Kemp's ridley sea turtle

Nesting Kemp's Ridley Sea Turtle
Click on the image above to learn more about efforts of the Division of Sea Turtle Science and Recovery to study and protect Kemp’s ridley sea turtles. NPS Photo.

Species: Kemp’s ridley (Lepidochelys kempii)
Size: Adult carapace (upper shell) length = 24-28 inches (60-70 cm) (National Marine Fisheries Service 2015)
Adult weight = 70-100 pounds (32-45 kg) (National Marine Fisheries Service et al 2011)
Coloration: Hatchlings are charcoal gray; adults are olive green above and yellow below
Range: Historic nesting –Historically, nesting occurred on Gulf of Mexico beaches from Mustang Island, Texas to Vera Cruz, Mexico; the vast majority of nesting occurred in
Tamaulipas, Mexico; nesting was first documented in both Mexico and Texas in the 1940s (National Marine Fisheries Service et al 2011).

Current nesting – Currently, nesting occurs on Gulf of Mexico beaches from Bolivar Peninsula, Texas to Vera Cruz, Mexico; 95% of worldwide nesting occurs in Tamaulipas, Mexico; each year a few nests are found in other U.S. states (National Marine Fisheries Service et al 2011)
Non-nesting – Juveniles occur in nearshore waters along the Gulf of Mexico and the Atlantic coasts as far north as Nova Scotia; a few juveniles have been recorded in Europe; adults occur in nearshore waters along the Gulf of Mexico coast from Florida to the Yucatan Peninsula (Shaver et al. 2005, Morrealle et al. 2007, Shaver and Rubio 2008, National Marine Fisheries Service et al 2011, Shaver et al. 2013)
Diet: Primarily crabs and also fish, jellyfish, and mollusks (Shaver 1991, National Marine Fisheries Service 2015)
Lifespan: Unknown; reach sexual maturity at 10-16 years (Caillouet et al. 2011, National Marine Fisheries Service et al 2011)
Status: Federally endangered

Nesting season: Mid-March through August; females nest every 1-3 years and can lay 1-4 clutches in one nesting season; each nest contains an average of 100 eggs that take 6-8 weeks to hatch (Shaver 1992, National Marine Fisheries Service et al 2011)
Historic population: At least 40,000 females nesting in Mexico annually in the 1940s (National Marine Fisheries Service et al 2011)
Lowest population: Less than 300 females nesting in Mexico in 1985 (National Marine Fisheries Service et al 2011)
Current population: Current estimates include 5,500 females nesting in Mexico annually and about 55 females nesting in Texas annually
Population trends: Declining; populations increased 12-19% annually in Texas and Mexico from 1997 through 2009 (National Marine Fisheries Service et al 2011); reduced numbers were found in 2010, 2013, 2014, and 2015; the numbers found in 2011 and 2012 were similar to 2009 levels
Reasons for decline: Historic direct harvest of eggs and nesting adults; historic and ongoing incidental capture in fishing gear; other ongoing human impacts and environmental degradation of the Gulf of Mexico (Caillouet et al. 1991, Caillouet et al. 1996, Shaver 1998a, Shaver 1998b, National Marine Fisheries Service et al 2011)
Current threats: Incidental capture in fishing gear; degradation of marine and nesting habitat (Lewison et al. 2003, National Marine Fisheries Service 2015)

FUN AND FASCINATING FACTS about the Kemp’s ridley:

