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Turtles are wonderful painting subjects, exhibiting many fascinating and sophisticated adaptations, as befits their long lineage. Every time I paint one, I discover a visual feature that invites a deeper look into the “why” behind it.

For the Museum of Life and Science’s Creek Week, I chose two native species: the yellow-bellied slider and the common snapping turtle. For each subject, I created an initial sketch from specimens at the North Carolina Museum of Natural Sciences Naturalist Center. These studies became the foundation for both watercolor paintings and ink versions used as coloring pages for visitors. In developing the educational copy for the coloring pages, I discovered that “sliders” (often seen basking on logs) are named for their habit of sliding quickly into the water when threatened. Somehow, I’d never come across that explanation before.

Yellow-bellied Slider (coloring page)

Comparing the two species raised some interesting questions. One of the first differences I noticed was the snapping turtle’s much longer skull. At first, I assumed this might simply provide additional space for muscle attachment, but the reality is more nuanced. As a predator, the snapping turtle benefits from a long, wedge-shaped skull that increases strike reach, accommodates powerful jaw musculature, and helps channel the stresses of a forceful bite. In contrast, the slider’s skull is adapted for less forceful feeding, such as cropping vegetation.

Sketch of Common Snapping Turtle Skull and Lower Jaw

The second point of interest was that the eye coloration pattern differs noticeably. Turtle eyes vary widely in appearance. Some, like sea turtles, have eyes that appear almost gentle—and even eerily human. In my Creek Week subjects, the slider has a horizontal bar of darker color across the iris, while the snapping turtle’s eye includes both horizontal and vertical bars, creating a “crosshair” effect.

Detail of Yellow-bellied Slider and Snapping Turtle paintings

There are several hypotheses behind these patterns, and two in particular stood out to me.

One idea is that the snapping turtle’s “crosshairs” function as disruptive coloration, helping to obscure the eye and making it harder for prey to detect exactly where the turtle is looking. Predators such as tigers show somewhat similar strategies, with facial striping that breaks up the outline of the eyes and even “eyespots” on the backs of their ears.

Another hypothesis is that horizontal bars—seen in both species—may help reduce glare from the water’s surface and enhance contrast along the horizon. Interestingly, grazing mammals like horses and goats achieve a similar visual effect through horizontally elongated pupils, suggesting a comparable functional goal reached through a different anatomical solution.

I’m looking forward to exploring turtle morphology further—there always seems to be another layer of structure and function waiting just beneath the surface.

Snapping Turtle, watercolor