A little snake’s big gulp may put all other snakes to shame

Hulking hunters like Burmese pythons may be famous for scarfing up deer, alligators and other enormous prey (SN: 11/25/15). But one unassuming little African snake may take the title for most outsized meals. The nonvenomous, nearly toothless Dasypeltis gansi can open its mouth wider than any other snake of its size, biologist Bruce Jayne reports August 8 in the Journal of Zoology.

D. gansi, sometimes called the Gans’ egg-eater, swallows bird eggs whole, cracks them with its spine and ingests the contents before spitting out the shells. At the University of Cincinnati in Ohio, Jayne inspected 15 egg-eaters ranging from about 20 to about 90 centimeters long. After euthanizing the animals, he slid increasingly wide 3-D printed cylinders into their gaping maws to determine the biggest thing they could swallow.

On the left, a large snake appears with a cylinder inside its mouth, while a small snake appears on the right with a cylinder inside its mouth. — The biggest Gans’ egg-eater that biologist Bruce Jayne inspected (left) was about 94 centimeters long and could wrap its mouth around a cylinder 5 centimeters wide. The smallest egg-eater examined (right) was about 21 centimeters long and could fit a cylinder 1.4 centimeters wide in its mouth.B.C. Jayne/*Journal of Zoology* 2023

The biggest Gans’ egg-eater Jayne examined had a roughly 1-centimeter-wide head but could swallow a cylinder about five centimeters across. Previous data show that a petite Burmese python (Python molurus bivittatus) of the same length could gobble up prey just 4.4 centimeters wide. The western diamondback rattlesnake (Crotalus atrox) rivaled the python’s gift for gulp, but no other species came close.

The egg-eater can open so wide because the soft tissue between the tips of its left and right lower jaws at the “chin” is so stretchy. “In Burmese pythons, about 40 percent of that gape area is a result of the stretch of the skin between the lower jaws, but these guys edge out the pythons,” Jayne says, with about half of the Gans’ egg-eater’s gape due to soft tissue stretch.

This species may have evolved such an impressive stretch because, compared with prey that other snakes eat, such as rodents, “an egg is super short,” he says. “You have a limited ability to have a very long egg. But if you get your mouth wider, then you can consume these larger eggs.”

Open wide! This Gans’ egg-eater snake swallows a bird egg whole, uses its spine to crack the egg open, ingests the contents and regurgitates the shattered shell.

So far, maximum mouth size has been measured for only 13 of more than 3,500 known species of snakes. “Because the amount of stretch in the skin varies so radically in different species,” Jayne says, “it’s much more difficult to measure gape than simply take some calipers on a preserved museum specimen and measure bones.”

Jayne plans to keep investigating mouth sizes for a wider variety of snakes, such as those that dine on fish. Those data could reveal whether egg-eaters truly have the biggest gulp for their gullet.