age of reproductive maturity of turtles
Science and Technology. For the first time scientists are using carbon-14 dating of shell tissue to estimate age, growth, and maturity in sea turtles. The most basic questions of sea turtle life history are also the most elusive,says Kyle Van Houtan. (Credit: iStockphoto) Female sea turtles must come ashore to build nests and lay their eggs. 1  Females usually nest during the warmest months of the year. The exception is the leatherback turtle, which nests in fall and winter.  Females of most species usually come ashore at night, alone, most often during high tide. This is the first time carbon-14 dating of shell tissue has been used to estimate age, growth, and maturity in sea turtles. Previously, scientists employed other, less precise methods such as using turtle length as a proxy for age, or analyzing the incomplete growth layers in hollow bone tissue. 1 Estimates of sexual maturity in sea turtles vary not only among species, but also among different populations of the same species. Maturity may range from as early as three years in hawksbills to 12-30 years in loggerheads to 20-50 years in green sea turtles.  Sexual maturity often is related to carapace size. Studies have shown that hawksbills reach sexual maturity at a carapace size of 60 to 95 cm (24-37 in.); loggerheads reach maturity at a carapace size of 79 cm (31 in.); and green sea turtles reach maturity at 69 to 79 cm (27-31 in.). Some languages do not have this distinction, as all of these are referred to by the same name. For example, in Spanish, the word tortuga is used for turtles, tortoises, and terrapins. A sea-dwelling turtle is tortuga marina, a freshwater species tortuga de río, and a tortoise tortuga terrestre. Radiocarbon dating of atomic bomb fallout found in the shells of sea turtles is a reliable way to estimate the age, growth rate, and reproductive maturity of sea turtles in the wild, a new study shows. It measures no more than 8 cm (3.1 in) in length and weighs about 140 g (4.9 oz). Two other species of small turtles are the American mud turtles and musk turtles that live in an area that ranges from Canada to South America. The shell length of many species in this group is less than 13 cm (5.1 in) in length. The earliest known members of this group date from 157 million years ago, making turtles one of the oldest reptile groups and a more ancient group than snakes or crocodilians. Of the 327 known species alive today, some are highly endangered. Most land-dwelling chelonians are in the Testudinidae family, only one of the 14 extant turtle families. Terrapin is used to describe several species of small, edible, hard-shell turtles, typically those found in brackish waters, and is an Algonquian word for turtle. However, because of their high metabolic rate, leatherback sea turtles have a body temperature that is noticeably higher than that of the surrounding water. Turtles are classified as amniotes, along with other reptiles, birds, and mammals.
20-50 years