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MARINE TURTLE POPULATIONS OF PULAU REDANG
:
THEIR STATUS AND RECOMMENDATIONS FOR THEIR MANAGEMEN T
B y
JEANNE A
. MORTIME
R
A Report Submitted to th
e
Turtle Sanctuary Advisory Council of Terenggan u
Produced Unde
r
WWF Project No
. 386
8
September 199
1
WWF Malaysi
a
Locked Bag No
. 91
1
Jalan Sultan P
.O
.
46990 Petaling Jaya, Selango
r
Telephone
: (03)757-9192 / Telefax
: (03) 756-5594
CONTENTS
Pag
e
EXECUTIVE SUMMARY
1
ACKNOWLEDGMENTS
5
SECTION
1
.
INTRODUCTION
6
1
.1
Importance
of the Island as Turtle Habitat
6
1
.1 .1
The
Nesting Populations
6
1
.1
.2
Habitat
for
Juvenile and Subadult
Turtles
6
1
.2
The Aim of this Paper
6
SECTION
2
.
BIOLOGY
OF THE BREEDING POPULATIONS
6
2
.1
The Nesting Season
6
2
.2
Nesting Distribution Around
the
Island
7
2
.3
Characteristics
of
the Nesting Beaches
7
2
.4
Characteristics
of
the Natural
Nests
8
2
.4 .1
Nest Site Selection on
the
Beach Platform
8
2 .4 .2
Depth
of the Natural
Nests
9
2
.4
.3
Clutch Size in Natural
Nests
9
SECTION
3
.
THREATS
TO THE TURTLE POPULATIONS
9
3.1
Over-harvest of Eggs
9
3 .1 .1
Methods
of
Egg Harvest
1
0
3 .1 .2
The
Intensity
of
the Egg Harvest
1
0
3 .1 .3
Why Egg Harvest Should Stop
1
1
3 .1 .4
Egg Harvest Within
the Marine National Park
1 1
3
.2
Accidental Capture
in
Fishing Gear
1
2
3
.3
Habitat Destruction
1
2
SECTION
4
.
NESTING BEACH SANCTUARIES
1 3
SECTION
5
.
TURTLE TOURISM--A SUSTAINABLE FORM
OF
EXPLOITATION
1 3
5 .1
Turtle Watching
1 3
5 .2
Maintaining Captive
Turtles as a
Tourist Attraction
1 4
SECTION
6
.
THE HATCHERY OPERATION
1 4
6 .1
Methodologies Employed
1 4
6
.1 .1
Turtle Species
1 4
6
.1
.2
Location
of the Hatchery
1
4
6 .1 .3
Collection and Translocation
of
Eggs
1
5
6 .1 .4
Clutch
Size in the
Artificial Nests
1 5
6 .1 .5
Physical Characteristics
of the
Artificial Nests
1 5
6 .1 .6
Rates
of
Hatching Success
in the
Hatchery
15
i
CONTENTS
Page
6
.1 .7
Hatchling
Release
1
6
6
.2
Problems Observed at the Hatchery
1 6
6 .2
.1
"Imprinting"
of Turtle
Offspring
to the
Wrong
Nesting Beach
1 6
6
.2 .1 .1
Incubation of Eggs in the Beach a
t
Pulau Pinang
1
6
6 .2
.2
Improper
Release of Hatchlings
1
6
6
.2 .2 .1
Release of Hatchlings at Pulau Pinang
1
6
6
.2 .2 .2
Keeping Hatchlings in Holding Tank
s
Prior to Their Release
1
6
6.2 .3
Skewed Sex Ratios in
the
Offspring
17
6
.2
.4
Lowered Rates of Hatching Success
1
7
6.2 .5
Headstarting
1 8
SECTION
7
.
RECOMMENDATIONS
1 8
7
.1
In Situ Incubation
in Natural Nests
1 8
7
.1
.1
The Benefits of In Situ Incubation
1
8
7
.1
.2
Possible Problems Associated
with
In Sit
u
Incubation
1
9
7
.1 .2
.1
Egg Theft
1
9
7
.1 .2 .2
Excavation
of Egg
Clutches
b y
Nesting Turtles
1
9
7
.1
.2
.3
Predation by Lizards
2
0
7
.1 .3
Compensation to the Villagers for the Eggs
2
0
7
.1 .3 .1
Direct Compensation
2 1
7
.1 .3 .2
Turtle
Tourism as a Source
o
f
Village Income
2 2
7
.2 Translocate the Hatchery to a Natural Nesting Beach
2 2
SECTION 8
.
CONCLUSIONS
23
REFERENCES
2 4
TABLE
1
.
The amount of Green Turtle nesting in the State o
f
Terengganu that occurs at Pulau Redang
2 6
TABLE 2
.
Proportion of the total eggs laid by Green Turtles an
d
Hawksbill Turtles incubated in the hatchery each year
2
7
TABLE
3
.
Relationship between nesting density and documente
d
levels of density dependent mortality
2 8
ii
CONTENTS
Pag
e
FIGURE 1
.
Map showing Pulau Redang and nearby Pulau Pinang
2 9
FIGURE 2
.
Graphs showing the seasonal distribution of egg layin
g
by green turtles and hawksbills during 1990
3 0
FIGURE 3
.
Diagram showing the destruction of
a nestin
g
population through over-harvest of eggs
3 1
iii
EXECUTIVE SUMMAR
Y
Backgroun
d
Each year, 33-54% of all green turtle nestings and almost 70% of th
e
hawksbill
nestings reported in Terengganu occur at Pulau Redang
; bu
t
due to logistical difficulties, proper management of the turtl
e
resource has been impossible
. The management and conservatio
n
practices currently employed at the island are not only inadequate t
o
maintain these populations, but also harmful to the turtles
. Becaus
e
the Department of Fisheries has recently completed construction of it
s
Marine Park Headquarters, however, it should now be possible to tackl
e
these management problems
.
Threats to the turtle populations of Pulau Redang include th
e
following
:
1)
Severe Over-harvest of Eggs
.
During the decades prior to 1988
,
less than 3% of green turtle eggs laid at Pulau Redang wer
e
protected
. Recent efforts to increase the level of protectio
n
are still inadequate
. Between 1988 and 1990, only 14
.8% of th
e
green turtle eggs laid were protected
. Scientists believe tha
t
to maintain an already healthy population, at least 70% of th
e
eggs should be protected
. So, considering past levels of over
-
harvest, 100% protection is warranted at Pulau Redang
.
Continued exploitation of turtle eggs at Pulau Redang i
s
incompatible with the long-term survival of the population, an
d
also with the objectives of a Marine National Park as stated i
n
the Fisheries Act of 1985
.
2)
Damage Caused by the Hatchery at Pulau Pinang
.
Unnatura
l
conditions in the hatchery cause the following problems
:
a)
Offspring
That
May Never Return to the Nesting
Beaches
o
f
Pulau
Redang
.
The following management practices ma
y
interfere with the ability of the turtles to "imprint" to th
e
nesting beaches of Pulau Redang
:
i)
Incubating eggs in the beach hatchery at Pulau Pinan
g
rather than in the natural nesting beaches of Pula
u
Redang
. (Developing embryos may "memorize" navigationa
l
cues such as magnetic fields or chemical factors in th
e
sand that would later direct them to the nesting beac
h
as breeding adults
.
