Cooperative Fish and Wildlife Research Units Program: Arizona
Education, Research and Technical Assistance for Managing Our Natural Resources

The ability to display multiple defensive behaviors may increase the chances of an individual avoiding predation. Morphological and physiological condition often influences the display of particular behaviors. Understanding the factors influencing the display of particular behaviors from a suite of potential behaviors can help understand the conditions under which displaying certain suites of defensive behaviors will confer the greatest advantage. Drymarchon couperi (Eastern Indigo Snake) is a large, non-venomous snake that exhibits multiple visual, auditory, olfactory, and physical defensive behaviors. We studied the responses of wild D. couperi to human capture and examined how the number and presence of individual behaviors were related to extrinsic and intrinsic variables using encounters from 84 snakes. Snakes were more likely to flee from the observer at warmer body temperatures and, once captured, exhibited wide variation in defensive behaviors with less costly (i.e., less aggressive) behaviors predominating. Individuals were more likely to display any type of defensive behavior earlier in the field season (i.e., November through January). However, our variables had relatively little influence on the presence of particular defensive behaviors although, for some behaviors, the probability of displaying a behavior increased as the number of other behaviors exhibited increased. Our study shows that D. couperi defensive behavior is quite variable and that the factors contributing variation are unclear. Environmental factors (e.g., distance to retreat site) or individual predispositions may contribute to some of this variation.