Kemp's ridley sea turtles

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Kemp’s ridleys are the smallest and most critically endangered sea turtle species. Adults are 2 feet long and weigh only 70-100 pounds. In Texas, Kemp’s ridley sea turtles occur in nearshore Gulf of Mexico waters, bays, and passes, where they feed mostly on crabs, and occasionally fish, sea jellies, and mollusks.

Since the mid-1970s, the National Park Service at Padre Island National Seashore has been an integral member of the bi-national, multi-agency Kemp’s Ridley Sea Turtle Recovery Program. Its mission? To save the critically endangered Kemp’s ridley sea turtle species from extinction.  Dr. Donna J. Shaver, our Division Chief, has spent the last 40 years helping with these efforts, which include a program to increase nesting at Padre Island National Seashore and form a secondary nesting colony of this species here as a safeguard against extinction. Though their main nesting beach is in Mexico, more Kemp’s ridleys nest at Padre Island National Seashore than any other place in the United States. Padre Island National Seashore, the longest stretch of undeveloped barrier island beach in the United States, is the perfect location for the ongoing establishment of a secondary nesting colony. Padre Island National Seashore holds 20-25 public releases of Kemp’s ridley hatchings each year and this is the most popular interpretive program held at the park, with hundreds to more than 1,000 people attending each release.

The Kemp’s ridley sea turtle is unique from other sea turtle species because it nests during the day and nests in group events called “arribadas.” Find out more interesting facts about the Kemp’s ridley sea turtle below!

 
Nesting Kemp's Ridley Sea Turtle
A nesting Kemp's ridley sea turtle.

NPS Photo.

Species Profile

Species: Kemp’s ridley (Lepidochelys kempii)

Status: Federally endangered

Size: Adult carapace (upper shell) length is 24-28 inches (60-70 cm) (National Marine Fisheries Service 2020)

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

Historic Nesting Range: 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 Range: 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 Range: 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).

 
A Kemp's ridley sea turtle hatchling crawls on the beach next to yellow and brown sargassum seaweed.
A Kemp's ridley sea turtle hatchling.

NPD Photo.

Diet: Primarily crabs, as well as fish, sea jellies, and mollusks (Shaver 1991, National Marine Fisheries Service 2020)

Lifespan: Unknown; reach sexual maturity at 10-16 years (Caillouet et al. 2011, National Marine Fisheries Service et al. 2011)

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; ocean pollution/marine debris (Lewison et al. 2003, National Marine Fisheries Service 2020)
 

Fun Facts about the Kemp's Ridley Sea Turtle!

 
Looking down on the almost round shell of a nesting Kemps ridley sea turtle
Looking down on the almost completely round shell of a Kemp's ridley sea turtle.

NPS Photo.

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). 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. 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 et al. 2011).

There’s something about Padre! Most Kemp’s ridley nests are found in Mexico however, south 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).

 
Dr. Shaver and turtle mascot "Seashore Sandy" stand in front of a sea turtle mural painted on the side of a building in downtown Corpus Christi, Texas
Dr. Shaver standing with Seashore Sandy in front of the mural "A Breath of Fresh Air", located in downtown Corpus Christi, Texas.

Jan Roberson, NPS Volunteer.

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 and city murals to festivals and more. The state legislature has even designated the Kemp’s ridley as the Texas State Turtle!

Arribada! Kemp’s ridleys are the only sea turtles nesting in groups called arribadas (Spanish for “arrivals”). Just prior to an arribada, female sea turtles gather offshore. When weather conditions and timing is right, the females make their way towards the shore, crawling onto the beach to nest during a single nesting event. Biologists believe nesting in groups is a strategy to reduce predation by overwhelming the predators with numbers. Eventually, thousands of hatchlings will emerge around 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). For more information see The Story of the Kemp’s Ridley.

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 on the brink of extinction. Although Mexico initiated conservation efforts in the 1960s, the population continued to decline. By the 1970s, what little nesting that was occurring took place almost exclusively 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, the Kemp’s ridley population has 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 of nests were found in 2010, 2013, 2014, and 2015. The number of nests 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).

 

Kemp’s Ridley Sea Turtle 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. 2020. Kemp’s Ridley Sea Turtle (Lepidochelys kempii) species page. Retrieved from https://www.fisheries.noaa.gov/species/kemps-ridley-turtle

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: October 10, 2020

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