Snakes eating snakes! Study finds cannibalism in over 200 snake species across continents

Cannibalism in snakes has usually appeared as a footnote rather than a focus. It shows up in old field notebooks, brief case reports, or unexpected moments in captivity. Taken on its own, each record feels unusual. Looked at together, they begin to feel less so. A recent large scale review pulls together observations spanning more than a century, collecting reports from across regions and families. Instead of treating each case as an exception, the study asks what happens when they are read side by side. The result is not a neat pattern, but a broad one. Cannibalism does not belong to a single place or group. It turns up where anatomy, opportunity and feeding habits quietly overlap.The review documents more than 500 cannibalism events involving over 200 snake species from 15 families. These records come from every continent where snakes are found. Some are tropical, others temperate. Many involve species that are already well known and widely studied, including colubrids, vipers and elapids. That imbalance likely reflects research effort as much as behaviour. Nearly half of the cases occurred in captivity, where encounters are easier to witness. Still, a substantial number were recorded in the wild. Taken together, the distribution suggests the behaviour is not tied to a specific environment. It appears wherever snakes live and feed.In most cases, there was no clear trigger. The snake was not guarding eggs, competing for territory, or engaging in mating behaviour. It simply encountered another snake and consumed it. These events were classified as opportunistic, and they form the majority of the records. This lack of context may be the point. Cannibalism often looks less like a special behaviour and more like ordinary feeding extended to a familiar body shape. If a snake can overpower another snake of suitable size, it may do so without much distinction.Where body measurements were reported, size mattered. Larger snakes tended to eat larger conspecifics rather than targeting only juveniles. This mirrors patterns seen in other prey choices. Bigger prey offers more energy, but also more risk. Cannibalism appears to follow that same balance. It does not stand apart from normal foraging decisions. In this sense, the behaviour is not random. It reflects the same constraints that shape what snakes eat more generally.All confirmed cases involved snakes with highly flexible jaws capable of swallowing large prey. These species belong to a group with mobile skull elements that allow wide gape expansion. No cases were recorded in lineages with reduced jaw movement, such as blind snakes. This absence is telling. Regardless of behaviour or opportunity, anatomy sets a boundary. Without the physical ability to swallow another snake, cannibalism is unlikely to occur.Elapids stood out in particular. For these snakes, consuming another snake may not differ greatly from consuming any other elongated prey. Venom may also play a role, reducing the danger of attacking a similar sized animal. In these cases, cannibalism does not require a behavioural shift. It fits within an existing feeding strategy.Many cannibalism events were recorded in captivity, often under conditions of stress, limited space or food restriction. These factors likely lower the threshold for such behaviour. Still, captivity does not appear to invent it. The same patterns occur in the wild. Enclosures make the behaviour easier to see, and sometimes harder to avoid, but they do not fully explain its presence.Cannibalism involving offspring or reproductive contexts was uncommon. A small number of cases involved mothers or siblings, mostly in boas and pythons. These situations exist, but they sit at the edges of the dataset rather than defining it.Cannibalism in snakes does not resolve into a single explanation. It appears uneven, shaped by anatomy, feeding ecology and chance encounters. It is neither exceptional nor universal. It simply occurs, quietly, where conditions allow.