Sea turtles, large and lovable to their fans, have endured a long decline around the world and in the Chesapeake Bay. But a team of international scientists has delivered a bit of good news, at least on a global scale.
The results of their study, published in the September issue of Science Advances, show that some species of sea turtles, after years of decline from harvesting practices and lost habitat, are beginning a modest rebound on a global basis.
Whether or not that rebound extends to the Chesapeake remains to be seen.
While the average, global population of sea turtles may be on the rise, the increase is not the same in all locations or for all species. The study, conducted by Greek and Australian scientists, looked at 299 nesting surveys recorded over time periods of six to 47 years. While they found 95 significant increases, they also found 35 significant decreases and note that some species, like the leatherback turtles in the Eastern and Western Pacific, remain in decline.
No studies currently target sea turtle populations in the Chesapeake Bay. Turtle advocates, though, including biologists like Ruth Boettcher, would like to see signs of improvement close to home.
Boettcher, who works at the Virginia Department of Game & Inland Fisheries, said there are several factors believed to be contributing to the recovery of sea turtles in U.S. waters. The most important consist of regulations and gear modifications applied to commercial fisheries that impact sea turtles, such as shrimp trawling, gill-netting and offshore long-lining. Another is an increase in the protection of nesting habitat and a minimization of threats stemming from artificial lighting, vehicular traffic, mechanical beach cleaning, shoreline stabilization and hardening, sand fencing and other human influences.
Today, Boettcher said, “virtually all U.S. Atlantic coast sea turtle nesting beaches have some sort of nest-monitoring program in place that protects nests from human disturbance and harassment as well as predators.” Sea turtles almost always nest on oceanfront beaches as opposed to the shores of the Bay.
Seven species of sea turtles exist globally, and five are known to visit the Chesapeake. They are, in order of likely sightings: the loggerhead, Kemp’s ridley, green, leatherback, and hawksbill turtles, each with different ecological needs and are present in the Bay only during narrow windows throughout the year.
While some species have been recorded as far north as Maine, the Bay generally represents the northernmost extent of these animals’ range. They are more likely to be seen near the Atlantic Ocean. Virginia records reveal more details about turtle sightings in the Bay. Little information is available for the Maryland portion of the Bay, although the Maryland Department of Natural Resources has recovered a yearly average of 26 sea turtle carcasses from 2008 to this year from both Bay and Atlantic shorelines. Most of those were loggerheads.
Loggerhead sea turtle
The loggerhead sea turtle (Caretta caretta) was listed as threatened by the U.S. Fish and Wildlife Service in 1978. Loggerheads are named for their outsized heads and powerful armored jaws, easily capable of crushing the horseshoe crabs, clams, mussels and other invertebrates that are their primary food. Their shells can reach lengths of 3.5 feet.
Loggerheads are the most common sea turtle in Virginia and occur throughout the state’s coastal waters, including the lower Chesapeake and the channels and lagoons between the Delmarva Peninsula and the seaward barrier islands. Most loggerheads seen in the Bay are juveniles and sub-adults, accompanied by a small number of breeding adults.
Boettcher said that from 1970 to this year, 185 loggerhead nests were documented in Virginia, 70 percent of them on southern mainland beaches. The remainder were on barrier islands, with a single nest on the western shore of the Bay on Gwynn’s Island.
The Kemp’s ridley (Lepidochelys kempii) is the world’s most critically endangered sea turtle, according to the International Union for Conservation of Nature, and was listed as a federally endangered species in the United States in 1973. Kemp’s ridley turtles reach about 2 feet in length and weigh 100 pounds, with crabs making up most of their diet.
Kemp’s ridleys are unique among sea turtles in that they nest during daylight hours. In the heart of their breeding range, multiple females will come ashore at the same time, a mass nesting behavior referred to as an “arribada.” According to the World Wildlife Fund, in the 1940s, tens of thousands of pregnant females were recorded as having launched a one-day arribada on a Mexican beach. By the 1980s, only a few hundred remained.
