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Cannibalism has occurred in several species of snakes throughout evolutionary history. |Image source: Popular Pictures, Getty Images
Scientists speculate that cannibalism appears to be a rare and unnatural phenomenon, but the behavior has occurred in several snake lineages throughout evolutionary history, often triggered by environmental stress.
When researchers reviewed 500 reports of cannibalism snake According to a study published in the journal on November 2, 2025, they found that cannibalism has evolved independently at least 11 times Biological Reviews.
The researchers say these cannibalistic behaviors occur in different environments, but overall, cannibalism is common and appears to occur repeatedly because it benefits the snakes in situations where they need to make opportunistic dietary choices.
“For us humans, we don’t think of cannibalism as a common thing – it’s a weird and disgusting thing,” Bruna FalcaoThe study’s lead author, a graduate student in biology at the University of São Paulo, told LiveScience. “But for snakes, it’s good for them; it’s good for their ecological fitness… It’s strategic.”
The evolutionary advantages of cannibalism
Some of the most famous examples of cannibalism in nature can be seen during the mating of spiders and praying mantises, as it may be good for women Eat their mates. “Cannibalism is common throughout the animal kingdom,” Xavier Glaudasa biologist and National Geographic explorer who was not involved in the study told Live Science.
Although scientists previously thought this behavior was maladaptive—meaning it was not beneficial to the species as a whole—a growing number of studies report cannibalism in animals and hypothesize why the behavior evolved. For example, it can help parents Control brood sizeor it may serve as a pair Available resources are limiteda form population controlor a opportunistic prey selection.
Glaudas said cannibalism in snakes is often described in brief, isolated reports. For example, His research team describes Male Montpellier snake (Mabolo) Feeding on female snakes in France – this behavior is thought to be driven by limited food resources, especially during times of scarcity outside of the mating season. (It is considered unusual for males to eat females during the mating season, as this reduces the chance of mating.)
According to the study, which combines numerous reports to explain the behavior, in addition to being widespread among snakes, cannibalism evolved independently in different snake lineages and regions.
The research team collected 503 cases of cannibalism in 207 species of snakes. These reports cover a wide range of snake species, and all continents where snakes live, and include reports of both wild and captive snakes.
“None of us expected … that snakes could be so cannibalistic, and no one talked about it,” Falcao said. “The more we search, the more cases we find.”
The team found that cannibalism was most common in the families Colubridae, Viperidae and Viperidae. Colubridae are the largest snake family, accounting for 29% of all reports. However, since the family does not typically prey on snakes, the authors suggest that most cannibalistic incidents in this group may be related to stressors such as a lack of other food sources. Members of the family Viperidae (including venomous snakes) accounted for 21% of all reports of cannibalism. But the researchers note that these are mostly captive situations, so the stressors associated with captivity, such as being confined to a small space with limited food, may lead to cannibalism.
Snakes in the family Viperidae (including cobras) account for approximately 19% of reported incidents of this type. Researchers say this is not surprising as cobras are known to prey on other snakes in the wild.
According to the study, almost half of all man-eating snake species have a general diet, and the researchers linked this dietary flexibility to cannibalism when necessary. However, Glaudas said the link may not be clear-cut because the researchers only defined 47.7 percent of man-eating snake species as generalists; if the percentages were higher, he said, the evidence for the relationship would be stronger.
“I’m skeptical of the data presented to the idea that cannibalism may be more common in generalist species,” Glaudas said.
The behavior of cannibalism does appear to be related to jaw structure, so whether a snake’s jaw can open wide enough to eat another snake is a key factor; there are no reports of cannibalism in snakes that do not possess this ability.
When researchers analyzed cannibalism in snakes’ evolutionary history, they concluded that the behavior evolved independently at least 11 times in the snake’s evolutionary tree.
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Since most reports of snake cannibalism are anecdotal, this study provides a useful overview, Glaudas said. Glaudas said this was a “welcome study that allows us to better understand the factors associated with cannibalism in snakes”.
Snakes are a very successful branch of the evolutionary tree. They are found on all continents except Antarctica and have adapted to most ecological niches, the study authors note. Because cannibalism is practiced by many different types of snakes around the world, it may reflect their ability to opportunistically adapt to their environment, Falcao said. “It’s really surprising [cannibalism] It evolved independently 11 times in the snake’s lineage,” she noted.
Falcao said this review cannot capture all reports of snake cannibalism — many are in less accessible, older books and archives — so there may be more to be discovered about the topic.
