© 1989 by The Society for Integrative and Comparative Biology
Social Displays of the American Alligator (Alligator mississippiensis)1
University of Florida, Department of Zoology Gainesville, Florida 32611
Adult alligators perform two conspicuous social displays, bellows and headslaps. Both of these behaviors are performed from a "head oblique tail arched" (HOTA) posture. Bellow displays, by both males and females, involve the production of a loud, roaring vocalization. Male alligators also produce a infrasonic signal, termed subaudible vibrations, just prior to the audible bellow. Bellowing occurs throughout the year but is most frequent during the courting season, when alligators bellow daily in choruses. Chorus length appears to be correlated with the size of the adult population. Chorusing is frequently initiated by females but seems to be perpetuated by male alligators. Bellowing may serve to attract alligators of the opposite sex and possibly to space out animals of the same sex.
The headslap display is an assertion display consisting of eight component behavioral acts: the elevated posture, HOTA posture, subaudible vibrations, headslap, jawclap, growl, inflated posture, and tail wag. Each act component is variable in presence and intensity producing a highly variable, graded signal. The alligator typically remains motionless in the HOTA posture for about 16 sec before executing the headslap/jawclap acts. The headslap display involves a rapid clapping shut of the jaws as the undersurface of the head is slapped against the water surface. Headslapping is most common in early morning and afternoon hours. Analysis of 1,050 headslap displays by 91 known individuals indicates that 94.5% of the observed displays were performed by males. Headslap displays are generally performed from typical display sites which the alligator seeks out prior to the display. Responses to headslap displays include headslapping by others, lunges, approaches, and bellow growling. The headslap display functions as a declaration of presence.
A musky odor is commonly detected in association with both of these social displays, suggesting a possibly important, but little understood, pheromonal component of these behaviors.
The displays both involve complex signals including visual, auditory, olfactory and possibly tactile channels of communication. Most of the behaviors described are shared with many other species of crocodilians.