)
ii) Release of hatchlings at Pulau Pinang rather than at th
e
natural nesting beaches of Pulau Redang
. (Hatchlin
g
turtles may memorize navigational cues during thei
r
initial journey out to sea
.)
1
iii)
Keeping hatchlings in holding tanks prior to thei
r
release may cause them to "imprint" to conditions in th
e
holding tanks instead of in the sea
.
b)
Skewed
Sex Ratios
in the Offspring
.
Few (if any) mal
e
offspring are likely to be produced in the hatchery, due t
o
the high incubation temperatures caused by the following
:
i)
Not enough shade
. About 64% of the natural nests ar
e
heavily shaded by beach vegetation, while none (0%) o
f
nests in the hatchery is shaded
.
ii)
Shallow nest depth. The average depth measured in th
e
natural nests was 75.9 cm, while that in the hatcher
y
was only 62
.0 cm
.
c)
Excessive
Mortality Among the Turtle Hatchlings
.
Increase
d
predation of hatchlings by fishes in nearshore waters i
s
caused by
:
i)
Releasing hatchlings at the same time and place eac
h
day
. (Fishes learn when and where they can find a mea
l
of young turtles
.
)
ii)
Keeping hatchlings in holding tanks prior to thei
r
release
. The continuous swimming of the confine
d
hatchlings may prematurely exhaust the energy reserve
s
stored in their yolk sacs
. The weakened hatchlings ma
y
be less able to avoid predation when released
.
Recommendation
s
The Ideal Management Option--In Situ Incubation of Eggs in Natura
l
Nests
.
One or more of the three major nesting beaches should be se
t
aside as a total sanctuary for nesting turtles
. All eggs laid a
t
these beaches should be allowed to incubate in their natural nests
.
The most important beach to protect is Cagar Hutang, where th
e
greatest amount of nesting occurs
. The following factors need to b
e
considered
:
1)
Compensation
of
the Villagers
Who Are Presently Dependent o
n
Income from Collection of Eggs
. This may be done in th
e
following ways
:
a) Rather than pay the villagers to collect eggs and bring the
m
to a hatchery, the Authorities should compensate th
e
villagers according to how many egg clutches are left t
o
hatch in the sanctuary beach(es)
. The amount of compensatio
n
could be based on one of the following
:
i) an average of the amount earned by the villagers for eg
g
sale during the past 3-5 years
. This figure could b
e
calculated from the records of the Fisheries Department
.
2
ii) daily beach surveys (see section 7
.1 .3
.1)
. The averag
e
number of eggs laid per clutch is already known (se
e
section 2
.3
.3)
.
b) Sustainable exploitation of the turtles as a touris
t
attraction should be encouraged
. The villagers could deriv
e
an alternate source of income from guiding and supervisin
g
tourists at the nesting beaches, and also by operating smal
l
scale tourist businesses such as chalets (see Section 5)
.
Over a period of time, when these businesses have bee
n
established, monetary compensation to the villagers should b
e
reduced or done away with
.
2)
Egg
Theft
.
Guards should be posted at the sanctuary beaches
.
(See section 7
.1 .2
.1
.
)
3)
Excavation of Egg Clutches by Nesting Turtles
.
Although turtle
s
will occasionally excavate previously laid egg clutches, fewe
r
than 5% of the eggs laid are likely to be damaged in this manne
r
(see section 7
.1 .2
.2)
.
A pilot study should be conducted, during which density dependen
t
mortality would be monitored
.
4)
Predation
by
Lizards
.
The extent to which lizards prey upo
n
turtle eggs and hatchlings needs to be evaluated during a pilo
t
study of in situ
incubation
.
An Alternate Management Option--to Locate the Hatchery at One of th
e
Three Major Nesting Beaches Instead of at Pulau Pinang
.
See sectio
n
7
.2 for detailed management recommendations
. Suggestions include
:
1)
Duplicate conditions in the natural nests
by
:
a)
Planting the nests in shaded and unshaded parts of the beac
h
in approximately the same proportions as they occur naturall
y
(see section 2
.3
.1)
.
b)
Constructing artificial nests whose depths are similar t
o
those of the natural nests (see section 2
.3
.2)
.
2)
In order to allow the newly emerged hatchlings to enter the se
a
as quickly and naturally as possible, the
nests should be
"self
-
releasing
."
This can be accomplished in the following ways
:
a) No cylindrical mesh enclosures should be used to restrain th
e
hatchlings when they emerge from the nest
.
b)
The fence around the hatchery should prevent nesting female
s
from entering the hatchery and digging up the eggs, bu
t
should not restrain the migration of the hatchlings toward
s
the sea
. Heavy wooden stakes separated from each other b
y
several inches would serve this function
.
3
(The possible impact of lizard predation would need to b
e
monitored during the initial stages of such hatcher
y
operation, to determine if additional fencing would b
e
needed
.
)
3)
Eqq
Collection
by
the
Villagers
should
be
Phased
Out
.
Compensation as suggested earlier could also be applicable here
.
4
ACKNOWLEDGMENT
S
I wish to thank Y
.B
. Dato' Setia Wangsa (the State Secretary o
f
Terengganu), En
. Mazlan bin Jusoh (the Deputy Director of Fisheries)
,
the Terengganu Turtle Sanctuary Advisory Council, and the Federal an
d
Terengganu Fisheries Departments for their co-operation and advice
.
Special thanks are also due Dr
. Mikaail Kavanagh (WWFM), En
. Brahi
m
bin Salleh (Federal Fisheries), En
. Wan Harujan bin Sulaiman (UPE
N
Terengganu), En
. Abd
. Rahim bin Gor Yaman (Federal Fisheries) and En
.
Ismail Taufiq bin Md. Yusoff (Terengganu Fisheries) for their time an
d
advice during the past two and one-half years
.
Ms
. Sarala Aikanathan collaborated in the collection of beach transec
t
data as well as that describing natural and artificial nests at Pula
u
Redang
. Mr
. Lee Kup Jip and En
. Ishaak Ariffin (WWFM) too
k
measurements of the nesting beaches
.
I am grateful to the following people for their assistance over th
e
years and for the opportunity to exchange ideas with them
: En
.
Baharuddin bin Abdullah, En
. Sukarno bin Wagiman, En
. Abdul Rahman bi
n
Kassim, En
. Ahmad Taufiq, En. Norley bin Hashim, En
. Jamlus bin Md
.
Nor
., and En. Zainal Abidin bin Hj
. All
.
Thanks go to the Village Head at Pulau Redang, En
. Ladin bin Awang
,
and his family for their warm hospitality during my visits to th
e
island
.
Thanks are due to Mr
. Ken Scriven, En
. Dzuhari bin Daud, Mr
. Din
o
Sharma, Ms
. Cynthia Low, Ms
. Loh Lo Mei, Ms
. Cindy Cheah, Ms
. Susa
n
Abraham and all other WWFM staff members for their support
. Mr. Le
e
Kup Jip and Dr
. Mikaail Kavanagh made helpful comments on an earlie
r
draft of this manuscript
.
This report was produced under WWF Project No
. 3868
.
5
1.
