Comparative display behaviour of the native Iguana delicatissima with the non-native Iguana in the Guadeloupe Archipelago (Lesser Antilles)

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.