Journal of Threatened Taxa |
www.threatenedtaxa.org | 26 April 2021 | 13(5): 18122–18131
ISSN 0974-7907 (Online) | ISSN 0974-7893
(Print)
https://doi.org/10.11609/jott.6878.13.5.18122-18131
#6878 | Received 09 November 2020 | Final
received 07 March 2021 | Finally accepted 05 April 2021
Nesting and hatching behaviour of Olive Ridley Turtles Lepidochelys olivacea (Eschscholtz, 1829) (Reptilia: Cryptodira: Cheloniidae) on Dr. Abdul Kalam Island, Odisha, India
P. Poornima
Divisional Forest
Officer, Bhadrak Wildlife Division, Bhadrak, Odisha, India.
poornimapandian4@gmail.com
Editor: Raju Vyas, Vadodara,
Gujarat, India. Date of
publication: 26 April 2021 (online & print)
Citation: Poornima. P. (2021). Nesting and hatching
behaviour of Olive Ridley Turtles Lepidochelys
olivacea (Eschscholtz,
1829) (Reptilia: Cryptodira:
Cheloniidae) on Dr. Abdul Kalam Island, Odisha, India. Journal of Threatened
Taxa 13(5): 18122–18131. https://doi.org/10.11609/jott.6878.13.5.18122-18131
Copyright: © Poornima 2021. Creative Commons
Attribution 4.0 International License. JoTT allows unrestricted use, reproduction, and
distribution of this article in any medium by providing adequate credit to the
author(s) and the source of publication.
Funding: None.
Competing interests: The author
declares no competing interests.
Author details: Poornima P.—an Indian Forest Service
(IFS) Officer, working as Divisional Forest Officer in Odisha, India.
Acknowledgements: I thank Shri. Subash
Chandra Nayak, Range officer, Chandbali, Shri. Sushanta Mohanty, Dy Ranger, Shri
Gadadhar Biswal, Forester, Dhamra
and members of Olive Ridley Protection Squad, Bhadrak
WL Division for helping in data collection.
Abstract: This paper reports
the nesting, impact of lunar phase and rainfall on mass nesting, hatching, and
hatchling behaviour of L. olivacea in Dr. Abdul Kalam Island, Bhadrak District, Odisha.
The study site is a well-known rookery for this species. A study of 15 mass nesting events between
2003 and 2020 using Rayleigh’s test indicated that the onset of mass nesting
was not uniform across a lunar month, but was most intense towards the
beginning of the fourth quarter moon (mean lunar day = 22.44). Also, rainfall and mass-nesting data from
2015 to 2020 revealed that ≥3.2 mm rainfall in February delayed mass nesting
from the second fortnight of February to the end of the first fortnight of
March. Sporadic nesting continued after
hatching commenced in May, and continued until the end of May 2020, with an
average of three turtles nesting each day.
At night, a cohort of hatchlings from individual nests emerged
synchronously. Before emergence they
remained a little beneath the sand surface in airy-shallow pits. During hatchling emergence these pits fill
with sand, leaving depressions described as “emergence craters” in recent
literature on L. olivacea. To study hatchling emergence 30 such craters
were examined in May 2020, and the numbers of emerged hatchlings per cohort
varied from 28 to 182. Of 30 craters
examined, 28 were circular and two were elliptical, with diameters varying
between 10 and 26 cm. Pearson’s
correlation coefficient between the numbers of emerged hatchlings and crater
diameter was 0.38. Hatchlings took 17
min 22 sec (SD= ±5min 30 sec) on average to reach the sea from a mean distance
of 34.6m.
Keywords: Arribada, Bhadrak
District, cohorts, emergence crater, hatchling emergence, moon phase,
sporadic nesting.
Introduction
The Olive Ridley Sea
Turtles Lepidochelys olivacea
are the second smallest sea turtles in the world next to the Kemp Ridley Lepidochelys kempii (Van Buskirk &
Crowder 1994). Lepidochelys
olivacea have a circumtropical
distribution and occur in India, Mexico, Costa Rica, and the Arab Peninsula,
further to coastal Africa along the warm tropical and subtropical waters of the
Indian and Pacific Oceans (Pritchard 1997; Pritchard & Mortimer 1999). They do not migrate from one ocean to another
but move between the oceanic and neritic zones within the same ocean (Plotkin
et al. 1995).
Lepidochelys olivacea
populations are well known for ‘arribada’
(a Spanish term, meaning ‘arrival by sea’) wherein 1000s of pregnant turtles
arrive at the same beach site to lay their eggs and nest for the next few
days. The mass nesting sites for L. olivacea include Costa Rican and Mexican beaches
(Pritchard 1997) and the Odisha coast (Bustard 1976) along the Pacific and
Indian Ocean, respectively. In Odisha, Gahirmatha Wildlife Sanctuary in Kendrapada
District (Bustard 1976), the Devi River mouth in Puri
District (Kar 1982) and Rushikulya in Ganjam District (Pandav et al.
