The leatherback sea turtle is the largest of the five species that have been found in the northern Gulf of Mexico. With a carapace (top shell) length between 6-7 feet and weighing between 800-1000 pounds it is truly a magnificent creature. Any encounter with them is amazing.
Most encounters occur with fishermen or divers who are out searching for artificial reefs to fish or dive. Though very rare, they have been known to nest in this area. They feed exclusively on jellyfish and will follow them close to shore if need be. But what do leatherbacks do with most of their time? Do they hang offshore and follow jellyfish in? Do they circle the entire Gulf of Mexico and we see them as they pass? Based on past studies, many encounters with this turtle occur in the warmer months. They often become entangled in commercial fishing longlines set in the central Gulf of Mexico. But what do they do during the fall and winter? One of the tagging projects presented at a recent workshop tried to answer that question.
The project was led by Dr. Christopher Sasso of the National Oceanic and Atmospheric Administration. The tag chosen for this was a satellite tag. Since the leatherback must surface to breath air, and often is found near the surface following jellyfish, orbiting satellites would be able to follow them. As we mentioned in Part 1, catching the creature is step 1, and catching a six-foot 1000-pound sea turtle is no easy task.
The team used a spotter aircraft to locate the turtles. Once found, the pilot would radio the chase boat who would zip in with a large net. The net was connected to a large metal hoop and was designed to give way once it was around the turtle. Once in the net the turtle was hauled onto a small inflatable boat where the work of tagging could be done. They would measure the animal, take blood samples, place a PIT tag within them (similar to a microchip in your pet) and then attach the satellite tag by a tether to the tail end of the turtle before releasing it. The entire operation took less than 30 minutes.
Between 2015-2019 19 leatherbacks were tagged in the northern Gulf. 17 of these were females and 2 were males. Data obtained from these tags ranged between 63 and 247 days at liberty. The behavior the team noticed was divided into foraging behavior (feeding on jellyfish) and transiting behavior (direct swimming ignoring all).
The turtles foraged in this part of the Gulf until the fall season. At that point most of them moved south along the Florida shelf, past the western peninsula of the state, heading towards the Keys. A few chose to swim directly south against the Loop Current, and a small number remained in the area.
Those moving along the Florida shelf appeared to be foraging as they went. Those crossing the open Gulf may have foraged some but seemed to be focused on getting south to the nesting beaches. Almost all of the turtles entered the Caribbean on the east side of the Yucatan channel, following the currents, with their final destination being their nesting beaches. When they returned, they did so in the warmer months and used the western side of the channel – again following the currents – until they once again reached the northern Gulf and foraging began again. One interesting note from this study, the two males tagged did not leave the Gulf.
The tagging studies do show that leatherbacks use the Gulf of Mexico year-round. They usually head south to the Caribbean when it gets colder and use the currents to do so. It is during the warmer months we are most likely to see them here foraging on jellyfish. It is an amazing experience to encounter one of these large turtles. I hope you get to experience it one day.
Satellite tracks of leatherback movement in the GoM. Red (2015), Blue (2018), Black (2019).
Image: Sasso (et.al.) 2021.
Reference
Sasso, C.R., Richards, P.M., Benson, S.R., Judge, M., Putman, N.F., Snodgrass, D., Stacy, B.A. 2021. Leatherback Sea Turtles in the Eastern Gulf of Mexico: Foraging and Migration Behavior During the Autumn and Winter. Frontiers in Marine Science., Vol. 8., https://doi.org/10.3389/fmars.2021.660798.
This is one of the most beloved animals on the planet… sea turtles. Discussions and debates over all sorts of local issues occur but when sea turtles enter the discussion, most agree – “we like sea turtles”, “we have nothing against sea turtles”. There are nonprofit groups, professional hospitals, and special rescue centers, devoted to helping them. I think everyone would agree, seeing one swimming near the shore, or nesting, is one of the most exciting things they will ever see. For folks visiting our beaches, seeing the white sand and emerald green waters is amazing, but it takes their visit to a whole other level if they encounter a sea turtle.
