Research

SEA TURTLE Research

Beginning at the break of dawn on March 1st until October 31, the Boca Raton Sea Turtle Conservation and Research Program, based at Gumbo Limbo Environmental Complex, conducts nesting research on a stretch of 5 miles of Boca Raton's beaches. Researchers are looking for evidence left behind from one of the three sea turtle species (loggerheads, greens, leatherbacks) that regularly nest here. Basic research includes determining the species of turtle that emerged the night before from the tracks, and then determine if eggs are present (a nest) or not (a false crawl). Changes in the nest/false crawl ratios for a species of sea turtle may indicate a problem such as too much light on the beach, or too many people on the beach at night. When it is determined that eggs are present, the nest is marked with a "Sea Turtle Nest" sign and may be protected with wire mesh placed over the egg chamber which protects the nest from raccoons and foxes trying to dig it up and eat the eggs. Each nest is monitored daily for the next two months; it is recorded whether the nest was washed over by waves, if a fox or raccoon dug at it, and finally, when it hatched. When the nest hatches, the hatchling tracks are checked to see if they go straight to the water; if they do not, a "disorientation" is reported and photographed to determine what light caused the disorientation. For 160 million years, hatchlings have found their way to the water by looking for the lightest horizon, hence their attraction to light. In the past 75 years, we have artificially lit the beach at the dune which causes the hatchlings to be attracted away from the water, often to their death. If this happens, the source of light is found and corrected as soon as possible.

The Boca Raton Sea Turtle Program now records every crawl on hand-held pocket computers that communicate with a GPS (Global Positioning Satellite).This allows the crawl to be recorded in the computer, which can then be analyzed with GIS (Geographic Information System) software. For all the apparent complexity, this simply means that the crawl can be located on a map or aerial photograph of the beach. If you click on any crawl with the mouse, all of the data about the nest is displayed such as the date, species, how many hatched, etc. In the near future, we hope to have this data available on the city of Boca Raton's website so anyone can see where the nests and false crawls are in Boca Raton. Putting the data on the computer in this manner greatly simplifies the data analysis, which is important to effectively protect and monitor our nests.

The Boca Raton Sea Turtle Program is known for its research on sea turtle nest predators such as raccoons and foxes. From 1976 to 1996, all sea turtle nests in Boca Raton were caged with a wire mesh structure. In 1996, the Boca Raton Sea Turtle Program joined up with Dr. Mike Salmon at Florida Atlantic University to study the effectiveness of these cages for protecting the eggs. From this study, it was shown that the cages actually attracted the raccoons, which meant a caged nest was more likely to be destroyed by predators. After that was determined, cages were used sparingly in areas with high human traffic to protect the nest site from humans. Research demonstrated that an abnormally high population of raccoons was present in the city parks which put heavy pressure on the sea turtle nests in these areas. Nests in the parks are now routinely screened with a 4 foot square wire mesh buried just under the sand. The mesh is large enough to allow the hatchlings to crawl through it.

Following this study, researchers studied whether hot pepper would be a solution. Hot pepper sauce proved to be marginally effective as it attracted fire ants. A few years ago, habenero pepper powder was used by sprinkling it into the digs made by raccoons or foxes. That evening when the raccoon or fox returned, it would stick its nose in the dig and sniff. This effectively stopped continued digging. The hot pepper powder is "hot" only to mammals and does not affect the sea turtle hatchlings or shore birds. For the past four years, the predation rates in Boca Raton have dropped from 15% to less than 4%. In 2007, the rate jumped to 10% outside of city parks despite the use of hot pepper. The problem was determined late in the season when beachfront residents began complaining about neighbors feeding the foxes. This feeding caused a fox population explosion in areas that are generally not a problem, which resulted in the partial or total destruction of 70 sea turtle nests.

Feeding wild animals is illegal and upsets the delicate balance that exists with wildlife in an urban environment. When this happens, other species such as sea turtles, birds, snakes, etcetera suffer under the predation pressure.

Another strong point of the Boca Raton Sea Turtle Program is research on lighting and sea turtle behavior. Using the GIS computer data, problem areas were noticed where false crawls were higher than the number of nests and the number of crawls total was very decreased. As one large area was a city park that had no existing lights, a new problem needed investigation.

The culprit appears to be Sky Glow from the City to the west of the beach that leaves a lighter horizon appearance over the dune. To a female sea turtle emerging from the water in this area, the lighter horizon in front of her makes it appear as though water were ahead of her, so she avoids the area, fearing that the eggs will be drowned. Conversely, nesting concentrates in shaded areas such as parks with high dunes and Australian Pine trees, and in front of tall, wide condominium buildings. The City's lighting ordinance keeps the beach dark and the buildings and trees help shade the beach from the sky glow. Sky Glow largely comes from decorative lighting that illuminates trees and buildings. Such lighting serves no purpose such as enhancing safety and security. Sky Glow can be controlled by using full cut-off lighting fixtures, which direct light towards the ground where it serves the public best. The International Dark-Sky Association estimates that 4 billion dollars' worth of electricity a year is lost to Sky Glow. Such a waste of electricity also causes more mercury pollution when the electricity is generated by coal-fired power plants.

