The effect of lighting and temperature on the eggs and hatchlings of olive ridley turtles at Rushikulya, India A Thesis Submitted to The Manipal University In partial fulfillment for the degree of Master of Science in Wildlife Biology and Conservation 2008 By Divya Karnad Post-Graduate Program in Wildlife Biology & Conservation Centre for Wildlife Studies and National Centre for Biological Sciences UAS-GKVK Campus Bangalore – 500 065 ii iii To those who teach by example, especially my family, Arun and Sashirekha. iv EXECUTIVE SUMMARY The olive ridley turtle (Lepidochelys olivacea) nests both sporadically and en masse along the Indian Coast. Of the three mass nesting sites along the East coast of India, the Rushikulya rookery may currently have the most regular nesting population of olive ridley turtles and is therefore likely to play a key role in maintaining the Indian Ocean population of the species. The sporadic nesting site of Chennai is completely altered by human activity and represents a set of conditions completely different from those in Rushikulya. Olive ridley turtles in India are protected and have been studied for several years but detailed studies on factors affecting nesting and hatching have not been conducted. The present study examines the effect of temperature and lighting on egg and hatchling survival of the olive ridley turtle. The response of the hatchlings to different lighting regimes on the beach, as well as to specific combinations of wavelength and intensity of light was studied. Hatchlings responded to both intense point sources of light at Rushikulya as well as glows from hidden point sources. A mixed age plantation of Casuarina equisetifolia proved to be an effective light barrier that prevented disorientation of hatchlings. Preference for light of lower wavelength and higher intensity was observed, although hatchlings responded differently to light in the violet band depending on its intensity. Olive ridley hatchlings were indifferent to red light indicating that the use of this wavelength could be recommended as a photo pollution management measure. Incubation temperature and hatching success of selected nests were monitored within hatcheries at both sites. Incubation temperature did not have a significant influence on mortality in nests; however, based on these temperatures, female biased sex ratios of hatchlings at both sites were predicted. v Acknowledgements My advisor Kartik Shanker allowed me the freedom to pursue this research at my own pace, put up with a fair amount of indecision and provided much needed support through this whole process. Ajith Kumar, my course director has been an unending source of inspiration, with his breadth of knowledge and enthusiasm. I would not have achieved half as much without his motivation, kindness and humour. Kavita Isvaran with her kindness and patience is someone I can go to for advice or help. She has helped mould this idea and many others before it. My classmates have been the most important part of my two years here and it is hard to think of a better set of people to be stuck with for that long. I thank them for helping me learn much about wildlife, music, philosophy, acceptable dinner-time conversation, teamwork, forgiveness, adventure and most of all having fun! In particular I treasure the moments of sanity with Kiran; a true friend, philosopher and guide, of insanity with Umesh, Nandini, Dharma, Dipti and Swapna, of thought-filled discussion with Kulu and general discussion with Robin, of laughter and tears with Aathira and of comfort and friendship with Priya, Priyanka, Nachiket and Kaavya. I am grateful to the Centre for Wildlife Studies (CWS) and the Centre for Ecological Studies (IISc) for funding this work, to Manipal Academy of Higher Education (MAHE) and the National Centre for Biological Sciences (NCBS) for providing the framework for this course, as well as the Forest Department for Orissa for its co-operation and support, in particular Mr B.K. Patnaik (PCCF Wildlife), Dr CS Kar and Mr Ajay Jena (DFO, Berhampur). A number of local conservation bodies including the Rushikulya Sea Turtle Protection Committee (RSTPC) vi and the Students Sea Turtle Conservation Network (SSTCN) provided logistic and other support. I am thankful to the generosity of those organisations and their volunteers. Rabindranath Sahu, Ganapathy Sahu, Somanath Rao, Simhadri and Mohendra Naik in Orissa, as well as Shreya Bhat, Madhavan, Asha, Shravan Krishnan, Karunakaran, Akhila and Arun V. in Chennai helped me with field work. A number of others including including Samjukta Sahu, Coralie D’lima and especially Suresh Kumar helped with logistics, advice and suggestions. Devcharan Jathanna, Rashid Raza, Suhel Quader, Nibedita Mukherjee, Geoff Hyde and Chaitanya Krishna added valuable comments and inputs that helped shape my thesis. I am grateful to all these people for the time and effort they spared for me. My parents, grandmothers and brother have long supported my decisions and encouraged my work. That I have come this far is due credit to them and their love. vii CONTENTS INTRODUCTION ....................................................................................................................2 BACKGROUND ..................................................................................................................4 LITERATURE CITED ..........................................................................................................6 ORIENTATION OF OLIVE RIDLEY TURTLE HATCHLINGS IN RESPONSE TO LIGHT IN RUSHIKULYA, ORISSA.......................................................................................................10 ABSTRACT .......................................................................................................................10 INTRODUCTION...............................................................................................................11 METHODOLOGY..............................................................................................................14 Study area.....................................................................................................................14 Experiment 1: Impact of photic regions on the beach ...................................................15 Experiment 2: Testing light quality ................................................................................16 Model of expected orientation .......................................................................................17 Analysis.........................................................................................................................18 RESULTS..........................................................................................................................18 Experiment 1 .................................................................................................................18 Experiment 2 .................................................................................................................19 Orientation model..........................................................................................................22 DISCUSSION....................................................................................................................23 LITERATURE CITED ........................................................................................................27 TEMPERATURE DEPENDANT EFFECTS ON THE EGGS AND HATCHLINGS OF OLIVE RIDLEY TURTLES ALONG THE EAST COAST OF INDIA ................................................31 ABSTRACT .......................................................................................................................31 INTRODUCTION...............................................................................................................32 METHODOLOGY..............................................................................................................34 Study area.....................................................................................................................34 Field methods................................................................................................................36 Analysis.........................................................................................................................37 RESULTS..........................................................................................................................38 DISCUSSION....................................................................................................................43 LITERATURE CITED ........................................................................................................47 CONCLUSION......................................................................................................................52 1 INTRODUCTION There are seven species of sea turtles found across the world – the leatherback (Dermochelys coriacea), green (Chelonia mydas), loggerhead (Caretta caretta), hawksbill (Eretmochelys imbricata), Kemp’s ridley (Lepidochelys kempii), olive ridley (Lepidochelys olivacea) and Australian flatback (Natator depressus) (Frazier 2002). The study of factors affecting the mortality of these species is important since they are all threatened species (IUCN 2007). Of the five that are known to inhabit the coastal waters of India, the olive ridley sea turtle is the most common. It nests along much of the Indian coast, but is most numerous along the east coast (Shanker and Choudury