INTRODUCTIO
N
1
.1
Importance of the Island as Turtle Habita
t
1
.1 .1
The Nesting Population
s
Pulau Redang (see map Figure 1) harbors the larges
t
breeding populations
of both green turtle
s
(Chelonia
mydas)
and hawksbills
(Eretmochely
s
imbricata)
in the State of Terengganu
.
Betwee
n
1984 and 1990, 33-54% of all green turtle nestin
g
occurred at that island alone (see Table 1)
. I
n
1990, 49 hawksbill nests were recorded on Pula
u
Redang--i
.e
. 68% of the total reported for th
e
entire State
. On occasion, olive ridley
s
(Lepidochelys
olivacea)
also nest at Pulau Redang
-
as identified from photos in the WWF-Malaysi
a
Resource Center
.
1
.1
.2
Habitat for Juvenile and
Subadult
Turtle
s
Pulau Redang
has important developmental habita
t
for young green turtles and hawksbills
.
Juvenile
s
and
subadults of both species are
regularly
encountered on the coral reefs and the sea gras
s
and algae beds around the island
. These animal
s
are usually greater than 20 cm in carapace length-
-
typical of the size range that can be expected i
n
near shore waters
.
In April 1991, a reliable informant reported seein
g
a group of about 100 turtles (of unknown species
)
with carapace lengths of less than 15 cm swimmin
g
quite close to shore (pers
. comm
. Baharuddin b
.
Abdullah to J
. Mortimer
.) This observatio
n
indicates that Pulau Redang may also serve a
s
critical habitat for the animals during the poorl
y
known first years in their life cycle
.
1
.2
The Aim of this Pape
r
This is a report on observations about turtl
e
biology and management at Pulau Redang that WW
F
Malaysia has made during the past 2
.5 years
.
Included are suggestions for ways to improv
e
management of the island's turtle populations
.
2.
BIOLOGY OF THE BREEDING POPULATION
S
2
.1
The Nesting Seaso
n
Figure 2 shows the seasonal distribution of nestin
g
emergences for green turtles and hawksbills a
t
Pulau Redang during 1990 (Jabatan
Perikanan
,
1990a)
. The green turtle season extends
fro
m
6
January through October with a peak during th
e
months of June and July
. The hawksbill seaso
n
extends from March through August, with a peak i
n
April and May
.
2
.2
Nesting Distribution Around the Islan
d
During 27-30 May and 25-30 June of the 1990 nestin
g
season, Sarala Aikanathan and I accompanied the eg
g
collectors of the island in order to survey th
e
nesting beaches
.
We examined tracks made b
y
breeding
turtles during 84 nesting emergence
s
made the following observations
:
an
d
1)
In
descending
orde
r
th
e
beach
o
f
tota
l
were
importance,
th
e
proportions
o
f
deposited at each
egg
clutche
s
the following
:
Number of Percentag
e
of Tota
l
Egg Clutche
s
Egg Clutche
s
Beach
Lai
d
Cagar Hutang
28 45
.9
%
Mak Kepit
20 32
.8
%
Mak Simpan
10 16
.4
%
Pasir Che Keling
2
3
.3
%
Kg
. Lama
1
1
.6
%
2) Eggs were laid during 61 of the 84 nestin
g
emergences recorded--i
.e
. 73% of the time
. I
n
other words, for each egg clutch laid, turtle
s
made an average of 1
.4 nesting emergences
.
This figure is low compared to what has bee
n
observed at many other green turtle rookerie
s
(Mortimer 1988,1990
; Mortimer and Carr, 1987
;
Mortimer and Dzuhari, in prep
.), and indicate
s
that turtles find it relatively easy to di
g
nests in the beach sand at Pulau Redang
.
2
.3
Characteristics of the Nesting Beache
s
We examined the following parameters of the thre
e
major nesting beaches at Pulau Redang
:
1)
Beach length
;
2)
Area of the beach platform above the high tid
e
line available for nesting
;
7
3)
Percentage of the beach platform available fo
r
nesting that is shaded by vegetation
.
To determine the beach area and what proportion o
f
it is shaded, we conducted 57 beach transects
.
Each transect extended from the rear of the beac
h
to the water line
. We recorded the location o
f
shade cover along each transect line, as well a
s
that of the high tide line
.
We recorded the following characteristics at eac
h
nesting beach
:
BEACH PLATFORM AVAILABL
E
FOR NESTIN
G
------------------------
-
LENGTH
ARE
A
(m)
(m2)
% SHAD
E
Cagar Hutang
338
6,077
49 %
Mak Kepit
150
2,910
34 %
Mak Simpan
234
3,510
49 %
2
.4
Characteristics of the Natural Nest
s
2
.4 .1
Nest Site Selection on the Beach Platfor
m
Studies done elsewhere have demonstrated that th
e
position of the nest on the beach platform relativ
e
to the vegetative shade cover influences th
e
temperature of the nest, and ultimately the se
x
ratio of the offspring (Standora and Spotila
,
1985)
.
During our surveys of Pulau Redang, we classifie
d
each nest according to the degree to which it wa
s
shaded
. Three degrees of shading were noted
:
1) Densely shaded--i
.e
. the nest site was shade
d
by tree foliage or shrubbery
throughout
th
e
day
;
2)
Partially shaded--i
.e
. the nest site wa
s
a)
shaded by tree foliage or
shrubber
y
duringpart of the day, o
r
b)
covered by low ground cover such a
s
Ipomea,
grasses or creepers
;
BEACH
8
3)
Unshaded sand
.
Following are the proportions of 50 nest sites tha
t
fell into each category
. The majority of the nest
s
were at densely shaded sites
:
1)
Densely shaded
:
64
.0
%
2)
Partially shaded
:
14
.0
%
3)
Unshaded sand
:
22 .0%
These proportions are almost identical to those
I
recorded for green turtles at Pulau Selingaan i
n
the Turtle Islands of Sabah
: densely shaded-
-
64 .7%
; partially shaded--14
.7%
; and unshaded sand-
-
20
.6% (Mortimer, 1991)
.
Although only 34 - 49% of the beach platfor
m
available for nesting at Pulau Redang was shade
d
(see section 2
.3), the turtles placed 58% of thei
r
nests in the shade
. This suggests that the turtle
s
are preferentially choosing shaded nest sites
.
2
.4 .2
Depth of the Natural Nest
s
At the time the egg collectors removed the egg
s
from the natural nests, we measured the distanc
e
between the bottom of the nest and the surface o
f
the sand
.
For green turtles, the average nest depth recorde
d
among 55 nests was 75
.9 cm (SD = 10
.0
; range = 54
-
95)
.
We encountered only one hawksbill nest
.
It was
5 6
cm deep
.
2
.4
.3
Clutch
Size in Natural Nest
s
For
green
turtles,
the average
clutch
size
w
e
measured
in 57 natural nests was 105
.8 eggs
(SD
=
19
.0
;
range = 72-148)
.
3
.
THREATS TO THE TURTLE POPULATION
S
3
.1
Over-harvest of Egg
s
The
greatest
threat facing the
survival
of
th
e
turtle
nesting population at Pulau Redang
is
th
e
9
continued
over-harvest
of
eggs
for
huma
n
consumption
.
