By Sumedha Korgaonkar, Wildlife Institute of India, Dehradun, Uttarakhand, India. 248001, [email protected]

and Dr Kuppusamy Sivakumar, Ex-Scientist F, Wildlife Institute of India, Dehradun, Uttarakhand, India. 248001 / Professor, Ecology and Environmental Science, Pondicherry Central University, Kalapet, Puducherry, India 605014

Climate change is profoundly affecting the life history traits of sea turtles both on the land and in the sea (Patrício et al., 2021). Changing climate affects the timing of marine turtle migration from the foraging sites to their nesting sites, copulatory behaviour and nesting period (Mazaris et al., 2008, Pike 2009, Patel et al., 2016). A significant shift in the peak nesting season of olive ridley turtles is observed on the west coast of India. Two decadal data of turtle nesting showed a shift in the peak nesting season from winter (December) to summer (February and March) (Graph1). This resulted in the nest’s incubation period extending to the harsh summer months of April in tropical India. The west coast of India comprises five coastal districts having olive ridley nesting sites. Maharashtra coast being one among them has the few best sporadic nesting sites with effective conservation measures implemented by the forest department. To safeguard the nests from predators and inundation, they are relocated to the temporarily established hatcheries during the nesting season. The state forest department does the relocation with the help of local communities trained as hatchery managers. To address the reduction in the emergence of hatchlings on these conservation sites, we undertook this research in 2017.

During post-incubation excavation, we observed well-developed normal hatchlings trapped inside the nest. Some were alive and exhausted, and many died (Fig 1). The sand inside the nest has hardened and become compacted. The nest having incubation and emergence period in April and May showed such hardening of sand. In the absence of any interventions, it resulted in zero emergences of hatchlings. The west coast of India, except Gujarat state, has western ghats giving rise to rivers forming a big or small estuary (Fig 1). Most of the nesting sites have an estuary on one side, depositing placer minerals, fine sand and silt on the beach. The increased incubation temperature and moisture with fine sand of the nest must have resulted in the hardening of the sand inside the nest, trapping the hatchlings and increasing the mortality rate. A protocol for rescuing trapped hatchlings was developed, standardized and implemented on nesting sites.

To mitigate the effect of increased incubation temperature of the nest, an indigenously developed temperature data logger modified for the hatchery was installed. The temperature data logger units were installed on seven high nesting sites (>20 nest /season/site). The datalogger is encased in IP 65 box to protect it from the corrosive and harsh environment. Each logger has eight high-accuracy sensors (± 0.1oC) powered by a solar panel. The logging of the temperature data was set for 10 mins. An in-built GSM system (Global system for mobile communication) transmitted the data for analysis (Fig2). The display screen on the datalogger showing temperature data of the nest helped the hatchery manager monitor the nest’s incubation temperature. The hatcheries were covered with a green shade net. However, the shade net was inefficient in reducing the incubation temperature with temperature data. Other methods like sprinkling water around the nest or keeping an overturned cane basket over the nest with moist jute cloth were tried (Fig2). Both methods effectively reduced the incubation temperature of the nest. It was observed that the incubation temperature, when maintained below a threshold temperature of 33oC, increased the natural emergence of the hatchlings.

Another strategy that helped in mitigation was erecting the hatchery inside the casuarina plantation. The exotic casuarina introduced in India in the 1860s has covered the entire coastline of India. In India, it has been planted by state agencies as a wind break and storm barrier on the beach. It has a definitive role in the prevention of sand/beach erosion. Though in countries like the US and South Africa, it is invasive, there is no reporting of it being invasive in India (Invasive species compendium, 2021). Some precautionary measures are highlighted in its plantation on mangrove sites (Das et al., 2014). In Maharashtra, it has been present at least for more than 100 years and has very much become a part of its natural habitat. Erecting a hatchery inside the dispersed plantation kept the incubation temperature below the threshold level throughout the nesting season. The sex ratio estimated through the indirect temperature method showed a well-balanced sex ratio of hatchlings (Laloe et al. 2014, 2016). The hatchlings were larger and showed normal morphology compared to other sites. Hatchlings emerged naturally from the nest without any intervention. It was contrary to previous years when they were seen trapped inside the nest. A protocol for selecting hatchery sites inside the plantation was developed and standardized (Fig 3). The hatchery inside the plantation on the site has shown promising results in the 2021 and 2022 nesting seasons.

Temperature data loggers installed on seven different nesting sites spread across the 350 km coastline of Maharashtra state monitor 56 nests simultaneously. The sensors can be reused and reintroduced in other nests during the nesting season. The data logger is sustainable so that the project can be implemented for many years with an additional recurring cost. Analytical software and a database site are needed to manage the data. The project funded by the Mangrove Foundation of Maharashtra State Forest Department from 2019- to 2021 will be extended in future. Implementation of this project has collected significant incubation temperature data for the nesting population of olive ridley turtles from the Indian Ocean west. Moreover, it has helped implement appropriate management strategies for mitigation of incubation temperature and inculcated a scientific fervour in hatchery managers. Using an indigenously made temperature data logger and natural plantation for hatchery should be considered to mitigate the impact of high temperature on the terrestrial life stages of sea turtles.

Acknowledgement: We sincerely thank Society for Conservation (Marine Chapter) for giving grants to develop a single temperature data logger in 2019. We thank Mr Virendra Tiwari, APCCF, Mangrove Cell & Executive Director of Mangrove Foundation for providing additional funding to this project from 2019 – 2021. We also thank Dr Manas Manjrekar, Deputy Director (Research and Capacity building) of Mangrove Foundation for facilitating the project. They have taken a keen interest in implementing the research outcome through hatchery management improvisation in Maharashtra. We thank the PCCF(WL) of the Maharashtra State Forest Department for granting us permission for this research. This project is successful due to the hatchery managers who are doing commendable work in the conservation management of olive ridley turtles.

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