Belly Up: Snakes Elaborate Belly Patterns

Plain or patterned bellies can help snakes avoid predators.

The eye-catching checkerboard belly of the corn snake is a good example of this body décor. It resembles an ear of maize, which is likely what inspired the snake’s name. 

But, “patterns are not very common on snake bellies," says Kate Jackson of Whitman College in Washington State. Instead, the reptiles typically display solid colors that are paler or brighter than their topsides.

Snakes don’t typically have elaborate patterns on their bellies. One exception is the corn snake, which has an eye-catching checkerboard pattern evocative of an ear of maize. [Photograph by Breck P. Kent, National Geographic]

This contrast is called countershading, a type of camouflage that "occurs across the majority of animal groups," says Whit Gibbons, author and herpetologist at the University of Georgia’s Savannah River Ecology Laboratory.

One example is the smooth green snake. Sunlight makes the dark green on its back appear lighter, so that it blends with the pale green on the lower part of its body. The result is a uniform color that is harder to see, especially against green grass.

But other colors are meant to be seen. “Red, orange and yellow are called ‘warning colors’,” Jackson says, because they are often associated with venomous species. And sometimes, the contrast of colors—such as the non-venomous ringneck snakes, which are black on top and pale red below—serve as “flash coloration” that can briefly confuse a predator.

"When the snake is noticed by a predator and disturbed, say picked up or turned over, the startle value of the pale underside or the warning colors (yellow/orange) might buy the snake a moment to escape,” says Gibbons.

The different color schemes are also apparent in aquatic snakes. Banded watersnakes have elaborate belly patterns and spend a lot of time swimming. Their patterns "might be very effective against a predator like a snapping turtle or big fish looking up from below," Gibbons says.

By contrast, the plain-bellied watersnake, true to its name, doesn’t have an elaborate pattern. Since it spends a lot of time on land where its belly doesn't show, it benefits more from countershading than from flash coloration.

Lee Fitzgerald, a herpetologist at Texas A&M University, says that the dizzying color variations of snakes can also enable mimicry.

The colorful bands of the venomous eastern coral snake serve as a warning to would-be predators. [Photograph by Joel Sartore, National Geographic Creative]

The eastern coral snake, for example, is a venomous snake with colorful bands that signal trouble to would-be predators. The scarlet king snake is harmless, but uses its coloration to masquerade as the lethal coral snake. The two look so closely alike that a rhyme had to be invented to help us remember which is which.

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