Description
The Loggerhead Turtle is the second largest turtle
in the world (exceeded only by the Leatherback) and may reach 2 m
carapace length and 450 kg
although it is
typically smaller. It has a carapace
which is elongate with a keel along the centre line and coarse
serrations along the back edge. It is reddish brown to olive with
yellow borders on some scutes.
The plastron is cream to yellow and
has two
longitudinal ridges except in older adults. The limbs are
paddle-like and both they and the tail are dark above, yellow
beneath with yellowish edges. Males have a large curved claw on
each forelimb and more yellow on the head than females.
Confusing Species
The Loggerhead Turtle is similar to the other
hard-shelled sea turtles, however is it larger than either the Green Turtle or the Atlantic Ridley Turtle. Both of the
these
turtles lack the keel along the carapace
although the Ridley does have knobs instead of a keel. Neither of these two species
is ever
reddish.
Distribution
Although the Loggerhead Turtle is found in the Atlantic
and Pacific oceans, in Canada it has only been found on the
Atlantic coast. It ranges as far north as the southeast coast of
Newfoundland and is also seen along the east coast of Nova Scotia.
Its global distribution also includes the Indian Ocean and the
Caribbean and Mediterranean Seas.
Habitat
Loggerhead Turtles have been found as far as 240 km
from shore in open seas but they are usually found within the Gulf
Stream. Hatchlings and juveniles are found in drifting mats of
Sargassum algae. Nesting occurs on continental or occasionally
island beaches above the high-tide mark.
Reproduction
Loggerhead Turtles may take 10-30 years to reach
maturity. Most nesting beaches are on subtropical to temperate
coastlines although some are in the tropics. There are nesting
beaches as far north as New Jersey. Females breed every 1-7 years
but may lay several clutches of over 100 eggs in a season. Nesting
can occur throughout the year but is earlier in Atlantic
populations and later in the Pacific. The sex of the embryos is
temperature-dependent. Hatchlings emerge from the nest at night
and rush towards the sea.
Natural history
Loggerheads are omnivorous and eat a wide variety of
invertebrates, algae and aquatic plants. They may spend up to 85%
of their time submerged. Hatchlings have a small amount of
magnetic material in their heads which allow them to detect the
earth's magnetic field. They may use this to help navigate.
Juveniles have been re-captured over 6000 km from their original
capture site. Loggerheads can swim up to 20 km/hr.
Conservation Concerns
Loggerheads are the most abundant sea turtle in North
America. Nevertheless many of their nesting beaches have been
destroyed by development. Each year many are killed by collisions
with boats or drowned in fishing nests. Because Loggerheads are so
long-lived it is unclear if juvenile survivorship is high enough to
replace the population.
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