  • Roundabout! The Kemp’s ridley is the only sea turtle with an almost circular carapace (upper shell).
  • I’ll take the day shift…..Kemp’s ridleys are the only sea turtles nesting primarily during the day. This may be a strategy to make it harder for nocturnal predators like raccoons to follow their tracks or scent and find their eggs.
  • She’s hot, and he’s cool! The gender of each baby turtle is determined by the temperature at which the egg incubates, with warmer temperatures creating females and cooler temperatures creating males (National Marine Fisheries Service et al 2011, LeBlanc et al. 2012).
  • All eggs are not created equal….Despite incubating together, the eggs from one nest do not usually produce hatchlings that are all the same gender. In a typical nest, eggs in the center of the clutch are warmer than eggs at the outside edge due to metabolic heat created by the surrounding eggs. So hatchlings from eggs in the center are more likely to be females, and hatchlings from eggs on the outer edges are more likely to be males (LeBlanc et al. 2012).
  • A life at sea! Once they enter the water shortly after hatching, male Kemp’s ridleys never come ashore again unless injured or sick (National Marine Fisheries Service 2011).
  • There’s something about Padre! Most nests are found in Mexico. Southern Texas is at the northern end of the Kemp’s ridley documented historic nesting range. More nests are found at Padre Island National Seashore than any other location in the United States (Shaver and Caillouet 2015)!
  • A true Texas turtle…. Texas is the only state in the U.S. where Kemp’s ridleys are native, with nesting records dating back to the 1940s. Kemp’s ridleys almost disappeared, but intensive conservation efforts increased populations in both Texas and Mexico. Communities have expressed support for this unique part of Texas heritage in many ways, from water tower murals to festivals and more. The state legislature has even designated the Kemp’s ridley as the Texas State Turtle!
  • Arribada! Ridleys are the only sea turtles nesting in groups called arribadas (Spanish for “great arrivals”). Just prior to an arribada, Females gather off shore. Suddenly, the females make their way towards the shore, crawling onto the beach to nest during a single nesting event. Biologist believe nesting in groups is a strategy to reduce predation by overwhelming the predators with numbers. Raccoons and other predators may find and eat some of the eggs. Eventually, thousands of hatchlings will emerge about the same time, again overwhelming potential predators such as crabs, birds, and fish.
  • Turtles as far as the eye could see….in 1947, a pilot flying over Rancho Nuevo in Tamaulipas, Mexico, witnessed thousands of sea turtles crawling on the beach! He heard rumors of such an event and was prepared with a video camera. He landed and filmed the turtles as they nested. When scientists discovered this film in the 1960s, they analyzed the footage and estimated 40,000 female Kemp’s ridley sea turtles came ashore to nest on the beach at Rancho Nuevo on that one day (National Marine Fisheries Service et al 2011)!
  • All their eggs in one basket…. Kemp’s ridleys are the most endangered sea turtles in the world. The known world annual nesting population plunged from at least 40,000 females in the 1940s to less than 300 females in the mid-1980s! The species was very vulnerable to extinction. Although, Mexico initiated conservation efforts in the 1960s, the population continued to decline. By the 1970s, almost all known nesting was occurring at Rancho Nuevo (National Marine Fisheries Service et al 2011).
  • Back from the brink? In 1978, the U.S. joined conservation efforts. A multi-agency, international program was conducted to boost nesting at Padre Island National Seashore. This helped to re-establish a nesting colony at a protected area in the U.S. where nesting had previously occurred and provided safeguards against species extinction (Fontaine and Shaver 2005, Shaver 2005, Shaver and Wibbels 2007, Caillouet et al. 2015, Shaver and Caillouet 2015). Since then, extensive conservation efforts have continued in Mexico and the U.S., including the current work done by the Division of Sea Turtle Science and Recovery at Padre Island National Seashore. As a result, populations increased 12-19% annually in Texas and Mexico starting in 1997 and reached a peak of nearly 20,000 nests found in 2009 (National Marine Fisheries Service et al 2011)!
  • The job’s not over! Unfortunately, Kemp’s ridley nesting stopped increasing and suddenly and unexpectedly began decreasing in 2010. Reduced numbers were found in 2010, 2013, 2014, and 2015. The numbers found in 2011 and 2012 were similar to 2009 levels. Scientists are still working to determine the cause of this reversal. (Caillouet 2014, Shaver and Caillouet 2015).