1994) are the three principal nesting sites for L. olivacea. Among these, Gahirmatha
Wildlife Sanctuary is the largest known nesting centre for L. olivacea (Bustard 1976) with 1–8 lakh turtles nesting
per year (Pattnaik et al. 2001).
Breeding and nesting
of L. olivacea occur through the year in Costa
Rican and Mexican coasts, with mass nesting in the rainy months of July‒December
(Hart et al. 2014), mostly during the third quarter moon (Plotkin 1994). In the Odisha coast mass nesting occurs in
the dry months of January–March (Dash & Kar 1990). In Gahirmatha
Wildlife Sanctuary in particular, breeding of L. olivacea
starts in November and mass nesting occurs in January–March (Behera et al.
2010). Lepidochelys
olivacea have the ability to delay nesting in
response to heavy rainfall, because high moisture level in the beach sand
reduces hatching success in the nest (Plotkin et al. 1997). The numbers of turtles participating in mass
nesting are variable (Pattnaik et al. 2001). Sporadic nesting by a few individuals of L.
olivacea along the eastern coast of India from
North 24 Parganas District to Kanyakumari (21.6380N, 89.0750E)
between December and April are common (Pandav &
Choudhury 2000; Tripathy et al. 2008). After 45–50 days of incubation, the
hatchlings return to the sea in April.
Hatching within a
nest is synchronous (Spencer et al. 2001) and emergence occurs through group-digging
behaviour customarily described as ‘social facilitation’ (Carr
& Hirth 1961).
The emergence of hatchlings from a single nest occurs in 1–4 cohorts
over a few days, with the first cohort having the largest number of hatchlings
(Rusli et al. 2016).
Before emergence, hatchlings rest in an air-filled pit in sandy soil and
during emergence, the surface sand sags into the pit (Salmon & Reising 2014), leaving a depression described as ‘emergence
crater’ (Bishop et al. 2011). Hatchling
emergence in L. olivacea has been studied
using various methods. Among them, the
numbers of hatchlings leaving the emergence crater (Burney & Margolis 1998)
is considered a reliable index of hatchling emergence. After emergence, the hatchlings crawl
radially out of the crater and the crawl marks are used in describing hatchling
emergence (Bishop et al. 2011).
Hatchlings emerge
nocturnally (Mrosovsky 1968) and move towards
negative surface gradient (Salmon et al. 1992).
Also, hatchlings exhibit positive phototaxy. Since the sea surface reflects moon light
better than the land surface, they move seawards (Mrosovsky
& Shettleworth 1968). Artificial illuminations placed on the land
distract the seaward movement of hatchlings (Tuxbury
& Salmon 2005). In the absence of artificial
illumination, disorientation in hatchling movement is high on new moon days (Salmon
& Witherington 1995).
Lepidochelys olivacea
populations have declined in many countries due to
various reasons: collection of eggs (Arauz 2000),
destruction of nesting beaches (Pandav &
Choudhury 1999), trapping of adults (Fretey 2001),
intensive fishing practice using trawlers and banned nets (Pandav
2000), diseases (Herbst 1994), and global warming (Hays et al. 2003) are a few
significant ones. The IUCN Red List of
Threatened Species has evaluated L. olivacea under
‘Vulnerable’ category (Abreu-Grobois & Plotkin
2008).
In Gahirmatha Wildlife Sanctuary, mass nesting was delayed
between February and March 2020 probably because of sporadic rainfall in
February (3.2mm). Also, the nesting
period (14–20 March 2020) coincided with waning phase of the moon. These observations prompted further study
exploring the effect of certain environmental variables, viz., lunar phase and
rainfall on mass nesting and hatching behaviour of L. olivacea. Although the nesting and hatching behaviour
of L. olivacea have been reasonably well
explored in Gahirmatha (Dash & Kar 1990; Silas et
al. 1985; Pandav 2000; Behera et al. 2010), little
information exists pertaining the influence of lunar phase and rainfall on mass
nesting, and behaviour of hatchlings post emergence.
Therefore, I
proceeded with this study keeping the following objectives in focus: (1) mass
nesting and its relation with lunar phase, (2) effect of rainfall on mass
nesting, (3) the duration of sporadic nesting, (4) the patterns in hatchling
emergence and emergence craters, and (5) behaviour of hatchlings post
emergence.
MATERIALS AND METHODS
Study Area
Dr. Abdul Kalam
Island (previously Wheeler Island, 20.7530N, 87.0720E)
falls under the Gahirmatha Wildlife Sanctuary,
managed by the forest department of the state of Odisha (Figure 1). The Gahirmatha
Beach is 2.4 km long with varying widths.
