Species Description: The loggerhead sea turtle (Caretta caretta) is the only remaining extant member in this genus. It is known for its relatively large head (thus the name "loggerhead"). Adult carapace length averages about 100 cm and weighs about 165 kg. (Conant 1975). Record weights and carapace lengths are 227 kg and 114 cm, respectively (Lowe et. al 1990). The carapace is reddish-brown with five or more pleural scutes. The broad head varies from reddish-olive brown to yellow. The limbs are modified as flippers. Adult males are distinguished by long tails that extend beyond the rear carapace in addition to a narrowing of the carapace that tapers posteriorly (Ernst and Barbour 1989). Hatchlings are dull brown in color. Average size at hatching is 45 mm long; average weight is 20 g.
Regional Occurrence: The loggerhead turtle is circumglobal, and inhabits continental shelves, bays, estuaries, and lagoons in temperate, subtropical, and tropical waters throughout the world. In the Atlantic, the loggerhead turtle's range extends from Newfoundland to as far south as Argentina, with no clear home-ranges defined to date (Lowe et al. 1990). During the summer, nesting occurs in the lower latitudes, but not in the tropics. The world's largest nesting population is found on the beaches of Oman. The second largest nesting group is found along Florida's east coast, and it is with this stock that the U.S. Fish and Wildlife Service is primarily concerned. Loggerheads have been seen in estuaries as far north as New England and the Canadian Maritime Provinces. Nesting is common from Florida through North Carolina, but again, the majority of loggerheads are found in Florida.
Southern Japan is the only known breeding area in the North Pacific. In the eastern Pacific, loggerheads have been sighted from Alaska to Chile, with occasional sightings also reported from coastal Washington. The majority of U.S. West Coast sightings involve juveniles spotted off the California coast.
IRL Distribution: Caretta caretta occurs throughout the Indian River Lagoon.
Abundance: The loggerhead turtle was listed by the U.S. Fish and Wildlife Service as threatened in June 1970, and its status has remained unchanged. Several nesting subpopulations of loggerheads in the western North Atlantic have been identified based on genetic research. The northern subpopulation occurs from North Carolina to northeastern Florida, and produces approximately 6,200 nests/year. This subpopulation declined throughout the mid-1980s, and thereafter no population trends have been detected. Recent surveys of South Carolina nesting beaches (utilized by more than 30% of the nesting northern subpopulation) indicate a downward trend, and thus the subpopulation is apparently stable or declining.
The South Florida subpopulation, occurs from just north of Cape Canaveral, Florida and extends to Naples on the west coast of Florida. The South Florida subpopulation appears to have shown significant increases over the last 25 years, suggesting the population is recovering. An increase in the number of adult loggerheads has been reported in recent years in Florida waters, however, there has been no detectable increase in the number of benthic juveniles. Since loggerheads take approximately 20-30 years to mature, the effects of decline in immature loggerheads might not be apparent on nesting beaches for decades. If real, this decline of juveniles would signal an overall population decline.
Loggerhead populations in Panama, Mexico, the Bahamas, Cuba, Honduras, Colombia, Israel, Turkey, Greece, and Japan, have been declining in recent years, and can be primarily attributed to human impacts. Coastal development, increased human use of nesting beaches, and pollution cause the most severe impacts to loggerhead nest sites, while shrimp trawling negatively impacts loggerheads in open waters. Shrimping is thought to have played a significant role in the worldwide population declines observed for the loggerhead.
Locomotion: Primarily swimming; walks while nesting on ocean beaches
Reproduction: Caretta caretta reaches sexual maturity at 12-35 years, with Lutz and Musick (1997) reporting 25-35 years. Copulation occurs at sea at no particular time of day or night. Nesting occurs throughout the summer, predominately at night on ocean beaches with well-drained sand dunes. Females use their flippers to dig nests in the soft sand, and deposit clutches of approximately 100-120 eggs into the nests. After nesting, females cover the eggs with sand and return to the water. Eggs require up to 60 days to develop before hatching. Females may nest 2 - 4 times per season, with 4 nests per season reported by Hopkins and Murphy (1984). Two- and three-year nesting cycles have been reported.
Several factors affect the sexual determination of the hatchlings but much of it can be accounted for by nest sand temperature. The pivotal temperature for this species is approximately 29.0°C. Lower temperatures encourage male development, while warmer temperatures influence the development of females. Mrosovsky and Provancha (1992) found hatchlings at Cape Canaveral were predominately females (80-95%) over a five-year study.
Temperature: Optimum temperature range of both juveniles and adults is subtropical and warm temperate.
