Tag: snake ecology

More than it can chew: ambitious adder takes on hare in rare interaction

See footage of the interaction below.

A new paper published in the open-access journal Herpetozoa records a rarely documented event in the world of snake predation: an adult female Common European Adder (Vipera berus) attempting to kill and swallow a young European Hare (Lepus europaeus) nearly ten times its own mass.

Watch below (warning: contains footage some may find distressing):

Aadult female adder, Vipera berus, examining a young hare or leveret, Lepus europaeus and biting its left hind leg. The adder was disturbed by the observer’s presence and escaped into the tall grass. Credit: Klaus Birch.

The incident, observed on the Danish island of Læsø in August 2022, saw the adder, which was likely in a state of nutritional deficit after giving birth, attack a young hare (a leveret) in open grassland. Researchers Henrik Bringsøe, Daniel Jablonski, and Klaus Birch document the interaction in their research paper.

The snake was seen biting and examining the hare’s limbs and head, which is how adders assess whether prey can be swallowed. Despite the adder’s determined efforts, intervention from the observer prevented the snake from attempting ingestion, and the hare succumbed to its injuries shortly after. The research paper’s authors suggest it is likely that, without intervention, the snake would have abandoned its excessively large prey after careful examination anyway.

The adder returned from the grass vegetation to the hare and continued examining it, especially the front legs and the head. Credit: Klaus Birch.

The sheer size difference between predator and prey makes the observation noteworthy. The adder, estimated at 60 cm in length and weighing around 110 grams, was facing a hare of about 30 cm and 1,000 grams. 

Such attempts at oversized prey are not unknown among snakes, but they are poorly represented in scientific literature and may be more common than previously thought. Snakes often abandon prey that proves impossible to consume, but these events are seldom reported.

The authors contextualise this event with similar cases from around the world, including rattlesnakes and other vipers attacking animals too large to swallow. Sometimes, these ambitious meals can even prove fatal for the snakes themselves. The paper suggests that the drive for a high-energy meal, particularly after energetically costly events like giving birth, may push snakes to take such risks.

Snake attempting to eat a rabbit much larger than itself.
Male Crotalus lutosus having killed a young Sylvilagus audubonii (Desert Cottontail) which it tried to swallow, however, it was unable to finish the job. Likely its first meal attempt during the spring. St. George, southwestern Utah, USA, 29 April 2023 at 09:15 h. Photo by Cameron Rognan.

Lead author of the study, Henrik Bringsøe, has a history of recording rare and entirely new snake feeding behaviour, such as snakes disemboweling and feeding on the organs of living toads, and two snakes playing tug-of-war with a limbless amphibian.

Tug of war: two snakes battle for prey in a scientific first

This remarkable observation highlights the need for more documentation of such underreported phenomena in snake ecology, and serves as a reminder that in the wild, even the most experienced predators can be a little too optimistic.

Original source

Bringsøe H, Jablonski D, Birch K (2025) Overly optimistic adder, Vipera berus (Linnaeus, 1758), killing and intending to swallow an oversized young hare, Lepus europaeus Pallas, 1778. Herpetozoa 38: 155-159. https://doi.org/10.3897/herpetozoa.38.e143850

Follow Herpetozoa on Bluesky and Facebook.

Guest blog post: Snakes disembowel and feed on the organs of living toads in a first for science

A Small-banded kukri snake with its head inserted through the right side of the abdomen of an Asian black-spotted toad, in order to extract and eat the organs. The upper part of the front leg is covered by foaming blood, likewise, mixed with air bubbles from the collapsed lung.
Photo by Winai Suthanthangjai

Guest blog post by Henrik Bringsøe

Our observations on the quite small-bodied Asian kukri snakes in Thailand have documented a feeding behaviour which differs from anything ever described in snakes. 

Normally, snakes would swallow their prey whole. However, this particular species: the Small-banded Kukri Snake (Oligodon fasciolatus), would instead use its enlarged posterior maxillary teeth to cut open the abdomen of large poisonous toads, then inserts its entire head into the cavity to pull out and eat the organs one by one, while the prey is still alive! 

During those macabre attacks, we managed to capture on camera three times, the toads struggled vigorously to escape and avoid being eviscerated alive, but, on all occasions, this was in vain. The fights we saw lasted for up to a few hours, depending on the organs the snake would pull out first.

The toads observed belong to the quite common species called Asian Black-spotted Toad (Duttaphrynus melanostictus), which is known to secrete a potent toxin from their prominent parotid glands, located on the neck and all over the back. Could it be that the snakes have adopted this sophisticated and gory approach to avoid being poisoned?

In a fourth, and equally important, case, an adult kukri snake attacked a somewhat smaller individual of the same toad species. However, this time, the snake swallowed the entire toad. Why did the snake swallow the juvenile toad, we still don’t know. Perhaps smaller toads are less toxic than adults? Or, could it be that kukri snakes are indeed resistant to the Asian Black-spotted toad’s poison, yet the large size of the adult toads prevented the snakes from swallowing them in the three afore-mentioned cases?

Adult Small-banded kukri snake swallowing a large Asian black-spotted toad juvenile
(Phitsanulok, Thailand, 5 June 2020).
Photo by Kanjana Nimnuam

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.

Perhaps you’d be pleased to know that kukri snakes are, thankfully, harmless to humans. However, I wouldn’t recommend being bitten by one of those. 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, called Duvernoy’s glands and located behind the eyes of the snakes, are likely beneficial while the snakes spend hours extracting toad organs.

Small-banded kukri snake having managed to slit through the left side of the abdomen of the toad underneath the left front leg. Two liver lobes next to the already dead toad are visible.
(Loei, Thailand, 9 August 2016).
Photo by Winai Suthanthangjai

***

Publication:

Bringsøe H, Suthanthangjai M, Suthanthangjai W, Nimnuam K (2020) Eviscerated alive: Novel and macabre feeding strategy in Oligodon fasciolatus (Günther, 1864) eating organs of Duttaphrynus melanostictus (Schneider, 1799) in Thailand. Herpetozoa 33: 157-163. https://doi.org/10.3897/herpetozoa.33.e57096