The average annual temperature is 27oC and the average annual
rainfall is 1,530mm. Ipomoea pescaprae (Convolvulaceae)
and Suaeda maritima
(Amaranthaceae) usually occur abundantly on the sandy
shoreline.
Methods
Hatchlings from each
nest dig synchronously upwards in cohorts, forming emergence craters on the
sand surface. The hatchlings gradually
leave the craters and reach the surface, beginning their movement towards the
sea. The number of emerged hatchlings
per cohort was determined through visual observation of emergence from such
craters. During the hatching period, 2–7
May 2020, 30 craters were sampled randomly and each crater was observed from
20.00h to 06.00h, and the numbers of hatchlings emerging from each crater were
counted. From each crater, the movements
of the first 5–10 hatchlings to the sea were observed individually and the time
taken by each of them was measured using a stopwatch. The overall shape of each crater was measured
for the diameter using measuring tapes.
The nesting data of L. olivacea for
2003–2020 were obtained from the archives of the Rajnagar Wildlife Division
Office, Kendrapada.
The rainfall data of Dr. Abdul Kalam Island for 2015–2020 were obtained from the nearest
meteorological office of Dhamra Port Company Limited,
Dhamra, Bhadrak District,
Odisha.
The lunar days
corresponding to the starting of each mass nesting were obtained from
keisan.casio.com (CASIO Computer Co Ltd, 2020, Tokyo, Japan). The lunar days were then converted into
angular data for using Rayleigh’s test, which was done using MS Excel 2019 to
verify uniformity in the occurrence of onset of mass nesting across a lunar
month. The correlation between variables
in the scatter plot was calculated using Pearson’s correlation. Photographs of nesting and hatching were made
using a COOLPIX P1000 (125X Optical Zoom Camera, Nikon Corporation, Tokyo,
Japan).
RESULTS
Mass nesting (Arribada) and Lunar phase
Mass nesting of L.
olivacea revealed that 407,204 individuals laid
eggs between 14 and 20 March 2020 (Table 1).
Maximum numbers (n= 98,700) nested on 17 March (fourth day) and the
minimum (n= 3,600) on 20 March (seventh day) (Table 1). Mass-nesting data obtained from Rajnagar
Wildlife Division for 2015–2020 revealed that a maximum of 664,897 individuals
nested in 2018 and a minimum of 51,995 in 2016 (Table 2)
Rayleigh’s test was
done to determine if the onset (in lunar days) of 15 mass nesting events
between 2003 and 2020 (Table 3) was non-uniformly distributed across a lunar
month. Results indicated a highly
non-uniform distribution (n= 15, r= 0.504, z= 3.81, zcritical=
2.945, α= 0.05) with a mean lunar day
of 22.44 (i.e., the onset
of mass nesting is at the beginning
of fourth quarter moon).
Nesting period and
rainfall
Mass nesting and the
rainfall data for 2015–2020 (Table 4) were analysed in conjunction to study the
impact of rainfall on nesting. When the
rainfall in February was less than 3.2mm, mass nesting occurred in the last
fortnight of February or in the first week of March. When the rainfall increased ≥3.2mm in February,
mass nesting was delayed to the end of the first fortnight of March; however,
rainfall in the first week of March did not delay mass nesting further, since
the nesting season for L. olivacea ended in
March.
Sporadic nesting
Sporadic nesting of L.
olivacea at Gahirmatha
started from the second fortnight of December 2019 and continued after mass
nesting from 14–20 March to 1–10 May 2020.
Between December and February, an average of 15 individual females of L.
olivacea nested per day. The numbers increased to 40 per day for a
week prior to and after mass nesting.
During hatching (2–7 May), an average of three turtles nested on the
beach every day.
Hatchling emergence
The hatchlings dug
through the sand above synchronously to emerge from their sandy nests. At the time of emergence, usually after
sunset, an emergence crater formed on the sand surface due to synchronous,
collective, digging effort by a single cohort of L. olivacea
from a nest. These craters lasted
for 7–10 days and eventually were either eroded or filled up with sand spread
by wind. The hatchlings reached the
surface gradually with the hatchlings present near the surface pushed by
emerging hatchlings below in the crater.
On reaching the surface they spread themselves radially in different
directions, but moved towards the sea.
The numbers of
hatchlings emerging from the 30 observed individual craters were 2,763. The maximum and minimum numbers of emerged
hatchlings per cohort were 182 and 18 with an average of 92.1 hatchlings per
cohort. The craters were mostly circular
(93.3%) and occasionally elliptical (6.7%).
