Hybridization of sea turtle species is becoming better documented and may not be as uncommon as once thought. Hybrid turtles involving all species except the leatherback have been confirmed through genetic analysis.
Hybridization occurs when animals of different species mate to produce offspring that is different from each parent. A common hybrid is the mating of a horse and a donkey to produce the mule.
Hybridization of marine turtles has occurred among all species of the shelled marine turtles in Florida waters, which all belong to the Family Cheloniidae*. Hybridization is being documented more frequently, although we don’t know if this is because it is becoming more common or if it is simply a case of better identification and documentation by those who collect data and study turtles.
Unfortunately, hybrid sea turtles pose more questions right now than answers! There has been little study of these animals and the following are some questions to think about:
1) Is hybridization becoming more common or are we just getting better at recognizing the offspring?
2) Are hybrid offspring fertile? We know that some are. The photo below shows a female loggerhead-hawksbill hybrid nesting on a central Florida beach. Her body appears classically loggerhead, but her head is quite narrow and the upper jaw has the classic elongation of a hawksbill. She nested in 2001 and nested again in 2004. Both times her eggs were viable and hatched. (Thanks to Dean Bagley of University of Central Florida Marine Turtle Research Group.)
3) Why does hybridization occur? Is it because of declining populations (difficulty finding a mate of your own species)? Or because the ratio of males to females is being skewed in some areas?
4) Do the hybrid turtles share characteristics and feeding behaviors of both parents? Or just one? Would a loggerhead-hawksbill hybrid eat both sponges and lobster? Could this be an evolutionary advantage for future generations?
5) How does hybridization affect migration and nesting behavior?
* Leatherback turtles are not known to have hybridized. They belong to the Family Dermochelyidae and branched apart from the shelled turtles long ago.