Kemp’s ridleys occupy the same waters as loggerheads in the Bay region and their residency time is similar as well, occurring in Virginia from May to October, but remaining longer if water temperatures remain warm enough into fall and winter. After loggerheads, they are the second most commonly recorded sea turtle in the Bay. Virginia’s population is almost exclusively juveniles.
In recent years, Boettcher said, an increasing number of Kemp’s ridleys appear to be hanging around recreational fishing piers, waiting to snatch up fresh bait accidentally dropped by fishermen — and, conservationists hope, not getting hooked themselves.
Boettcher said that Virginia’s first reported Kemp’s ridley nest was discovered in 2012 north of Sandbridge, at the northernmost tip of the Outer Banks, and a second nest was documented two years later just south of there at False Cape State Park. Both sites are far north of typical nesting grounds.
Green sea turtle
Green sea turtles (Chelonia mydas) were listed as federally threatened in 1978. They are big animals, 5 feet long and more than 700 pounds. Unlike other sea turtle species, the young green sea turtles start their lives as carnivores but become strictly herbivorous once they become established in coastal habitats. Based on stomach contents of stranded carcasses found in Virginia, Boettcher said, most green sea turtles in the mid-Atlantic are dependent on eelgrass and sea lettuce.
Although historically reported as abundant in Virginia’s coastal waters, today, green turtles occur in relatively low numbers. Boettcher said this may be correlated with significant losses of eelgrass in the Lower Bay since the 1930s. Efforts under way to restore eelgrass off the Virginia coast have met with considerable success, she said, which may yield more turtles in the Bay region.
The mighty leatherback turtle (Dermochelys coriacea), listed as a federally endangered species since 1973, is the world’s largest, farthest traveling and deepest diving sea turtle. It is also the most widely distributed reptile in the world. Growing up to 6 feet in length and weighing in at 1,100 pounds, the leatherback is distinctive for its lack of a bony shell. It instead sports a thick rubbery carapace interwoven with thousands of tiny bone plates.
This enormous reptile subsists almost entirely on protein-poor jellyfish, wielding delicate jaws that would be damaged by hard-bodied prey.
Although leatherbacks are known to spend a significant amount of time in offshore waters, Boettcher said that commercial and recreational fishermen and boaters regularly see them in the Lower Bay. Leatherbacks occur in mid-Atlantic waters primarily from May to September, but have been observed in Virginia during late fall and early spring, when water temperatures are still too low for other sea turtles.
Leatherbacks nest chiefly along the Florida coast. Even so, occasional nesting has been documented since the late 1990s in North Carolina. To date, there are no records of leatherbacks nesting in Virginia, but a leatherback “crawl,” or trail in the sand, was discovered at Assateague National Seashore in Maryland in 1996.
Hawksbill sea turtle
The hawksbill turtle (Eretmochelys imbricata), another federally endangered species, runs about 3 feet long and weighs up to 155 pounds. The shell is thin and flexible, and the beak is narrow and pointed like a raptor’s, ideal for poking around in corals for its preferred diet of shrimp and squid.
Large, intricate scaling on the head and flippers highlights the hawksbill’s giraffe-like color pattern — a feature that’s played a major role in its decline, as it’s been marketed to artisans.
The IUCN has listed the hawksbill sea turtle as critically endangered, meaning that the species is considered one step away from extinction in the wild. Only two hawksbills have been identified in Virginia waters.
According to the Maryland DNR, hawksbill turtles have never been officially recorded in Maryland, but the Maryland Biodiversity Project reports two sightings by amateur naturalists in the waters of Calvert and Worcester counties.
International agreements that protect habitat, limit harvest and reduce bycatch mortality are indispensable, conservationists say, for the survival of sea turtles over the long term, in the Bay and elsewhere.
“Sea turtles are bellwethers,” said Roderic Mast, co-chairman of the IUCN marine turtle group. “They’re flagships that we use to tell the story of what’s going on in the oceans. And that’s why people should care about turtles.”