The crater diameter varied between 10 and 26 cm (n= 30). Pearson’s correlation indicated a low but
positive correlation (0.38) between the numbers of emerged hatchlings per
crater and crater diameter. Therefore,
when the number of emerging hatchlings per cohort increases, the crater
diameter also tends to increase.
Movement of
hatchlings towards sea
As soon as the
hatchlings emerged, they moved towards the sea.
The pace and direction of movement varied among individuals. Time taken by 280 hatchlings from 30
emergence craters to reach the sea indicated that the minimum time taken was 6
min 12 sec and the maximum was 35 min 9 sec.
The average time taken by hatchlings to reach the sea from a mean
distance of 34.55m was 17 min 22 sec. (SD= ± 5 min 30 sec).
DISCUSSION
Mass nesting and
lunar phase
Previous reports on
the numbers of mass nesting L. olivacea individuals
at Gahirmatha Wildlife Sanctuary indicate varying annual
numbers (Bustard 1976; Kar & Bhaskar 1982; Silas et al. 1985). The data for 2015–2020 also revealed that
numbers of turtles differed every year with 51,995 turtles in 2016 and 6,64,897
in 2018. It is possible that the
variation was due to changes in productivity in their foraging areas, because
females needed sufficient nutrients to support their migratory and reproductive
activities (Valverde et al. 2012). Also,
an increase or decrease in hatching rates over many years may result in varying
adult population participating in arribada (Cornelius
et al. 1991). Beach exchange, where
Olive Ridleys move to another beach for nesting,
mortality in nets (Valverde et al. 1998) also affects the nesting population
numbers. The exact reason for variation
in the number of individuals in mass nesting, however, requires further study.
At Gahirmatha, the
onset of mass nesting occurred at the beginning of the fourth quarter
moon. Rayleigh’s test showed a highly
non-uniform distribution of onset of mass nesting across the lunar month with a
mean lunar day of 22.44 days. According
to Silas et al. 1985, mass nesting occurred on 7th day after the
full moon in Gahirmatha, i.e., after 20.77 days. In Ostional Beach, Costa Rica, mass nesting
usually began in the fourth quarter moon with mean lunar days of 23 (Bezy et al. 2020).
In Mexico, mass nesting coincided with the third quarter moon (Plotkin
1994). In Ghana, a majority of L. olivacea nesting occurred in third quarter, which could
be due to less light because of waning moon, and thus to avoid predators (Witt
2013). Another possible advantage of
nesting during waning moon was greater prey availability post-nesting (Pinou et al. 2009) because L. olivacea
feed primarily on crabs, which are nocturnal (Shaver & Wibbels
2007).
Nesting period and
rainfall
In Gahirmatha, rainfall (≥3.2mm) in February 2020 delayed mass
nesting of L. olivacea from February to first
week of March 2020. High sand moisture
content due to rainfall is indicated as a reason for reduced hatching success
in the nest chamber (Packard et al. 1977).
In the eastern Pacific Coast, L. olivacea
individuals delayed nesting during extreme rainfall (>50 cm) (Plotkin et al.
1997), but not during normal precipitation levels (9cm) (Coria-Monter & Duran-Campos 2017) because arribadas
coincided with rainy seasons in the eastern Pacific (Cornelius 1986). Whereas in Gahirmatha,
even modest rainfall (3.2mm) delayed the mass nesting, because nesting occurred
in dry periods in Odisha (Dash & Kar 1990).
Since the nesting season of L. olivacea
ended in March (Behera et al. 2010), there was no further delay in nesting
beyond second week of March 2020 despite rainfall in the first week.
Sporadic nesting
Sporadic nesting of L.
olivacea occurred almost every month along the
Odisha coast, but more frequently between February and April (Dash & Kar
1990). Sporadic nesting occurred mainly
between December and May along the eastern coast of India (Pandav
& Choudhary 2000). During the study
period in Gahirmatha, sporadic nesting was noted
mainly between December and May. Between
December and February, an average of 15 L. olivacea
individuals nested sporadically. The
numbers increased to 40 per day for a week prior to and after mass nesting (14–20
March). In Gahirmatha,
more than 10 turtles arrived for sporadic nesting per night (Tripathy 2008). Our
observations in Gahirmatha match with those of Tripathy (2008) till April 2020 but the numbers of turtles
nesting sporadically in May 2020 was, on an average, only three per night.
