The federally endangered leatherback sea turtle (Dermochelys coriacea) is the largest turtle species on Earth and the only surviving member of its scientific family, Dermochelyidae. All six other sea turtle species are in the scientific family Cheloniidae.
Leatherbacks are one of the five sea turtle species that visit Florida’s shores to nest each year. Four of those species can be found on Sanibel and Captiva Islands — though not necessarily all four nest every year, and some are much more common than others.
Species that nest on Sanibel and Captiva, in order of average nesting abundance
- Loggerhead (Caretta caretta) – Threatened
- Green turtle (Chelonia mydas) – Threatened
- Leatherback (Dermochelys coriacea) – Endangered
- Kemp’s ridley (Lepidochelys kempii) – Endangered
Hawksbill turtles (Eretmochelys imbricata) nest in small numbers in other regions of Florida, but they have not been documented on Sanibel or Captiva (though the Sanibel-Captiva Conservation Foundation confirmed a hawksbill/loggerhead hybrid turtle in 2022!).
About Leatherbacks
So why is it named a leatherback? Because this sea turtle actually lacks a hard shell like the other six species — its carapace is instead made up of a thick layer of fat tissue under small interlocking dermal bones, all overlaid by a layer of ‘leathery’ skin. They are also able to dive deeper and in colder waters than the other sea turtle species.
Leatherbacks have existed since the age of the dinosaurs, but current threats from bycatch, boat strikes, loss or degradation of nesting habitat, and illegal collection of eggs (especially overseas) have led to troubling population declines. One estimate suggests the global population has declined 40 percent over the past three generations, according to NOAA Fisheries.
They primarily nest on the Atlantic coast of Florida, and more rarely nest on the Gulf Coast. Globally, the largest remaining leatherback nesting regions are found in Trinidad and Tobago, West-Indies, and Gabon, Africa.
The Sanibel-Captiva Conservation Foundation (SCCF) has only recorded a leatherback nesting on our beaches during four separate seasons — 2009, 2015, 2020, and in 2024 with the first sea turtle nest of the season.
So far in 2024, leatherback nest counts statewide are up from last year, which was itself a strong nesting season for the species.
Preliminary statewide nesting totals as of April 30
- 400 loggerhead nests (1,410 in 2023)
- 0 green turtle nests (3 in 2023)
- 735 leatherback nests (640 in 2023)
- 2 confirmed Kemp’s ridley nests (6 in 2023)
The evidence of a leatherback nest is hard to miss, with their tracks indicating the females’ massive size — an average of 6 feet long and between 500-1,500 pounds. In 2020, SCCF worked with Florida Leatherbacks, Inc. to track a leatherback that nested six times on Sanibel and Captiva throughout the season!
Threatened vs. Endangered Species
Like all sea turtles that nest in the U.S., Sanibel and Captiva’s four sea turtle species are each listed under the Endangered Species Act of 1973.
There are two ways a species can be listed under the Endangered Species Act (ESA) — as “endangered” or “threatened.” The main distinction is that endangered species are “in danger of extinction throughout all or a significant portion of its range,” while threatened species are “likely to become an endangered species within the foreseeable future throughout all or a significant portion of its range.”
Leatherbacks and Kemp’s ridley turtles are listed as endangered. The loggerheads and green turtles in our region are listed as threatened, while other regional populations of these same species are classified as endangered. These “Distinct Population Segments” (DPSs) were created for loggerheads and green turtles since they face different levels of threats in different areas of the world.
Both threatened and endangered species listed under the Endangered Species Act are protected from federal actions that would jeopardize the species’ continued existence. The designation also makes it illegal for someone to take (kill or remove from the wild), transport, or sell these species, among other protections from harm. Lastly, federal agencies are required to develop and carry out recovery plans to contribute to these species’ survival.
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