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Cannibalism has appeared in several lineages of snakes throughout evolutionary history. | Credit: VW Pics via Getty Images
Cannibalism might seem like a rare and unnatural event, but the behavior has appeared in several lineages of snakes throughout evolutionary history, often triggered by environmental stressors, scientists theorize.
When researchers analyzed 500 reports of cannibalistic behavior from around the world snake species, found that cannibalism evolved independently at least 11 times, according to a study published Nov. 2, 2025, in the journal. Biological Reviews.
These cannibalistic behaviors occur in diverse contexts, but in general, cannibalism is common and appears to occur repeatedly because it is beneficial to snakes in situations where they have to make opportunistic dietary choices, the researchers suggest.
“For us humans, we don’t think of cannibalism as something common – it’s something strange and disgusting.” Bruna Falcaolead author of the study and a graduate student in biology at the University of São Paulo, told Live Science. “But for snakes, it’s good for them; it’s good for their ecological capacity… It’s strategic.”
The evolutionary advantages of cannibalism
Some of the best-known examples of cannibalism in nature are seen in spiders and praying mantises during mating, as can be beneficial for females to eat its mate. “Cannibalism is widespread throughout the animal kingdom,” Xavier Glaudasa biologist and National Geographic Explorer who was not involved in the study, told Live Science.
Although scientists previously considered the behavior maladaptive—that is, not beneficial to a species as a whole—a growing number of studies reporting cannibalism in animals are hypothesizing about the evolutionary reasons for the behavior. For example, it could help parents control brood sizeor may occur in response to limited availability of resourcesa form of population controlor one opportunistic choice of prey.
Cannibalistic behavior in snakes has typically been reported in brief, isolated reports, Glaudas said. For example, described his research team male Montpellier snakes (Malpolon monspessulanus) feed on female snakes in France—a behavior thought to be driven by limited food resources, especially during periods of scarcity outside of the mating season. (It would be considered unusual for males to eat females during mating season, as this would reduce mating opportunities.)
In addition to being widespread in snakes, cannibalism has evolved independently in different snake lineages and regions, according to the study, which combined numerous reports to explain the behavior.
The research team collected 503 reported cases of cannibalism in 207 snake species. The reports spanned a wide range of snake groups as well as all continents where snakes live, including reports of snakes both in the wild and in captivity.
“None of us expected … snakes to be so cannibalistic and no one was talking about it,” Falcão said. “The more we search, the more cases we find.”
Cannibalism was most common in the families Colubridae, Viperidae and Elapidae, the team found. Colubridae is the largest family of snakes and accounted for 29% of all reports. Because this family is not known to prey on snakes, however, the authors proposed that most cases of cannibalism in this group may be related to stressors such as a lack of other food sources. Members of the Viperidae family, which includes vipers, accounted for 21% of all cannibalism reports. But these were mostly cases in captivity, the researchers noted, so stressors related to captivity, such as confinement in small spaces with limited food, could have led to cannibalism.
Elapidae, the family of snakes that includes cobras, accounted for about 19% of cannibalism reports. This was not very surprising, the researchers said, as cobras are known to prey on other snakes in the wild.
Nearly half of cannibal snake species have generalist diets, according to the study, and the researchers linked this dietary flexibility to cannibalistic behavior when necessary. However, Glaudas suggested that this link may not be clear, as researchers defined only 47.7% of cannibal snake species as generalists; the evidence for the relationship would be stronger if the percentage were higher, he said.
“Regarding the idea that cannibalism might be more common in generalist species, I’m a little more skeptical about the data presented,” Glaudas said.
Cannibalistic behavior appears to be correlated with jaw structure, so whether a snake has jaws that can open wide enough to consume another snake is a key factor; there have been no reports of cannibalism in snake species without this ability.
When the researchers analyzed cannibalistic behavior throughout the evolutionary history of snakes, they concluded that the behavior evolved independently at least 11 times along the snake evolutionary tree.
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Because most reports of cannibalism in snakes are anecdotal, Glaudas said, the study provides a useful overview. This is a “welcome study that allows us to better understand the correlates of cannibalism in snakes,” Glaudas said.
Snakes form 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 noted. Because cannibalistic behavior occurs in many different types of snakes around the world, Falcão said, it could reflect their ability to opportunistically adapt to their circumstances. “It’s really surprising for [cannibalism] to evolve independently 11 times in the serpent lines,” she noted.
The review was unable to capture all reports of cannibalism in snakes—many are in older, less accessible books and archives—so there is likely much more to discover on the topic, Falcão said.