By Maymie Higgins
The moonlight reflected off the North Carolina shoreline, illuminating the way she used her strongly developed forelimbs to drag herself several yards towards the dunes, just as her mother had done. This Loggerhead Sea Turtle (Caretta caretta) is truly a miracle. She survived to the age of ten to thirty years, becoming a young adult, which is an age only 1 in 1000 sea turtles reach. Her ability to migrate thousands of miles and find the same beach upon which she had hatched, known as natal philopatry, is a miracle as well. In the waters just offshore, she will continue to mate several times in the seasonal nesting grounds, and come ashore up to seven times to deposit and bury her eggs in a nest made by excavating and then covering a hole 18 inches deep in the sand. Each clutch might contain 100-126 eggs; even under the best-case scenario, the odds are against any of her offspring surviving until adulthood. And while this sea turtle is fortunate to return to a birthplace that has not been destroyed by development or climate change, as so many nesting sites have, she cannot stay to protect the nests. She has no physical capabilities to protect her eggs or to even to survive on land for very long. The eggs and hatchlings are on their own.
Loggerhead Sea Turtle nests make up the vast majority of nests on North Carolina’s beaches. Four other of the seven species of sea turtles, Green Sea Turtles (Chelonia mydas), Leatherback Sea Turtles (Dermochelys coriacea) and rarely, the Kemp’s Ridley Sea Turtle (Lepidochelys kempii) will also nest there. A fifth sea turtle species, the Hawksbill (Eretmochelys imbricata), visits North Carolina waters, but does not nest.
All sea turtles are listed as either threatened or endangered under the U.S. Endangered Species Act. There are a number of factors, in addition to development and climate change, that adversely affect the survival rate in sea turtles. Before eggs have hatched, many of them are preyed upon by beach residents including raccoons, foxes, birds and humans. Hatchlings that successfully emerge must follow the moonlight to guide them to the ocean, but artificial light often leads hatchlings in the wrong direction, leading to car strikes in the roadways that run parallel to the shore. Other predators for hatchlings include crabs, more species of birds and, for those sea turtles making it safely into the water, carnivorous fish. Sea turtles cannot retract their heads into their carapace like other turtles and the skin of hatchlings is not yet tough, therefore providing no protection from predators.
Sea turtle hatchlings are also very tiny. When I was an aquarist intern at the Virginia Aquarium and Marine Science Center, we affectionately called our four publicly exhibited hatchlings “chicken nuggets” because they are about that size and weight at hatching. With all these initial threats, the greatest threat still is at sea in the form of incidental capture in gill nets, shrimp trawls and other fishing gear.
In 1983, the N.C. Sea Turtle Protection Program was created by the North Carolina Wildlife Resources Commission and now coordinates the efforts of more than 1000 volunteers annually who monitor sea turtle nests along 330 miles of beaches from May to October during the 50-60 day incubation period. An elaborate network that includes state and federal natural resource agencies, private organizations, veterinarians, wildlife rehabbers, the Karen Beasley Sea Turtle Rescue and Rehabilitation Center and all three North Carolina Aquariums combine their skills and resources to protect nests. These efforts include nighttime nest sitting, rescue and rehabilitation of injured sea turtles and release of those healthy enough to survive in the wild again.
The North Carolina Aquariums play a key role in providing temporary housing for hatchlings that are too weak to get to the ocean on their own or are found far from the ocean when artificial light has led them in the wrong direction. Once the hatchlings show the ability to eat and dive effectively, they are released into the Gulf Stream offshore. Some of the hatchlings remain at the aquariums until reaching one to four years of age and during that time serve as ambassadors for educating aquarium visitors about sea turtle conservation. These turtles are released as well.
All three North Carolina Aquariums respond to help sea turtles that have been stranded by causes such as propeller strike, hypothermia and entanglement in fishing gear. The North Carolina Aquarium on Roanoke Island is home to the Network for Endangered Sea Turtles (NEST) Rehabilitation Facility. The Karen Beasley Sea Turtle Rescue and Rehabilitation Center on Topsail Island provides medical care for turtles rescued in the central and southern parts of the North Carolina coast. The North Carolina Aquariums at Pine Knoll Shores and Fort Fisher also take in turtles in need of rehabilitation.
On a broader scale, it is not unusual for the North Carolina Aquariums to take in cold-stunned sea turtles rescued in other states and give them care and housing until fully recovered and healthy enough for release. Sea turtles are cold-blooded and therefore cannot regulate their own body temperature internally. They are vulnerable to the temperature of their environment and must move to warmer or cooler environments to thermoregulate. Cold-stunning occurs when sea turtles are suddenly exposed to cold water, causing them to become lethargic and unable to swim to warmer waters. More often this happens to juveniles who have not left feeding grounds prior to the first cold front, usually in late November or early December. There can be as many as 100 cold-stunned sea turtles being held over winter in the aquariums, sea turtle hospital and in other wildlife rehabilitation locations approved by the North Carolina Wildlife Resources Commission.
Sea turtles are of ecological importance for many reasons. Unhatched eggs and hatchlings that do not survive provide nutrients for sea dune vegetation. Sea turtle eggs also serve as food source for predators in the ecosystem and as a food source for humans in some parts of the world. On the ocean floor, sea turtles graze on seagrass, which stimulates productivity and nutritional content of seagrass blades. Hawksbill Sea Turtles forage on marine sponges from coral reefs, allowing the coral to colonize and grow and preventing sponges from dominating the reefs, which are important to other sea life as well. Leatherback Sea Turtles have been known to eat up to 440 pounds of jellyfish in a day, providing some control over the increase in jellyfish due to commercial overfishing of finfish populations. Sea turtles have on their carapaces barnacles, algae and other organisms known as epibionts. Fish species such as sheepshead, wrasse, and angelfish as well as shrimp create “cleaning stations” which sea turtles visit to have these organisms eaten off. Birds often consume these epibionts too, while also taking advantage of a floating turtle oasis that provides refuge from sharks or just for a roosting rest in the sun during migration.
The sea turtle story is one of many examples of biologists, veterinarians, keepers and aquarists at zoos and aquariums throughout the world working hard with other governmental organizations, NGOs, volunteers and sometimes even corporations to conserve and preserve the natural world.