3 min readHere’s what you’ll learn when you read this story:
- Snakes have been known to prey on other snake species, but a new study suggests this behavior is more widespread than originally believed.
- The study analyzed 503 documented cases of serpent cannibalism and found that the behavior can be seen in different snakes across the world in different contexts, whether between mates, siblings, or rivals.
- The only family of snakes not known to participate in cannibalism were blind snakes, which researchers hypothesize is likely due to the fact they don’t possess an unfused jaw.
One of the most enduring serpent symbols in human culture is the ouroboros, an image of a snake devouring its own tail in a symbol honoring the cyclic and enduring nature of life. Now a new study suggests that this ancient emblem may also represent some uncomfortable biological truths as well, chief among them being that snakes have an unsavory tendency to snack on their own species.
In other words, snakes are cannibals.
In a study published in the journal Biological Reviews, biologist Omar Entiauspe-Neto, a Ph.D. student at the Universidade de São Paulo, and his co-authors analyzed 503 recorded cases of snake cannibalism across 207 species. Most of these cases occurred within three families—Colubridae, Viperidae, and Elapidae—with Colubridae, the largest of the snake families at 249 genera worldwide, accounting for nearly 30 percent of recorded cannibalism events.
Researchers were aware that snakes ate other snake species, and that a few scattered reports of cannibalism also existed, but this study shows that the practice is more pervasive than originally thought—and that it may have a biological benefit. Because this behavior is so widespread among snake species, geography, and cannibalism categories (whether it happens in mating pairs, related individuals, or combating males), the authors note that it’s possible this behavior evolved separately in the snake evolutionary lineage at least 11 times.
“Each new record reinforced the idea that cannibalism in snakes is not an anomaly or a rare curiosity, but a widespread and ecologically relevant behavior that we had been systematically underestimating,” Universidade de São Paulo master student Bruna Falcão, lead author of the study, told Smithsonian Magazine.
Snakes are far from the only species in the animal kingdom known for munching on one of its own. Spiders such as black widows, insects such as preying mantises, and even large mammals, such as bears, all are known to engage in cannibalism. The researchers note, however, that blind snakes (Typhlopidae) don’t eat their own, probably due to the limitations of their jaws, which never evolved an unfused mandible—the evolutionary trick that allows snakes (particularly Alethinophidia) to eat things considerably larger than themselves.
The study discerned that nearly half of the species displaying cannibalistic behaviors had a generalist diet, suggesting that this dietary flexibility may lead to higher rates of cannibalism. Some of the recorded cases also involved snakes held in captivity where environmental pressures could push snakes to consume their slithering brethren with greater frequency than if they were out in the wild.
“We conclude that cannibalism is a widely distributed behaviour both taxonomically and geographically, has been recorded on all continents in which snakes occur, and [happens] in many of the known families,” the authors write. “In captivity, confinement in enclosures, movement restriction, lack of enrichment, close proximity to conspecifics, and handling are all known to be stressors that may trigger cannibalism”
In the future, scientists will try to learn whether snake cannibalism is genetic, opportunistic, or maybe a little bit of both—and whether cannibalism played a role in making snakes one the most successful members of the class Reptilia.
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Darren lives in Portland, has a cat, and writes/edits about sci-fi and how our world works. You can find his previous stuff at Gizmodo and Paste if you look hard enough.