Trophic Mode: Caretta caretta is omnivorous, with a diet that includes sponges, crabs, clams, mussels, various fish. It is also known to eat jellyfish, seaweed and seagrass (Ernst and Barbour 1989). Mendonca and Ehrhart (1982) reported that the predominant food item found in Mosquito Lagoon loggerheads was Limulus polyphemus, the horseshoe crab. Recent studies by Provancha et al. (1997) indicate this prey item is in severe decline.
Competitors: The loggerhead is the most abundant of the sea turtle species in Florida waters, however, it most likely competes with other sea turtles for food.
Habitat: The loggerhead wanders throughout marine waters in its range. It enters bays, lagoons, and the mouths of rivers. There are essentially four habitats along the Florida coast used by loggerheads. Nesting adults utilize ocean beaches to deposit their eggs for incubation. Considerable nesting occurs along the IRL beaches each summer between April and September. About 98% of all sea turtle nests are those of loggerheads (Provancha and Ehrhart 1987). Hatchling sea turtles emerge from the nesting beach and enter the sea, swimming out to the sargassum driftlines where they find shelter and food (Carr 1986). The post-hatchling size class of 20-40 cm, previously known as the "lost year", drifts its way to the eastern Atlantic, where it forages and grows along the Azores and Canary Islands. The IRL estuary provides developmental habitat for subadult animals, 50 to 80 cm SL carapace length, (Ehrhart 1983, Provancha et al 1997). Netting surveys in the late 1970's, 1990's and various cold-stunning episodes (see species report on the green turtle) have yielded basic data about the lagoon population (Witherington and Ehrhart 1989, Provancha et al 1997). The loggerhead displays some degree of residency in the lagoon but appears to migrate to and from the ocean more than the green turtle (Chelonia mydas).
Activity Time: Loggerhead turtles are seen on land almost exclusively in the evening hours, but are active throughout the day.
Special Status: Threatened/Endangered
Notes on Special Status:: Caretta caretta is listed as threatened by U.S. Fish & Wildlife Service. The most significant threats to loggerhead populations are coastal development, commercial fisheries, and marine pollution.
Benefit in the IRL: Aesthetic value; may also be good indicator species whose population trends are reflective of habitat degradation.
Ackerman, R.A. 1980. Physiological and Ecological Aspects of Gas Exchange by Sea Turtle Eggs. Amer. Zool. 20:575-583.
Bjorndal, K.A., and A.B. Bolten. 1988. Growth Rates of Immature Green Turtles, Chelonia mydas, on Feeding Grounds in the Southern Bahamas. Copeia 3:555-564.
Carr, A. 1980. Some Problems of Sea Turtle Ecology. Amer. Zool. 20:489-498.
Carr, A., L. Ogren, et al. 1981. Apparent Hibernation by the Atlantic Loggerhead Turtle Caretta caretta Off Cape Canaveral, Florida. Biological Conservation 19:7-14.
Collard, S.B., and L.H. Ogren. 1990. Dispersal Scenarios for Pelagic Post-Hatchling Sea Turtles. Bulletin of Marine Science 47(1):233-243.
Ehrhart, L.M. 1983. Marine Turtles of the Indian River Lagoon System. Florida Scientist 46(3/4):337-346.
Grassman, M.A., and D.W. Owens. 1982. Development and Extinction of Food Preferences in the Loggerhead Sea Turtle, Caretta caretta. Copeia 4:965-969.
Hendrickson, J.R. 1980. The Ecological Strategies of Sea Turtles. Amer. Zool. 20:597-608.
Henwood, T.A. 1987a. Distribution and Migrations of Immature Kemp's Ridley Turtles (Lepidochelys kempi) and Green Turtles (Chelonia mydas) Off Florida, Georgia, and South Carolina. Northeast Gulf Science 9(2):153-159.
Henwood, T.A. 1987b. Movements and Seasonal Changes in Loggerhead Turtle Caretta caretta Aggregations in the Vicinity of Cape Canaveral, Florida (1978-84). Biological Conservation 40:191-202.
Hirth, H.F. 1980. Some Aspects of the Nesting Behavior and Reproductive Biology of Sea Turtles. Amer. Zool. 20:507-523.
Johnson, S.A., K.A. Bjorndal, et al. 1996. Effects of Organized Turtle Watches on Loggerhead (Caretta caretta) Nesting Behavior and Hatchling Production in Florida. Conservation Biology 10(2):570-577.
Killingley, J.S., and M. Lutcavage. 1983. Loggerhead Turtle Movements Reconstructed from O and C Profiles from Commensal Barnacle Shells. Estuarine, Coastal and Shelf Science 16:345-349.