Literature Cited:
Caillouet, C.W., Jr. 2014. Interruption of the Kemp’s Ridley Population’s Pre-2010 Exponential Growth in the Gulf of Mexico and its Aftermath: One Hypothesis. Marine Turtle Newsletter 143:1-7.
Caillouet, C.W., Jr., M.J. Duronslet, A.M. Landry, Jr., and D.J. Shaver. 1991. Sea turtle strandings and shrimp fishing effort in the northwestern Gulf of Mexico, 1986-1989. Fishery Bulletin 89(4):712-718.
Caillouet, C.W., Jr., D.J. Shaver, W.G. Teas, J.N. Nance, D.B. Revera, and A.C. Cannon. 1996. Relationship between sea turtle strandings and shrimp fishing effort in the northwestern Gulf of Mexico: 1986-1989 versus 1990-1993. Fishery Bulletin 94(2):237-249.
Caillouet, C.W., Jr., D.J. Shaver, A.M. Landry, Jr., D.W. Owens, and P.C.H. Pritchard. 2011. Commentary: Kemp’s ridley sea turtle (Lepidochelys kempii) age at first nesting. Chelonian Conservation and Biology 10(2):288-293.
Caillouet, C.W., Jr., D.J. Shaver, and A.M. Landry Jr. 2015. Kemp’s ridley sea turtle (Lepidochelys kempii) head-start and reintroduction to Padre Island National Seashore, Texas. Herpetological Conservation and Biology 10(Symposium):309-377.
Fontaine, C.T., and D.J. Shaver. 2005. Head starting the Kemp’s ridley sea turtle, Lepidochelys kempii, at the National Marine Fisheries Service Galveston Laboratory (1978 -1992): A review. Chelonian Conservation and Biology 4(4):838-845.
LeBlanc, A.M., T. Wibbels, D.J. Shaver, and. J. S. Walker. 2012. Temperature-dependent sex determination in the Kemp’s ridley: Effects of incubation temperatures on sex ratios. Endangered Species Research 19:123-128.
Lewison, B., L. Crowder, and D.J. Shaver. 2003. The impact of Turtle Excluder Devices and fisheries closures on loggerhead and Kemp’s ridley strandings in the western Gulf of Mexico. Conservation Biology 17(4):1089-1097.
Morrealle, S.J., P.T. Plotkin, D.J. Shaver, and H. Kalb. 2007. Migration and movements of ridley turtles. In: Biology and Conservation of Ridley Sea Turtles, p. 213-230. P.T. Plotkin (editor). Smithsonian Institution Press.
National Marine Fisheries Service. 2015. Kemp’s Ridley Sea Turtle (Lepidochelys kempii) species page. Retrieved from http://www.nmfs.noaa.gov/pr/species/turtles/kempsridley.htm
National Marine Fisheries Service, U.S. Fish and Wildlife Service, and SEMARNAT. 2011. Binational Recovery Plan for the Kemp’s Ridley Sea Turtle (Lepidochelys kempii), Second Revision. National Marine Fisheries Service, Silver Spring, Maryland. 156 pp. + appendices.
Shaver, D.J. 1991. Feeding ecology of Kemp's ridley in south Texas waters. Journal of Herpetology 25(3):327-334.
Shaver, D.J. 1992. Kemp's ridley sea turtle reproduction. Herpetological Review 23(2): 59.
Shaver, D.J. 1998a. Sea turtle strandings along the Texas coast, 1980-94. In: Characteristics and Causes of Texas Marine Strandings, p. 57-72. R. Zimmerman (editor). NOAA Technical Reports NMFS 143.
Shaver, D.J. 1998b. Sea turtle strandings in Texas. In: Report of the Sea Turtle Health Assessment Workshop, 2-3 February 1998, Part I: Background and Information Needs, Charleston, South Carolina, p. 75-80. P.A. Fair and L.J. Hansen (editors). NOAA Technical Memorandum NOS-NCCOS-CCEHBR-003.
Shaver, D.J. 2005. Analysis of the Kemp’s ridley imprinting and headstart project at Padre Island National Seashore, Texas, 1978-88, with subsequent Kemp’s ridley nesting and stranding records on the Texas coast. Chelonian Conservation and Biology 4(4):846-859.
Shaver, D.J., B.A. Schroeder, R.A. Byles, P.M. Burchfield, J. Pena, R. Marquez, and H.J. Martinez. 2005. Movements and home ranges of adult male Kemp’s ridley sea turtles (Lepidochelys kempii) in the Gulf of Mexico investigated by satellite telemetry. Chelonian Conservation and Biology 4(4):817-827.
Shaver, D.J., and T. Wibbels. 2007. Headstarting of Kemp’s ridley turtles. In: Biology and Conservation of Ridley Sea Turtles, p. 297-324. P.T. Plotkin (editor). Smithsonian Institution Press.
Shaver, D.J. and C. Rubio. 2008. Post-nesting movement of wild and head-started Kemp’s ridley sea turtles (Lepidochelys kempii) in the Gulf of Mexico. Endangered Species Research 4:43-55.
Shaver, D.J., K. Hart, C. Rubio, A.R. Sartain, J. Pena, P.M. Burchfield, D. Gomez Gamez, and J. Ortiz. 2013. Foraging area fidelity for Kemp’s ridleys in the Gulf of Mexico. Ecology and Evolution 3(7): 2002-2012. doi: 10.1002/ece3.594.
Shaver, D.J., and C.W. Caillouet, Jr. 2015. Reintroduction of Kemp’s ridley (Lepidochelys kempii) sea turtle to Padre Island National Seashore, Texas and its connection to head-starting. Herpetological Conservation and Biology 10(Symposium):378-435.

 

Last updated: December 6, 2018

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