Green turtles nest survival: Quantifying the hidden predation

Area of Science:

• Marine Biology
• Ecology
• Conservation Science

Background:

• Trindade Island is a critical nesting site for green turtles (Chelonia mydas) in Brazil and the Atlantic.
• The terrestrial crab Johngarthia lagostoma is abundant on the island, including nesting beaches.

Purpose of the Study:

• To document crab predation on green turtle eggs for the first time.
• To analyze the behavior of the predatory crab species and quantify egg loss.

Main Methods:

• Observation of crab predation on sea turtle nests using images and videos.
• Analysis of predation patterns during the 2017/18 and 2018/19 breeding seasons.

Main Results:

• Unprecedented records of Johngarthia lagostoma preying on Chelonia mydas eggs were obtained.
• An average of 3 eggs per nest were lost to predation.
• The highest predation risk occurred between 0:00 and 3:00 AM.
• Mortality in the egg stage was 5% per nest, with an estimated 21,600 eggs lost per reproductive season.

Conclusions:

• Terrestrial crab predation represents a significant threat to green turtle nesting success at Trindade Island.
• Understanding these predator-prey dynamics is crucial for green turtle conservation efforts in the region.