Occurrence and evolution of cannibal behaviour in extant snakes

Area of Science:

• Herpetology
• Evolutionary Biology
• Behavioral Ecology

Background:

• Snake (Serpentes) feeding ecology is well-studied, but cannibalism remains poorly documented.
• Existing reports of snake cannibalism are scattered, often anecdotal, and lack comprehensive analysis.

Purpose of the Study:

• To extensively review and analyze cannibalistic behavior in extant snakes.
• To investigate the evolutionary origins and ecological correlates of snake cannibalism.
• To test if foraging theories apply to cannibalistic events in snakes.

Main Methods:

• Compiled 503 case events of cannibalism from scientific literature, encompassing wild and captive snakes.
• Analyzed species distribution, predator-prey body size relationships, and phylogenetic history.
• Utilized maximum-likelihood ancestral character estimation to infer evolutionary patterns.

Main Results:

• Cannibalism documented in 207 species across 15 snake families, with high occurrence in Colubridae, Viperidae, and Elapidae.
• Prey and predator body size are positively correlated (R=0.81), supporting foraging strategy application.
• Cannibalism evolved independently at least 11 times and is associated with macrostomate mandibular morphotypes in Alethinophidia.

Conclusions:

• Cannibalism is a widespread and potentially opportunistic behavior in snakes.
• The behavior is influenced by evolutionary history, diet, morphology, and ecological factors.
• Snake cannibalism is not random but linked to specific adaptations and evolutionary pathways.