Light, P. 1980. Evolutionary and Functional Aspects of Pituitary Gonadotropins in the Green Turtle, Chelonia Mydas. Amer. Zool. 20:565-574.
Lohmann, K.J., M. Salmon, et al. 1990. Functional Autonomy of Land and Sea Orientation Systems in Sea Turtle Hatchlings. Biol. Bull. 179:214-218.
Mendonca, M.T., and L.M. Ehrhart. 1982. Activity, Population Size and Structure of Immature Chelonia mydas and Caretta caretta in Mosquito Lagoon, Florida. Copeia 1:161-167.
Mendonca, M.T. 1983. Movements and Feeding Ecology of Immature Green Turtles (Chelonia mydas) in a Florida Lagoon. Copeia 4:1013-1023.
Meylan, A., B. Schroeder, et al. 1995. Sea Turtle Nesting Activity in the State of Florida 1979-1992. Florida Marine Research Publications, Number 52. (51 pages).
Mrosovsky, N., and P.C.H. Pritchard. 1971. Body Temperatures of Dermochelys coriacea and Other Sea Turtles. Copeia 4:624-631.
Mrosovsky, N. 1980. Thermal Biology of Sea Turtles. Amer. Zool. 20:531-547.
Mrosovsky, N., and J. Provancha. 1989. Sex Ratio of Loggerhead Sea Turtles Hatching on a Florida Beach. Can. J. Zool. 67:2533-2539.
Mrosovsky, N., C. Lavin, et al. 1995. Thermal Effects of Condominiums on a Turtle Beach in Florida. Biological Conservation 74:151-156.
Ogren, L.H., J. Watson, et al. 1977. Loggerhead Sea Turtles, Caretta caretta, Encountering Shrimp Trawls. Marine Fisheries Review 39(11):15-17.
O'Hara, J. 1980. Thermal Influences on the Swimming Speed of Loggerhead Turtle Hatchlings. Copeia 4:773-780.
Owens, D.W. 1980. The Comparative Reproductive Physiology of Sea Turtles. Amer. Zool. 20:549-563.
Pritchard, P.C.H. 1980. The Conservation of Sea Turtles: Practices and Problems. Amer. Zool. 20:609-617.
Rabalais, S.C., and N.N. Rabalais. 1980. The Occurrence of Sea Turtles on the South Texas Coast. Contributions in Marine Science 23:123-129
Salmon, M., and K.J. Lohmann. 1989. Orientation Cues Used by Hatchling Loggerhead Sea Turtles (Caretta caretta L.) During Their Offshore Migration. Ethology 83:215-228.
Salmon, M., M.G. Tolbert, et al. 1995. Behavior of Loggerhead Sea Turtles on an Urban Beach. II. Hatchling Orientation. Journal of Herpetology 29(4):568-576.
Salmon, M., and B.E. Witherington. 1995. Artificial Lighting and Seafinding by Loggerhead Hatchlings: Evidence for Lunar Modulation. Copeia 4:931-938.
Talbert, J.O., S.E. Stancyk, et al. 1980. Nesting Activity of the Loggerhead Turtle (Caretta caretta). Copeia 4:709-718.
Timko, R.E., and A.L. Kolz. 1982. Satellite Sea Turtle Tracking. Mar. Fish. Rev. 44(4):19-24.
Uchida, I. 1967. On the Growth of the Loggerhead Turtle, Caretta caretta Under Rearing Conditions. Bulletin of the Japanese Society of Scientific Fisheries 6:497-507.
Wibbels, T., R.E. Martin, et al. 1991. Female-Biased Sex Ratio of Immature Loggerhead Sea Turtles Inhabiting the Atlantic Coastal Waters of Florida. Can. J. Zool. 69:2973-2977.
Witham, R., and C.R. Futch. 1977. Early Growth and Oceanic Survival of Pen-Reared Sea Turtles. Herpetologica 33:404-409.
Witham, R. 1980. The "Lost Year" Question in Young Sea Turtles. Amer. Zool. 20:525-530.
Witherington, B.E. 1991. Orientation of Hatchling Loggerhead Turtles at Sea Off Artificially Lighted and Dark Beaches. J. Exp. Mar. Biol. Ecol. 149:1-11.
Wood, J.R., and F.E. Woof. 1980. Reproductive Biology of Captive Green Sea Turtles Chelonia mydas. Amer. Zool. 20:499-505.
Worth, D.F., and J.B. Smith. 1976. Marine Turtle Nesting on Hutchinson Island, Florida, in 1973. Florida Marine Research Publications 18:1-17.
Zangerl, R. 1980. Patterns of Phylogenetic Differentiation in the Toxochelyid and Cheloniid Sea Turtles. Amer. Zool. 20:585-596.