Eglin AFB property, with a mean hatchling emergence rate of 59%. Sea turtles generally nest in two- or three-year cycles, and nesting by the Atlantic green turtle has occurred every other year since 1990 (Conley and Hoffman 1987). To date, there have been 47 nesting occurrences and 36 false crawls by Atlantic green sea turtles on Eglin AFB. The mean hatchling emergence success rate for the Atlantic green sea turtle has been 37%. Since 1987, nesting by this endangered species has been recorded in increasing numbers on Eglin and on other sections of undeveloped public beaches in the same county, thus placing further emphasis on SRI as a critical habitat (Meylan et al. 1995). A tropical storm in 1994 caused a decrease in hatching success rates for both species, since most nests were destroyed. However, two hurricanes in 1995 impacted only loggerhead nesting as green sea turtles did not nest that year. Overall, it is believed that if it were not for these natural occurrences the success rates would have been higher in both years.

Florida accounts for one-third of the worlds' loggerhead nesting beaches and over 90% of all nesting in the United States (Meylan et al. 1995). As development continues to explode in the counties surrounding SRI, the nests on military land are afforded protection in a way that is generally not possible on public lands. Factors that negatively impact sea turtle nesting or hatchlings reaching the ocean (see Table 1) can be avoided or managed. Eglin AFB will continue to be an important steward for sea turtle conservation as nesting areas around SRI are lost. On Eglin as elsewhere, military installations are proving to be some of the last areas of vast undeveloped land and a permanent habitat for threatened and endangered species.

Conley, W.J., and B.A. Hoffman. 1987. Nesting activity of sea turtles in Florida, 1979-1985. Florida Scientist 50:201-210.

Hardesty, J.L. and C. Kindell. 1997. Conserving Ecosystems at Eglin AFB. Endangered Species Bulletin 22:8-9.

Meylan, A, Schroeder, B., & Mosier, A. 1995. Sea turtle nesting activity in the State of Florida 1979-1992. State of Florida, Department of Environmental Protection, Florida Marine Research Institute Publications 52:1-16.

Mortimer, J.A. 1981. Factors influencing beach selection by nesting sea turtles. Pages 45-51 in K. Bjorndal, editor. Biology and Conservation of Sea Turtles, Proceedings of the World Conference on Sea Turtle Conservation, November, 1979.

Salmon, M. 1990. Photic stimuli and the orientation of hatchling sea turtles. American Zoologist 30: 693.

Verheijen, F.J. 1985. Photopollution: Artificial light optic spatial control systems fail to cope with. Incidents, causations, remedies. Experimental Biology 44:1-18.

Andrea Helmstetter is a biologist for SWCA, Inc. in Phoenix, Arizona and is also with the South Walton Turtle Watch. Debby Atencio is an endangered species biologist with Eglin Air Force Base, Florida.