Behavioral and hormonal responses in the defensive repertoire during provocation in captive monocled cobra (Naja kaouthia).

ABSTRACT

The hooding behavior exhibited by cobras is a distinct defensive mechanism against predators, encompassing both visual and auditory displays. This behavior can be triggered by natural predators or humans. Considering that human provocation may potentially stimulate the hypothalamic-pituitary-adrenal (HPA) axis, the present study aimed to determine the pattern of the HPA axis response following human provocation-induced hooding behavior (PV) and provide a detailed analysis of the behavioral PV displays. Our primary hypothesis was that a 5-minute PV could activate the HPA axis to a degree comparable to that in the restraint-induced stress model (RS). The PV, RS-1 (1-minute), and RS-5 (5-minute) restraint models indeed activated the HPA axis. However, the pattern of plasma corticosteroid (CORT), but not arginine vasotocin, in the PV group differed from that in the RS-1 and RS-2 groups. The present study revealed the behavioral components of the PV. The first component appeared to be related to an increase in apparent size that is an intimidation display, while the second hissing and striking component consisted of a bluff charge. Moreover, no correlation was observed between the pattern of plasma CORT and any specific PV display. Finally, the body temperature (Tb) of cobras from RS-5 gradually increased, while the Tb of cobras from PV (5 min) remained unchanged. In conclusion, the activation of the HPA axis emerges as the main physiological response after human provocation. Within 5 min of provocation, the cobras' hooding behavior comprised two display components that were not related to the pattern of plasma CORT.