A Snake Nicknamed "Hannibal" Helped Reveal Cannibalism Is Common In Cobras

A cape cobra (Naja nivea). Martin Prochazkacz/Shutterstock

Aliyah Kovner 26 Oct 2018, 23:44

A team of South African snake researchers inadvertently discovered that cobras in the region are quite prone to cannibalism after they stumbled onto a scene of one cape cobra contently swallowing another.

In the ensuing study, now published in the journal Ecology, the trio of biologists recount how this serendipitous observation has shifted perceptions of snake behavior and opened the door for a new area of research.

“During fieldwork in January 2018, we found ourselves at our study site in South Africa’s Kalahari Desert in search of cape cobras (Naja nivea) and boomslang (Dispholidus typus) to surgically implant with radio-transmitters. While searching for snakes one morning, we were alerted by a tour guide via radio to the presence of ‘two large yellow snakes fighting’,” they wrote. 

“However, arriving some 15 minutes later, we were greeted not by two males in ritualised combat as initially expected, but rather by a large male cape cobra in the process of swallowing a smaller male conspecific. Instead of capturing two potential study animals, we found one well-fed study animal, now known as NN011, or more casually, Hannibal.”

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Intrigued by the sight of a 1.7-meter (5.6-foot) long cobra chowing down on a 1.3-meter (4.3-foot) individual of the same species, lead author Bryan Maritz and his colleagues decided to investigate if such an occurrence is truly a rare anomaly, as previous studies have suggested, or if it is perhaps more common than we ever imagined.

Due to the elusive nature of wild snakes and the fact that they only feed infrequently, it has always been difficult for scientists to document their natural feeding habits. Based on the limited observations that have been reported, scientists concluded that cape cobras regularly target other snake species. Indeed, according to one recent review, other snakes make up as much as one-third of their diet. But because of the high risk of injury associated with attacking perfectly matched prey, it was assumed that most snakes evolved an instinct to avoid cannibalism unless presented with an easy opportunity.

“The total number of observations of cobras eating in the wild isn’t a big number, and the observations of cannibalism in the wild are even rarer, so I think it’s easy to dismiss as a one-off thing,” Maritz told Science News.

To get to the bottom of this mystery, Maritz’s group scoured through information from published scientific reports, minor and difficult to access publications, and posts from a social media group created to collect reports of wild reptile hunting behavior witnessed by other scientists and laypeople. Although there are approximately 30 species of cobra found throughout Africa and Asia, they chose to focus on six species found in South Africa that belong to the "true" cobra genus, Naja.

The results of their data analysis indicate that all six types – the cape cobra, Anchieta's cobra, snouted cobra, Mozambique spitting cobra, zebra spitting cobra, and brown forest cobra – readily pursue other snakes for snacks.

“We found that snakes account for 13-43% of all prey species detected in the diets of wild cobras,” they wrote. All types save for the zebra spitting cobra were found to eat members of their own species. Curiously, all cannibalistic events were between male cobras, a pattern Maritz hopes to explore in future research.

“I could see it playing a role in competition for resources or mates," he told Science News. "What better way to get ahead in life [than to] eat the guy who is taking your food and mating with females that you might want to mate with?”

[H/T: Science News]

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