A field study of the headbob displays of male green iguanas (Iguana iguana): Variation in form and context

Headbob displays play an important role in the social behaviour of male green iguanas (Iguana iguana). Four types of headbobs were identified, and the variability in form and context were determined from quantitative analyses of displays filmed in the field. The Roll is a conspicuous advertisement display. The Shudder, the most variable in form, occurred during close contact between males and females. The Roll-shudder is intermediate between the Roll and Shudder in its form and use. The Signature Bob, the most stereotyped display in form, punctuates much activity and is the most variable in contextual use. This display encodes species identity, and possibly individual identity. The conspicuous nature of the headbob displays was enhanced by the intensified colour of territorial males, and by the selection of highly visible display posts. This system of visual displays is viewed as the product of related sets of constraints, including the iguanas' physical capacities, the forest environment, and the social environment.