Hatchling emergence
Mrosovsky (1968) and
Witherington et al. (1990) observed that the emergence of L. olivacea hatchlings onto the sand surface was
predominantly nocturnal. The hatchlings
emerged only after sunset and before sunrise, in Gahirmatha
as well. After synchronous hatching from
the nests, hatchlings exhibited group-digging behaviour to reach the sand
surface (Hendrickson 1958; Carr & Hirth 1961). At Gahirmatha, this behaviour was prevalent in all the nests observed. Final emergence by hatchlings on to the sand
surface created emergence craters (Bishop et al. 2011) due to collapse of the
cavity in which hatchlings were present (Salmon & Reising
2014). Also, the hatchlings emerged in
cohorts of 1–4 from a single nest, over a period of 4–8 days, with the first
cohort having maximum number of hatchlings (Rusli et
al. 2016). At Gahirmatha,
every time a cohort of hatchlings from a nest emerged, an emergence crater
formed on the surface, which lasted 7–10 days before being either eroded or
filled up with sand by wind.
The minimum and
maximum number of hatchlings from individual craters (per cohort) were 18 and
182, respectively, with an average of 92.1 hatchlings. These numbers represent the emergence per
cohort. Therefore, the maximum egg count
per nest (clutch size) found in Gahirmatha was ≥182
considering the mortality in the nest and mortality during emergence. Whereas, Kumar et al. (2013) observed maximum
egg counts of 168. The craters were
mostly circular (93.3%) and occasionally elliptical (6.7%). Their diameters varied between 10cm and
26cm. There was a low but positive
correlation (0.38) between numbers of hatchlings per crater and respective
crater diameter, as per Pearson’s correlation.
Movement of
hatchlings towards sea
After emergence
hatchlings typically move towards
negative slope gradient (Limpus 1971), which
was observed in Gahirmatha. Hatchlings also typically exhibit positive
phototaxy, leading them to move towards the sea since moon light is reflected
more by water than land (Carr & Ogren 1960; Mrosovsky & Shettleworth 1968).
These findings also match with observations in Gahirmatha. The minimum time taken by hatchlings to move
one metre was 11 sec, whereas the maximum time was 2 min 4 sec. The average time taken by hatchlings to move
one metre was 33 sec (SD= ±15 sec). This
is less than the time taken by L. olivacea in
Costa Rica, 52.4 sec (Burger & Gochfield 2014)
and Indonesia, 36–48 sec (Maulaney et al. 2012). Of 280 hatchlings, 62.5 % took 20–40 sec to
move one metre. Considering the total
time taken to reach the sea, minimum and maximum time taken was 6 min 12 sec
and 35 min 9 sec, respectively. The
average time taken by hatchlings in Gahirmatha to
reach the sea was 17 min 22 sec (SD= ± 5 min 30 sec) for a mean distance of
34.55m, whereas it was 19 min 12 sec for a mean distance of 27.7m in Ostional
Beach, Costa Rica (Burger & Gochfield 2014).
Conclusion
The sandy beaches of
Dr. Abdul Kalam Island in Gahirmatha
Wildlife Sanctuary, even though geographically small in area, continue to be
one of the most important nesting site for L. olivacea population in the
world. Adequate measures are undertaken
every year by Odisha Forest and Wildlife Department to ensure protection of L.
olivacea along the Odisha coast. Further, study of environmental factors such
as rainfall, lunar phase, temperature and winds on mass nesting in Odisha in
general and Gahirmatha in particular, would further
enhance our understanding of L. olivacea’s intricate nesting and hatching behaviour.
Table 1. Mass nesting
data of L. olivacea in 2020.
Day |
Population numbers |
14 March |
10,076 |
15 March |
68,311 |
16 March |
98,135 |
17 March |
98,700 |
18 March |
95,541 |
19 March |
32,841 |
20 March |
3,600 |
Total |
407,204 |
Table 2. Mass-nesting
of L. olivacea turtles, 2015–2020.
Year |
Population numbers |
2015 |
413,334 |
2016 |
51,995 |
2017 |
603,962 |
2018 |
664,897 |
2019 |
450,949 |
2020 |
407,204 |
Table 3. Date of
initiation of 15 arribada events and corresponding
lunar days, 2003–2020.
Sno |
Year |
Date of initiation of arribada |
Lunar days (out of 29.53 days in a lunar month) |
Sno |
Year |
Date of initiation of arribada |
Lunar days (out of 29.53 days in a lunar month) |
1 |
2003 |
28Feb |
26.8 |
9 |
2013 |
17 March |
5.4 |
2 |
2007 |
11Feb |
23.1 |
10 |
2015 |
12 March |
21.3 |
3 |
2009 |
20Mar |
23.2 |
11 |
2016 |
03 March |
23.7 |
4 |
2010 * |
24Feb |
10.2 |
12 |
2017 |
22 Feb |
25.3 |
5 |
2010** |
19Mar |
2.4 |
13 |
2018 |
04 March |
16.4 |
6 |
2011* |
26Feb |
23.2 |
14 |
2019 |
26 Feb |
21.4 |
7 |
2011** |
20Apr |
16.7 |
15 |
2020 |
14 March |
19.6 |
8 |
2012 |
15Mar |
22.3 |
- |
- |
- |
- |
Source of mass
nesting data: Archives of Rajnagar Wildlife Division, Kendrapada,
Odisha Forest Department. *—First mass
nesting | **—Second mass nesting. |
Table 4. Yearly
rainfall and mass nesting data for Gahirmatha Beach,
Dr Abdul Kalam Island, 2015–2020.