3
.1 .1
Methods of Egg Harves
t
The rights to collect turtles' eggs from th
e
nesting beaches of Pulau Redang are tendered to
a
cooperative of men from the village
. They pay
a
tenderer's fee of approximately $ 30,000 per yea
r
(this sum varies from year to year)
. Th
e
cooperative usually comprises more than 15 men wh
o
take turns harvesting the eggs
.
In order to avoid disturbing the turtles, no one i
s
allowed in the vicinity of the nesting beache
s
during the night
. Eggs are harvested early in th
e
morning
.
Each morning, shortly after dawn, one of the eg
g
collectors, using his own boat, travels around th
e
perimeter of the island, and stops to collect egg
s
from those beaches where fresh turtle tracks ar
e
visible
. When a fresh nest is identified, the ma
n
uses an "egg stick" to probe the sand in order t
o
locate the exact position of the egg clutch
.
Depending on the number of egg clutches collecte
d
and also on the speed of the boat used for th
e
operation, the egg collector may return to th
e
village with the eggs, any time between 09
.00 a
.m
.
and 3
.00 p
.m
.
At that time, a portion of the eggs collected i
s
taken to Pulau Pinang for burial in the hatchery
.
The remainder are marketed
.
3
.1 .2
The Intensity of the Egg Harves
t
Turtle eggs have been intensely harvested at Pula
u
Redang for several decades
. Prior to 1984, ther
e
was no hatchery at Pulau Redang
. Between 1984 an
d
1988 less than 3% of the green turtle eggs laid a
t
Pulau Redang were allowed to hatch (Table 2)
.
During 1989 and 1990, 42.2% of all green turtl
e
eggs were protected
. Although this is a grea
t
improvement over previous efforts, significantl
y
more eggs need to be protected in order to save th
e
nesting population from extinction
.
The hawksbill turtle population has enjoye
d
somewhat better protection during the past decade
.
Between 1984 and 1988, 14
.1% of all hawksbill egg
s
laid were protected in the hatchery
. During 198
9
and 1990, 79
.3% of the eggs were protected
.
10
3
.1 .3
Whv Egg Harvest Should Sto
p
To offset the damage caused by excessive egg over
-
harvest at Pulau Redang during the past severa
l
decades, egg protection needs to be significantl
y
increased
. Ideally the eggs should receiv
e
complete protection
.
Although there are still large numbers of turtle
s
nesting at Pulau Redang each year, this can not b
e
taken as an indication that the nesting populatio
n
is healthy
. The fact that green turtles matur
e
very slowly has been well documented (Bjorndal an
d
Bolten, 1988)
. From 20 to 50 years pass betwee
n
the time a hatchling emerges from its own egg an
d
when it is ready to return to the nesting beach a
s
a breeding adult
.
Because there is such a long delay between hatchin
g
and maturity, there is also a time lag between th
e
onset of egg over-harvest at any particular nestin
g
beach and the subsequent decline in the numbers o
f
nesting females
. This is because 20 to 50 year
s
must pass after egg over-harvest occurs before th
e
absence of the offspring that
would have grown int
o
breeding adults is noticed
.
Over-harvest of eggs destroys a population "fro
m
the bottom up"
. In other words, the juvenil
e
animals will decline in number before there is
a
similar decline in the adult population
.
But
,
because the juvenile turtles live underwater, thei
r
decline usually goes unnoticed
. Moreover, th
e
foraging habitat for juvenile green turtles i
s
usually located hundreds or even thousands o
f
kilometers away from the breeding beach
. Thus, i
t
is possible to severely over-exploit a breedin
g
population for several decades before the number o
f
nesting females declines (see Figure 3)
.
But, once there is a crash in the numbers o
f
breeding females, the turtle population will b
e
more difficult (if not impossible) to rebuild
. I
n
order to save the nesting population at Pula
u
Redang, it is critical to protect as many eggs a
s
possible
now,
while there is still a sizabl
e
population of egg-producing females
.
3
.1 .4
Egg Harvest Within the Marine National Par
k
Considering the endangered status of its turtl
e
population, now that Pulau Redang is a Marin
e
National Park, continued harvest of turtle eggs i
s
incompatible
with the following objectives of
a
11
Marine National Park as stated in the Fisheries Ac
t
of 1985
: "to -
-
1)
afford special protection to the aquatic flor
a
and fauna of such area or part thereof and t
o
protect, preserve and manage the natura
l
breeding grounds and habitat of aquatic life
,
with particular regard to species of rare o
r
endangered flora and fauna
;
2)
allow for the natural regeneration of aquati
c
life in such area or part thereof where suc
h
life has been depleted"
.
3
.2
Accidental Capture in Fishing Gea
r
During the 1990 nesting season 10 dead gree
n
turtles
were found at Pulau Redang
(Jabata
n
Perikanan, 1990a)
. Most of these animals wer
e
probably drowned in fishing nets--either in traw
l
nets ("pukat tunda") or the ray net ("pukat pari")
.
3
.3
Habitat Destructio
n
The development of massive tourist facilities i
s
now underway at Pulau Redang
. These wil
l
eventually include a golf course, sports complexes
,
and deluxe accommodations for up to 845 people
.
There is a danger that the development wil
l
negatively impact the sea turtle populations o
f
Pulau Redang in two ways
:
1)
By destroying the coral reef and sea gras
s
ecosystems on which the juvenile
turtle
s
depend
.
The worst damage to these system
s
would be caused by
:
a)
siltation resulting from erosion
; an
d
b)
pesticides, herbicides and fertilizer
s
that run-off from the golf-course int
o
the sea
.
For more information about this problem se
e
the report by WWF Malaysia (1991) entitle
d
"Notes on the Planned Development at Pula
u
Redang
.
"
2) Disruption of the behavior of breeding adult
s
and also younger turtles by heavy boat traffi
c
and water sports activity in the vicinity o
f
the island
.
12
4
.
NESTING BEACH SANCTUARIE
S
In December 1990, the State Government o
f
Terengganu set aside three major nesting beaches o
n
the island as "Turtle Nesting Sanctuary Areas
.
"
These included (see Figure 1)
:
1)
Pasir Cagar Hutang
;
2)
Pasir Mak Kepit
; an
d
3)
Pasir
. Mak Simpan
.
This far-sighted step should protect the breedin
g
habitat from those forms of coastal developmen
t
known to be incompatible with nesting turtles
.
However, all eggs are now taken away from thes
e
nesting beaches and incubated at Pulau Pinang
.
It would be better if all eggs laid at the thre
e
protected beaches were allowed to incubate an
d
hatch out at these same beaches (see section
s
6 .2
.1, 6
.2
.2 and 7
.1
.1)
.
5
.
TURTLE TOURISM--A SUSTAINABLE FORM OF EXPLOITATIO
N
5
.1
Turtle Watchin
g
Many people feel that an economic motivation i
s
necessary
to justify preservation
of
turtl
e
populations
.
But, if egg harvest continues as i
t
has during recent years, the turtles of Pula
u
Redang will become extinct
. An alternate form o
f
exploitation, which is sustainable, is "Turtl
e
Watching" for tourists
.
