Effect of Artificial Lights on Sea Turtle Hatchlings orientation

Bc. Tereza Znachorová

Master's thesis

Abstract:

The topic of the thesis was the effect of artificial lighting on the orientation of hatchling sea turtles. The subject of the research study was to obtain data that would lead to a description of the behaviour of hatchlings in relation to artificial lighting. This thesis aimed to clarify sea turtle biology and evaluate the probability of disorientation of hatchlings concerning artificial lighting present nearby. The thesis first focused on describing the biology of sea turtles (Chelonioidae). In the introduction, physiological features and morphological characters were generally described. Furthermore, the thesis focused on nesting and reproductive behaviour and also on possible threats to the species. In the next section, the taxonomy of sea turtles was described, focusing on the issue of one particular species - the green sea turtle. The following part of the thesis was directed to the main topic: the threat to green sea turtle hatchlings by artificial lighting. The possible threats and endangerments of green sea turtles were mentioned. In addition to the general threats due to trade and industrial development, the thesis described the issue of artificial lighting near nesting beaches. It specifically dealt with the effect of artificial lighting on the behaviour of hatchling sea turtles. The possible disorientation of hatchlings became the subject of research for this thesis. The research part of the thesis was carried out in collaboration with a Sea Turtle Conservancy organization. The study site was Tortuguero beach on the northern Caribbean coast of Costa Rica, in the province of Limón. This beach has black sand and is approximately 29 km long and is one of the most preferred locations by nesting females. For data collection, it was necessary to obtain hatchlings, which were gently collected from the nests and transferred to the laboratory of STC. The experiment was then conducted at night, the study site being a 1.2 km long section of beach bordered on one side by vegetation and the other by the sea. Hatchlings were released in a total of 26 circular arenas, repeated at different distances from the town. The necessary data were collected for the next part of the thesis by consistently observing the young in their sea-finding ability. The data were then evaluated to determine the dispersion and disorientation. The results of the research showed an effect of artificial lighting that was not so significant. Despite the illuminated town, most of the hatchlings decided to go in the right direction towards the sea, only in some cases in the presence of artificial lighting they decided to follow it. Despite the fact that a minority were affected by the artificial lights, these findings can be applied to local conservation activities that seek to limit the intensity of light smog through local ordinances and regulations.

Keywords

Green sea turtle, Chelonia mydas, sea turtles biology, light pollution, disorientation, nesting biology, marine biology, vision, Tortuguero, Costa Rica

Language used: English

Date on which the thesis was submitted / produced: 22. 4. 2022

Thesis defence

• Supervisor: Ing. Miloslav Petrtýl, Ph.D.
• Reader: Tomáš Husák, Ing.

Czech University of Life Sciences Prague

Faculty of Agrobiology, Food and Natural Resources

Master programme / specializace:
Wildlife and Livestock Production, Management and Conservation / Wildlife Management and Conservation