Territorial and mating displays are a key mechanism affecting sexual selection, species recognition, and may affect success of non-native species in the presence of closely related ones. The green Iguana (Iguana iguana) has invaded Caribbean islands from their mainland range, affecting and possibly inter-breeding with native Iguana. However, important display behaviours have not been studied, even though it may be a rare opportunity to study adaptation and evolutionary change. Here, we describe the display-action-patterns (DAP) characterising the head-bob display of the two Iguana species of the Caribbean islands Iguana delicatissima (endemic Lesser Antillean Iguana) and non-native Iguana (closely related non-native species) in the Guadeloupe Archipelago. First, the DAP sequence of non-native Iguana is completely different from mainland animals, with reversed positions of the long and short head bobs. In the non-native Iguana, two long head-bobs (>
1.0 s) separated by a highly variable pause (0.1 - 2.8 s) are followed by a series of 3-7 (up to 9) rapid head bobs (<
0.5 s), is followed by one phase always with two longer. In native I. delicatissima, the DAP is always initiated with a vibratory gular movement of the extended dewlap in I. delicatissima, but not in the non-native Iguana. Duration of the DAP sequence is significantly shorter in non-native Iguana, always beginning with one singular long head bob (>
1.5 s) followed by 3-6 more rapid head bobs. In addition, we observed significant among individual variation in all aspects of the DAP studied, indicating the potential for natural selection to further act on head-bob displays in the non-native and native species. This study now sets the stage to for future studies to determine if behaviour is a cause or consequence of invasion success.