With proper management, tourism and turtles ca
n
benefit each other
. Without management, th
e
association can be disastrous for the turtles
. Th
e
following are suggestions for ways to exploit th
e
turtle populations as a tourist attraction
:
1)
The most important nesting beach, Caga
r
Hutang, should be set aside as a stric
t
reserve area and no one should be allowed t
o
visit the beach at night
.
2)
Chalets could be built between Mak Kepit an
d
Mak Simpan, but
well out of sight
of
thes
e
beaches
.
Lights from the chalets
shoul
d
neither be visible from the beach nor from th
e
sea at night
.
Such small scale
touris
t
businesses,
including bed
and
breakfas
t
13
facilities, might form an alternate source o
f
income for the former egg collectors
.
3)
Guided tours of the two beaches (Mak Kepit an
d
Mak Simpan) could be arranged
. The former eg
g
collectors of Kg
. Redang could also be hire
d
as guides for the tourists
. No tourist
s
should be allowed near the nesting beache
s
without a guide from the village
.
4)
It is critical that the activities of th
e
tourists be strictly controlled
. No on
e
should be allowed to shine lights near th
e
beach or to approach too near the animals
.
Green turtles are extremely sensitive to ligh
t
and to other forms of disturbance--in fact
,
they are even more sensitive than leatherbac
k
turtles
.
5)
No camping should be allowed on any of th
e
three protected beaches
.
5
.2
Maintaining Captive Turtles as a Tourist Attractio
n
A small number of turtles could be maintained o
n
display in captivity for the enjoyment of th
e
tourists at the park center located at Pula
u
Pinang
.
6
.
THE HATCHERY OPERATIO
N
The following is a discussion of the methodologie
s
now employed at the hatchery and some of th
e
problems associated with them
.
6
.1
Methodologies Employe
d
6 .1
.1
Turtle Specie
s
The egg collectors are requested to bring to th
e
hatchery all the hawksbill eggs that they collect
,
and a portion of the green turtle eggs (see Tabl
e
2)
.
6
.1 .2
Location of the Hatcher
y
The hatchery is located near the Fisherie
s
Headquarters at the north end of Pulau Pinang, jus
t
south of Pulau Redang (see map, Figure 1)
.
14
6
.1 .3
Collection and Translocation of Egg
s
Eggs procured for the hatchery are collected by th
e
same men using the same methods as those procure
d
for the market (see section 3
.1
.1)
. The distanc
e
the eggs must travel between the nesting beach an
d
the hatchery ranges from 6 km to 19 km by sea
,
depending on the route taken by the egg collector
.
Some of the egg collectors handle the egg
s
carefully, while others are very rough
.
6
.1 .4
Clutch Size in
the Artificial
Nest
s
The average number of eggs recorded in 22 gree
n
turtle nests in the hatchery was 89
.6 eggs (SD
=
20
.7
; range = 53-136)
. A Mann-Whitney U tes
t
showed that the average clutch size in the hatcher
y
nests was significantly smaller than the 105
.8 egg
s
recorded in the natural nests (see section 2
.3
.2)( N
= 79
; p = 0
.0048
; z = 2
.82)
. This suggests tha
t
the egg collectors are either removing some egg
s
from
the
egg
clutches,
or
preferentially
surrendering smaller egg clutches to the hatchery
.
The average number of eggs recorded per hawksbil
l
egg clutch was 128
.2 (Source
: Department o
f
Fisheries Statistics
. )
6
.1 .5
Physical Characteristics
of the Artificial Nest
s
There is no shade in the hatchery
. All the nest
s
are in the open sun
. (Recall that only 22
.0% o
f
the natural nests were unshaded (section 2
.4
.2)
.
)
During the 1990 nesting season, the average dept
h
of 21 nests in the hatchery was 62
.0 cm (SD = 3
.0
;
range = 56-67)
. (Recall that the average depth o
f
the natural nests was 75
.9 cm (section 2
.4
.2)
. )
6
.1 .6
Rates of Hatching Success in the Hatcher
y
Following are the average rates of hatching succes
s
in the hatchery at Pulau Redang during the 1989 an
d
1990 nesting seasons, for the two species o
f
turtles (Jabatan Perikanan 1989, 1990b)
:
Green Turtle
Hawksbill Turtl
e
1989
49
.8
%
1990
77
.9%
47
.2
%
56
.9
%
15
6
.1
.7
Hatchlinq Releas
e
Hatchling release usually takes place at
th
e
hatchery beach on Pulau Pinang
.
6
.2
Problems Observed
at
the Hatcher
y
6
.2 .1
Imprinting"
of
Turtle
Offspring
to
the
Wron
g
Nesting Beac
h
6
.2
.1
.1
Incubation of Eggs in the Beach at Pulau Pinan
g
The mechanisms by which sea turtle offsprin
g
memorize the navigational cues they will need t
o
find the nesting beach as breeding adults are, a
s
yet, unknown
. There is a strong possibility
,
however, that they may "memorize" physical an
d
chemical information about the breeding beach whil
e
they are still embryos incubating in the nest
.
During that time, they may acquire informatio
n
about magnetic fields or chemical factors in th
e
sands
. (Note that magnetic materials have bee
n
found in the bodies of hatchling turtles (Jac
k
Rudloe, pers
. comm
. to J
. Mortimer)
.) Thus, t
o
incubate the egg clutches at Pulau Pinang instea
d
of at the natural nesting beaches, poses the ris
k
that the offspring may, as embryos, "imprint" t
o
the beach of Pulau Pinang rather than to th
e
nesting beaches of Pulau Redang
.
6
.2 .2
Improper Release of Hatchling
s
6
.2 .2 .1
Release of Hatchlings at Pulau Pinan
g
Hatchlingturtles may also memorize sensory cues a
t
the time they first enter the sea that will hel
p
them navigate to the nesting beach at a later date
.
Most of the hatchlings are now released on th
e
beach at Pulau Pinang--a site located severa
l
kilometers away from the covehead beaches wher
e
natural nesting occurs (see Figure 1)
.
6
.2 .2
.2
Keeping Hatchlings in Holding Tanks Prior to
Thei
r
Releas
e
During the day prior to their release, hatchling
s
are often kept in barrels of water
. This practic
e
may be harmful for two reasons
:
1) The continuous futile swimming of the turtle
s
during this period wastes the energy reserve
s
(present in the yolk sac) which the youn
g
16
turtle needs for the journey between th
e
shoreline and the deep water offshore
.
2) There is a possibility that the young turtle
s
will "imprint" to cues in the holding tank
s
rather than those in the sea adjacent to th
e
nesting beach
.
6
.2 .3
Skewed Sex Ratios in the Offsprin
g
The sex ratio of turtle offspring is determined b
y
the temperature of incubation
. Warmer temperature
s
produce more females and cooler temperatures mor
e
males
.
The temperature within a nest is influenced by it
s
depth below the surface of the sand and also by th
e
amount of shade at the nest site (see sectio
n
2
.3
.1)
.
The following indirect evidence suggests that th
e
temperatures within the artificial nests wer
e
significantly warmer than those of the natura
l
nests, and may thus be producing an unnaturall
y
high proportion of female offspring
:
1)
Most of the natural nests sites (64
.0%) wer
e
heavily shaded by trees and shrubs, while non
e
(0
.0%) of the artificial nests was shaded
.
2)
The average depth of the hatchery nests (62
.
