By Stacey Venzel
Just like human babies have different needs from adults, turtles use varying color to help adapt to life stages from hatchling to juvenile and adult.
When a turtle grows and develops, pigmentation or reflections in its shell, skin and eyes can alter relative to its living situation. Coloration and patterns can offer protection as well as signify seasonal changes.
CAUSE OF COLORS
Pigment cells called chromatophores cause bright colors in turtles, such as the common yellow stripes seen in species like the Florida red-bellied cooter. Melanophores cause dark coloration, but every animal can lack melanophores and appear as an all-white albino. One species, the male painted terrapin, uses increased blood flow to the orange dot atop its head to change the spot to red.
REASON FOR SHELL PATTERNS
In the same way that a chameleon changes colors to blend in with its surroundings, patterns on a turtle’s shell help it camouflage from predators and prey. The circular pattern on the shell of some aquatic species, as in the juvenile ringed map turtle, resembles the water’s surface so that a wading bird could easily overlook it. The South American matamata employs dark skin and shell to become unrecognizable by swimming fish, so that the turtle can sit and wait to snatch up the fish when it gets too close.
AGING COLOR CHANGES
As a turtle matures, hormonal changes result in the onset of coloration alterations to suit new needs. For example, a vulnerable snake-necked hatchling has an orange belly to warn off catfish but loses the coloration when it reaches a size too big for a catfish’s meal.
SEASONAL COLOR CHANGES
During breeding season, some of the males become more brightly colored to attract females. The most dramatic shift in color is seen in the male painted terrapin whose body changes from gray and orange to white and red.
In 2015, biologists discovered a glowing turtle, the first reptile ever recorded to exhibit biofluorescence. Unlike bioluminescence, the turtle does not make its own coloration. Rather, it uses the blue light of the ocean to reflect different colors off its shell. The result is a turtle that appears to shimmer neon at night! First noticed in a hawksbill sea turtle swimming in the Pacific, scientists theorize the coloration could be a way to attract prey or to camouflage from predators.
Carl J Franklin, Turtles: An Extraordinary Natural History 245 Million Years in the Making (St. Paul, Voyageur Press, 2007), 8, 31-32, 40.
Whit Gibbons, Judy Greene, Turtle: The Animal Answer Guide (Baltimore, The John Hopkins University Press, 2009), 25-29.
Jareem Imam, “Scientists find their first biofluorescent reptile, a Pacific sea turtle,” CNN, September 30, 2015,http://www.cnn.com/2015/09/29/world/biofluorescent-sea-turtle-discovered/.