 Conservation
Birds
Tortoises
Beach
Two endangered species of sea turtles nest on the beaches of Bird Island
--.the Hawksbill Turtle (classified by IUCN as "Critically Endangered")
and the Green Turtle (listed as "Endangered").
In 1994 Seychelles passed a law which protected all species of sea
turtles, and in recent years heavy fines and even jail sentences have
been imposed on persons found to be interfering with turtles or in
possession of turtle products.
Sea Turtle Life Cycle
Sea turtles have complicated life cycles which confound efforts to
conserve their populations. In the Indo-Pacific, both Hawksbills and
Green Turtles take some 30 to 40 years to reach sexual maturity.
Nevertheless, genetic studies show that female turtles return to breed
in the vicinity of the beach where they were born turtles have
complicated life cycles which confound efforts to conserve their
populations. In the Indo-Pacific, both Hawksbills and Green Turtles
take some 30 to 40 years to reach sexual maturity. Nevertheless,
genetic studies show that female turtles return to breed in the vicinity
of the beach where they were born.
Turtles have complicated life cycles which confound efforts to conserve
their populations. In the Indo-Pacific, both Hawksbills and Green
Turtles take some 30 to 40 years to reach sexual maturity.
Nevertheless, genetic studies show that female turtles return to breed
in the vicinity of the beach where they were born turtles have
complicated life cycles which confound efforts to conserve their
populations. In the Indo-Pacific, both Hawksbills and Green Turtles
take some 30 to 40 years to reach sexual maturity. Nevertheless,
genetic studies show that female turtles return to breed in the vicinity
of the beach where they were born.
Adults:
Mating
usually occurs in waters near the nesting beach, but only females come
ashore.
Males are smaller than females and the tail is longer, extending well
beyond the shell.
In one
nesting season the average female lays 4 to 5 egg clutches separated by
two week intervals. (Individual females may lay 1 to 7 egg clutches
during the season.) After laying all her eggs for the season the female
then migrates away from the breeding beach to her feeding grounds (which
may be located up to 2000 km away). There she remains for several years
fattening herself in preparation for her next breeding migration.
 Eggs:
Egg
clutches typically comprise 100 to 250 eggs (depending on the species),
and take 55 to 70 days to hatch. Temperature determines how quickly
eggs develop and also the sex of the offspring produced -- warmer egg
clutches develop more quickly and produce more females.
Hatchlings & Pelagic Juveniles:
After
exiting the egg, hatchlings take a few days to leave the nest. They
usually emerge from the surface of the sand at night shortly after
dark. They immediately head towards the brightest point on the horizon
which, under natural conditions, takes them towards the sea. On
reaching the surf they swim straight out to sea perpendicular to shore.
During the next several days they get caught up in currents and drift
lines -- eventually settling into a pelagic life in very deep water, at
the surface of the sea, living in the midst of floating weeds and
invertebrates and associated fishes. This is how they spend the first
few years of their lives.
Juveniles & Sub-Adults:
After
reaching a shell length of some 30 cm, both green turtles and hawksbills
move from the pelagic habitat into shallow waters (less than 25 metres
deep) where they feed on plants and animals growing on the sea floor.
Characteristics peculiar to green turtles and
hawksbills are described below for each species.
Hawksbill Turtle (Eretmochelys
imbricata)
 Habitat:
Hawksbill
Turtles are the most tropical of all sea turtles. They are found in
warmer waters of the Atlantic, Pacific, and Indian Oceans and adjacent
seas. Those 30 cm and longer frequent rocky areas, coral reefs,
mangroves, shallow coastal areas, and narrow creeks and passes.
Feeding:
The
hawksbill turtle is an omnivore that eats sponges, soft-bodied
invertebrates and algae. They sometimes eat dead marine creatures, and
in Seychelles will unfortunately take bait off fishing hooks and accept
scraps from picnic lunches.
Nesting Behaviour: The
predominantly daytime nesting habits of Hawksbills in Seychelles (and
the western Indian Ocean region) are unique in the world.
Size: Seychelles
hosts some of the largest hawksbills recorded, with carapace lengths
ranging from 83 to 92 cm and weights of up to 80 kg
Features: Hawksbills
have narrow pointed heads which help them feed in crevices. Their
carapace (upper shell) is covered by overlapping scales which are brown with splashes of yellow, orange or reddish brown. The
plastron (under shell) is yellowish with black spots in animals larger
than about 10 cm.
Eggs & Nests:
Average clutch size
in Seychelles is 170 eggs, but as many as 280 eggs have been recorded.
Average nest depth is about 55 cm.
Conservation:
:
The decline of this species is primarily due to over exploitation for
shell ("tortoiseshell") especially to satisfy the Japanese demand for
shell between 1960 and the 1990s. Although legal international trade in
tortoiseshell stopped in 1992, illegal trade continues. Other threats
include loss or degradation of nesting habitat from coastal development
and beach armoring; disorientation of hatchlings by beachfront lighting;
excessive nest predation by native and non-native predators; degradation
of foraging habitat; marine pollution and debris; watercraft strikes;
and incidental take from commercial fishing operations
Green Turtle (Chelonia mydas)
Habitat:
Green
turtles most commonly occur in warm waters of all oceans and adjacent
seas (usually between latitudes 35°N and 35°S), especially in shallow
sea grass and algae pastures. But, they are also found in the same
variety of habitats as hawksbills.
Feeding:
Animals
that have moved to benthic habitats (i.e., those upwards of 30 cm in
length) are vegetarian and feed primarily on sea grasses and algae.
Nesting Behaviour:
Green
turtles nest almost exclusively at night.
Size:
Adult
carapace length in Seychelles usually ranges from 90 to 130 cm, with
weights up to 200 kg.
Features:
Green turtles are so
named for the colour of their fat. Carapace scales are olive to dark
brown, and do not overlap. The plastron is white or cream colored.
Their heads are larger and more rounded than those of Hawksbills,
enabling them to forage in grass pastures.
Hatchlings:
Newly hatched Green Turtles are beautifully
marked, with a dark upper (dorsal) surface, and a white underside. All
four flippers are edged in white.
Eggs & Nests.
Green turtles
typically lay 100 to 150 eggs in each nest. Average nest depth is 80 cm
Conservation:
Green turtles are endangered because they have been over harvested by
people for meat and eggs. Their populations worldwide have been
particularly impacted by the export of "calipee" (the cartilage inside
the shell) to Europe. Calipee was used to produce "green turtle soup",
especially during the 19th and 20th centuries.
Today the meat of Green Turtles is still considered a delicacy by many
people in Seychelles, although harvest is illegal. Green Turtles are
also subject to the same pressures of habitat destruction and accidental
mortality described above for Hawksbills.
Bird Island hosts the largest remaining population of nesting Green
Turtles in the inner islands of the Seychelles. |
