Colour Preference of Post Hatchling Hawksbill (Eretmochelys imbricata) and Green (Chelonia mydas) Sea Turtles in Captivity

TL;DR

This study found that hawksbill and green sea turtles show different color preferences, likely due to their distinct habitats and foraging behaviors.

Contribution

The study introduces new behavioral evidence of color preference differences in two sea turtle species under controlled captivity.

Findings

Hawksbill turtles prefer shorter wavelengths like dark blue and cyan.

Green turtles consistently prefer longer wavelengths, especially yellow.

Color preferences may reflect adaptations to their respective foraging niches.

Abstract

Sea turtle vision has adapted to life in air and in water up to great depths. In some studies, the visual capability of certain turtle species to see and respond to colour have found turtles can see most of the wavelengths within the visible and ultraviolet spectrum. Using coloured water balloons, we compared the behavioural responses and colour preferences of hawksbill and green turtles as they aged from 15 months to 22 months. We found that hawksbill and green turtles reacted differently to each of the colours tested. Hawksbill turtles had an attraction to shorter wavelengths such as dark blue and cyan, and green turtles had an attraction to longer wavelengths with a consistent yellow hue preference. The differences found between these species likely result from the different habitats and depths that they occupy and the effect of depth on longer wavelengths.

Variations in the ecological roles of sea turtle species may lead to differentiations in ocular design and visual sensitivity to the colour spectrum. Behavioural colour preference studies in air and in water on hatchling and post-hatchling green turtles found evidence of a blue hue attractiveness when given a choice between blue, red, and yellow. This paper assessed and compared the colour preferences to singular colours via the behavioural responses of eleven hawksbill turtles and twelve green turtles at 15 months of age and at 22 months of age. Turtles were presented with one coloured water balloon per day (purple (400–450 nm), dark blue (450–490 nm), cyan (490–520 nm), green (520–560 nm), yellow (560–590 nm), orange (590–635 nm), and red (635–700 nm)). Time to contact balloons with beak and behaviours exhibited by turtles were recorded. Hawksbill turtles had the greatest level of interactions across both phases to shorter wavelengths with hue preference being between 450 and 490 nm. Green turtles consistently had the greatest level of interaction to longer wavelengths with a yellow (560–590 nm) hue preference. The results of this study support behavioural differences between two co-occurring turtle species that may reflect an adaptive preference for colour wavelengths associated with the optimal foraging niche for each.

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