Evidence of non-strike induced chemosensory searching by eastern copperheads (Agkistrodon contortrix) during cicada predation
Gull, Henderson Cyrenius
Department of Biology
Eastern Kentucky University
Richmond, Kentucky USA
New evidence of active foraging by eastern copperheads (Agkistrodon contortrix) contradicts its description as an envenomation-reliant ambush predator. Recent studies on foraging excursions by A. contortrix in the Red River Gorge (Kentucky) showed potential use of non-strike induced chemoreception to track cicada nymphs during seasonal emergences. Lab evidence of this behavior was previously found in a congener, the cottonmouth (A. piscivorus), but could not be replicated with A. contortrix. I hypothesized that A. contortrix does actively forage for cicadas using chemoreception without envenomation, and that tongue flick rates would be higher for foraging behaviors than for non-foraging behaviors. Behavior of 12 A. contortrix was filmed at a campsite in Kentucky during foraging excursions in the summer of 2020. Recordings were analyzed for tongue flick rates and presence or absence of seven behavioral activities. Each minute of recording was assigned to a behavioral category (ground movement, climbing, post-consumption movement, pausing, periscoping, eating, and fighting) based off behaviors within the minute and ecological context of the recording. I found statistically significant differences between tongue flick rates of foraging and non-foraging related behaviors, differences among distinct foraging categories, and no differences in tongue flick rate between non-foraging categories. I also compared predatory movement tongue flick rates between successful events of tracking cicadas to unsuccessful attempts and found a significant difference in tongue flick rates. My results support the hypothesis that elevated tongue flick rates in movement categories appear to be evidence of active chemoreceptive searching without reliance on envenomation cues. Previous studies evaluating this behavior in A. contortrix did not find evidence supporting its use, and this behavior has not been previously documented in a wild population. Documentation of this behavior provides ecological context for how this behavior is used during predation, and provides knowledge useful in supporting future laboratory replication of the behavior.