Download 243 - UAE Interact

T H E E M I R AT E S – A N AT U R A L H I S T O R Y
MARINE REPTILES
MARINE REPTILES
TWO GROUPS OF MARINE REPTILES ARE PRESENT in UAE waters: sea turtles and sea snakes. Little is currently known about
local populations of either, although recent research has begun to collect information on commonly encountered
turtles. Frequent sightings of sea snakes suggest that this group is also common here, although dedicated research
has yet to be undertaken.
S E A T U RT L E S
Of the seven recognised species of marine turtle, four occur in
the waters of the UAE; green turtle Chelonia mydas, hawksbill
turtle Eretmochelys imbricata, loggerhead turtle Caretta caretta and
leatherback turtle Dermochelys coriacea. A fifth species, the olive
ridley turtle Lepidochelys olivacea, is known from neighbouring
Oman and is almost certainly a visitor to UAE waters. The most
frequently occurring species are the green and the hawksbill,
both of which feed and nest in the UAE.
Sea turtles in the UAE have not been extensively studied and
most data are only recently collected. Early publications include
that by Brown (1985), who documented the occurrence of green
and loggerhead turtles. Heath (1989) reported a hawksbill from
Das Island, and Brown (1990) suggested a wider distribution of
green turtles, including Qarnein Island. It is now known that both
green and hawksbill turtles are widely distributed in the shallow
waters of the UAE where seagrass and coral reef habitats exist
(Aspinall 1995; Baldwin 1995; Al-Ghais 1998). Other species are
known from very few records. Leatherback turtles have been
was preferred. It was suggested that this may indicate preferential
feeding in deeper water, where H. ovalis appears to be prevalent,
during summer months. Stomach contents have revealed that some
individuals in the UAE had fed on a mixed diet that included
three species of seagrasses, numerous species of algae, sponges
and ascidians (Baldwin 1995).
A survey of feeding green turtles conducted in waters off Ra’s
al-Khaimah (Al-Ghais et al. 1998) revealed a considerable size
range (37–102 centimetres) of green turtles. This prompted the
authors to suggest the existence of a resident population comprised
of all post-pelagic age/size classes, something confirmed by aerial
surveys. Satellite-tagged green turtles from this area also remained
within Ra’s al-Khaimah waters for the entire period (ERWDA,
pers. comm.). Arabian Gulf residency of foraging turtles has been
sighted on rare occasions and may feed in UAE waters on
seasonally abundant jellyfish, whilst loggerhead turtles are known
from skulls found on beaches in western Abu Dhabi (Baldwin
1995). It is likely that the latter species, as well as the olive ridley
turtle, feeds in UAE waters from time to time.
The Environmental Research and Wildlife Development Agency
(ERWDA 2002) concurs with earlier authors (Aspinall 1998;
Baldwin 1995) that the most commonly occurring turtle in the
UAE is the green, thousands of which come to feed on the vast,
rich seagrass and algal communities, particularly in the shallow
offshore waters of western Abu Dhabi. The number of feeding
green turtles that visit the UAE is undetermined, although Preen
et al. (2000) estimated a population of over 12,000 turtles based
on aerial surveys of the southern Arabian Gulf, in which most
sightings were of green turtles in western Abu Dhabi waters. This
makes the area of global importance for this species.
Studies of the diet of green turtles in the UAE have revealed
that two species of seagrass, Halodule uninervis and Halophila
ovalis are favoured (Baldwin 1995; Hasbun et al. 2000). The latter
authors noted that during May, the turtles consumed a significantly
higher proportion of H. uninervis. In August, however, H. ovalis
BACKGROUND PHOTO:
A hawksbill turtle returning to the water at sunrise.
RIGHT: Hawksbill turtle Eretmochelys imbricata
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MARINE REPTILES
identified elsewhere in the region, such as in Saudi Arabia (Miller
1989). However, at least some of the green turtles that feed in
UAE waters migrate, as proven by tagging experiments on nesting
green turtles in the Sultanate of Oman, which include returns
from turtles found in UAE waters (Salm and Salm 2001).
Recent research using mitochondrial DNA (mtDNA), from
samples obtained from foraging green turtles off the coast of Ra’s
al-Khaimah, revealed two types of mtDNA patterns, suggesting a
mixed population in this region (D’Aloia and Al-Ghais 2000).