The Boca Raton Sea Turtle Program also works closely with faculty from Florida Atlantic University and other universities. Past studies with Duke University demonstrated that some nests in Boca Raton had eggs that had high levels of pesticide contamination. This correlates with a decline in egg viability in recent years which is now undergoing further study and analysis. With Dr. Jeannette Wyneken at FAU, we have participated in hatchling gender ratio studies since 2002. Because the temperature of the sand that the eggs develop in determines the gender of the hatchlings, it is important to know what the ratio of boys to girls is coming off our beaches, as global warming becomes an ever-increasing problem. This research resulted in two loggerhead sea turtle hatchlings, Milton and FeeBee, to be raised at Gumbo Limbo as educational display turtles. This is the first time we have had two turtles of known gender, one boy and one girl. In 2007, the Boca Raton Sea Turtle Program provided tissue samples to the University of Georgia for a large population genetics study of loggerhead, green, and leatherback turtles. This is the first time such a detailed study was performed over a large number of different beaches in different states. The results of this study are being anxiously awaited.

The Boca Raton Sea Turtle Program is also responsible for stranded, dead or injured sea turtles in the southern third of Palm Beach County. Live turtles are given first aid and are transported to sea turtle rehabilitation facilities around the state. This research involves determining the cause of death or injury of each turtle. In Palm Beach County, almost one third of the stranded sea turtles have been hit by boats which is a major problem in Southeast Florida. Loggerhead sea turtles killed by the long-line fishing industry are also being noted. Long-line fishing is responsible for a decline of almost 50% in loggerhead nesting in the United States since 1999. Because Southeast Florida is the second largest nesting site in the world for loggerheads, this represents a significant loss to the world's loggerhead population.

To end on a good note, your support and help for sea turtle conservation programs such as Boca Raton's is making a difference for the green and leatherback sea turtles. Boca Raton recorded record high nests from these two species in 2007 and the trend for these species in the United States is definitely up. Since greens are vegetarians and leatherbacks eat jellyfish, they are not impacted by the fishing industry as the loggerheads are. This shows that your help with beachfront issues such as lighting and poaching make a difference!

SHARKS

The Elasmobranch Research Laboratory (ERL) at Florida Atlantic University primarily studies the sensory systems of sharks, skates and rays. Although the sensory systems of sharks are legendary, many claims about their sensory acuity are based upon anecdotal observation with a paucity of supporting evidence. The graduate students at the ERL collect empirical data to investigate the true sensory capabilities of sharks and their relatives.

The students conduct much of their research at the Gumbo Limbo Environmental Complex where they maintain many of their study animals in the public display tanks.

Vision
The myth that sharks have poor eyesight has persisted for decades when, in fact, most sharks have excellent vision and demonstrate various visual adaptations, such as a retractable lens and a dilatory iris, that are typically associated with more advanced organisms. Mikki McComb employs an electro-retinogram technique to determine the extent of the visual field - how much of the environment an animal can see at any given time. She also examines what wavelengths of light are the most stimulatory and the frequency at which sharks can resolve a flickering light. Particularly interesting is the question of whether hammerhead sharks, with their eyes at the distal tips of the broad head, possess significant binocular overlap of the left and right visual fields. Short answer: yes they do!

Olfaction
How often have you heard it stated that a shark can detect a single drop of blood in an Olympic-sized pool or track an odor from a mile away? These sorts of myths have been perpetuated in the absence of any empirical data.

Tricia Meredith is asking the question, "How well do sharks smell?" Tricia tests the response of various elasmobranch species to a variety of odorants including pure amino acids (the building blocks of proteins), as well as metabolites from natural prey items. She has already discovered that although sharks are very sensitive to odorants, they do not demonstrate any greater sensitivity than other fishes. So the idea that sharks are "super-smellers" is not strongly supported.

Electroreception
All elasmobranch fishes possess a unique sensory system that enables them to detect weak electric fields in their environment. That means that if a prey item were to bury in the sand and not provide any visual, olfactory, or audible cues, the shark could still detect the weak electric fields emanating from the body of the prey. Dave McGowan is studying how this exquisitely sensitive electrosensory system functions in the Atlantic stingray that lives in both a highly conductive saltwater environment as well as an insulative freshwater environment. Dave uses behavioral assays to determine the sensitivity of the rays in different salinities. He has found that the rays demonstrate much greater sensitivity in saltwater and need to be much closer to the target to initiate a response in freshwater.

Electric rays
Instead of examining one sensory system across several species, Laura Macesic conducts a suite of experiments on one particularly interesting species, the lesser electric ray. This ray uses electric organs in the pectoral fins to generate up to 60V which it uses to shock potential predators. However, the large electric organs constrain how the electric rays swim; they cannot undulate their pectoral fins like most other rays.

Instead, they have a thickened tail that they oscillate from side to side and augment that by punting along the seafloor with their modified pelvic fins. In addition to measuring the electric organ discharge, Laura is also comparing the swimming kinematics of the electric ray with a variety of other species.

The combined assets of the ERL and Gumbo Limbo Environmental Complex provide a truly world class facility that can support the diverse, innovative and avant-garde research conducted by the graduate students at the ERL.