Habitat & Distribution

Sea Turtles

Habitat & Distribution

Distribution

  1. Various species of sea turtles are found in warm and temperate seas throughout the world. (See the table below for more information.)

Habitat

  1. Adults of most species are found in shallow, coastal waters, bays, lagoons, and estuaries.
  2. Some also venture into the open sea.
  3. Juveniles of some species may be found in bays and estuaries, as well as at sea. (See table below for descriptions of each species habitat.)

Migration

  1. Some sea turtle populations nest and feed in the same general areas; others migrate great distances.
  2. Migration habits differ not only among species but also among different populations of the same species.
    • Green sea turtle populations migrate primarily along the coasts from nesting to feeding grounds. However, some populations travel 2,094 km (1,300 miles) across the Atlantic Ocean; from Ascension Island nesting grounds (in the middle of the South Atlantic) to Brazilian coast feeding grounds.
    • Loggerheads leave foraging areas and travel on breeding migrations that can be a few thousand kilometers (1 kilometer = 0.62 miles) each way.
    • Kemp's ridley turtles follow two major routes in the Gulf of Mexico: one northward to the Mississippi area, and the other southward to the Campeche Bank, near the Yucatan Peninsula.
    • Populations of olive ridleys have been observed in large flotillas traveling between feeding and nesting grounds in the Eastern Pacific and Indian Oceans.
    • Hawksbill migration studies have been limited. Evidence suggests that some hawksbill populations show cyclic nesting migrations. Other researchers have documented nonmigratory and short-distance migratory populations.
    • Flatbacks move from their nesting grounds on the northern coast of Australia and its islands to feeding grounds in shallow waters of northeastern Australia. Distance covered ranges from 215 to 1,300 km (134-807 miles).
    • Leatherbacks have the longest migration of all sea turtles. They have been found more than 4,831 km (3,000 miles) from their nesting beaches.
  3. Historically, scientists tracked a free-ranging sea turtle by tagging a flipper and documenting where the turtle was sighted. Although this method yields information on migration destinations, it does not reveal travel routes.
  4. Scientists track free-ranging sea turtles by placing a metal tag on the front flipper.

    Scientists track free-ranging sea turtles by placing a metal tag on the front flipper.

  5. Most recently radio and satellite tracking have become more common in successfully monitoring sea turtle movements.
  6. Hubbs-SeaWorld Research Institute has developed a radio/satellite transmitter harness for leatherback turtles. Its design allows secure attachment of a transmitter without affecting turtle mobility. The harness was designed to release within several months.

Population

  1. Total population figures are often unknown because juvenile and male sea turtles do not come ashore and are difficult to count.
  2. Population data are usually based on the numbers of adult females that come ashore to nest. Even then, the numbers are ambiguous - some females nest every two to three years; some may nest more than once on the same beach in a season; and some visit more than one nesting beach in a season.
  3. Researchers rely on the changing numbers of nesting females from year to year to determine population trends. Because broad year-to-year fluctuations in numbers of nesting females make short-term data misleading, surveys of a decade or less may be insufficient to determine a population trend.
    • The Kemp's ridley is the most endangered sea turtle. In 1947, 42,000 nests were counted in a single day. The numbers declined dramatically until the 1980s. Currently, because of protection of nesting beaches and the use of turtle excluder devices in commercial shrimp fishing, Kemp's ridley populations seem to be slowly increasing.
    • Nesting populations of green sea turtles have not been surveyed long enough to determine worldwide population numbers. Experts estimate that in the past 120 to 140 years green sea turtle numbers have declined by 48 to 67 percent (IUCN 2004). Between 200 and 1,000 green sea turtles nest on beaches in the continental U.S.
    • Little data are available on hawksbill populations. Probably about 15,000 female hawksbills nest each year worldwide, although accurate estimates of population sizes are difficult by aerial assessment. Tracks in the sand do not last long and are difficult to see, and nests are often obscured by beach vegetation.
    • The major loggerhead nesting grounds are in the southeastern U.S. Population trends of loggerheads show a decline in Georgia and South Carolina nesting areas, but no decline or a possible increase in southern Florida nesting areas. More years of nesting data and population biology studies are needed to assess the Florida trends. In the U.S., total estimates for loggerhead nests per year range from 68,000 to 90,000. The worldwide population is unknown, although most populations outside of U.S. waters are declining.
    • The olive ridley is the most abundant sea turtle in the world. There are probably more than several hundred thousand adult female olive ridleys. In 1991, an estimated 610,000 turtles nested in a single week on a beach in India.
    • The current population of flatback turtles is unknown. Because of its restricted distribution, the flatback is the most vulnerable of all sea turtles to habitat change or exploitation.
    • There are probably 26,000 to 43,000 adult female leatherbacks worldwide. Their numbers do not appear to be declining in the U.S.

