In early November, scientists in the Florida Everglades cut open the bulging stomach of an 18-foot Burmese python and dragged out a 5-foot alligator. The gator was eerily intact, with only parts of its skin degraded.
Pythons are notorious for swallowing gigantic prey—like deer, alligators and cattle—whole. But how can reptiles with such small heads eat animals so big?
Contrary to popular belief, pythons don’t unhinge their jaws to gulp down their food. Instead, a stretchy connective tissue between their cranium and lower jaw allows them to open their mouths four times wider than their skulls, per Scientific American's Bethany Brookshire.
In a study published in Integrative Organismal Biology, researchers at the University of Cincinnati tested exactly how far the snakes could stretch their jaws and how much the stretchy tissue contributes to their remarkable ability.
“It’s intriguing to think about the different potential limits of what animals can do in nature,” Bruce Jayne, lead author and a biologist at the University of Cincinnati, says in a statement. “What does anatomy permit? What does it limit?”
The team examined 43 euthanized Burmese pythons and 19 brown tree snakes, which are distantly related, and inserted cylindrical probes of varying sizes into the snakes’ mouths. The largest probe, which only one 130-pound python was able to fit, was 9 inches in diameter.
"The probe is big enough to fit over my head," Jayne tells Live Science’s Jennifer Nalewicki. "To give you an idea of how big that specimen was, it's too large to fit inside a 5-gallon [20 liters] bucket. That was a hefty one."
They also funneled dead prey species—rats, rabbits, chickens, raccoons and iguanas—and live, anesthetized alligators into the snakes.
The team found that the width of the snakes’ gape determined how large an animal it could eat, rather than its body or head size. Pythons had a 4 to 6 times greater maximal gape area than similarly-sized brown tree snakes.
Burmese pythons are highly invasive in Florida. With few predators, the snakes are free to devour native species unchecked. Since they were first found in the Everglades in 1979, their impact on the ecosystem has been immense. According to the U.S. Geological Survey, in the southern portion of the park, raccoon populations plummeted 99.3 percent, opossums 98.9 percent and bobcats 87.5 percent between 1997 and 2012. Marsh rabbits, cottontail rabbits and foxes mostly disappeared. All of these species, and larger prey, have been found in the stomachs of Burmese pythons.
The biggest python ever captured weighed a whopping 215 pounds and had recently consumed an entire white-tailed deer. But just because a snake can eat an animal that large doesn’t mean it will.
“Most [tree snakes and pythons] are opportunistic and will catch anything that passes by, [so] they will probably not target the largest prey,” Marion Segall, a herpetologist at London’s Natural History Museum, who was not involved in the study, tells Scientific American.
Still, knowing their potential could help researchers understand how they snakes are influencing the food chain, per the statement.
“It’s not going to help to control them,” Jayne says in the statement. “But it can help us understand the impact of invasive species. If you know how big the snakes get and how long it takes for them to get that size, you can place a rough upper limit on what resources the snake could be expected to exploit.”