0
cm) was shallower than that of the natura
l
nests
.(75
.9 cm)
. A Mann Whitney U test showe
d
this difference to be statisticall
y
significant (N = 76
; p = 0
.0000
; z = 5
.37)
.
6
.2 .4
Lowered Rates of Hatching Succes
s
The average rate of hatching success of eg
g
clutches planted in the hatchery at Pulau Redan
g
varied from year to year, and was probably relate
d
to the care with which the eggs were handled
. Th
e
conscientious hatchery caretaker employed durin
g
the 1990 season may have been largely responsibl
e
for the improved hatching success during 1990 (se
e
section 6
.1 .5
.)
.
Under ideal circumstances, green turtle hatch rate
s
of 80 to 90% can be expected (Parmenter, 1980)
.
However, to achieve such high rates of hatchin
g
success is extremely difficult at Pulau Redan
g
given that the eggs must be transported lon
g
distances between the nesting beaches and th
e
17
hatchery at the time they are most sensitive t
o
movement--i
.e
. from 3 hours old until 20 days ol
d
(Parmenter, 1980)
.
6
.2
.5
Headstartin
g
The headstarting of turtles, whereby hatchlings ar
e
reared in tanks prior to their release into the se
a
is not recommended
. Headstarting is an unprove
n
management technique which may well be harmful t
o
marine turtles (Mortimer, 1989)
.
7
.
RECOMMENDATION
S
In the following sections are two suggested option
s
for improving upon the management techniques no
w
employed
.
7
.1
In Situ Incubation in Natural Nest
s
7
.1 .1
The Benefits of In Situ Incubatio
n
The ideal option is to let the eggs incubate i
n
their natural nests
. One or more of the nestin
g
beaches should be set aside as a total sanctuar
y
for the turtles and the eggs should be left t
o
hatch
in situ
.
The best beach to set aside woul
d
be Cagar Hutang--which has the largest numbers o
f
nesting turtles
.
Such
in situ
incubation would avoid the followin
g
problems
:
1)
The
risk that the turtle
embryos
wil
l
"imprint" to the hatchery beach at Pula
u
Pinang, rather than to the three nestin
g
sanctuary beaches
.
2)
Artificially skewed sex ratios produced b
y
conditions in the hatchery
.
3)
Improper release of hatchlings
.
4)
Mortality caused by transporting eggs from th
e
nesting beach to the hatchery
.
5)
The expense of maintaining a hatchery progra
m
would be reduced
.
18
7
.1 .2
Possible
Problems
Associated
with
In
Sit
u
Incubatio
n
7
.1 .2
.1
Egg Thef
t
Ideally, a guard would be stationed at the beach
.
The Marine Park Authorities might minimize eg
g
theft by taking the following action
:
1)
Erasing all turtle tracks in the morning
;
2)
Making frequent patrols along the protecte
d
coast
; an
d
3)
Imposing heavy penalties for offenders
.
7
.1 .2
.2
Excavation of Egg Clutches
by
Nesting Turtle
s
At a natural nesting beach turtles occasionally di
g
up egg clutches previously laid by other turtles
.
Recent studies done in several parts of the world
,
however, have demonstrated that the amount of suc
h
egg mortality that occurs is relativel
y
insignificant
.
Table 3 summarizes the results of each of fou
r
studies conducted at three nesting sites--the gree
n
turtle rookery at Raine Island, Australia (Limpus
,
1988
; Limpus and Miller, 1989)
; the olive ridle
y
beach at Nancite, Costa Rica (Cornelius, 1985)
; an
d
the loggerhead turtle beach at Mon Repos, Australi
a
(Limpus, 1985)
.
The densest nesting was recorded at Raine Island
,
Australia, where in 1988 an estimated 100,000 eg
g
clutches were laid
. During that year
,
approximately 40 egg laying emergences occurred pe
r
meter of beach length, and about 1
.36 egg clutche
s
were laid per square meter of beach platform
. A
n
estimated 8
.6-25
.6% of total egg production wa
s
destroyed by nesting turtles (Limpus, 1988)
.
Of the four studies, the lowest nesting density wa
s
observed at Mon Repos, Australia where only 0
.8
6
egg laying emergences occurred per meter of beac
h
length
. There, an estimated 0
.43% of total eg
g
production was destroyed by nesting turtles
.
At Pulau Redang, an estimated 462-2251 egg clutche
s
are laid each year (source
: Department o
f
Fisheries Statistics)
. An average of 0
.6-3
.1 eg
g
laying emergences occur per meter of beach length
,
and
. about 0
.08-0
.37 egg clutches are laid pe
r
square meter of beach platform
.
These figure
s
19
indicate that nesting density at Pulau Redang i
s
less than that recorded at Raine Island in 198
9
where 3% of the eggs produced were destroyed b
y
nesting turtles, and slightly greater than tha
t
observed at Mon Repos where only 0
.4% of the egg
s
produced were destroyed by nesting turtles
. (Th
e
nesting density at Pulau Redang is much less tha
n
that recorded at either Raine Island in 1988 or a
t
Nancite, Costa Rica
.
)
Therefore, if all the egg clutches laid at Pula
u
Redang are allowed to incubate in their natura
l
nests, we can expect 0
.5-3
.0% of total eg
g
production to be destroyed by nesting turtles
.
This figure is minimal when compared to
th
e
negative
effects
presently
associated
wit
h
operation of the hatchery--i
.e
. reduced rates o
f
hatching success, increased predation upo
n
hatchlings, skewed sex ratios in the offspring, an
d
animals that are unable to return to the nestin
g
beach (see section 5
.2)
.
Another important observation made in th
e
Australian studies is that an average of only abou
t
17 to 28 eggs per clutch are destroyed when
a
nesting female green turtle digs into an alread
y
existing egg clutch (Limpus, 1988
; Limpus an
d
Miller, 1989)
. Some of those eggs are broken an
d
others die when they are strewn across the beac
h
surface
.
The remainder of the eggs in
th
e
disturbed nests, however, usually continue t
o
incubate and hatch out normally (Limpus, 1985)
.
Thus, the damage that actually occurs is less tha
n
one might have anticipated
.
7
.1 .2 .3
Predation
by Lizard
s
Monitor lizards are known to prey upon turtles an
d
hatchlings--especially upon those of the hawksbil
l
turtle (Limpus
et al
.,
1983), the nests of whic
h
are shallower than those of the green turtle
. Th
e
extent to which this may be a problem at Pula
u
Redang warrants further study
.
7
.1
.3
Compensation
to the Villagers for the
Egg
s
Because some villagers are dependent on income fro
m
egg collection, the Authorities have been reluctan
t
to prohibit egg harvest
. Instead they have opte
d
to pay the villagers for eggs that they surrende
r
to the hatchery
. Considering the negative impact
s
associated with the hatchery, however, other mean
s
of compensation would be preferable
.
20
7
.1 .3 .1
Direct Compensatio
n
One alternative solution would be to prohibit eg
g
collection at certain beaches, but to compensat
e
the villagers by paying them for eggs left t
o
incubate in the protected beaches
. The amount o
f
compensation could be based on one of th
e
following
:
1)
Old nesting records
. An average of the amoun
t
earned by the villagers for egg sale durin
g
the past 3-5 years could be calculated fro
m
the records of the Fisheries Department
.
