The Conservation of the Loggerhead Sea Turtle

The Conservation of the Loggerhead Sea Turtle

The Loggerhead Sea Turtle is one of the most common sea turtles in the ocean. With a reddish-brown heart shaped shell with rough scales they have length ranging from around 25 cm in juvenile turtles to 92 cm in mature loggerheads.

Loggerhead sea turtle swimming in the ocean. Source: https://www.wildrepublic.com/product/loggerhead-sea-turtle/

Diet

Loggerheads are mostly carnivores consuming mostly invertebrates. In studies from 2008 and 2011, they found that loggerheads have a wide range of prey, but the prey they most commonly found came from the taxas: Gastropoda (snails and slugs), Bivalia (clams, molluscs), Malacostraca (crustaceans), and Echinoidea (sea urchins). However, with their lack of discrimination in food choice, loggerheads will eat almost anything, making them prone to consuming ocean pollution. (Casale P et al.,2008; Lazar et al., 2011).

Loggerhead catching a lobster in the Bahamas. Source: http://www.wilddolphinproject.org/seaturtlerelease-kraken-conservation-win/

Life History

Loggerheads are very migratory animals and can be found almost anywhere in the world’s oceans, but prefer along the shallow coasts of the Atlantic, Pacific, and Indian Oceans (Parker et al., 2005. The estimated lifespan of a loggerhead is 62 years (Amorocho, 2003). A loggerhead’s life history can be divided into three periods of when the loggerhead is a hatchling, a juvenile, and a mature adult. As a hatchling, they live in the pelagic zone which is beyond the continental shelf, a relatively shallow part of the ocean. They stay in the pelagic zone as a juvenile, once they begin to mature they will move back to the coastal waters, or the neritic zone (Van Buskirk, J., etc.,1994; Witzell, W. N., 2002; Seminoff, J. A.,etc., 2004; Casale P, etc., 2008). Picture Source: https://www.slideshare.net/CREATIVEAvro/sea-turtles-introduction

Loggerhead hatchlings in North Carolina heading to the ocean. Source: https://www.popsci.com/world-turtle-day-pictures/#page-14

Loggerheads mate along the coast every two to five years and will nest their eggs on the natal beach, which is the beach where they were hatched (Seminoff et al., 2004). The temperature of the sand determines the sex of the hatchling. Warmer temperatures result in a female and colder temperatures result in a male, making them vulnerable to raising temperatures from climate change (Mrosovsky, etc., 1992). Loggerheads lay 2 to 10 nests per season with many eggs per nest because of a high mortality rate. According to one study, they found loggerhead hatchlings have a 0.53% chance of making it to the ocean after hatching (Van Buskirk, J., etc.,1994). 

Loggerhead hatchling coming out of its egg. Source: https://kids.nationalgeographic.com/animals/reptiles/loggerhead-sea-turtle/

Ecological Role

Loggerhead turtles are a keystone species meaning that their presence is crucial for the survival of their ecosystems. When the turtles lay their eggs, the shells provide nutrients for the beach environment, allowing more vegetation to grow in the sand dunes, contributing to the health of the ecosystem. These shells are also a food source of which more than a hundred species consume. The eggs and hatchlings also provide a food source for predators, without which would hurt these predator populations (Lovich et al., 2018).

Loggerhead nest at a Florida beach. Source: https://wildcumberland.org/sea-turtles/

Loggerheads also provide nutrients like calcium to the ocean floor through the excreted shell remains of the invertebrates they consume through a process called bioturbation. And with these species on their shell, as they travel through the ocean, some fish will feed off the organisms on their shell, especially in nutrient deficient areas. Loggerheads also help with nutrient distribution by shifting up the sand at the bottom of the ocean in search of shellfish and other invertebrates. (Lazar et al., 2011, Lovich et al., 2018). Loggerheads also provide an “epibiont community” of hundreds of species like barnacles, sponges, algae, slugs, sea snails and more. In other words, they are the host of many organisms on the back of their shells with 94% of loggerheads being the host of at least one species of barnacles on their shell and sometimes several dozens of species on their shell (MICHAEL et al.,1998; Rawson et al., 2003; Pfaller et al., 2008).

Loggerhead with epibionts on shell. Source: https://www.chesapeakebay.net/discover/field-guide/entry/loggerhead_turtle

Conservation Status

Loggerheads are listed as threatened by the U.S. Federal Endangered Species Act and vulnerable by the International Union for Conservation of Nature and Natural Resources. According to the 5-Year Review of the North Pacific Loggerhead Evaluation, they have the North Pacific Loggerhead has a small abundance of around 8,733 nesting females (Fisheries, NOAA, 2020).  Some of the biggest threats include coastal development in nesting areas, which causes erosion and destruction of the nesting habitats of the turtles, and fisheries that unintentionally capture the turtles in their nets. Other threats include excessive nest predation from native and nonnative species, hunting, ocean and beach pollution, artificial lighting (which disorients the hatchlings, preventing them from making it to the ocean), disease, and climate change. (Tomás et al., 2002; Salmon et al., 2003; Seminoff et al., 2004; Fisheries, NOAA, 2020). Of these threats almost all of them are human created that still pose risks to the species to this day. 

