Loggerhead Sea Turtle
Common Name: Loggerhead
Scientific Name: Caretta caretta
were named for their relatively large heads, which support
powerful jaws and enable them to feed on hard-shelled prey,
such as whelks and conch. The carapace (top shell) is slightly
heart-shaped and reddish-brown in adults and sub-adults, while
the plastron (bottom shell) is generally a pale yellowish
color. The neck and flippers are usually dull brown to reddish
brown on top and medium to pale yellow on the sides and bottom.
Mean straight carapace length of adults in the southeastern
U.S. is approximately 36 in (92 cm); corresponding weight
is about 250 lbs (113 kg).
reach sexual maturity at around 35 years of age. In the southeastern
U.S., mating occurs in late March to early June and females
lay eggs between late April and early September. Females lay
three to five nests, and sometimes more, during a single nesting
season. The eggs incubate approximately two months before
hatching sometime between late June and mid-November.
vary from light to dark brown to dark gray dorsally and lack
the reddish-brown coloration of adults and juveniles. Flippers
are dark gray to brown above with white to white-gray margins.
The coloration of the plastron is generally yellowish to tan.
At emergence, hatchlings average 1.8 in (45 mm) in length
and weigh approximately 0.04 lbs (20 g).
occupy three different ecosystems during their lives--the
terrestrial zone, the oceanic zone, and the "neritic"
zone. Loggerheads nest on ocean beaches,
generally preferring high energy, relatively narrow, steeply
sloped, coarse-grained beaches. Immediately after hatchlings
emerge from the nest, they begin a period of frenzied activity.
During this active period, hatchlings move from their nest
to the surf, swim and are swept through the surf zone, and
continue swimming away from land for about one to several
this swim frenzy period, post-hatchling loggerheads
take up residence in areas where surface waters converge to
form local downwellings. These areas are often characterized
by accumulations of floating material, such as seaweed (e.g.,
Sargassum), and, in the southeast U.S., are common between
the Gulf Stream and the southeast U.S. coast, and between
the Loop Current and the Gulf Coast of Florida. Post-hatchlings
within this habitat are observed to be low-energy float-and-wait
foragers that feed on a wide variety of floating items (Witherington
2002). As post-hatchlings, loggerheads may
linger for months in waters just off the nesting beach or
become transported by ocean currents within the Gulf of Mexico
and North Atlantic. Work by Lohmann and Lohmann (1994b, 1996)
and Lohmann et al. (1999) suggests that loggerheads
may continue some oriented swimming in order to keep from
being swept into cold North Atlantic currents.
individuals get transported by ocean currents farther offshore,
they've entered the oceanic zone. Within the North Atlantic,
juvenile loggerheads have been primarily studied in the waters
around the Azores and Madeira (Bolten 2003). Other populations
exist (e.g., in the region of the Grand Banks off Newfoundland),
but data on these populations are limited. The juvenile turtles
around the Azores and Madeira spend the majority of their
time in the top 15 feet (5 m) of the water column.
between the ages of 7 to 12 years, oceanic juveniles migrate
to nearshore coastal areas (neritic zone) and continue maturing
until adulthood. In addition to providing critically important
habitat for juveniles, the neritic zone also provides crucial
foraging habitat, inter-nesting habitat, and migratory habitat
for adult loggerheads in the western North Atlantic. To a
large extent, these habitats overlap with the juvenile stage,
the exception being most of the bays, sounds, and estuaries
along the Atlantic and Gulf coasts of the U.S. from Massachusetts
to Texas, which are infrequently used by adults. However,
adult loggerheads are present year-round
in Florida Bay, an important feeding area, probably because
of relatively easy access to open ocean and migratory routes.
The predominate foraging areas for western North Atlantic
adult loggerheads are found throughout the relatively shallow
continental shelf waters of the U.S., Bahamas, Cuba, and the
Yucatán Peninsula, Mexico. Migration routes from foraging
habitats to nesting beaches (and vice versa) for a portion
of the population are restricted to the continental shelf,
while other routes involve crossing oceanic waters
to and from the Bahamas, Cuba, and the Yucatán Peninsula.
Seasonal migrations of adult loggerheads along
the mid- and southeast U.S. coasts have also been documented.
Reproduction and Development
United States nesting season extends from about May through
August with nesting occurring primarily at night. Loggerheads
are known to nest from one to seven times within a nesting
season (mean is about 4.1 nests per season) at intervals of
approximately 14 days. Mean clutch size varies from about
100 to 126 along the southeastern United States coast. Incubation
ranges from about 45 to 95 days, depending on incubation temperatures,
but averages 55 to 60 days for most clutches in Florida. Hatchlings
generally emerge at night. Remigration intervals of 2 to 3
years are most common in nesting loggerheads,
but remigration can vary from 1 to 7 years. Age at sexual
maturity is believed to be about 20 to 30 years.