Hawksbill turtles also feed in UAE waters, apparently restricted
to coral reef areas, mostly in western
Abu Dhabi around offshore islands
(ERWDA 2002). This species
also uses these islands
as a nesting habitat
between the
months of March and June. Highest nesting concentrations are
reported by ERWDA (2002) on the islands of Yasat, Muhayimat, Bu
Tinah, Zirku, Qarnein, Arzanah and Dayyinah. Nesting also occurs
in lower concentrations on the islands of Umm al-Hatab, Junana,
Ghasha, Abu al-Abyadh and Dalma in Abu Dhabi waters, and on
Sir Abu Nu’air, part of Sharjah Emirate (Loughland, pers. comm.).
The numbers of nesting females has yet to be comprehensively
estimated, but limited data on individuals from Qarnein, Zirku and
Bu Tinah has revealed an average size of nesting females of 67.5
centimetres (curved carapace length). Nest site fidelity has been
shown to be high and the inter-nesting period averaged 12–13
days. Clutch size average was calculated at 74 and the
incubation period was recorded as approximately
58 days. Incubation temperatures were
measured at between 26 and 34°C.
This is lower than that recorded by
Green turtle Chelonia mydas
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the Centre for Environmental Research (CER) of the Emirates
Heritage Club in the month of June, when incubation temperatures
ranged from 33–38°C.
Between the years 1999 and 2002, five nesting hawksbills at
Qarnein were fitted with satellite transmitters and their movements
tracked daily for several months. This revealed a generally small
range including western Abu Dhabi waters, eastwards to Qatari
and Bahraini waters and northwards as far as nearshore waters of
Iran (ERWDA, pers. comm.).
Nesting by green turtles is poorly studied in comparison to
hawksbills. This may be partly due to a smaller nesting population.
ERWDA reported no nesting by green turtles on western Abu
Dhabi islands between 1999 and 2002. However, nesting beaches
are known to include those on offshore islands of UAE and
mainland shores of the eastern UAE (Miller et al. 2000; Baldwin
1995). It is likely that green turtles nest during late summer
months in the UAE, following the end of nesting by hawksbill
turtles. Such seasonal separation in nesting periods is known in
neighbouring Omani populations.
The precarious survival of turtles, so delicately balanced around
natural events, is further exacerbated by a whole gamut of
threats generated by man. Egg-collecting, hunting of turtles for
their meat, disturbance of nesting turtles, artificial lighting on
beaches and coastal development activities have all been implicated
as direct factors threatening turtles in the UAE (ERWDA 2002).
Ships and boats also strike and kill turtles at sea while pollution
affects turtles on an unknown scale. Fishing nets continue to
catch and drown turtles, in spite of laws that prohibit net fishing
The sex of future hatchlings is determined by the temperature at
which eggs incubate. Outer ones generally become males.
ABOVE RIGHT: A green turtle hatchling is prone to predation as it makes its
way from the nest to the water’s edge.
OPPOSITE TOP: Hawksbill turtle Eretmochelys imbricata
ABOVE LEFT:
in UAE waters. Dredging and other offshore activities degrade or
destroy habitats, such as seagrass beds and coral reefs.
All turtles that occur in the UAE are listed by the IUCN Red List
as ‘Endangered’ throughout their world range, or in the case of
hawksbill and leatherback turtles, ‘Critically Endangered’.
Conservation management of turtles is difficult, particularly as the
turtles may cross several international boundaries whilst migrating
between feeding and nesting grounds. Attempts at an international
approach to conservation have been made in the UAE (Al-Ghais
and Frazier 2001) and local management strategies have been
proposed (ERWDA 2002). UAE scientists have undertaken important
research into local turtle populations and have forged links with
international organisations and researchers interested in ensuring
the continued survival of the UAE’s turtles.
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distinctly circular and may be over a metre deep. The tracks left
by a nesting green turtle are easily recognisable as the fore
flippers are swept backwards together pulling the turtle along the
beach, the right flipper leaving a distinct linear groove in the
sand exactly opposite the left flipper, creating a series of parallel,
horizontal tracks on either side of the body.
Nesting beaches tend to consist of fine deep sand in the UAE
and include offshore islands and mainland sites. They are known
to migrate great distances (several thousands of kilometres in
some cases) and may be seen almost anywhere in UAE waters.
The largest numbers occur on feeding grounds to the west of Abu
Dhabi in shallow water over seagrass and algal beds.
H AW K S B I L L T U RT L E
Eretmochelys imbricata (Rüppell, 1835)
Hawksbill turtles are relatively small, measuring about 80
centimetres in length and weighing a maximum of about 50
kilograms. They are named after their pointed, slightly hooked
beak, which is accentuated by a narrow head. They can,
however, be mistaken for young green turtles. Both are similar in
colour and have four costal scutes on each side of the carapace.
