Scute News: Researchers Analyze Scutes to Study the Life Histories of Sea Turtles

by · May 30, 2026

Scutes covering the upper shell (carapace) can be seen in this
closeup of a female loggerhead sea turtle. Photo credit: Cindy Lang.

Overview

Sea turtle scutes are hard, keratin plates that cover both the upper shell (carapace) and lower shell (plastron) of hard-shelled sea turtles. These scutes form a layer of protection over the shell and their coloration provides camouflage. As the sea turtle grows, the scutes are shed in layers and replaced by new ones which grow underneath the old ones.

Each species of hard-shelled sea turtle has a different pattern of scutes which is used for identification. For example, greens have four lateral scutes on each side of their vertebral scutes (center row), and loggerheads have five lateral scutes. Use this link to see the scute configurations of each species (illustration by Dawn Witherington). (1)

What Can We Learn by Analyzing Scutes?

Just like our fingernails and hair, scutes are made of keratin and contain chemical information which indicates what the sea turtles have been eating and where they are foraging. It can also indicate changes to their marine environment (2).

In a recent study (3), researchers used radiocarbon dating to analyze scute samples taken from 24 deceased Florida loggerheads and greens collected between 2019 and 2022. For greens, they sampled the second lateral scute (see illustration), and for loggerheads, they took samples from the third lateral scute. All samples were removed from the thickest part of the scute so they could analyze the maximum number of layers which grew over a long period of time. Each sample was sliced into very thin sections about 50 microns thick. Using statistical modeling, the researchers calculated the average rate of scute growth, then determined that each scute section was approximately seven to nine months of growth. Knowing the date each sea turtle died, they dated each section.

Comparing all the samples, the researchers discovered that the scute growth rate of all the turtles slowed down between 2015 and 2018. (4) They found that this decrease in growth correlated to multiple red tides and large Sargassum seaweed events in Florida during those years. Although the scute growth rates stabilized after these events, the scutes did not grow at the same rate as they did prior to the events. For the researchers, this finding indicates that these harmful environmental events can have a long-lasting impact on sea turtles.

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