Sanibel Island Wildlife Series
SANIBEL ISLAND
WILDLIFE SERIES
VOLUME I
The Marine Turtles of
Sanibel & Captiva Islands
Designed & Edited by Charles LeBuff
This series is presented as an educational and public service by Amber Publishing.
Loggerhead Turtle — Pencil rendition by Warren Boutchia
Sanibel Island is a major resort destination on Florida's lower Gulf Coast. Hundreds of thousands of visitors are drawn to the island each year because of its relatively unspoiled charm. Leading attractions on Sanibel are the J. N. "Ding" Darling National Wildlife Refuge and the 12-mile curved, white beach which fronts on the Gulf of Mexico. This beach is reputed to be one of the best shelling beaches in the world. And, it's true — under the right conditions, shell collecting can be outstanding. Collecting seashells is regulated and only dead shells may be removed from the beach.
If the residents of any community ever were, the people of Sanibel and Captiva Islands are sea turtle-oriented. A successful sea turtle research and conservation effort was founded on the islands in 1959. Sea turtle egg hatcheries to protect eggs from predators, tagging of nesting adult female loggerheads, some hatchling head-starting efforts, and public education were among the workload of dedicated volunteers. The first documented instances of multiple nesting by Gulf Coast loggerheads and East Coast-tagged loggerheads later discovered renesting on Sanibel were recorded. Field studies also revealed that loggerheads are not as faithful in their selection of nesting sites as was supposed. Some female loggerheads moved along the Florida coast as far as fifty miles during their 11-day internesting interval. In 1968, this program became known as Caretta Research and this pioneering organization continued its important work until 1991. That year, the program was transferred to another foundation and similar efforts continue on the islands. Your support and financial assistance is important to the continued success of such programs. Sea turtles need your help!
Sanibel Island is situated at the seaward end of a large, interconnected marine ecosystem. The Caloosahatchee and Charlotte Harbor estuaries connect via Pine Island Sound and their waters mix around Sanibel and Captiva Islands. These two islands are noted for their seashells, fisheries, and diverse bird populations, all of which are enhanced because of the infusion of nutrients provided by the characteristics and biodiversity of this Florida estuary and its unique mangrove habitat.
The adjacent marine systems and the sandy beaches of these barrier islands are essential to the life cycle of five species of sea turtles. In recent years, three of these marine reptile species have been known to nest on the beaches of Sanibel and Captiva, the other two are transients and only seasonally occupy both the nearby deep and shallow marine habitats.
FLORIDA'S FABULOUS FIVE MARINE TURTLES
The images of the five species of sea turtles on this page were hand-carved by Charles LeBuff. They are part of his private collection*. Each rendition was carved from American basswood, and each is biologically correct. The carvings were hand-painted with acrylic paints and over coated with clear matte acrylic.
*This complete, unique one-of-a-kind collection is available for purchase by some discriminating collector or institution for US$2,500.00.
Each carving represents a large adult of its respective species and they are rendered in scale, one to the other. For reference to scale the stainless steel support shaft visible in the loggerhead photo is 1/4" in diameter.
The loggerhead's base is made from Sanibel Island buttonwood.
The green turtle's base is from white pine.
The ridley's base is from Honduran mahogany.
The hawksbill's base is from Captiva Island black mangrove.
The leatherback's base is from poplar.
The skulls that are pictured below were collected from stranded (dead) specimens at the collection sites indicated. They were collected or imported with valid state and federal permits. Otherwise, possession of an undocumented sea turtle part in the United States is illegal.
Loggerhead Turtle, Caretta caretta
The loggerhead turtle is the most
abundant form among Florida's sea turtles. It is the only species which regularly nests
in substantial numbers on the beaches of Sanibel and Captiva Islands. The
loggerhead is
considered to be a threatened species.
The loggerhead turtle is primarily carnivorous, feeding on shellfish, sponges, crabs, and other large invertebrates.
Females of these giants lumber up on our beaches at night between May and September to lay eggs. Each female loggerhead turtle will deposit 100 or more eggs, up to seven times each nesting season. The maximum clutch size from a Sanibel loggerhead is 182 eggs. In 1973, one tagged loggerhead laid a total of 920 eggs in six nesting visits to Sanibel Island.
As a general rule, the round, pliable-shelled eggs hatch following a 60-day incubation period.
To the right is the skull of an adult female loggerhead turtle. The actual overall length of this skull is 30.0 cm. The specimen is from Bowman's Beach, Sanibel Island, Lee County, FL.
Green Turtle, Chelonia mydas
Small green turtles are frequent seasonal visitors to local waters, like Tarpon
and San Carlos Bays. In Florida, the species is considered
endangered. In recent years, green turtles have again made nesting visits
to our Gulf beaches — including Sanibel Island
— an indication the species'
population may be on the road to recovery.
Green turtles are herbivores and feed primarily on turtle grass.
On the right is an adult female green turtle skull. The actual overall length of this skull is 20.0 cm. The specimen is from Brevard County, FL.
Kemp's Ridley, Lepidochelys kempii
The rarest and smallest of the sea turtles, the Kemp's ridley, occurs in the region year-round.
This declining species primarily congregates for mass nesting on the Mexican Gulf coast north of Vera Cruz. In the last two decades individual ridleys have nested in Florida, including a documented nesting on Sanibel Island. Because of its drastically reduced population the Kemp's ridley is considered endangered throughout its range.
The skull of a very large adult female Kemp's ridley. The overall length of this skull is 21.5 cm. This specimen was collected at Point Ybel, Sanibel Island, Lee County, FL.
Hawksbill Turtle, Eretmochelys imbricata
Juvenile hawksbill turtles are the most beautiful of all the world's marine
turtles. Through time the shell of this species has been highly valued because
it is the source of tortoise shell. Because of over-exploitation, the collection
of the shell is no longer sanctioned by most countries in the Americas. However,
Japan continues to import tons of the product from around the globe —
from
wherever tortoise shell is still harvested in Third World countries. Adult hawksbills resemble
loggerheads and it sometimes takes an expert to distinguish them apart in the
limited areas where they may utilize the same nesting habitat. The hawksbill is
primarily a creature of reefs and hard bottoms where it feeds on coral polyps
and sponges. The hawksbill is considered an endangered species.
A subadult hawksbill turtle skull. The actual overall length of this skull is 19.7 cm. This specimen is from Little Abaco, The Bahamas.
Leatherback Turtle, Dermochelys coriacea
The unique leatherback turtle is the largest
living reptile. A dead, stranded specimen weighed in at 2,016 pounds.
The
leatherback lacks a horny, bony shell like that of other sea turtles. Instead, the "shell" is
composed of small mosaic-arranged bones imbedded in a leather-like integument.
The leatherback turtle feeds almost exclusively on pelagic jellyfish. This species is a very rare visitor to the barrier island beaches of Southwest Florida, and there are no recent nesting records for the species here. Leatherbacks are infrequently observed offshore. The leatherback is listed as an endangered species.
To the right is the skull of an adult female leatherback turtle. The actual overall length of this skull is 26.0 cm. The specimen was collected in French Guiana.