MTN 128:23-24 Environmental Cues and Synchronised Nesting in Olive Ridleys

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Environmental Cues and Synchronised Nesting in Olive Ridleys

M. Muralidharan¹ & Adhith Swaminathan²
¹Wildlife Institute of India, Post Box # 18, Chandrabani, Dehradun 248001, Uttarakhand, India (E-mail: muralim86@gmail.com);
²Students Sea Turtle Conservation Network - SSTCN, No.2, 11th East Street, Thiruvanmiyur, Chennai 600041, Tamil Nadu, India (E-mail: adhith.me@gmail.com)

Environmental cues have been considered as major factors for the commencement of mass nesting in the ridley sea turtles. Several factors such as moon phase, pheromone release, tidal patterns, wind, etc. have been considered as the initiating factors for the synchronised nesting behaviour shown by the ridleys (Owens et al. 1982; Mendonça & Pritchard 1986; Plotkin et al. 1997). Three mass nesting beaches have been identified along the Indian Coast (Gahirmata, Devi, and Rushikulya) in the state of Orissa. Previous studies have recorded inter-rookery nesting between these beaches (Tripathy & Pandav 2007).

Figure 1. Rushikulya mass nesting beach

In 2009, mass nesting (arribada) of the olive ridleys was recorded in the Rushikulya beach from 15-20 February. During this period, several nesting females moved into a stagnant water body inland (~100-150 meters) of the nesting beach, formed from tidal action and sand deposition at the Rushikulya river mouth in 2008 (Figure 1). During the mass nesting at Gahirmata nesting beach (320 km north of Rushikulya) on 20-26 March, the turtles residing in the stagnant water body at Rushikulya emerged en masse from the water and began nesting (~65-70 nests). Apart from photoperiod the turtles present in the water body were largely devoid of oceanic factors (viz. tidal patterns, pheromonal release, etc), and it seems that some other factor may be responsible for them to emerge and nest. Other factors which could be responsible for this behavioural pattern observed include the inter-nesting interval observed in olive ridleys (~28 days, Dash & Kar 1990), causing the females present in the water body to emerge and release their eggs. But, several anecdotal references have shown the presence of a large scale nesting pattern of the olive ridleys during the period of mass nesting in all the sporadic as well as satellite nesting beaches along the entire Eastern Coast of India (Swaminathan pers. comm.). Our observations indicate the presence of larger temporal as well as spatial cues involved in the nesting pattern shown by the ridley sea turtles which could be investigated further.

DASH, M.C. & C.S. KAR. 1990. The Turtle Paradise: Gahirmatha. An Marine Turtle Newsletter No. 128, 2010 - Page 24 Ecological Analysis and Conservation Strategy. Interprint Press, New Delhi.

MENDONÇA, M.T. & P.C.H. PRITCHARD. 1986. Off-shore movements of post-nesting Kemp’s ridley sea turtles (Lepidochelys kempi). Herpetologica 12: 373-381.

OWENS, D.W., M.A. GRASSMAN & J.R. HENDRICKSON. 1982. The imprinting hypothesis and sea turtle reproduction. Herpetologica 38:124-135.

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: 17-22

TRIPATHY, B. & B. PANDAV. 2007. Beach fidelity and internesting movements of olive ridley turtles (Lepidochelys olivacea) at Rushikulya, India. Herpetological Conservation and Biology 3:40-45.