2008-2011 and during field work was presented respectively in Appendix 4a and 4b.
4.1.2. Nest Natural and artificial
4.1.2.1. Evening temperature of natural and artificial nests
Sand temperature is influenced by other factors such as air temperature, vegetation roots, humidity, sand grain size composition and position relative to
shade. Air temperature is directly influencing temperature of surface sand until few centimeters. Vegetation root system keeps the sand humidity within.
Humidity is lowering the temperature. The area under the shade is protected from sunlight so the temperature is cooler than the ones without shade. Sand grain
provides porosity which in turn influenced the sand humidity. On the other hand, temperature can also influence sand humidity. Temperature varied depended on
depth. Nest temperature of green turtle C. mydas natural nest and artificial nests
were measured in the evening. Natural nest temperature was measured during oviposition egg laying. All eggs from natural nests were relocated into artificial
nests prepared holes in the hatchery. Temperatures of artificial nests were measured before the relocated eggs were buried. Nests egg cavity were
measured at the upper rim and bottom part by using a non contactable infra-red thermometer. Surface sand around the nests were also measured.
There were 21 green turtle C. mydas natural nests measured during this study Table 10. The measurements were taken at each beach segmentPos.
Pangumbahan beach area is consist of 6 beach segmentPos. Highest density of natural nest were found in Pos 2 while the lowest was at Pos 6. Beach profile and
disturbance level probably caused this unevenly distribution. Pos 2 was the widest and has narrow beach slope. Pos 6 was much steeper and much disturbance from
local people. 26
Table 10 Evening temperature of green turtle C. mydas natural nests
Pos Temperature
measurement Range
°C Average ±
SD °C Nest characteristic
Nest depth cm
nest position
Shade area
range m
1
n = 4 nests
Surface sand n = 4
25.6 - 27.6 26.7 ± 0.9
46.0 - 64.5 56.1 ± 7.9
n = 4 no
vegetatio n canopy
220.7 Nest upper rim
n = 4 26.6 - 28.6
27.9 ± 0.9 Nest bottom
n = 4 28.0 - 29.8
28.9 ± 0.7
2
n = 7 nests
no vegetation
canopy Surface sand
n = 7 26.0 – 28.1
27.0 ± 0.9 50.0 - 75.4
63.3 ± 9.4 n = 8
448.6 Nest upper rim
n = 7 27.8–32.0
29.1 ± 1.4 Nest bottom
n = 4 28.3 - 29.2
28.7 ± 0.3 n = 3
nests under
vegetation canopy
Surface sand n = 3
25.6 – 28 27.1 ± 1.3
72.0 – 75.4 73.7±2.4
n = 2 3 nests
under vegetation
Sea pandan
Pandanus tectorius
Nest upper rim n = 3
27.8 – 28.9 28.2 ± 0.6
Nest bottom n = 3
28.3 – 29.2 28.7 ±0.5
3
n = 2 nests
Surface sand n = 2
26.8 - 27.5 27.2 ± 0.5
65.0 - 74.0 69.5 ± 6.4
n = 1 no
vegetatio n canopy
83.24 Nest upper rim
n = 2 28.6 - 29.6
29.1 ± 0.7 Nest bottom
n = 2 29.4 - 29.5
29.5 ± 0.5
4
n = 2 nests
Surface sand n = 2
27.7 - 27.8 27.8 ± 0.1
83.0 n = 1
no vegetatio
n canopy 203.8
Nest upper rim n = 2
28.5 - 29.5 29.0 ± 0.7
Nest bottom n = 2
30.1 - 30.5 30.3 ± 0.1
∗ at surface sand and nest upper rim and bottom part, see Appendix 5 for detailed shade area range in each beach segment and Appendix 6 for beach vegetation
pictures
Figure 11 Temperature distribution of green turtle C. mydas natural nests in Pangumbahan beach segments Pos 1-Pos 4. Measured in the evening
at the surface sand and nest upper rim and bottom, mean: 28.6±1.1°C at upper rim rim nest, 28.9±0.7°C at bottom nest, and
27.1±0.9°C at surface sand.
In general, it is obvious that the surface sand of natural nests were cooler than deeper sand, such as nest nest upper rim and nest bottom, see Figure 11.
Surface sand was directly influenced by air temperature so it will be fluctuating daily. Deeper sand was warmer than the surface because it was able to keep the
remaining warm temperature of day time. The deeper the sand depth the warmer it got. It was shown that, in general, temperature at nest upper rim was cooler than at
the bottom. However, a slight difference showed at temperature measurement in Pos
2. In this particular beach segment, there were three out of ten nest samples under the shade of vegetation. All other nests at Pos 1, 3 and 4 were not under
canopy of vegetation. Nest bottom temperature of samples which were under vegetation canopy were not significantly different with the samples without
vegetation canopy
25 26
27 28
29 30
31 32
33 34
5 10
15 20
Te m
p e
r atu
r e
° C
Number of nests
upper nest bottom nest
surface Pos 1
Pos 2 Pos 3 Pos 4
,
Figure 12 Temperature distributions of green turtle C. mydas artificial nests in Pangumbahan beach hatchery A open cage. Measured in the evening
at the surface sand and nest upper rim and bottom, mean: 27.4±1.0°C at upper rim nest, 29.6±1.3°C at bottom nest, and
29.7±2.7°C at surface sand.
It seems that temperature condition at hatchery was different than at its nature condition, see Figure 11 and 12. Surface sand was warmer than the nest
upper rim and bottom part. This condition was contrary to the natural condition which surface sand cooler than at natural nest.
Figure 13 Temperature comparisons of green turtle C. mydas natural nests and artificial nests in Pangumbahan beach. Measured in the evening at the
surface sand and nest upper rim and bottom. Mean: natural nests: 28.2±0.8°C at upper rim nest, 28.6±0.8°C at bottom nest,
26.7±0.8°C at surface sand; artificial nests 27.2±0.8°C at upper rim nest, 29.6±1.5°C at bottom nest and 30.3±2.5°C at surface sand.
25 26
27 28
29 30
31 32
33 34
5 10
15 20
T e
m p
e ra
tu re
° C
artificial nests
nest upper rim
nest bottom sand surface
25 26
27 28
29 30
31 32
33 34
35
25 26
27 28
29 30
31 32
33 34
35
A r
ti fi
c ial
n e
st °
C
Natural nest °C
nest upper rim
nest bottom surface sand
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