The thick costal scutes of the hawksbill tend to overlap in all but
the oldest individuals and the trailing edge of the carapace often
G R E E N T U RT L E
Chelonia mydas (Linnaeus, 1758)
Local Name: ‘Hamas’ or ‘Shiree’
A green turtle carapace (upper shell) can measure up to 120
centimetres in length and an adult of this size may weigh in
excess of 200 kilograms. The smooth, rounded carapace has four
pairs of large plates (costal scutes) on either side and is generally
dark brown in colour with lighter patches, although the colour
can vary considerably. The head is relatively small, the beak
blunt and rounded. A single pair of plates stretches from the
nostrils to the forehead between the eyes. Green turtle nests are
ABOVE:
Green turtles mating in the Arabian Gulf
BELOW: Tracks left by a nesting hawksbill turtle
appears jagged. There are two pairs of plates between the eyes,
compared to just one in the green turtle.
Hawksbill turtle nests are roughly circular and shallow, usually
less than half a metre deep. Unlike green turtles, hawksbills
move along the beach by alternately sweeping the fore flippers
backwards, much like a freestyle swimming stroke. The tracks
left by each flipper either side of the body are therefore parallel,
but not directly opposite each other as with the green turtle.
Nesting beaches may consist of anything from fine sand to
rocky, coarse sand beaches in the UAE and include offshore
islands and a few mainland sites. Feeding grounds are in shallow
water over coral or rocky reefs where they feed on soft corals,
sponges, ascidians and other soft-bodied animals. Hawksbill
turtles probably occur wherever there are coral reefs, suggesting
a range that includes much of the Gulf of Oman and Arabian Gulf
coastal waters. Most have been seen near the shallow, offshore
coral reefs to the west of Abu Dhabi.
LO G G E R H E A D T U RT L E
Caretta caretta (Deraniyagala, 1933)
Local Name: ‘Murah’
Adult loggerhead turtles are slightly smaller than green turtles, the
carapace usually measuring a little less than 100 centimetres in
length and weighing up to 160 kilograms. There are five pairs of
costal scutes, as opposed to four in both green and hawksbill
turtles. The carapace is relatively flat and is often light brown,
while the leathery skin has an orange tinge. The broad head is on
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MARINE REPTILES
S E A T U RT L E S I N T H E UA E
a thick neck and is large relative to body size. The beak is sharply
pointed but thick and solid.
Loggerheads feed on crabs, shells and other reef animals
relatively deep on the reef. Nesting beaches have not been
identified in the UAE, but in Oman preferred beaches are
composed of coarse sand.
The presence of loggerhead turtles in the UAE is known only
from discoveries of a few skulls and carapaces of dead animals
on offshore islands west of Abu Dhabi. No confirmed live
sightings have been recorded.
L E AT H E R BAC K T U RT L E
Dermochelys coriacea (Vandelli, 1761)
Leatherback turtles are giants among turtles. The largest on record
is reputed to have weighed nearly 1,000 kilograms and to have
measured an astonishing 3 metres in length. Most are substantially
smaller than this, weighing perhaps 400 kilograms. Unusual
turtles placed in their own family, they do not have plates like
other turtles, but a soft skin covering the shell with seven
prominent ridges running the length of the carapace. They are
mostly black with scattered white markings. The large smooth
head on a thick, short neck has a rounded beak with two cusps
at the end of the upper jaw.
Leatherbacks are truly pelagic, avoiding coral reefs and coastal
areas. They feed in the open ocean, almost exclusively on
jellyfish and planktonic organisms such as sea squirts. Nesting
sites are not in the UAE itself but elsewhere in the world, on
steep beaches with deep sand, often in areas of heavy surf with
deep water close to shore.
Leatherbacks are known only from a few sightings in the UAE,
which were made near Dubai. They may also occur off the East
Coast in the Gulf of Oman.
The head of a hawksbill turtle, showing the characteristic hooked beak for
which it is named.
SEA SNAKES
True sea snakes (family Hydrophiidae) are the most completely
marine of all extant reptiles. They never voluntarily come out of
the water, and live, reproduce, feed and die at sea. The origin and
relationships of the true sea snakes are still subject to debate, but
molecular phylogeny indicates that they are closely related to the
Australo-Papuan elapid land snakes, and probably originated in
which close when the snake is under water, and the tongue is short
with only the cleft portion protusible. The body form is variable, but
all have a laterally compressed, paddle-like tail for swimming. Fish-
that region (Keogh 1998; 2002; Slowinski and Keogh 2000).
Indeed they are often classified within the family Elapidae.
Like terrestrial snakes, all sea snakes have scaly skin. However,
diameter of the head and neck (Heatwole and Cogger 1993).