Range and Population Level
loggerhead sea turtle occurs throughout the
temperate and tropical regions of the Atlantic, Pacific,
and Indian Oceans. However, the majority of loggerhead
nesting is at the western rims of the Atlantic and Indian
oceans. The most recent reviews show that only two loggerhead
nesting beaches have greater than 10,000 females nesting per
year: South Florida (U.S.) and Masirah (Oman). Those beaches
with 1,000 to 9,999 females nesting each year are North Florida
through North Carolina (U.S.), Cape Verde Islands (Cape Verde,
eastern Atlantic off Africa), and Western Australia (Australia).
Smaller nesting aggregations with 100 to 999 nesting females
annually occur in Northwest Florida (U.S.), Cay Sal Bank (Bahamas),
Quintana Roo and Yucatán (Mexico), Sergipe and Northern Bahia
(Brazil), Southern Bahia to Rio de Janerio (Brazil), Tongaland
(South Africa), Mozambique, Arabian Sea Coast (Oman), Halaniyat
Islands (Oman), Cyprus, Peloponnesus (Greece), Island of Zakynthos
(Greece), Turkey, and Queensland (Australia). Although the
major nesting concentrations in the United States are found
in South Florida, loggerheads nest from Texas to Virginia.
Total estimated nesting in the U.S. is approximately 68,000
to 90,000 nests/year. About 80 percent of loggerhead nesting
in the southeastern U.S. occurs in six Florida counties (Brevard,
Indian River, St. Lucie, Martin, Palm Beach, and Broward Counties).
Adult loggerheads are known to make considerable migrations
between foraging areas and nesting beaches. During non-nesting
years, adult females from U.S. beaches are distributed in
waters off the eastern U.S. and throughout the Gulf of Mexico,
Bahamas, Greater Antilles, and Yucatán.
research involving analysis of mitochondrial DNA has identified
five different loggerhead nesting subpopulations in the western
Northern Subpopulation occurring from North Carolina through
(2) South Florida Subpopulation occurring from just north
of Cape Canaveral on Florida’s east coast and extending
up to around Sarasota on Florida’s west coast;
(3) Dry Tortugas, Florida, Subpopulation,
(4) Northwest Florida Subpopulation occurring on Florida’s
Panhandle beaches; and
(5) Yucatán Subpopulation occurring on the eastern
Yucatán Peninsula, Mexico.
data indicate that gene flow between these five regions is
very low. If nesting females are extirpated from one of these
regions, regional dispersal will not be sufficient to replenish
the depleted nesting subpopulation. The South Florida Subpopulation
has shown significant increases over the last 25 years, indicating
that the population has progressed toward recovery. However,
an analysis of nesting data for the years 1989-2002, a period
encompassing index surveys that are more consistent than surveys
in previous years, has shown no detectable trend. Past increases
in South Florida loggerhead nesting are likely to have slowed.
No long-term trends are available for the Northern Subpopulation,
although researchers have documented substantial declines
in nesting on some beaches since the early 1970s. From 1989-1998,
no nesting trends were detectable for North Carolina, South
Carolina, or Georgia. However, nests in Northeast Florida
may be increasing, although data were too variable to detect
a significant trend. Nesting surveys in the Dry Tortugas,
Northwest Florida, and Yucatán Subpopulations have
been too irregular to date to allow for a meaningful trend
face threats on both nesting beaches and in the marine environment.
The greatest cause of decline and the continuing primary threat
to loggerhead turtle populations worldwide
is incidental capture in fishing gear, primarily in longlines
and gillnets, but also in trawls, traps and pots, and dredges.
Directed harvest for loggerheads still occurs
in many places (e.g., the Bahamas, Cuba, and Mexico) and is
a serious and continuing threat to loggerhead recovery. For
more information, please visit our threats
to marine turtles page.
Management and Protection
the Southeast United States, major nest protection efforts
and beach habitat protection are underway for most of the
significant nesting areas, and significant progress has been
made in reducing mortality from commercial fisheries in U.S.
waters with the enforcement of turtle excluder device regulations.
Many coastal counties and communities in Florida, Georgia,
and South Carolina have developed lighting ordinances to reduce
hatchling disorientations. Important U.S. nesting beaches
have been and continue to be acquired for long-term protection.
The migratory nature of loggerheads severely
compromises these efforts once they move outside U.S. waters,
however, since legal and illegal fisheries activities in some
countries are causing high mortality on loggerhead sea turtle
nesting populations of the western north Atlantic region.
Due to the long range migratory movements of sea turtles between
nesting beaches and foraging areas, long-term international
cooperation is absolutely essential for recovery and stability
of nesting populations.