Snakes are creepy enough with their hissing, silent slithering, and potential for venomous bites. But new research has uncovered another reason to fear snakes.
It turns out that snakes have exhibited more and more cannibalistic behavior throughout the years.
Researchers compiled more than 500 documented events of cannibalistic behavior across several snake species and found that cannibalism has evolved at least 11 times. It is so common because it seems to benefit snakes in situations where their food sources are limited.
“For us humans, we don’t think of cannibalism as something common—it’s something weird and disgusting,” said Bruna Falcão, the lead author of the study and a graduate student in biology at the University of São Paolo.
“But for snakes, it’s good for them; it’s good for their ecological fitness. It’s strategic.”
Falcão came across a zoological collection containing a preserved Brazilian lancehead viper with a juvenile of the same species in its stomach during a summer internship in 2022.
She began looking into cases of cannibalism in snakes. The oldest record dates back to 1892, describing a common kingsnake in the United States cannibalizing another.
Over two years, Falcão and her team examined 503 cases of cannibalism in 207 snake species. The cases were divided up into different types of cannibalism, such as between related individuals, mating pairs, or males fighting each other.
The team’s findings showed that incidents of cannibalism were widespread across lineages and continents. Blind snakes were the only major snake group with no record of cannibalism.
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Blind snakes are from an ancient lineage that never evolved the ability to unhinge their lower jaw. The lack of this trait is likely what has prevented them from cannibalizing their peers.
Elapids, a group of snakes including cobras and kraits, were found to eat others of the same species. They made up approximately 19% of recorded cannibalism events. It wasn’t surprising because they are known to prey on other snakes in the wild.
The most cannibalistic snakes were in the Colubridae family, the biggest family of snakes. Colubridae represented 29% of all cannibalism reports.
Most of the cases were thought to stem from stressors like a lack of other food sources, since this family does not tend to prey on snakes.
In several snake families, the mother may consume her own eggs, which is referred to as maternal cannibalism. It’s not entirely clear why some mothers do this.
One possibility is to remove the bad eggs, helping to mitigate disease and protect the viable offspring from predators that would be attracted to the smell of dead eggs.
Snakes in captivity were more likely to prey on their own kin. About 43% of cannibalism reports were about snakes in captivity.
Vipers are the most cannibalistic snake group in the Americas, but in the majority of reports, they were in captivity, pointing to captivity-related stressors as the cause of most viper cannibalism.
Overall, the study allowed researchers to gain a better understanding of snake cannibalism. Scientists still have more to learn and will continue searching for more historical records and observations.
The study was published in Biological Reviews.
By Emily Chan
Emily Chan is a writer who covers lifestyle and news content. She graduated from Michigan State University with a degree in... More about Emily Chan
