A Rare Breed: Hybrid Sea Turtles

Sea turtle hybrids are not only rare, but unique in several ways. Despite the fact that the six hard-shelled species of sea turtles (in the family Cheloniidae) diverged from their common ancestor approximately 10 million years ago, they can still breed with each other. Hybrids occur naturally in the wild wherever the foraging and nesting areas of these different species overlap. Additionally, research has also shown that sea turtle hybrids are fertile and able to reproduce successfully. (1) As Senior Sea Turtle Conservation Biologist Blair Witherington said, “Sea turtles may be distinguished among the vertebrates in having the most distantly related lineages capable of producing fertile hybrids in nature.” (2)

What Do Sea Turtle Hybrids Look Like?

As you’d expect, hybrid sea turtles exhibit characteristics of both their parents. In the photos below, the head of this loggerhead-green hybrid (named Eclipse) is small like a green but has the coloration and beak of a loggerhead. Additionally, the hybrid’s shell has four scutes on the left side (like a green), five on the right side (like a loggerhead), and has the shape and color of a loggerhead.

However, the combination of inherited traits can vary and hybrids from the same two species don’t always look alike. One hybrid of a loggerhead and hawksbill can have the head color and shell shape of a hawksbill while another loggerhead-hawksbill hybrid can have a hawkbill’s shell shape but the coloration of a loggerhead. (2)

How Do Sea Turtle Hybrids Behave?

Studies on hybrids have been done using satellite tags to track their movements. They discovered that different varieties of hybrid loggerheads – all of which had loggerhead mothers – traveled to loggerhead foraging areas. (3) Both juvenile and nesting female hybrids were included in these studies.

More Research Is Needed

Because the highest numbers of sea turtle hybrids occur off the coast of Brazil and in the southwestern Atlantic, these are the best places to study them. Researchers want to discover why so much inter-specie breeding is occurring in this area. Also, more genetic research is needed to find out exactly how many hybrids exist in these populations.

References

(1) Luciano S. Soares, et al, “Effects of Hybridization on Sea Turtle Fitness”, (Conservation Genetics, 2018).

(2) Blair and Dawn Witherington, Our Sea Turtles: A Practical Guide for the Atlantic and Gulf, from Canada to Mexico (Pineapple Press, 2022), page 8.

(3) Luciano S. Soares, “How Rare Are Hybrid Sea Turtles, Really?” (The State of the World’s Sea Turtles, 2020).

Want to Learn More?

See the following for more detailed information on sea turtle hybrid research.

• “Brazilian Origin of a Neritic Juvenile Hybrid Loggerhead x Green Turtle Foraging in Florida”
• “Sea Turtle Hybridization: A Genetic, Ecological, and Behavioral Analysis”
• “Hybridization Among the Ancient Mariners: Characterization of Marine Turtle Hybrids with Molecular Genetic Assays”