Sea snakes can dive to depths as great as 100 metres, and may
remain underwater for two hours (Heatwole 1987). Eventually
unlike their land-dwelling relatives, they lack expanded belly scales
and the ability to move on land. Hence they are frequently left
stranded and helpless on the beach by strong onshore winds or
rapidly falling tides. The vertebral column of many sea snakes is
weak and does not provide sufficient support to cope well out of
they must surface to breathe, with most species having dorsal
nostrils so that they can breathe without exposing the rest of the
body to aerial predators. All true sea snakes bear live young and
generally produce clutches of between three and nine relatively
large neonates. The beaked sea snake Enhydrina schistosa is an
water and, as the skin lacks sufficient waterproofing, stranded sea
snakes may die from dehydration. Sea snakes have valved nostrils,
exception and produces large clutches, averaging 18.3, but
sometimes up to 30 (Heatwole and Cogger 1993).
eating species usually have a body shape similar to most terrestrial
snakes, but species that feed on burrowing eels have small heads
and fore bodies, with large deep hind bodies up to ten times the
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1991; Gallagher 1993; Gasperetti 1988). Research on the UAE’s
sea snakes has been minimal (e.g. Brown 1989; Gallagher 1993;
Rasmussen 1993) although they may be abundant in the warm
shallow seas of the Arabian Gulf, where they can frequently be
seen on the sea’s surface, and where they are known to engage
in mating behaviour. Boat-based surveys in the Straits of Hormuz
have revealed densities of up to 142 individuals per square
kilometre (Anonymous 2000), the vast majority of which were
the yellow-bellied sea snake Pelamis platurus.
The status of sea snakes in the UAE is unknown. None of the
species that occur in UAE waters are listed in IUCN’s Red List of
endangered species.
The following descriptions follow Gasperetti (1988) and Anon.
rare for them to bite humans.
(1991). Identification of the species may be difficult in some
Sea snakes occur in both the Arabian Gulf and the Gulf of Oman,
with nine species having been recorded in the area (Anonymous
cases and readers are referred to the more detailed descriptions
and keys in these works.
S E A S N A K E S I N T H E UA E
BEAKED SEA SNAKE
Enhydrina schistosa (Daudin, 1803)
The beaked sea snake can be up to 140 centimetres in length.
The body is moderately stout and vertically flattened and the
head rather small and only slightly wider than neck. The snout is
down-turned giving the characteristic beaked profile. The upper
part of head is dark greenish without markings. The dorsum of
adults is a dull olive green or greenish-grey with dark crossbands
that tend to fuse together towards the tail. Crossbands are
widest along the backbone and tend to come to points on the
LEFT AND BELOW:
MARINE REPTILES
Sea snakes are among the most venomous of the world’s
snakes (Warrell 1993) and the venom of all of those found in UAE
waters can be fatal to humans. The venom probably evolved in a
feeding context rather than for defence (Heatwole 1987).
The venom has to be powerful enough to rapidly overcome prey,
such as fish, crabs and squid, and also has a secondary role in
actively aiding digestion. The fixed, tubular fangs are just a few
millimetres in length and hang from the upper jaw at the front
of the mouth. Injection occurs by deliberate compression of the
venom glands, delivering a lethal combination of neurotoxins,
myotoxins and nephrotoxins, although the exact composition of
the venom varies between species and even individuals. Despite
their powerful venom, most sea snakes are docile and it is very
Annulated sea snake Hydrophis cyanocinctus
ARABIAN GULF SEA SNAKE
Hydrophis lapemoides (Gray, 1849)
Up to 96 centimetres, the Arabian Gulf sea snake is bulky, with a
relatively small head. It is yellow, sometimes pale dull green or
grey, with 33 to 35 dark bands along the length of the body, with
pale undersides. The top of the head is usually dark with a
narrow yellow band forward of the small eyes. It is similar in
appearance to the annulated sea snake H. cyanocynctus.
This species is found in warm, shallow waters over reefs, seagrass
or sand and has been recorded in fresh-water estuaries. This is
usually considered a rare species, but is relatively common in the
Arabian Gulf and in near-shore shallow waters in the Gulf of Oman.
REEF SEA SNAKE
Hydrophis ornatus (Gray, 1842)
Up to 95 centimetres, this is a medium-sized sea snake with
about 50 broad dark bars or rhomboidal spots separated by
narrow interspaces, on a yellow, olive, pale grey or even whitish
background. The head is olivaceous.
It frequents warm, shallow waters over reefs, seagrass or sand
of the Arabian Gulf and Gulf of Oman.
flanks. The crossbands usually disappear in older adults,
leaving a dull bluish-grey colour dorsally.
