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.
Highlights
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)
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)
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)
Summary
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). 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)
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