To eat food in one gulp or not, that is the question. Slice it into smaller pieces first and it becomes easier to swallow. Gulp it whole and there is less chance your food will escape, if it is still alive that is.

Most snakes do the first. They have no limbs to tear food apart and have an incredible ability to swallow food whole, even if it is much larger than them. 

Prey-dismembering behaviour may be widely used

But there are some exceptions. New research has found that one particular species of blindsnake (Indotyphlops braminus) breaks the head off its termite prey before swallowing the rest of its body.

First, the snake swallows the termite's body while its head remains outside the snake's mouth. The snake then rubs the termite's head against a surface – in this case its cage – until its head is separated from its body. This sequence of events can be seen in the photo below.

It swallows the rest of the termite after its head is disconnected. This process only takes three seconds and the decapitated heads are left uneaten. 

Occasionally these small snakes will even regurgitate a termite after swallowing it whole. Only then will it decapitate it before swallowing it again.

The research, published in the Journal of Zoology, discovered that the snakes only decapitated their termite meals about half the time.

This is an unusual feeding behaviour for a snake and was completely unexpected, says lead author of the study Takafumi Mizuno of the Kyoto Institute of Technology in Japan.

"Taken together with brief reports from 1950s and 1960s on similar behaviours in other blindsnakes, our finding implies that prey-dismembering behaviour may be widely used in poorly-known basal [ancient] snakes," he adds.

It did not take longer to eat a decapitated termite instead of swallowing one whole. The researchers therefore propose two reasons why the snakes may be doing so at least some of the time.

The heads contain toxic chemicals which could be bad news for the snake. The reptiles may therefore leave the termites' heads to avoid swallowing these unpleasant toxic compounds.

But those that do swallow them appear unaffected. The termite heads remain undigested. They come out the other end in the same physical state. So perhaps foregoing the heads saves space in a snake's gut.

This makes it stand out among 3,000 or so species of snake

Blindsnakes will always try to decapitate termites, says Mizuno, but it can be difficult for them to do so. "As a consequence decapitation rate are about 50%."

Though tearing food apart before eating it is rare, blind snakes are not the only ones to do so. Two species of Asian crab-eating snake break the legs off their prey before eating them.  

The blindsnake and the crab-eating snakes are genetically very different. They are separated by a common ancestor which lived 100 million years ago. This prey-tearing behaviour could therefore have evolved independently in these two lineages, the team proposes.

More research is needed to discover just how many other snakes have similar dietary preferences.

What we don't know about these snakes could fill an entire library, says Andrew Durso at Utah State University, US, who was not involved with the research.

This particular species is also the only known snake where all are female. That is, they are parthenogens, they have virgin births.

"It's very exciting. These researchers were able to discover something brand new about this snake, almost by accident, something that makes it stand out among 3,000 or so species of snake," says Durso.

It could also be present in many of the other 400 species of blindsnake, becoming another unusual habit they can add to their name.

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