Loggerhead Sea Turtle

1 Overview

The loggerhead sea turtle is a typical sea turtle, and as such many of its habits differ from those of other turtles, for example its migratory behavior is particularly distinctive and worth studying. Researchers have long wondered how, beneath the vast open water, the loggerhead navigates so accurately.

The loggerhead turtle (Caretta caretta) is also known regionally as the green sea turtle. It is distributed in the warm temperate waters of the Atlantic, Pacific, and Indian Oceans, and occurs in China’s South China Sea and East China Sea. It is large, reaching about 1 m in length and commonly weighing around 100 kg, feeding on fish, shrimp, crabs, mollusks, and algae.

Chinese scientific name: Loggerhead turtle (Caretta caretta)

Chinese common names: Red Sea Turtle, Red Loggerhead, Spirit Turtle

Scientific (Latin) name: Caretta caretta

English name: Loggerhead Sea Turtle

Described by and year: Linnaeus, 1758; Kingdom: Animalia

Phylum: Chordata

Subphylum: Vertebrata

Class: Reptilia

Order: Testudines

Family: Cheloniidae

Species: Loggerhead sea turtle

Distribution: Warm temperate waters of the Atlantic, Pacific, and Indian Oceans; South China Sea and East China Sea

Protection: Listed in Appendix I of CITES. On December 10, 1988, approved by the State Council, and on January 14, 1989, promulgated by the Ministry of Forestry and the Ministry of Agriculture as a Class II protected animal under the List of National Key Protected Wild Animals.

2 Physical Characteristics

The loggerhead is a branch of the sea turtles (Caretta) and a relatively large turtle, reaching up to 1 m in length, yet it has a gentle temperament. Because its meat is tasty and nutritious, it was once overharvested, which has made it a protected species.

The loggerhead is very large, reaching up to 1 m and commonly about 100 kg, with a maximum of 300-400 kg. The head and back are red or reddish-brown, the belly yellow. The jaws are hooked; the head is large and broad. Head scales are arranged symmetrically, with two pairs of prefrontals; the front edge of the carapace is oval and the rear tapers to a point with a slight central rise. Hatchlings have three strong keels that fade with age. There are 5-6 vertebral scutes and usually 5 pairs of costal scutes; the bridge has 3 enlarged inframarginal scutes. The limbs are paddle-like, the front limbs long, with 1-2 claws. It is found in warm temperate waters of the Atlantic, Pacific, and Indian Oceans; the Pacific loggerhead occurs in China’s South China Sea and East China Sea.

The loggerhead has two subspecies: the Atlantic loggerhead (C. c. caretta) and the Pacific loggerhead (C. c. gigas). The Pacific loggerhead’s main nesting beaches in the western Pacific are the sandy coasts of Okinawa, Kagoshima, Kumamoto, Tokushima, Aichi, Kanagawa, and Chiba prefectures in Japan.

3 Conservation Status

The declining number of loggerheads is an inevitable and already unfolding reality. Humanity’s overharvesting has put this turtle in jeopardy, and some even raid nesting beaches to steal eggs, causing populations to plummet.

I. Endangered Status of the Loggerhead

Indiscriminate hunting and the digging up of turtle eggs are major reasons the sea turtle resources of the Xisha (Paracel) Islands have sharply declined. According to reports: ‘Every year from April to July, large numbers of fishermen come to the Xisha Islands in groups, especially those from Qionghai County. They not only net turtles at sea but also land on islands to catch turtles and dig up eggs. Fishing boats hunting turtles can be seen near every island. At Zhongjian Island, the Qionghai boat No. 00258 was found with more than 20 turtles caught (the boat was later seized by fishery authorities at Tanmen Port in Qionghai, the turtles released, and a fine levied); at Coral Island, two boats loaded with turtles fled in panic when they saw the survey vessel approach. During peak nesting season, dozens of turtle-catching boats appear, with a single boat catching over 100 turtles a year and digging up over 1,000 eggs.’ (Ouyang Tong et al., 1992) According to that account, Hainan Island once also had many sea turtles, but capturing turtles and digging eggs caused them to vanish from Hainan over 20 years ago. Taiwan’s east coast once had beautiful beaches, but after human hunting and destruction, almost no turtles nest there anymore (Cheng Yijun, 1997).

II. Conservation Measures for the Loggerhead

Existing protections: Listed in Appendix I of CITES. On December 10, 1988, approved by the State Council, and on January 14, 1989, promulgated by the Ministry of Forestry and the Ministry of Agriculture as a Class II protected animal under the List of National Key Protected Wild Animals.

4 Behavior & Habitat

The loggerhead is a large marine reptile, so a transmitter’s size does not affect its behavior; however, because transmitters and data processing are very expensive, fewer than 200 such studies of loggerhead migration have been conducted worldwide, and fewer than 40 concern the loggerhead specifically. Researchers have found that sea turtle migration can be divided into two types: rapid cross-sea swimming and slow swimming along the edges of large islands or continents.

5 Diet & Reproduction

During its life, the loggerhead spends a great deal of time each day eating. Its main food sources are various mollusks and occasional fish and shrimp; it rarely consumes plants.

The loggerhead lives in seawater, feeding on fish, crabs and other crustaceans, and mollusks. The breeding season is May to July; it digs nests on coastal beaches and lays 60-150 eggs each time. The eggs are white, spherical, about 38-40 mm in diameter, and hatch after about 60 days under natural conditions. In the western Pacific, the main nesting sites are the coastal beaches of Kumamoto, Kagoshima, and Okinawa in Japan.

Shortcomings of the loggerhead:

1. Lacks athletic ability: The loggerhead’s top swimming speed is only half that of an old sea turtle; a talent you are born with, so it cannot be helped, call it an original sin.

2. Playful and showy: When turtles surface to breathe they are most vulnerable from below; the average turtle surfaces for only 2-3 seconds before dipping back down, but the loggerhead will bob around for 2-3 minutes, leisurely enjoying a sunbath before remembering the seabed is the safe place.

3. Greedy eater: You would not know without watching, the loggerhead spent a full two hours at a meal, eating dozens of clams, which makes one wonder whether this South Pacific native was somehow influenced by French dining culture; after such a gluttonous feast, how could it swim fast.