The largest of the sea turtles, the leatherback. Photo: Dr. Andrew Colman
They are one of the older members of the living reptiles dating back 150 million years. Not only are they one of the largest members of the reptile group, they are some of the largest marine animals we encounter in the Gulf of Mexico.
There are five species of marine turtles in the Gulf represented by two families. The largest of them all is the giant leatherbacks (Dermochelys coriacea). This beast can reach 1000 pounds and have a carapace length of six feet. Their shell resembles a leatherjacket and does not have scales. Because of their large size, they can tolerate colder temperatures than other marine turtles and found all over the globe. They feed almost exclusively on jellyfish and often entangled in open ocean longlines. There is a problem distinguishing clear plastic bags from jellyfish and many are found dead on beaches after ingesting them. Like all sea turtles, they approach land during the summer evenings to lay their eggs above the high tide line. The eggs incubate within the nest for 65-75 days and sex determination is based on the temperature of the incubating eggs; warmer eggs producing females. Also, like other marine turtles, the hatchlings can be disoriented by artificial lighting or become trapped in human debris, or unnatural holes, on the beach. These animals are known to nest in Florida and they are currently listed as federally endangered and are completely protected.
The large head of a loggerhead sea turtle. Photo: UF IFAS
The other four species are found in the Family Chelonidae and have the characteristic scaled carapace. Much smaller than the leatherback, these are still big animals. The most common are the loggerhead sea turtles (Caretta caretta). As the name suggest, the head of this sea turtle is quite large. Their carapace can reach lengths of four feet and they can weigh up to 450 pounds. The head usually has four scutes between the eyes and three scutes along the bridge connecting the carapace to the plastron. This animal prefers to feed on a variety of invertebrates from clams, to crabs, to even horseshoe crabs. It too is an evening nester and the young have similar problems as the leatherback hatchlings. The tracks of the nesting turtle can be identified by the alternating pattern made by the flippers. One flipper first, then the next. The loggerhead is currently listed as a federally threatened species.
A green sea turtle on a Florida beach. Photo: Florida Sea Grant
The green sea turtle (Chelonia mydas) is called so not for the color of its shell, but for the color of its internal body fat. They are fans of eating seagrasses, particularly “turtle grass” and other plants, which produce the green coloration of the fat. The fat is used to produce a world favorite, “turtle soup”, and has been a problem for the conservation of this species in some parts of the world. At one time, most green turtles nested in south Florida, but each year the number nesting in the north has increased. They can be distinguished from the loggerhead in that (1) their head is not as big, (2) there are only two scales between the eyes, and (3) their flipper pattern in sand is not alternating; green turtles throw both flippers forward at the same time. Green turtles are listed as federally threatened.
A hawksbill sea turtle resting on a coral reef in the Florida Keys. Photo: Molly O’Connor
The hawksbill turtle (Eretmochelys imbricata) is more tropical in distribution. They are a bit smaller, with a carapace length of three feet and a weight of 187 pounds, but their diet of sponges is another reason you do not find them often in the northern Gulf of Mexico. To feed on these, they have a “hawks-bill” designed to rip the sponges from their anchorages. Their shell is gorgeous and prized in the jewelry trade. “Tortoise-shell” glasses and earrings are very popular.
The most endangered of them all is the small Kemp’s Ridley sea turtle (Lepidochelys kempii). This little guy has a carapace length of a little over two feet and weighs in at no more than 100 pounds. These guys are commonly seen in the Big Bend area of Florida but for years no one knew where they nested. That was until 1947 when an engineer from Mexico found them nesting in large numbers (up to 40,000) at one time, in broad daylight in Rancho Nuevo, Mexico. This was problematic for the turtle because the locals would wait for the nesting to be complete before they would take the females and the eggs. Protected today they now face the problem that their migratory path across the Gulf takes them through Texas and Louisiana shrimping grounds, and through the 2010 Deep Water Horizon oil spill field. Not to mention that illegal poaching still occurs. Though all species of sea turtles have had problem with shrimp trawls, the Kemps had a particular problem, which led to the develop of the now required Turtle Excluder Device (T.E.D.S) found on shrimp trawls in the U.S. today. Sea turtles have strong site fidelity for nesting and in the 1980s many Kemp’s Ridley eggs were re-located to beaches in Texas in hopes to move the nesting to other locations. The program had some success and they have been reported to nest in Florida. Their diet consists primarily of crabs but there have been reports of them removing bait from fishing lines fishing from piers over the Gulf. This is species is federally endangered and is considered by many to be the most endangered sea turtle species on the planet.