Table: Sea Turtle Distribution & Habitat

Species Distribution Habitat
green sea turtle
(Chelonia mydas mydas)
Atlantic Ocean, Gulf of Mexico, along Argentine coast, Mediterranean Sea, and Indo-Pacific Tropical and subtropical areas near continental coasts and around islands
Green sea turtles are found in the Atlantic Ocean, Gulf of Mexico, Mediterranean Sea, and Indo-Pacific.
Species Distribution Habitat
black sea turtle
(Chelonia mydas agassizii)
West coasts of North and South America, from central Baja California to Peru. Bays and protected shores; not commonly seen in the open ocean
Black sea turtles are found along the west coasts of North and South America, from Baja California to Peru.
Species Distribution Habitat
loggerhead sea turtle
(Caretta caretta)
Worldwide Coastal tropical and subtropical; ventures into temperate waters, to boundaries of warm currents; prefer coastal bays, but found in coastal streams, creeks, and open ocean
Loggerhead sea turtles are found worldwide in temperate and tropical habitats.
Species Distribution Habitat
Kemp's ridley sea turtle
(Lepidochelys kempii)
Adults usually occur in the Gulf of Mexico. Juveniles and immatures range between temperate and tropical coastal areas of the northwestern Atlantic Ocean. Occasionally young turtles reach northern European waters and as far south as the Moroccan coast. Shallow areas with sandy or muddy bottoms rich in crustaceans
Adult Kemp's ridley sea turtles usually occur in the Gulf of Mexico.
Species Distribution Habitat
olive ridley sea turtle
(Lepidochelys olivacea)
Tropical regions of the Atlantic, Indian, and Pacific Oceans (rarely to central California); nearly unknown around oceanic islands. Mostly coastal; traveling or resting in surface waters
Olive ridley sea turtles are found in the tropical regions of the Atlantic, Indian, and Pacific Oceans.
Species Distribution Habitat
hawksbill sea turtle
(Eretmochelys imbricata)
Throughout central Atlantic and Indo-Pacific regions; most tropical of all sea turtles. Near coral reefs and rocky outcroppings in shallow coastal areas
Hawksbill sea turtles are found throughout central Atlantic and Indo-Pacific regions.
Species Distribution Habitat
flatback sea turtle
(Natator depressus)
Indigenous to northwestern, northern, and northeastern regions of Australia; the most restricted range of all sea turtle species. Completely coastal; does not go beyond the continental shelf
Flatback sea turtles are found in the northern, northwestern, and northeastern regions of Australia.
Species Distribution Habitat
leatherback sea turtle
(Dermochelys coriacea)
The most widely distributed of all sea turtles; found in the Gulf of Alaska and south of the Bering Sea in the northeastern Pacific to Chile in the southeastern Pacific. In the Barents Sea, Newfoundland and Labrador in the North Atlantic; around Argentina and South Africa in the South Atlantic. Throughout the Indian Ocean; and to Tasmania and New Zealand in the southwestern Pacific. This species is found farther north than any other reptile, marine or terrestrial. Highly oceanic, approach coastal waters only during breeding season
Leatherback sea turtles are found in the northeastern and southeastern Pacific, in the North and South Atlantic, and throughout the Indian Ocean.