Affixing colored glass beads to the nuchal crest has recently become popular among investigators studying large iguanas (Rodda et al. 1988; van Marken Lichtenbelt et al. 1993; G. Gerber and A. Alberts, personal communication; W. Hayes and R. Carter, unpublished studies). This method, developed for iguanas by Rodda et al. (1988), can be applied not only to adult iguanas but also to juveniles, as the number and sizes of beads affixed to the crest can be adjusted for animal size. Pain and ill effects associated with the procedure appear to be minimal. Occasional loss of the beads has been noted (Rodda et al. 1988; W. Hayes and R. Carter, unpublished observations), most likely resulting from degradation of beads (especially if plastic) and suture material (usually monofilament line), or biting of the beads by conspecifics. Glass beads not only retain their color better than plastic beads, but are also superior in resistance to crushing. Suture material should be selected for resistance to degradation by ultraviolet light. The beads are fairly visible from a distance, especially with the aid of binoculars, making this technique valuable for mark-recapture studies.
