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    Buck Island Reef

    National Monument Virgin Islands


Sea Turtles The Virgin Islands provide critical nesting, foraging, and developmental habitat for three species of sea turtle, the leatherback (Dermochelys coriacae) and hawksbill turtle (Eretmochelys imbricata) both endangered species, and the green turtle (Chelonia mydas), a threatened species. Loggerhead turtles (Caretta caretta) are transitory and only occasionally seen in the islands.

The Leatherback Sea Turtle (Dermochelys coriacea) U. S. Fish & Wildlife Services’ Sandy Point National Wildlife Refuge, St. Croix, is the principal nesting beach for leatherback turtles in the Northern Caribbean. Tagging studies have shown movement by females between regional nesting beaches in Puerto Rico, Anguilla, and St. Croix (McDonald, et al, 1995; Eckert, et al, 1989; Boulon, et al, in press). This long-term saturation-tagging program provides essential information on leatherback turtle population trends available nowhere else in U.S. properties. Since 1981, 342 leatherback turtles have been tagged with a range of 18 - 55 females nesting per year (Boulon, et al, 1996; MacDonald, 1995). Historically, it is possible that 100 percent of the nests laid at Sandy Point were either poached or lost to beach erosion (seasonally 50 to 60 percent). With the advent of the research program (1981) the beach is protected and nests threatened by erosion are relocated; nest loss is now less than five percent annually. It is possible to speculate that the increase in numbers of females nesting per season, given an average age to maturity for leatherbacks of 10 to 15 years, is a direct result of beach protection and nest relocation (Boulon, et al, 1996).

General Characteristics: Adult female leatherback turtles, primarily a pelagic species, migrate every 2 to 3 years to the tropics to nest (Boulon, et al, 1996).

• Shell is smooth, scaleless, and uniformly black with white spots, raised into seven

narrow ridges that extend the length of the carapace.

• “Pink spot” on dorsal surface of the skull. Its shape is considered similar to human

fingerprint and maybe used to identify individuals.

• Adult females are 140 to 160 cm long, and weigh 800 to 1600

• Nesting season March to June.

• Females nest on open sand beaches, free of shoreline reefs, with deep-water access.

• Crawl pattern is parallel flipper tracks approximately 2 meters across.

• Nest site is a large area of disturbance with several craters over 2 meters wide.

• Internesting Interval is 10 to 11 days.

• Each female can lay between 8 to 11 clutches per season.

• Clutch size ranges from 50 to 80 yolked eggs, the size of cue balls, plus 10 to 30

yolkless eggs varying from pea size up to cue ball.

• Nests incubation is between 55 to 75 days depending on time of season.

• Hatchling is black with small white dots. Plastron is lighter in color than adults aiding in

counter shading and pelagic predator avoidance.

• Hatchling is largest of all sea turtles - 2 ½ inches long (5 - 6 cm)

The Green Sea Turtle (Chelonia mydas) Observations of green turtle nesting populations have been collected incidentally by both leatherback and hawksbill turtle research programs in the Virgin Islands since 1980s. In 1993 and 1994 daytime beach surveys were conducted for green and hawksbill turtles on St. Croix (Mackay, et al, 1994; Mackay, et al, 1995). The Virgin Islands have never been a significant green turtle nesting area, but rather a juvenile foraging ground. The number of green turtle nesting activities remains low for all the islands, but there appears to be a gradual increase in numbers of juveniles observed in the foraging grounds since mid-1970s (Boulon, pers comm). The only island that still supports any amount of green turtle nesting is St. Croix with an average of 100 nests per year from 1980 - 1990 (Eckert, 1992). The largest concentration of green turtle nesting activities occurs on St. Croix's east end beaches averaging 15 nests per year (Mackay, et al, 1995). Buck Island Reef supports between 1 to 3 green turtles per season whose nesting activities result in 8 to 10 nests per year.

General Characteristics (Chelonia mydas):

• A bony-shelled sea turtle, dark gray/green domed shell and smooth white underbelly or plastron.

• Adults grow to over 1.5 meters long (4 feet) and weigh up to 400 lbs.

• Nesting season is between May and August.

• Nest along open sand beaches placing their nests up to the dune grass or beach vines.

• Crawl pattern is parallel tracks up to 2 meters wide

• Nest site includes several very deep craters, up to 1.5 m across and 1 m deep.

• Internesting interval is 11 to 14 days.

• Each female can lay between 5 to 7 clutches per season.

• Clutch size ranges from 100 to 120 yolked eggs, the size of golf balls.

• Nests incubation is between 55 to 75 days depending on time of season.

• Hatchlings are counter shaded; dark on top and bright white below.

