Repository logo

Browsing by Author "Plank, Karin"

Now showing 1 - 1 of 1
  • Factors affecting green turtle (Chelonia mydas) hatching success, and their temporal variation over 7 study years
    Publication . Plank, Karin; Vinagre, Catarina; Hughes, Morgan
    Sea turtles are considered one of the most important key species in marine ecosystems, leading top-down regulations in food-webs, transferring nutrients and functioning as sentinel-species for monitoring effects of climate change. However, heavy exploitation over years due to the trade and consumption of turtle meat and their eggs, and the challenges faced by climate change, have resulted in a concerning global population decline of sea turtles. On Playa Norte, Costa Rica, in the surrounding area of Tortuguero, which gives nesting habitat to the largest green turtle (Chelonia mydas) population of the Atlantic Ocean, the main threats for turtle eggs and hatching success are poaching, predation by dogs, erosion and flooding, overheating and microorganisms. This study examined if the relative impact of each cause changes within a nesting season, and if occurrences have a constant trend over a study period of 7 years. A local study of the seasonality of each impact could endorse the development of effective conservation actions and an adjusted management plan that can be applied strategically to each cause expected at a certain time of the year. Hatching success averaged 38.65% for the 7 study years and was not significantly different among years, nor between climatic periods within a nesting season. Primary reasons for egg loss were “poaching” (24.72%) and “dog predation” (18.11%), followed by natural predation (3.81%), temperature (3.59%), flooding (3.51%), moisture/wet (3.22%), erosion (2.89%) and maternal effects (1.50%). The impact of causes of egg loss were largely constant over the study period. Factors related to climate and weather generally displayed high fatality but a low number of occurrences. On the other hand, anthropogenic factors accounted for the highest turtle egg mortality aggregating both impact and number of events. In terms of seasonality, not all of the causes displayed significant differences between periods, however all causes reached their highest impact in period 3. This suggests that the focus of conservation actions on Playa Norte should be put on the months between September and December, with particular emphasis on anthropogenic factors rather than environmental stressors. An intensification of beach patrol in this period, and nest reburial into an enclosed hatchery are recommended to increase hatching success and ensure recruitment for this green turtle population.
    2023-03-13Master thesis Open access Show more