How a Small Snake Can Eat Meals Many Times Larger Than Its Head

The egg-eating African reptile uses its stretchy jaw skin to swallow huge prey, a feat that not even a python can match

Snake that swallowed an egg
The Gans' egg-eater swallows a quail egg far larger than its head. Bruce Jayne via the University of Cincinnati

A tiny egg-eating African snake may take the prize for swallowing the largest meals relative to its body size out of all snakes, outstripping even pythons—which are famous for gulping down massive alligators, cows, antelopes and even people whole. 

“They probably would hold the Guinness world record,” biologist Bruce Jayne at the University of Cincinnati Jayne, says in a statement. “It’s spectacular but on a small scale…People focus on big snakes eating big things, but if you correct for their size, these little guys are pretty scary.”

In a new study published in the Journal of Zoology, Jayne used 3D-printed probes to test the gape—or jaw width—of two egg-eating snake species: Dasypeltis gansi, or the Gans' egg-eater, and the North American species Pantherophis obsoletus. The three-foot-long D. gansi rely solely on bird eggs for their sustenance, while P. obsoletus, also called black rat snakes, are generalist eaters that consume mostly rodents, but also gulp down eggs, frogs, lizards and birds. 

Jayne found that D. gansi  “has spectacularly stretchy skin” between its left and right lower jawbones, allowing it to “add more than 50 percent of that gape area,” Jayne tells the New York Times’ Kate Golembiewski. Black rat snakes, on the other hand, could only expand their gape by about 19 percent. Jayne’s previous research has found that Burmese pythons can expand their mouths by 43 percent, allowing them to consume bigger animals like deer or alligators.

Dasypeltis gansi eating egg

Jayne says in the statement that the Gans’ egg-eaters’ larger gape may serve an important evolutionary purpose. Other rodent-eating species don’t need to open their mouths quite so far to consume the calories they need, because their prey is more elongated. But bird eggs are almost entirely spherical, so bigger mouths are more advantageous for swallowing more mass. 

Other parts of the Gans’ egg-eaters' little bodies are also tailored to their specialized diet. Their spine can contort in a way that allows them to crack open eggs after swallowing them, which releases the slimy innards before they spit up the shells. The snakes are also almost entirely toothless with a soft mouth that helps them grip smooth, round eggs, per the statement.

Snake spits up an egg shell
The Gan's egg-eater contorts its body to crack open an egg after swallowing it, and then spits out the empty shell. Bruce Jayne via the University of Cincinnati

Bryan Maritz, a biologist at the University of the Western Cape in South Africa, who was not involved with the study, tells the Times that the new research upends the way scientists have traditionally thought about snake mouths. 

“We’ve always just relied on proxies for snake gape,” Bryan Maritz, a biologist at the University of the Western Cape in South Africa, who was not involved with the study, tells the Times. “We’ve said, ‘Well, gape is correlated broadly with head length, and so you can measure a snake’s head length and you can estimate its gape.’ And this study really shows that that’s not the case.”

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