What We Have Learned
Abundance
One of the first things we learned about the Palm Beach aggregation is that there are many more hawksbills than were expected! So far, just over 300 individuals have been captured and documented between Jupiter and Key West, and we continue to encounter new ones on a regular basis. Though not abundant compared to other sea turtle species in Florida, this expanding database indicates how supportive the reefs of Florida are for young hawksbill turtles, which has a regional significance for their overall recovery.
Population Structure
The hawksbills of Palm Beach are primarily sub-adults, or “teenagers”. Hawksbills, like other sea turtles, can be found in different geographic locations based on their life-stage. We call the reefs of Palm Beach County “developmental habitat” for young turtles who will someday depart to spend the rest of their lives elsewhere as adults. Because they are youngsters, their gender cannot be determined externally, but we have used blood samples to estimate the male:female ratio at about 1:2.5.
Movements and Growth
Once tags are placed on a turtle, it can be distinguished from others. When these individuals are encountered repeatedly, we gain valuable insight to their movement and growth patterns. Dozens of tagged hawksbills have been reported within the study site, some individuals since the inception of the study in 2004, all within close proximity to where they were captured. Those that have been re-measured after at least one year grew (on average) 2.5 cm per year. These results suggest that at least some of the hawksbills found in the study site may remain there for the duration of their sub-adult life- stage, which is likely to be around 15 years.
Origins
Female sea turtles are famous for traveling long distances to return to their natal beach to nest. This marvelous trait allows us to genetically “fingerprint” sea turtle populations due to subtle differences in DNA sequences that have developed between various regional sub-populations. Since we know that the hawksbills of Palm Beach did not come from Florida (hawksbills don’t nest with any regularity here), we were curious about their origins, and by extension, their future destinations. Turns out, most hatched on the beaches of Mexico's Yucatan Peninsula!
Hawksbill Physiology
Many aspects of physiological function and well-being are revealed in the various components and constituents of blood. Much like a blood panel we may provide to a doctor, the blood we collect from hawksbills allows us to evaluate how a number of organ systems and the body as a whole are functioning. Though already completed for other sea turtle species, there has yet to be a thorough examination of hawksbill blood cells, blood analytes, and other metabolically active compounds in a wild population. Soon to be submitted for publication, the project included samples from nearly 100 Florida hawksbills ranging in size from small juveniles through adults.
Epibionts
Epibionts are, basically, organisms that live on other organisms. Many rely on hosts of different kinds, but others specialize on particular host species as obligate associates. Among the most recognizable of the epibionts on sea turtles are barnacles, small crustaceans that in some cases colonize all sorts of substrates underwater. There are, however, two kinds of sea turtle barnacles (Chelonibia testudinaria and C. caretta) that are quite similar in appearance, phylogeny, and lifestyle, but for some reason appear to segregate themselves among co-mingling populations of green and hawksbill turtles. This discovery suggests that these barnacles are differentially selecting their hosts, and we are actively exploring the mechanisms that underlie this phenomenon.
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