• Hatchling is second largest of Virgin Island’s sea turtles - 2 inches long (4 - 5 cm)

The Hawksbill Sea Turtle (Eretmochelys imbricata) There are very few places in the Caribbean where any large numbers of hawksbill turtles remain today (NMFS/USFWS, 1993). In the Virgin Islands hawksbill nesting occurs on St. Croix (Buck Island Reef NM and east end beaches), a few isolated beaches on St. John, St. Thomas (primarily on the offshore cays). In 1993 only 32-hawksbill nesting activities were observed on all of St. John's beaches, where over 50 percent of the island remains undeveloped national park (Mendelson, 1993). In 1994, 100 hawksbill-nesting activities were recorded on St. Thomas' offshore cays. Sixty-one percent of these hawksbill activities occurred on Greater Hans Lollick, which is threatened by a major hotel development (Boulon, 1994).

The most important concentrations of hawksbill turtle nesting activities remaining in the Virgin Islands occurs at Buck Island Reef National Monument and St. Croix's east end beaches (Jack's/Isaac's/East End Bays). Buck Island and St. Croix's east end beaches are supporting two remnant populations of between 20 - 40 nesting hawksbill turtles per season (Hillis, 1994; Mackay, et al, 1994). Since 1988, 200 individual hawksbill turtles have been tagged nesting on Buck Island Reef National Monument. Hawksbill turtles return to nest every 2 to 4 years indicating high degree of nesting beach fidelity (Hillis, 1991). Of these remigrants, between 50 to 80 percent have returned to nest in subsequent years representative of the high survivorship of adult sea turtles (Hillis, 1994; Frazer, et al, 1995, in press). Prior to 1996 annual recruitment of first time nesters at BUIS was less than 15%; in 1996 and 1997, the number of recruits increased to 50%of the nesting population (Hillis and Phillips, 1997). In 1994 a saturation-tagging program was initiated on St. Croix's east end beaches; 14 hawksbill turtle were tagged that season (Mackay, et al, 1994). In 1996 & 1997, the first intra seasonal movements of two hawksbill females were recorded. A Buck Island nesting female nested in Jack’s Bay and a East End tagged hawksbill female nested on BUIS twice.

Throughout their range, hawksbill turtles nest in low density; nesting aggregations consist of a few dozen, at most a few hundred individuals (NMFS/USFWS, 1993).

The smallest of the three species of sea turtle nesting in the Virgin Islands, hawksbill turtles are the most seriously endangered throughout their range. They are omnivorous, living and feeding in coral reefs and mangroves. They are best known for their beautiful shell, “tortoise-shell”, which has been prized for jewelry throughout the world -- also the cause of their present endangered status.

General Characteristics (Eretmochelys imbricata):

• A bony shelled sea turtle, golden skinned with a mottled brown shell.

• The scales of the carapace or scutes overlap like shingles on a roof (imbricated).

• Adults grow to over 1 meter long (3 feet) and weigh up to 200 lbs.

• Nesting season is between April-December, but hawksbill nesting has been recorded for every month of the year.

• They migrate to their nesting beaches every 2 to 4 years.

• Nest beaches fringed by coral reef frequently selecting a nest site deep into the beach forest vegetation.

• Crawl pattern is alternating gait, less than 1 meter wide.

• Nest site typically in vegetation or at the back of the beach at the base of a rock cliff.

• Nesting activity is typically a small area of disturbance with several aborted nest holes or one small shallow body pit.

• Internesting interval is 14 to 16 days.

• Each female can lay between 3 to 5 clutches per season.

• Clutch size ranges from 140 to 200 eggs, the size of ping-pong balls, plus 1 to 10 yolkless eggs varying from pea size to bird egg size.

• Nests incubation is between 55 to 75 days depending on time of season.

• Hatchlings are uniformly brown all over and are miniatures of the adults.

• Hatchling is smallest of Virgin Island’s sea turtles - 1.5 to 2.5 inches (5 to 8 cm).

Birds Buck Island is one of few places in the Virgin Islands where endangered brown pelicans and threatened least terns nest. Pelicans nest from June through March.

Least terns (Sterna antillarum) are migratory birds that come to nest on open sandy beaches from May to August. They lay small speckled, sand-colored eggs in shallow depressions on the beach. Both adults take turns sitting on the eggs, foraging for food, and protecting and incubating the eggs. The terns are easily disturbed by people walking nearby and will leave the eggs and fly toward the invader. When these birds are disturbed during their nesting period, the adults will leave their eggs or chicks unprotected. Every time a tern flies off the nest during the day, the eggs or chicks are exposed to excessive heat from direct sunlight and to possible predation.

Other birds commonly seen include Bahama ducks, bananaquits, gray kingbirds, greenthroated hummingbirds, kestrels, magnificent frigate birds, ospreys, pearlyeyed thrashers, and zenaida doves.

Lizards Buck Island provides very important habitat for two endemic lizards, the St. Croix anole and the cotton ginner dwarf gecko. Since the island-wide rat and mongoose eradications, Buck Island now also provides a suitable environment for the reintroduction of the endangered St. Croix ground lizard.

Environmental Assessment

Insects and Spiders Buck Island is also home to many insects and spiders. Most are harmless, however, some can bite. Beware of centipedes, scorpions, and fire-ants.

Did You Know?

Manchineel Tree on Buck Island

The tropical dry forest of Buck Island has over 180 native plant species that inhabit the island, including locally threatened species. It is threatened by non-native invasive plants which out compete native species.