Year |
Rainfall in 1–15 February (in mm) |
Rainfall in 16–28 (29) February (in mm) |
Rainfall in 1–15 March (in mm) |
Rainfall in 16–31 March (in mm) |
Period of mass
nesting |
2015 |
0 |
3.2 |
0 |
10.8 (29th) |
12–19 March |
2016 |
20.4 |
5.5 |
3.7 |
1 |
3, 12–20 March (48 turtles on
March 3rd) |
2017 |
0 |
0 |
0 |
18.2 |
22 Feb–1 March |
2018 |
0 |
0 |
0 |
0 |
4–13 March |
2019 |
0 |
1 |
1 |
1.8 |
26 Feb–5 March |
2020 |
6.4 |
6.0 |
7.8 |
10 (20th, 22nd, 23rd) |
14–20 March |
For
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REFERENCES
Abreu-Grobois, A & P. Plotkin (2008). (IUCN SSC Marine
Turtle Specialist Group), Lepidochelys olivacea. The IUCN Red List of Threatened Species 2008:
e.T11534A3292503. Downloaded on 07 March 2021. https://doi.org/10.2305/IUCN.UK.2008.RLTS.T11534A3292503.en
Arauz, R. (2000). Impact of high-seas
long time fishery operations on shark and sea turtles populations in Economic
Exclusive Zone of Costa Rica. Unpublished report, Earth Island Institute/Sea
Turtle Restoration Project (STRP), Costa Rica,15pp.
Behera, S., B. Tripathy,
B.C. Choudhury & S. Kuppusamy (2010). Behaviour of Olive
Ridley Turtles (Lepidochelys olivacea) prior to arribada
at Gahirmatha, Orissa, India. Herpetology 3:
273--–274.
Bezy, V.S., F.P. Nathan,
A.U. James, M.O. Carlos, G.F. Luis, M.Q.P. Wagner, A.V. Roldan & J.L.
Kenneth (2020). Mass-nesting events in Olive Ridley sea turtles:
environmental predictors of timing and size. Animal Behaviour 163:
85–94.
Bishop, G.A., F.L. Pirkle, B.K. Meyer & W.A.
Pirkle (2011). The foundation for sea turtle geoarchaeology and
zooarchaeology: morphology of recent and ancient sea turtle nests, St. Catherines Island, Georgia, and Cretaceous Fox Hills
Sandstone, Elbert County, Colorado, Chapter 13, pp. 247–269. In: Bishop, G.A.,
H.B. Rollins & D.H. Thomas (eds.). Geoarchaeology of St. Catherines Island, Georgia. American Museum of Natural
History Anthropological Papers 94.
Burger, J. & M. Gochfield
(2014). Factors affecting locomotion in Olive Ridley (Lepidochelys olivacea)
hatchlings crawling to the sea at Ostional Beach, Costa Rica. Chelonian
Conservation and Biology 13(2): 182–190.
Burney, C. & W. Margolis (1998). Technical report
1998, Sea Turtle conservation Program, Department of Natural Resources
Protection, Broward County, Florida, USA, 6pp.
Bustard, H.R. (1976). World’s largest sea
turtle rookery? Tiger Paper 3: 25.
Carr, A. & L. Ogren (1960). The ecology and migration of sea
turtles 4: The Green turtle in the Caribbean sea. Bulleting of the American
Museum of Natural History 121: 1–48.
Carr, A. & H. Hirth (1961). Social facilitation in green
turtle siblings. Animal Behaviour 9: 68–70.
Coria-M, E. & E. Durán-Campos (2017). The relationship
between the massive nesting of the Olive Ridley Sea Turtle (Lepidochelys
olivacea) and the local physical environment at
La Escobilla, Oaxaca, Mexico, during 2005. Hidrobiológica 27(2): 201-–209.
Cornelius, S.E. (1986). The Sea Turtles
of Santa Rosa National Park. Fundacion de Parques Nacionales, Monograph,
San Jose, 134pp
Cornelius, S.E., M.A. Ulloa, J.C. Castro, M.M. Del
Valle & D.C. Robinson (1991). Management of Olive Ridley Sea
Turtles (Lepidochelys olivacea)
nesting at Playas Nancite and Ostional, Costa Rica,
pp. 111–115. In: Robinson, J.G. & K.H. Redford (Eds.). Neotropical
Wildlife Use and Conservation. The University of Chicago Press, Chicago.
