Using natricine snakes to test how prey type and size affect predatory behaviors and performance

Area of Science:

• Evolutionary Biology
• Animal Behavior
• Herpetology

Background:

• Predation success is influenced by predator-prey interactions, including behavior, morphology, and size.
• Snakes that swallow prey whole face limitations in prey size (gape) and challenges in consuming live prey.
• Coiling and envenomation are behaviors that have evolved in snakes to restrain or kill prey.

Purpose of the Study:

• To investigate the stereotyped predatory behaviors (coiling and envenomation) in the snake species *Liodytes rigida* when feeding on crayfish.
• To determine how prey type (hard-shell vs. soft-shell crayfish) and size influence the use of coiling and envenomation.
• To gain insights into the evolutionary trajectory of coiling and envenomation within the *Liodytes* genus by comparing with *Liodytes pygaea*.

Main Methods:

• Experimental manipulation of crayfish prey type and size for the snake *Liodytes rigida*.
• Observation and quantification of stereotyped predatory behaviors: envenomation, coiling, and swallowing latency.
• Comparative analysis with a closely related species, *Liodytes pygaea*, and previous studies on *L. alleni*.

Main Results:

• *Liodytes rigida* consistently used envenomation on hard-shell crayfish, with reduced but still significant use on soft-shell crayfish, especially with larger or recently molted prey.
• Coiling was more frequent with hard-shell crayfish and increased with the time since molting for soft-shell prey, but was independent of prey size.
• *Liodytes rigida* exhibited delayed swallowing until prey immobility, with longer delays for hard-shell crayfish; *L. pygaea* did not use coiling or envenomation.

Conclusions:

• Coiling likely evolved ancestrally within the *Liodytes* clade for specialized crayfish predators.
• Envenomation subsequently evolved in *L. rigida* as an additional adaptation for subduing formidable crayfish prey.
• These traits provide proximate benefits that support their evolution for enhanced feeding performance on challenging prey.