Colour vision of green turtle (Chelonia mydas) hatchlings: do they still prefer blue under water?

Background. Several anatomical studies have concluded that green turtles (Chelonia mydas) possess the necessary anatomy for colour vision. Behavioural experiments were conducted with newly emerged hatchlings, testing their attraction towards light sources of different colours on their journey into the ocean. It was concluded that they are attracted to shorter wavelengths compared to longer ones, suggesting a possible attraction towards blue. Methods. Forty-one green turtles at six months of age were tested for their colour discrimination capabilities during a three-choice experiment under water. Three colours were selected for experimentation: blue, yellow, and red. Four different saturations (25, 50, 75, and 100%) of each of these colours were created, in total 12 colours were tested. The colour stimuli was printed and laminated paper colour blocks with food attached to force an interaction. Turtles were individually placed into their housing tanks with three different colours in front of them, from the same level saturation. The colour of the colour plate first approached and bitten by the turtle was noted. Results. The colour of the plate significantly influenced the likelihood that one food plate was selected more than another. Overall blue was selected 66.1%, yellow 18.2% and red 15.7%. There was also a significant interaction between the colour plate selected and the colour of the housing tank. Discussion.The findings of this study are consistent with previous research, concluding that green turtles are attracted to shorter wavelength colours, blue, compared to longer wavelength colours such as yellow or red. As the colour saturation changed and the colours became darker, turtles still chose food from the blue plates compared to the other options. These results indicate an attraction towards the colour blue, and as these research animals have never been in the wild, it is suggested that this attraction be an innate behavioural characteristic for green turtles