Kukri snakes cut open toads and frogs before sticking their heads in their bodies and eating their organs one by one while the prey is still alive, scientists report.
Biologists have published three studies, each describing the horrific feeding behavior in one of three different species of kukri snakes in Asia.
The three closely related species of snakes, all within the genus Oligodon, keep prey alive for “ up to a few hours, ” the study authors said.
The images below show one – the Taiwanese kukri snake (Oligodon formosanus) – with its head buried deep within the belly of the striped bullfrog (Kaloula pulchra).
In the bloody attacks seen in the wild, toads struggled vigorously to escape and “avoid being eviscerated alive” – but their efforts were in vain.
The attacks can last for several hours, depending on which organs the snake takes out first.
An Ocellated kukri snake (Vietnam) first pierced this venomous Asian common toad and buried its head deep in the amphibian’s abdomen, as it likely ate the organs. As can be seen in the photo, the kukri snake swallowed the toad whole
The footage also shows the relentless snake repeatedly rotating its body lengthways in an elaborate performance known as a ‘death roll’.
“We believe the purpose of these death scrolls was to tear organs out and then be swallowed,” said study author Henrik Bringsøe, a herpetologist based in Køge, Denmark.
Two of the three articles describing the horrific behavior, all written by Bringsøe, were published this month.
One reports the gruesome feeding strategy of the Taiwanese kukri snake (Oligodon formosanus) and the other the same strategy of the Ocellated kukri snake (Oligodon ocellatus).
The other paper, published last September, describes the same behavior in the small-banded kukri snake (Oligodon fasciolatus).
The closely related three species of snakes within the Oligodon genus have developed this unusual and gripping behavior.
Still from footage of a Taiwanese kukri snake cutting open the abdomen of a striped bullfrog (Kaloula pulchra) and pulling out various organs that it bites and chews. The video shows the snake while swallowing. The sighting took place in Hong Kong. The full footage of this meeting can be viewed below
Interestingly, these species have also been recorded to feed in a more conventional way – by swallowing their prey whole.
It is therefore likely that this alternative strategy evolved to accommodate much larger animals.
One of the new studies reports two cases from Hong Kong where Taiwanese kukri snakes were observed to take apart striped bullfrogs.
In one instance, the snake had cut open the frog’s belly and stuck its head into the frog’s belly, before performing its death roll repeatedly.
In the other case, the frog’s organs had been pushed out of its belly.
The second newly published research paper describes the behavior of Ocellated kukri snake, which was observed eating the venomous Asiatic black spotted toad (Duttaphrynus melanostictus) in Vietnam.
Asiatic black spotted toad is known to secrete a potent toxin from the parotid glands in the neck, but these did not appear to have a lethal effect on the predator.
Initially, the snake was seen to have buried its large head eyes deep in the amphibian’s belly.
Eventually, despite its toxicity, the snake swallowed the toad whole, providing evidence that kukri snakes are resistant to the toads’ cardiac glycoside toxins.
The less recent September newspaper marked the announcement of the eating habit – described as “never seen before in a snake.”
It described multiple cases of the small-banded kukri snake (Oligodon fasciolatus) feeding on the Asiatic black-spotted toad.
At the time, the research team pointed out that smaller toads of this species tended to be swallowed whole – possibly because they are less poisonous than adults.
A small-banded kukri snake with its head inserted through the right side of the belly of an Asiatic black-spotted toad, to extract and eat the organs. Tissue from a collapsed lung (top left) and possibly adipose tissue, covered with clear liquid foam that mixes with air bubbles from the lung as it expires. The upper part of the foreleg is covered with foamy blood, also mixed with air bubbles from the collapsed lung
In one of the new articles, Bringsøe and his team include a new detail from a new sighting of the Small-banded Kukri Snake (Oligodon fasciolatus).
The team reveals that it prefers to swallow its prey whole after the same ‘kill roll’.
This has led scientists to believe that it is the size of the prey that determines exactly how the snake would eat.
“We hope that future observations can reveal additional aspects of the fascinating feeding habits of kukri snakes, although we can indeed call them gruesome,” Bringsøe said.
All research papers have been published in the peer-reviewed, open access journal Herpetozoa.