Experimental evidence that oral secretions of northwestern ring-necked snakes (Diadophis punctatus occidentalis) are toxic to their prey

Ring-necked snakes (Diadophis punctatus) are suspected of being venomous because their Duvernoy's gland secretions have high levels of phospholipase activity, which is characteristic of many viperid and elapid venoms, and because anecdotal reports of feeding behavior are consistent with the use of a venom. We tested the toxicity of northwestern ring-necked snake oral secretions to a natural prey species, northwestern garter snakes (Thamnophis ordinoides), by injecting 2-35 μl of oral secretions intraperitoneally. All doses were 100% lethal within 180 min. The dose significantly affected the time to loss of a righting response. Neither injection of saline nor denatured oral secretions resulted in loss of a righting response or any visible detrimental effects. We suggest that northwestern ring-necked snakes may have evolved venom to subdue larger prey items than the snake would otherwise be capable of taking.