2)
Daily beach surveys
. These could be conducte
d
by a member of the Fisheries Departmen
t
(perhaps accompanied by an experienced eg
g
collector from the village)
. Each morning th
e
protected beaches would be surveyed and al
l
tracks encountered on the beach would b
e
examined to determine how many egg clutche
s
were laid during the night
.
"Egg sticks" should
not
be used to make thi
s
determination
. Eggs that are inadvertentl
y
broken by the stick will pollute the remainde
r
of the clutch and lower hatching
. success
. No
r
should egg clutches be dug up
. Rather one o
f
the following methods could be used
:
a)
Count the number of tracks that look a
s
though
they involved successful
eg
g
laying
.
In most instances, when eg
g
clutches are laid, a large area o
f
disturbed damp sand is visible adjacen
t
to the body pit
. By simply looking at
a
track, an experienced egg collector ca
n
usually judge whether or not eggs wer
e
laid
.
b)
The total number of nesting emergence
s
that occurred could be counted eac
h
morning and this figure divided by a
n
estimate of the average number of nestin
g
emergences that occur for each egg clutc
h
laid
. The WWF study conducted in 199
0
estimated that 73% of nesting emergence
s
resulted in egg laying (see section 2
.2)
.
The Department of Fisheries might want t
o
carry out further research to refine thi
s
estimate
. Note that this figure wil
l
vary somewhat depending
on the amount
o
f
rainfall
that has
occurred
(Mortimer
,
1990)
.
21
7
.1 .3 .2
Turtle Tourism as a Source of Village Incom
e
The villagers could economically benefit by guidin
g
tourists to the nesting beach and also providin
g
accommodation and meals for them
. See also sectio
n
5
.
7
.2
Translocate the Hatchery to a Natural Nesting Beac
h
Locating the hatchery at a natural nesting beach
,
instead of at Pulau Pinang, would solve many of th
e
problems now plaguing the hatchery operation a
t
Pulau Pinang
. Following are some points t
o
consider about the operation of a hatchery at th
e
natural nesting beach
:
1)
The risk of embryos "imprinting" to the wron
g
nesting
beach would be
eliminated
(se
e
section 6
.2
.1)
.
2)
Hatchling release would occur at the natura
l
nesting beach
.
This would eliminate
th
e
concern that hatchlings might becom
e
"imprinted" to the wrong place (see sectio
n
5
.2
.3)
.
3)
Some artificial nests could be placed in th
e
shade and some in unshaded parts of the beac
h
in approximately the same proportions as the
y
occur naturally
. Such a system would produc
e
sex ratios in the offspring that are mor
e
natural (see section 2
.3
.1)
.
4)
No long distance translocation of eggs woul
d
be necessary
. Thus, higher rates of hatchin
g
success could be expected (see section 5
.2
.1)
.
5)
The same section of beach could be used as
a
hatchery site year after year if the content
s
of the nests were removed and disposed o
f
after hatching occurred
.
By removing th
e
rotten
nest contents, disease
could
b
e
minimized
.
The contents of nests should
not
be throw
n
into the sea, as this could attract predaciou
s
fish to the waters near the nesting beach
.
6)
Ideally, no cylindrical mesh enclosures woul
d
be
used for this hatchery
.
Thus,
th
e
hatchlings could "release themselves" an
d
enter the sea as immediately as possible afte
r
emerging from their nests
.
22
The
fencing around the hatchery could also b
e
made of materials that would keep the adul
t
females from entering the hatchery area, whil
e
allowing the hatchlings to escape from th
e
hatchery without human assistance
.
7) The extent to which lizards prey upon turtl
e
eggs and hatchlings needs to be evaluated an
d
appropriate action taken
.
8
.
CONCLUSION
S
At Pulau Redang, drastic steps are needed to
:
1)
Reduce the harvest of turtle eggs for huma
n
consumption
;
2)
Ensure that the eggs are allowed to incubat
e
under natural conditions so tha
t
a)
egg viability is maximized
,
b)
natural sex ratios in the offspring ar
e
produced, an
d
c)
embryos do not "imprint" to the wron
g
nesting beach
;
3) Enable the hatchling turtles to enter the se
a
at the appropriate time and place so tha
t
predation is minimized and "imprinting" to th
e
proper beaches is allowed to take place
.
Continued exploitation of turtle eggs at Pula
u
Redang is incompatible with the long-term surviva
l
of the population, and also with the objectives o
f
a Marine National Park as stated in the Fisherie
s
Act of 1985
. With careful management, the nestin
g
turtles at Pulau Redang could be maintained as
a
tourist attraction
.
23
REFERENCE
S
Bjorndal, K
.A
. and A
.B
. Bolten
. 1988
. Growth rates of immatur
e
green turtles,
Chelonia
mydas,
on feeding grounds in th
e
southern Bahamas
. Copeia 3
.
Cornelius, S
. E
. 1985
. Abundance, distribution and movements o
f
olive ridley sea turtles in Costa Rica, V
. Unpublishe
d
final report on U
.S
. Fish and Wildlife Service Contrac
t
No
. 14-16-0002-81-225
. April 1985. 120 pp
.
Jabatan Perikanan
.
1989
.
Projek Penetasan Penyu Neger
i
Terengganu Darul Iman 1989
.
Report to the Turtl
e
Sanctuary Advisory Council, 20 December 1989
. pp
. 62-69
.
Jabatan Perikanan
. 1990a
. Laporan Pendaratan dan Kematian Peny
u
Terengganu 1990
. Report to the Turtle Sanctuary Advisor
y
Council, 19 December 1990
. pp
. 32-44
.
Jabatan Perikanan
. 1990b
. Laporan Program Penetasan Peny
u
Terengganu 1990
. Report to the Turtle Sanctuary Advisor
y
Council, 19 December 1990
. pp
. 21-31
.
Limpus, C
. J
.
1985
.
A study of the loggerhead sea turtle
,
Caretta
caretta,
in Eastern Australia
. Unpublishe
d
Doctoral dissertation submitted to Zoology Department
,
University of Queensland
. June 1985
. Vol
. 1, 269 pp
. an
d
Vol . 2, 212 pp
.
Limpus, C
. J
. 1988
. Queensland Turtle Research Raine Islan
d
Study
: 1987-1988 Report to Raine Island Corporation
.
Unpublished report
. 15 pp
. and 4 appendices
.
Limpus, C
. J
. and J
. Miller
. 1989
. Queensland Turtle Researc
h
Raine Island Study
: 1988-1989 Report to Raine Islan
d
Corporation
. Unpublished report
. 25 pp
. and
3
appendices
.
Limpus, C
. J
., J
. D
. Miller, V. Baker and E
. McLachlan
. 1983
.
The hawksbill turtle
Eretmochelys
imbricata
(L
.), i
n
north-eastern Australia
: the Campbell Island rookery
.
Aust
. Wildl
. Res
. 10
:185-197
.
Mortimer, J
.A
. 1988
. Green turtle nesting at Aldabra Atoll-
-
population estimates and trends
. Biol
. Soc
. Wash
. Bull
.
No
. 8
:116-128
.
