How big is too big? Using crustacean-eating snakes (Homalopsidae) to test how anatomy and behaviour affect prey size and feeding performance

• Published in: Biological journal of the Linnean Society Vol. 123; no. 3; pp. 636 - 650
• Main Authors: Jayne, Bruce C, Voris, Harold K, Ng, Peter K L
• Format: Journal Article
• Language: English
• Published: UK Oxford University Press 02.03.2018
• Subjects: ecology; functional morphology; predator–prey interactions; evolutionary innovation; snake; phylogeny; feeding behaviour; Decapoda; diet; evolution
• ISSN: 0024-4066; 1095-8312
• DOI: 10.1093/biolinnean/bly007

Abstract The evolutionary innovations that allow snakes to swallow large prey whole provide a model system for testing how anatomy constrains what predators eat. For a clade of three snake species with the unusual diet of decapod crustaceans, we quantified maximal gape, prey size and feeding behaviour. Fordonia leucobalia eats hard-shelled crabs and had maximal gape similar to a piscivorous relative (Cerberus schneiderii). Gerarda prevostiana and Cantoria violacea eat freshly moulted crabs and snapping shrimp, respectively, and their maximal gape was significantly smaller than for both Ce. schneiderii and F. leucobalia. From smallest to largest prey size consumed relative to maximal gape, the rank order was F. leucobalia, Ca. violacea and G. prevostiana. Unusual specialized behaviours included: (1) a closed-mouth strike and using the chin to pin the crabs (F. leucobalia), (2) breaking off crab legs (F. leucobalia, G. prevostianta) and (3) ripping apart the crab carapace aided by body coiling (G. prevostiana). Behavioural innovations and choice of prey allowed G. prevostiana to consume crabs two to four times larger than their maximal gape area and handle prey approximately nine times faster than F. leucobalia. This is a striking example of how the evolution of specialized behaviours can improve performance and circumvent anatomical constraints on prey size.