These Snakes Slice Open Toads and Eat Their Organs One-by-One While the Prey Is Still Alive

Researchers have observed a gruesome feeding behavior in a snake species native to southeast Asia during which the serpent cuts open the body of its toad prey and eats the organs, one-by-one, while the helpless animal is still alive.

The "macabre" feeding behavior, documented in small-banded kukri snakes (Oligodon fasciolatus) in northeastern Thailand between 2016 and 2020, has never been seen before in any other serpent species, according to a study published in the journal Herpetozoa.

The vast majority of snakes known to science swallow their prey whole and it is unusual for them to tear or cut off parts of their prey. But a team of Thai researchers—Maneerat Suthanthangjai and Winai Suthanthangjai from Loei Rajabhat University, Thailand and unaffiliated scientist Kanjana Nimnuam—documented three occasions when small-banded kukri snakes used their teeth to cut open the abdomen of a live, poisonous Asian black-spotted toad (Duttaphrynus melanostictus.)

In these three cases, the toads struggled desperately to save themselves while secreting a toxic white liquid in an attempt to fend off the snakes. But eventually the serpents "inserted their heads into the abdomen of the toads, pulled out some of the organs and swallowed them," the authors wrote in the study.

These struggles between the kukri snakes and black-spotted toads lasted up to around three hours, the researchers said.

"These are the first known cases of serpents inserting their heads into prey and subsequently extracting and eating organs, then discarding the rest of the prey," the authors wrote in the study.

The researchers also documented a fourth case, where a small-banded kukri snake attacked and swallowed an Asian black-spotted toad whole. This particular Asian black-spotted toad was notably smaller and younger than the fully-grown adults that were observed in the other three incidents.

The reasons behind the snake's unusual tendency to open up its prey and eat the organs one-by-one remains something of a mystery. The researchers speculate that the serpents may have evolved this technique because the adult toads are too toxic to be swallowed all at once, while the smaller toads are less toxic.

small-banded kukri snake
A small-banded kukri snake with its head inside the abdomen of an Asian black-spotted toad. Researchers have documented the snakes using this technique to extract and eat the organs of the toad. Winai Suthanthangjai

Asian black-spotted toads—a species that's relatively common in southern and southeastern Asia—secrete a potent toxin from special glands on their neck and back.

On the other hand, the researchers suggest that the snakes might actually be resistant to these toxins. The fact that the smaller toad was swallowed whole may indicate that the others were simply too large to eat, even for adult small-banded kukri snakes, which can grow up to around three feet in length.

It is also possible that both factors may apply: the adult toads may be both too large and too toxic to swallow, the researchers said.

"At present, we cannot answer any of these questions, but we will continue to observe and report on these fascinating snakes in the hope that we will uncover further interesting aspects of their biology," Danish researcher Henrik Bringsøe, one of the authors of the study said in a statement.

Small-banded kukri snakes are found throughout southeastern Myanmar, Thailand, Cambodia, Laos and Vietnam. They are part of a larger group of Kukri snakes containing 80 species, which inhabit large swathes of Asia. These serpents are known for their ability to inflict large, bleeding wounds. This trait has led them to be named after the kukri knives used by Nepali Gurkha soldiers.

"I wouldn't recommend being bitten by one of those," Bringsøe said. "The thing is that they can inflict large wounds that bleed for hours, because of the anticoagulant agent these snakes inject into the victim's bloodstream. Their teeth are designed to inflict lacerations rather than punctures, so your finger would feel as if cut apart!"

"This secretion, produced by two glands located behind the eyes of the snakes, are likely beneficial while the snakes spend hours extracting toad organs."

Bringsøe told Newsweek that the implications of the latest findings are "far-reaching" with the potential to expand our understanding of snakes and their diversity.

"So far, when it comes to animal species that are capable of attacking toxic toads from the abdomen, thus avoiding contact with their poison glands on the neck and back, we have often focused on mammals and birds with high cognitive abilities," he said.

"Now we have also realized that other vertebrates—snakes are quite close relatives to birds—without such cognitive abilities can adapt to similar behavior. Such behavior provides a new perspective on serpent behavioral strategies, which have proved very diverse."