Mortimer, J
.A
. 1989
. Threats to the Survival of Terengganu'
s
Sea Turtles and a Review of Management Options
. A repor
t
submitted to the Turtles Sanctuary Advisory Council o
f
Terengganu, duly 1989
. 21 pp
.
24
REFERENCES (CONT'D
)
Mortimer,
J
.A
.
1990
.
The
influence
of
beach
san
d
characteristics
on the nesting behavior and clutc
h
survival of green turtles
(Chelonia mydas)
.
Copei
a
1990(3)
:802-817
.
Mortimer, J
.A
. 1991
. Recommendations for the Management o
f
Turtle Islands Park, Sabah
. Unpublished report to WW
F
Malaysia
. March 1991
. 28 pages
.
Mortimer, J
.A
. and A
. Carr
. 1987
. Reproduction and migration
s
of the Ascension Island green turtle
(Chelonia mydas)
.
Copeia 1987(1)
:103-112
.
Parmenter, C
.J
. 1980
. Incubation of the eggs of the green se
a
turtle,
Chelonia
mydas,
in Torres Strait, Australia
: th
e
effect of movement on hatchability
. Aust
. Wildl
. Res
.
7
:487-91
.
Standora, E
.A
. and J
. R
. Spotila
. 1985
. Temperature dependen
t
sex determination in sea turtles
. Copeia 1985(3)
:711-722
.
WWF Malaysia
. 1991
. Notes on the Proposed Development of Pula
u
Redang
. Unpublished report
. 20 pages
.
25
TABLE
1
. The proportion of green turtle nesting in the State of Terengganu that occurs at Pula
u
Redang (Source
: raw data from the Department of Fisheries)
.
GREEN TURTLE EGGS
GREEN TURTLE EGG CLUTCHE
S
------------------------- ---------------
-
------------------------------------------
-
YEAR
TOTAL LAI
D
I
N
TERENGGANU
NUMBER LAI
D
A
T
PULAU REDANG
% OF TOTA
L
LAID IN
TERENGGANU
TOTAL LAI
D
I N
TERENGGANU
NUMBER LAI
D
AT
PULAU REDANG
% OF TOTA
L
LAID I
N
TERENGGAN
U
1984
370,134 139,771
37 .8%
4292
1438
33
.5
%
1985
107,135
45,108
42
.4%
1169
462
39
.5
%
1986
417,981
213,893
51
.2%
4492
2251 50
.1
%
1987
142,234
74,382
52
.3%
1469
755
51 .4 %
1988
336,813
80,453
53
.6%
3542
1864
52
.6
%
1989
287,659 119,471
41
.5%
3007 1226
40
.8
%
1990
145,809
71,408
49
.0%
1561
735
47 .1%
TABLE
2
.
The
proportion
of eggs laid by green turtles and hawksbill
s
at Pulau Redang that were incubated in the hatchery eac
h
year
.
G R E E N T U R T L E
S
1984
139,771
4,613
3
.
3
1985
45,108
5,000
11
.
1
1986
213,893
4,980
2 .3
2
.
6
1987
74,382
0
0
1988
180,453
2,087
1
.2
1
33,389
19,243
57
.6
42
.
4
71,408
25,000
35
.
0
H A W K S B I L L
S
TOTAL
EGGS INCUBATED IN
HATCHER
Y
NUMBER OF
YEAR
EGGS LAID
NUMBER
% OF TOTA
L
1984
5,493
391
7
.1
\
1985
2,077
0
0
1986
4,757
318
6
.7
14
.
1
1987
3,246
0
0
1988
3,629
2,000
55
.1
1
1989
1,373
757
55
.1
79
.
3
1990
5,959
5,059
84
.
9
TOTA
L
NUMBER O
F
EGGS LAID
EGGS INCUBATED IN HATCHER
Y
YEAR
---------------
---------------
-
NUMBER
% OF TOTA
L
198
9
1990
27
TABLE
3
.
Relationship
between
nesting
density
and documented levels
of
density
dependent
mortalit
y
observed
at
various
nesting sites (Limpus, 1988
; Cornelius,
1985
;
Limpus
and
Miller,
1989
;
Limpus,
1985
;
Jeff Miller,
pers
.
comm
.)
.
Locality
Species
Beac
h
Length
Beac
h
Area
# o
f
Nesting
s
per Year
Average No
.
of Nests pe
r
Meter o
f
Beac
h
Length
Average No
.
of Nests pe
r
Square Mete
r
Beac
h
Area
% of Eg
g
Productio
n
Destroye
d
by Nestin
g
Turtle
s
Raine Island,
Green
2,500 m
136,000 m2
100,000
40
.0
1
.36
8
.6
-
Australia
Turtle
25
.
4
{1988
)
Nancite,
Olive
1,050 m
27,921 m2
97,000
92 .0 3 .50
16
.
9
Costa Ric
a
(1984)
Ridle
y
Turtl
e
Raine Island,
Green
2,500 m
136,000 m2
30,000-
12
.0-
0
.22-
3
.
0
Australia
Turtle 50,000
20
.0 0
.3
7
(1989
)
Mon Repos,
Loggerhead
1,400 m
1,203
0 .9
0
.
4
Australia
Turtle
(average
)
(1977-1982
)
Pulau Redang,
Green and
722 m
6,077 m2
462-*
0
.6-
0
.08-
0
.5-*
*
Terengganu Hawksbill
2,251
3
.1
0.37
3
.
0
(1984-1990
Turtles
*
Data courtesy of Department of Fisherie
s
** Expected valu
e
p
ASI
R
CAGA
R
HUTANG
012
P U L A
U
R E D A N
G
TELO
K
DALA
M
Kampun
g
Redan
g
FIGURE
1
. Map showing
Pulau
and nearb
y Also
in
dicated aree hegthree major nesting beache
s
(Pasir Mak Simpan, Pasir Mak Kepit
n
b
eache
s
H
utang),
and Telok Dalam), the an
d village, Caga
r
th
e
Department of Fisheries
the village,
th
e
ha
tchery,
Headquarters,
and
th
e
Fisherie
s
Hea
dquarters
50 —
.
24
FMA
M
J A S 0 N
D
M O N T H
S
4
0
30 —
219
G R E EN
T U R T L E
S
1
9 9
0
20 — N = 7 3
5
10 —
4
30
0
F M AM J J
A
S 0 N
D
M O N T H
S
FIGURE 2
.
Graphs
showing the seasonal distribution of eg
g
laying by green turtles and
hawksbills during 1990
.
30
=r
e
p
0
.13
*4
r
ItNtet'
i
UNEXPLOITED
+ +
.004
*
to
t
AFTER 10 YEARS OF 100% EGG HARVES
T
IF
*
400
*
AFTER 20 YEARS OF 100% EGG HARVES
T
AFTER 50 YEARS OF 100% EGG HARVES
T
AFTER 80 YEARS OF 100% EGG HARVEST
FIGURE
3
. Diagram showing the destruction of a nesting populatio
n
through over-harvest of eggs
. The
population
is destroye
d
"from the bottom up" because few hatchling turtles ar
e
allowed to enter the population
. Because green turtle
s
take 20 to 50 years to reach adulthood, at least 20 year
s
will pass before there is a decrease in the number o
f
nesting females
.
3
1
