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The snake that decapitates its prey

  • Blindsnakes behead termites before eating them.
  • Scientists think they do this to make the termites easier to digest.
  • Dismembering prey is rare for snakes, but a handful of species do it.

Snakes are impressive predators. They have super-flexible jaws that allow them to capture prey animals of all sizes. And once they do, they usually swallow their prey whole – whether it’s a small rat, or a large deer.

There are some exceptions to this behavior. Some snakes prefer to break their food down into smaller pieces instead of swallowing them whole.

The brahminy blindsnake (Indotyphlops braminus) is one such example. These tiny, worm-like snakes rip their preys’ heads off before swallowing them, a new study published in the Journal of Zoology has found.

Bhraminy blindsnakes are native to Africa and Asia, and live their lives completely underground. Because they have no need for normal eyesight, their eyes have nearly vanished, rendering them almost completely blind. Bhraminy blindsnakes are also distinctive in that the species consists entirely of females that reproduce asexually via a process called “parthenogenesis,” in which embryos develop from unfertilized egg cells.

And now, decapitation has been added to the bhraminy blindsnake’s list of peculiarities.

“I first found this behavior in the blindsnakes about a year ago,” Takafumi Mizuno, lead author of the study from the Kyoto Institute of Technology in Japan, told “And I was really surprised.”

To investigate this behavior further, Mizuno and his team collected seven blindsnakes from Hachijo-jima Island in Japan. They placed these snakes inside a plastic cage, introduced termites (Reticulitermes speratus) into the cage, and then videoed the snakes’ eating habits.

Generally, snakes swallow the head of their prey first. But Mizuno’s team found that the blindsnakes grasped the termites from behind, instead of the head, and ate them in such a way that the termite heads would stick out of their mouths.

Then, in nearly half of the feeding bouts, the blindsnakes rubbed the termite heads on the base of the plastic cage, and decapitated them. Even in instances that the snakes did swallow the termites whole, some vomited out the partially digested termites, and then beheaded them.

Sequential photos of a feeding event where a blindsnake decapitates a termite: (a) a blindsnake starts ingesting a termite from its abdomen; (b) the termite is transported into the mouth of the blindsnake; (c) the termite abdomen comes to lie in the oral cavity but its head remains outside of the mouth; (d) the blindsnake rubs the termite’s head against the bottom of the cage, which results in decapitation. Scale bar represents 2 mm. Source: Mizuno and Kojima, 2015.

But decapitation probably does not make it any easier for the snakes to swallow their prey, the authors write. This is because, in the experiments, it took the snakes about the same time to finish one termite serving, regardless of whether they swallowed the termites whole or decapitated them.

What advantage does decapitation have then?

The authors have put forward two possible explanations. First, the termite heads might be difficult to digest, they write. Blindsnakes eat a large number of animals during one feeding bout, so the authors speculate removing indigestible parts on the plate might be a smart move.

The second reason why blindsnakes might be decapitating the termites could be because the termite heads contain toxic compounds, according to the authors.

The most likely reason of the two remains unclear. But this unique decapitating behavior puts these blindsnakes in the exclusive company of just a few other prey-tearing snakes.

A blindsnake lies among termites, which have heads…for now. Photo courtesy of Takafumi Mizuno.

Some crab-eating snakes like the crab-eating water snake (Fordonia leucobalia) and cat-eyed watersnake (Gerarda prevostiana), for example, tear apart crabs into smaller bite-sized pieces before eating them.

But blindsnakes and crab-eating snakes are not close relatives. They are in fact far apart on the evolutionary tree. How did they then develop similar behavior?

According to the authors, this trait would have evolved independently in the two groups of snakes. But the common feature that links crab-eating snakes with blindsnakes is that they all feed on arthropods – segmented animals that include insects, spiders and crustaceans.

“The legs of most species of crabs break off quite easily, and for a wide variety of arthropods the bodies of the animals break much more easily at the joints between different parts of the exoskeleton, rather than within a single part of the exoskeleton,” Bruce Jayne, a professor at the University of Cincinnati in the U.S., told “Such weaknesses appear to be exploited both by blindsnakes in the current study and both species of crab-eating snakes.”

Despite this common feature between the distantly related snakes, their behaviors have some interesting differences, he added.

For example, crab-eating water snakes usually pin down hard-shelled crabs to the mud, break their legs off, and then swallow each leg one by one. For these snakes, the hard-shelled crabs are too large and awkwardly shaped to swallow whole. So it makes sense to eat the crab legs first, since these are easier to break off. On the other hand, blindsnakes are physically capable of swallowing the small termite prey whole. But they choose not to, on most occasions.

The cat-eyed water snake shows another interesting variant, Jayne said. This snake often rips apart the external shell of freshly-molted or soft-shelled crabs in places that do not necessarily correspond to the easily-detachable joints, he added.

But whatever the differences, discovery of blindsnakes’ strange eating habits tells us that there is a whole lot about snakes that we still don’t know.

“This study is a nice example of how much basic natural history we still have to learn,” Jayne said. “Who knows what other fascinating secrets remain to be discovered in the future?”



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