Dash, M.C. & C.S. Kar (1990). The Turtle
Paradise: Gahirmatha. Interprint,
New Delhi, 295pp.
Fretey, J. (2001). Biology and
Conservation of Marine Turtles of the Atlantic Coast of Africa. CMS
Technical Series Publication No. 6. UNEP/CMS Secretariat, Bonn, Germany, 429pp.
Hays, G.C., A.C. Broderick, F. Glen & B.J. Godley
(2003). Climate change and sea turtles: a 150-year
reconstruction of incubation temperatures at a major marine turtle rookery. Global
Change Biology 9(4): 642–646.
Hart, C.E., C.L. Quiñónez,
A.M. Gasca, A.Z. Norzagaray
& F.A.A. Grobois (2014). Nesting
characteristics of olive Ridley turtles (Lepidochelys
olivacea) on El Naranjo Beach, Nayarit, Mexico. Herpetological
Conservation and Biology 9: 524–534.
Hendrickson, J.R. (1958). The Green Sea Turtle
Chelonida mydas (Linn.)
in Malaya and Sawarak. Proceedings of the
Zoological Society, London 130: 455–535.
Herbst, L.H. (1994). Fibropapillomatosis of marine turtles. Annual
Review of Fish Diseases 4: 389-–425.
Kar, C.S. (1982). Discovery of second
mass nesting ground of the Pacific Olive Ridley Sea Turtles in Orissa, India. Tiger
Paper 1: 5–7.
Kar, C.S. & S. Bhaskar (1982). The status of sea
turtles in the eastern Indian Ocean, pp. 365–372. In: Bjorndal,
K. (ed.). The Biology and Conservation of Sea Turtles. Smithsonian
Institution Press, Washington, D.C.
Kumar, S., J. Sajan, S. Kuppusamy & B. Choudhary (2013). Egg laying duration
in the olive Ridley turtle Lepidochelys olivacea and its relevance for the estimation of mass nesting
population size. The Herpetological Journal 23: 23–28.
Limpus, C.J. (1971). Sea turtle ocean
finding behaviour. Search 2: 385–387.
Maulany, R.I., D.T. Booth
& G.S. Baxter (2012). The effect of incubation temperature on
hatchling quality in the olive ridley turtle, Lepidochelys olivacea,
from Alas Purwo National Park, East Java, Indonesia:
implications for hatchery management. Marine Biology 159: 2651–2661.
Mrosovsky, N. (1968). Nocturnal emergence
of sea turtles. Control by thermal inhibition of activity. Nature 220:
1338–1339.
Mrosovsky, N. & S.J. Shettleworth (1968). Wavelength
preferences and brightness cues in the water finding behaviour of sea turtles. Behaviour
32(4): 211–257.
Packard, G.C., M.J. Tracy, & J.J. Roth (1977). The physiological ecology
of reptilian eggs and embryos, and the evolution of viviparity
within the Class Reptilia. Biological Reviews
52: 71–105.
Pandav, B. (2000). Conservation and
Management of Olive Ridley Sea Turtles (Lepidochelys
olivacea) in Orissa, India. Final Report,
Wildlife Institute of India, 61pp.
Pandav, B., B.C. Choudhury
& C.S. Kar (1994). A status survey of Olive Ridley Sea Turtle (Lepidochelys olivacea) and their
nesting beaches along the Orissa coast, India. Wildlife Institute of India,
Dehradun, India, 48pp.
Pandav, B. & B.C.
Choudhary (1999). An update on the mortality of Olive Ridley Sea
Turtle in Odisha, India. Marine Turtle Newsletter 83: 10–12.
Pandav, B. & B.C.
Choudhury (2000). Conservation and Management of Olive Ridley Sea
Turtle (Lepidochelys olivacea)
in Orissa, India. Final Report. Wildlife Institute of India, Dehradun, 70 pp.
Pattnaik, S.K., C.S. Kar
& S.K. Kar (2001). A Quarter Century of Sea Turtle Conservation
in Orissa. Wildlife Wing, Forest Department, Government of Orissa,
Bhubaneshwar, 34pp.
Pinou, T., K.J. Pacete, A.P. Niz, L. Gall &
E. Lazo-Wasem (2009). Lunar illumination
and sea turtle nesting. Herpetological Review 40: 409–410.
Plotkin, P.T. (1994). Migratory and
reproductive behavior of the Olive Ridley Turtle, Lepidochelys olivacea
(Eschscholtz, 1829) in the eastern Pacific Ocean. PhD
Thesis. Texas A & M University, College Station, Texas.
