Stressed snakes strike first: Hormone levels and defensive behavior in free ranging cottonmouths (Agkistrodon piscivorus)

Abstract

Stress is believed to be an important factor mediating animal behavior. Here we explore the relationship between concentrations of a stress hormone and defensive behavior of a snake. The cottonmouth (Agkistrodon piscivorus) is an abundant, large-bodied pitviper that is well known for its intense defensive behaviors. The defensive behaviors and hormonal ecology of cottonmouths have been studied extensively, but the interaction between these is not well understood. We conducted field trials, recording the snake's behavior and obtaining blood samples to quantify plasma CORT concentrations, both upon first encountering a snake and after a 30min standardized confinement stressor. We found that snakes with elevated levels of baseline CORT at first encounter were more likely to strike than exhibit a threat display when approached in the field. However, this behavior was not related to the magnitude of the snake's CORT increase following confinement, suggesting that more stress-prone snakes are not more defensive. Post-stressor antipredator behavior was also not related to any of our CORT measures. This study suggests that baseline CORT levels can be important correlates of defensive behavior. If this is a causative relationship, environmental challenges that increase baseline stress levels of populations may elevate cottonmouth defensive behavior. This would increase costs associated with defensive behavior (energetic, lost opportunity, etc.) and have important consequences for animal-human interactions.

Deadly dormmate: A case study on Bungarus candidus living among a student dormitory with implications for human safety

“…Long‐distance translocation of snakes from urban and rural environments to less‐disturbed areas generally provides people with a good moral feeling (compared to the negative stigma associated with killing the snake); however, it often results in poor snake health and survival (Barve et al., 2013; Butler et al., 2005; Devan‐Song et al., 2016). Furthermore, snakes are more likely to elevate defensive behaviours and bite when experiencing higher baseline stress levels (Herr, Graham, & Langkilde, 2017), which requires further study within the context of snakebite management and conflict. Snakes translocated to natural areas outside of their home ranges still sometimes move into surrounding human settlements (Butler et al., 2005), which also requires further investigation as to whether that represents an increase in risk for potential snakebite and conflict within human populated areas near to the receiving natural areas.…”

Investigating Welfare Metrics for Snakes at the Saint Louis Zoo

“…While high levels of corticosterone play a primary role in energy mobilization in mammals, it is unclear how high levels impact reptiles, as their energetic demands are very different [72,73]. Some species may maintain higher baseline corticosterone concentrations in predator rich environments [74,75], preparing the animal for necessary antipredator behaviors [76]. Furthermore, corticosterone levels may play a role in mediating life history trade-offs.…”

Does repeated human handling of study animals during the mating season affect their offspring?

“…For example, mate choice and competition trials frequently involve experimentally pairing and separating animals from mates at trial conclusion (e.g., Chen & Lu, ; Cheong et al., ; Friesen et al., ; Shine, Webb, Lane, & Mason, ). Studies focused on learning and behavioral responses to predation can include the need for repeated recapture of test subjects (e.g., Brust, Wuerz, & Krüger, ; Herr, Graham, & Langkilde, ; Langkilde, ). Virtually all tests of animal personality and behavioral syndromes require individuals to be subjected to multiple trials, with handling occurring between each trial repetition (Carter, Feeney, Marshall, Cowlishaw, & Heinsohn, ; Sih et al., ; Stamps & Groothuis, ).…”

“…For example, mate choice and competition trials frequently involve experimentally pairing and separating animals from mates at trial conclusion (e.g., Chen & Lu, 2011;Cheong et al, 2008;Friesen et al, 2014;Shine, Webb, Lane, & Mason, 2006). Studies focused on learning and behavioral responses to predation can include the need for repeated recapture of test subjects (e.g., Brust, Wuerz, & Krüger, 2013;Herr, Graham, & Langkilde, 2017;Langkilde, 2010).…”