Inhabiting shallow waters with muddy or sandy bottoms,
they are plentiful at mouths of rivers and have been found
upstream in various localities. They are common in the Gulf of
Oman but rare in the Arabian Gulf.
A N N U L AT E D S E A S N A K E
Hydrophis cyanocinctus (Daudin, 1803)
This is a large sea snake, up to 188.5 centimetres in length,
having a moderate-sized head and the greatest body diameter,
about 2.5 times the diameter of the neck. The colour is
variable but there are 50 to 75 black bars or rings on a yellow
or olive background, particularly in younger individuals. These
bars are broader dorsally, with interspaces less than half the
bar width, and usually taper to points on the flanks.
This species frequents warm, shallow waters over reefs,
seagrass or sand and is reported as common in the Arabian
Gulf and also occurs in shallow waters in the Gulf of Oman.
A mating pair of beaked sea snake Enhydrina schistosa
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ABOVE:
Arabian Gulf sea snake Hydrophis lapemoides
RIGHT: Shaw’s sea snake Lapemis curtus
Y E L LOW S E A S N A K E
Hydrophis spiralis (Shaw, 1802)
The yellow sea snake is perhaps an exception to the generally
docile nature of sea snakes and is said to be aggressive. Large
and dangerous, its bite is potentially fatal. The largest of the sea
snakes, it may reach 2 metres or more in length, though is
relatively less bulky than the Arabian Gulf sea snake. The colour
pattern is yellow with 30 to 60 narrow black rings, wider dorsally,
along the length of the body, with pale undersides. The head of
young snakes is blackish with a yellow horseshoe-shaped mark
on top, while in adults the head is entirely yellow.
In UAE waters, it has been recorded from the Gulf of Oman
and the Arabian Gulf, but is restricted to warm shallow waters
over reefs, seagrass or sand.
S H AW ’ S S E A S N A K E
Lapemis curtus (Shaw, 1802)
Up to 86 centimetres in length, the body is relatively short, neck
indistinct and the head broad and slightly flattened. It is yellow,
olive or grayish above, with 45 to 55 dark bands, often taking on
a rough diamond shape, thicker and almost touching over the
spine and converging to points at the flanks. They have pale
undersides and may have dark patches above each eye. Males
may have well-developed spines on the body scales. Juveniles are
more strikingly coloured, bright yellow against black, and the
dark bands may form complete rings.
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This species is to be found in warm, shallow waters over reefs,
seagrass or sand, but is less often seen than the Arabian Gulf and
yellow sea snakes. It has been recorded from the Gulf of Oman
and is common in the Straits of Hormuz.
G R AC E F U L S M A L L- H E A D E D S E A S N A K E
Microcephalophis gracilis (Shaw, 1802)
Up to 102.5 centimetres, the head is extremely small and the
forebody narrow compared to the size in this snake. The head is
black to dark olive. Adults are greyish above and paler below,
with indistinct markings. Juveniles have a series of whitish dorsal
bands or oval spots on the narrow anterior part of the body and
more or less complete bands posteriorly.
A specialist feeder on bottom-living eels, this species probably
dives deeper than most other sea snakes. It has been reported
from the Arabian Gulf and Gulf of Oman.
Y E L LOW- B E L L I E D S E A S N A K E
Pelamis platurus (Linnaeus, 1766)
Generally less than 90 centimetres in length, the upper surface
along the back is uniform brown (often very dark), sides and
undersides pale yellow and the tail black with a bold yellow
diamond-shaped pattern. The head is small and narrow and is
also coloured dark above, pale below. The colour pattern of this
species is unique and not easily mistaken for any other species.
The eye is relatively large.
Most plentiful in clear, warm, shallow water where surf and
currents are weak, they may also be found far out at sea. It is a
ABOVE:
Shaw’s sea snake Lapemis curtus
BELOW: Yellow-bellied sea snake Pelamis platurus
current lines over deep water. The most widespread species of
sea snake, it has been recorded both in the Arabian Gulf and the
Gulf of Oman.
VIPERINE SEA SNAKE
Praescutata viperina (Schmidt, 1852)
Up to 78 centimetres, the body is moderately thick, cylindrical
towards the head. It is variable in colour, often with 24 to 35 dark
rhomboidal spots, which are more or less confluent dorsally, on a
greyish background. The crown of the head is dark grey or black.
Males have spines on the distal side of the dorsal scales and a
row of spines on the rear edge of the wide, anterior ventral scales.
It frequents warm, shallow waters over reefs, seagrass or sand and
has been recorded in both the Arabian Gulf and the Gulf of Oman.
Robert Baldwin and Drew Gardner
surface feeder and has often been observed along distinct surface
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