Turtle friendly lighting. Photo: Rick O’Connor
Sea turtles face numerous human-caused problems including (1) artificial lighting that disorient hatchlings and cause mortality to 50% (or more) of the hatchlings, (2) items left on beaches (such as chairs, tents, etc.) that can impede adults and entrap hatchlings, (3) large holes dug on beaches in which hatchlings fall and cannot get out, (4) marine debris (such as plastics) which they confuse with prey and swallow, (5) boat strikes, sea turtles must surface to breath and can become easy targets, and (6) discarded fishing gear, in which they can become entangled and drown. These are simple things we can correct and protect these amazing Florida turtles.
References
Buhlmann, K., T. Tuberville, W. Gibbons. 2008. Turtles of the Southeast. University of Georgia Press, Athens GA. Pp. 252.
There are five species of sea turtles that nest from May through August on Florida beaches, with hatching stretching out until October. The loggerhead, the green turtle, and the leatherback all nest regularly in the Panhandle, with the loggerhead being the most frequent visitor. Two other species, the hawksbill and Kemp’s Ridley nest infrequently. All five species are listed as either threatened or endangered under the Endangered Species Act. Due to their threatened and endangered status, the Fish and Wildlife Conservation Commission/Fish and Wildlife Research Institute monitors sea turtle nesting activity on an annual basis.
A group checks out a recently hatched sea turtle nest on the dunes in south Walton county in Florida.
Annual total nest counts for loggerhead sea turtles on Florida’s index beaches fluctuate widely and scientists do not yet understand fully what drives these changes. From 2011 to 2018, an average of 106,625 sea turtle nests (all species combined) were recorded annually on these monitored beaches. In 2018, there was a slight decrease in nests with only 96,945 nests recorded statewide. This is not a true reflection of all of the sea turtle nests each year in Florida, as it doesn’t cover every beach, but it gives a good indication of nesting trends and distribution of species.
2015-2018 Florida Panhandle turtle nesting totals for all species.
If you want to see a sea turtle in the Florida Panhandle, please visit one of the state-permitted captive sea turtle facilities listed below, admission fees may be charged. Please call the number listed for more information.
Between multiple days below freezing, tough traveling, and the flu it has been a brutal winter season so far.
Dead Kemps Ridley Sea Turtle washed ashore in Little Sabine near Pensacola Beach. This turtle died of ingesting monofilament fishing line. Photo: Betsy Walker
It is not that different for some of our marine wildlife friends. The low temperatures have driven marine water temperatures down as well, particularly in the shallow areas. There have been many reports of cold stunned sea turtles up and down the Florida panhandle – over 900 of them. There have been reports of cold stunned iguanas falling from trees and the loss of pythons in south Florida. The question sometimes comes up – “how do they deal with this apparent return from the dead?”
One has to remember we are dealing with reptiles – cold-blooded creatures. Actually, the more correct term is poikilothermic. It really does not pertain to the temperature of their blood but their core body temperature in general. Some animals, like humans, can maintain a constant body temperature, like 98.6°F, no matter what the environmental temperatures are – these are referred to as homotherms. Heterotherms can allow their body temperatures fluctuate within a range – but are in control of their body temperatures. The poikilotherms cannot control their body temperature and are thus at the mercy of the environment – the classic “cold blood”. Some of these poikilotherms have been known to actually freeze and thaw – with no observable problems, not so much for our “warm blooded” friends.
So what’s up with the cold-stunned situation?
Well… even with the “cold bloods”, extreme temperature changes can be very stressful. Some respond by changing their behavior, others their physiology, others both. They will alter their feeding – basically stop. In some, the pH and ion balance within their blood becomes unbalanced, which can trigger the feeding reduction response and increase ion exchange within the lungs. The partial pressure within the venous blood can decrease and this, along with the chemical imbalance and feeding reduction, can trigger a “lethargic” response and even a “floating” response in the marine turtles.