Recovery Plan

In an effort to combat this, a recovery plan has been put in place in an attempt to decrease the threats against loggerheads so they no longer require protection under the Endangered Species Act. Five recovery units were established in nesting areas of Northwest Atlantic Loggerheads in an effort of conservation. In the plan, 77 actions were put into place with varying priority. Costs and actions are still ongoing. One example of an ongoing Priority 1 action is action number 122 which is to keep track of the nesting trends on beaches, this action has a cost of $3750. The Responsible parties for this action the Florida Fish and Wildlife Conservation Commission (FFWCC), Georgia Department of Natural Resources(GDNR), South Carolina Department of Natural Resources (SCDNR), North Carolina Wildlife Resources Commission (NCWRC), Alabama Department of Conservation and Natural Resources (ADCNR). A full list of the current actions, costs, and responsible parties can be found at:

https://ecos.fws.gov/docs/recovery_plan/090116.pdf, (Pg. 201-239)

Loggerhead turtle with satellite tag on shell for tracking. Source: https://www.fisheries.noaa.gov/species/loggerhead-turtle#science

Conclusion

As a keystone species, the survival of the Loggerhead turtles is critical. Without Loggerheads, animals will lose food sources, nutrients will not get distributed, organisms will lose their habitats, and the health of the overall ecosystem will decline. Without them, there would be detrimental effects and that is why the costs of the recovery plan are a necessity. An effort needs to be made to save these turtles or many more organisms will die. The future looks hopeful for the loggerheads with the 5-Year Review of the North Pacific Loggerhead Evaluation noting a 2.3% annual increase in population growth for the species with conservation efforts in place. However, more needs to be done to see not just improvement, but a full recovery.

References

Amorocho, D. (2003). Monitoring nesting loggerhead turtles (Caretta caretta) in the central caribbean coast of Colombia. Marine turtle newsletter, 101, 8-13.

Casale P, Abbate G, Freggi D, Conte N, Oliverio M, Argano R (2008) Foraging ecology of loggerhead sea turtles Caretta caretta in the central Mediterranean Sea: evidence for a relaxed life history model. Mar Ecol Prog Ser 372:265-276.

Fisheries, N. (2020, April 07). North Pacific Ocean Distinct Population Segment of Loggerhead Sea Turtle 5-Year Review. Retrieved August 31, 2020, from https://www.fisheries.noaa.gov/resource/document/north-pacific-ocean-distinct-population-segment-loggerhead-sea-turtle-5-year

Lazar, B., Gračan, R., Katić, J., Zavodnik, D., Jaklin, A., & Tvrtković, N. (2011). Loggerhead sea turtles (Caretta caretta) as bioturbators in neritic habitats: an insight through the analysis of benthic molluscs in the diet. Marine Ecology, 32(1), 65-74.

Lovich, J. E., Ennen, J. R., Agha, M., & Gibbons, J. W. (2018). Where have all the turtles gone, and why does it matter?. BioScience, 68(10), 771-781.

MICHAEL, G. F., Williams, K. L., & MICHAEL, R. (1998). Epibionts associated with nesting loggerhead sea turtles (Caretta caretta) in Georgia, USA. Herpetological Review, 29, 4.

Mrosovsky, N. A. J. P., & Provancha, J. (1992). Sex ratio of hatchling loggerhead sea turtles: data and estimates from a 5-year study. Canadian Journal of Zoology, 70(3), 530-538.

Parker, Denise M. and Cooke, William J. and Balazs, George H. (2005) Diet of oceanic loggerhead sea turtles (Caretta caretta) in the central North Pacific. Fishery Bulletin, 103(1), pp. 142-152.

Pfaller, J. B., Frick, M. G., Reich, K. J., Williams, K. L., & Bjorndal, K. A. (2008). Carapace epibionts of loggerhead turtles (Caretta caretta) nesting at Canaveral National Seashore, Florida. Journal of Natural History, 42(13-14), 1095-1102.

Rawson, P. D., Macnamee, R., Frick, M. G., & Williams, K. L. (2003). Phylogeography of the coronulid barnacle, Chelonibia testudinaria, from loggerhead sea turtles, Caretta caretta. Molecular Ecology, 12(10), 2697-2706.

Salmon, M. (2003). Artificial night lighting and sea turtles. Biologist, 50(4), 163-168.

Seminoff, J. A., Resendiz, A., Resendiz, B., & Nichols, W. J. (2004). Occurrence of loggerhead sea turtles (Caretta caretta) in the Gulf of California, Mexico: evidence of life-history variation in the Pacific Ocean. Herpetological Review, 35(1), 24.

Tomás, J., Guitart, R., Mateo, R., & Raga, J. A. (2002). Marine debris ingestion in loggerhead sea turtles, Caretta caretta, from the Western Mediterranean. Marine Pollution Bulletin, 44(3), 211-216.

Van Buskirk, J., & Crowder, L. B. (1994). Life-history variation in marine turtles. Copeia, 66-81.

Witzell, W. N. (2002). Immature Atlantic loggerhead turtles (Caretta caretta): suggested changes to the life history model. Herpetological Review, 33(4), 266.

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