Plotkin, T., R.A. Byles, D.C. Rostal
& D.W. Owens (1995). Independent versus socially facilitated oceanic
migrations of the Olive Ridley Lepidochelys
olivacea. Marine Biology 122: 137–143.
Plotkin, P.T., D.C. Rostal,
R.A. Byles & D.W. Owens (1997). Reproductive and
developmental synchrony in female Lepidochelys
olivacea. Journal of Herpetology 31(1):
17–22.
Pritchard, P.C. (1997). Evolution, phylogeny,
and current status, pp. 1–28. In: Lutz, P.L. & J.A. Musick
(eds.). The Biology of Sea Turtles. CRC Press, Boca Raton, Florida.
Pritchard, P.C. & J.A. Mortimer (1999). Taxonomy, external
morphology, and species identification, pp. 21–38. In: K. Eckert, K. Bjorndal, F. Abreu-Grobois &
M. Donnelly (eds.). Research and Management Techniques for the Conservation of
Sea Turtles. IUCN/SSC Marine Turtle Specialist Group Publ. No. 4, Washington,
D.C.
Rusli, M.U., D.T. Booth
& J. Joseph (2016). Synchronous activity lowers the energetic cost
of nest escape for sea turtle hatchlings. Journal of Experimental Biology
219: 1505–1513.
Salmon M., J. Wyneken, E.
Fritz & M. Lucas (1992). Sea finding by hatchling sea turtles: Role of
Brightness, Silhouette and beach slope as orientation cues. Behaviour
122: 56–77.
Salmon, M. & B. Witherington (1995). Artificial lighting
and seafinding by loggerhead hatchlings: evidence for
lunar modulation. Copeia 4:
931–938.
Salmon, M. & M. Reising
(2014). Emergence Rhythms of Hatchling Marine Turtles:
Is a Time Sense Involved?. Chelonian Conservation and Biology 13(2):
282–285.
Shaver, D.J. & T. Wibbels
(2007). Head-starting the Kemp Ridley Sea Turtle, pp.
297–323. In: Plotkin, P.T. (ed.). Biology and Conservation of Ridley Sea
Turtles. Johns Hopkins Univ. Press, Baltimore, Maryland.
Silas, E.G., M. Rajagopalan, S.S. Dan & A.B.
Fernando (1985). On the second mass nesting of Olive Ridley Turtles Lepidochelys olivacea
at Gahirmatha, Orissa during 1984. Proceedings of the
Symposium on Endangered marine animals and marine parks 1: 234–241.
Spencer R.J., M.B. Thompson & P.B. Banks (2001). Hatch or wait? A
dilemma in reptilian incubation. Oikos 93: 401–406.
Tripathy, B. (2008). An assessment of
solitary and arribada nesting of Olive Ridley Sea
Turtles (Lepidochelys olivacea)
at the Rushikulya rookery of Orissa, India. Asiatic
Herpetological Research 11: 134–140.
Tripathy, B., R.S. Kumar,
B.C. Choudhury, K. Sivakumar & A.K. Nayak (2008). Compilation of
Research Information on Biological and Behavioural Aspects of Olive Ridley
Turtles along the Orissa Coast of India – A Bibliographical Review for
Identifying Gap Areas of Research. Wildlife Institute of India, Dehra Dun, 8pp.
Tuxbury, S.M. & M.
Salmon (2005). Competitive interactions between artificial lighting
and natural cues during sea finding by hatchling marine turtles. Biological
Conservation 121: 311–316.
Valverde, R.A., S.E. Cornelius & C.L. Mo (1998). Decline of the Olive
Ridley Sea Turtle (Lepidochelys olivacea) nesting assemblage at Nancite
Beach, Santa Rosa National Park, Costa Rica. Chelonian Conservation and
Biology 3(1): 58–63.
Valverde, R.A., C.M. Orrego,
M.T. Tordoir, F.M. Gómez, D.S. Solís, R.A. Hernández,
G.B. Gómez, L.S. Brenes,
J.P. Baltodano, L.G. Fonseca & J.R. Spotila (2012). Olive Ridley mass
nesting ecology and egg harvest at Ostional Beach, Costa Rica. Chelonian
Conservation and Biology 11(1): 1–11.
Van Buskirk, J. & L.B. Crowder (1994). Life-history variation
in marine turtles. Copeia 1: 66–81.
Witherington, B.E., K.A. Bjorndal
& C.M. McCabe (1990). Temporal pattern of nocturnal emergence of
loggerhead turtle hatchlings from natural nests. Copeia
4: 1165–1168.
Witt, D.W. (2013). Tidal and lunar
correlates on sea turtle emergence patterns in Ada Foah,
Ghana. MSc Thesis. The Faculty of the College of Arts and Sciences, Florida
Gulf Coast University, Fort Myers, Florida, USA, 36pp.