Locally, it seems to be the sea turtles who are having the most problems. In south Florida, scientists have noticed the American Crocodile and the invasive pythons struggle with these cold temperatures but the wider ranged American Alligator and numerous species of native snakes do not. The “locals” seem to alter their behavior to adjust for these extreme temperature drops – a method that the tropical species are not practicing. It is known that certain native freshwater turtles over winter in frozen ponds, and diamondback terrapins are known to “hunker down” in muddy bottoms of salt marsh creeks when water temperatures drop below 59°F.
With sea turtles, the larger migratory individuals offshore are still moving at 43°F but is the smaller inshore juveniles that are the subject of stunning events. The water temperatures change more rapidly in shallower water and at 43°F, these smaller sea turtles become lethargic and float – which increases their chance of predation. Data suggest that Green Sea Turtles begin to slow activity and Kemps Ridleys become more agitated when water temperatures drop below 68°F, both become dormant, reduce feeding and breathing when they drop below 59°F. It is believed the real problems from being cold stunned are from the reduction of food as much, if not more than, the actual temperature itself. The “cold bloods” bask to increase their body temperatures so that they can actually digest their food.
It is a problem frequently encountered along the American east coast but not as much in Florida. However, this year has been different. The staff and volunteers from government agencies and local aquaria have done a champion job rescuing and rehabilitating many of these animals.
References
Mazzotti, F. J., M. S. Cherkiss, M. Parry, J. Beauchamp, M. Rochford, B. Smith, K. Hart, and L. A. Brandt. 2016. Large reptiles and cold temperatures: do extreme cold spells set distributional limits for tropical reptiles in Florida? Ecosphere 7(8):e01439. 10.1002/ecs2.1439
Moon D.Y., D.S. MacKenzie, D.W. Owens. 1997. Simulated Hibernation of Sea Turtles in the Laboratory: I. Feeding, Breathing Frequency, Blood PH, and Blood Gases. The Journal of Experimental Zoology. 278: pp. 362-380.
Milton, S.A., P.L. Lutz. 2003. The Biology of Sea Turtles, Volume II. Edited P.L. Lutz, J.A. Musick, J. Wyneken. CRC Press. Pp. 510.
There are five species of sea turtles that nest from May through October on Florida beaches. The loggerhead, the green turtle and the leatherback all nest regularly in the Panhandle, with the loggerhead being the most frequent visitor. Two other species, the hawksbill and Kemp’s Ridley nest infrequently. All five species are listed as either threatened or endangered under the Endangered Species Act.
Due to their threatened and endangered status, the Fish and Wildlife Conservation Commission/Fish and Wildlife Research Institute monitors sea turtle nesting activity on an annual basis. They conduct surveys using a network of permit holders specially trained to collect this type of information. Managers then use the results to identify important nesting sites, provide enhanced protection and minimize the impacts of human activities.
Statewide, approximately 215 beaches are surveyed annually, representing about 825 miles. From 2011 to 2015, an average of 106,625 sea turtle nests (all species combined) were recorded annually on these monitored beaches. This is not a true reflection of all of the sea turtle nests each year in Florida, as it doesn’t cover every beach, but it gives a good indication of nesting trends and distribution of species.
If you want to see a sea turtle in the Florida Panhandle, please visit one of the state-permitted captive sea turtle facilities listed below, admission fees may be charged. Please call the number listed for more information.
To watch a female loggerhead turtle nest on the beach, please join a permitted public turtle watch. During sea turtle nesting season, The Emerald Coast CVB/Okaloosa County Tourist Development Council offers Nighttime Educational Beach Walks. The walks are part of an effort to protect the sea turtle populations along the Emerald Coast, increase ecotourism in the area and provide additional family-friendly activities. For more information or to sign up, please email ECTurtleWatch@gmail.com. An event page may also be found on the Emerald Coast CVB’s Facebook page: facebook.com/FloridasEmeraldCoast.
