It is known that the body coloration of white-beaked dolphins (Lagenorhynchus albirostris) varies greatly, although this variation has never been the topic of a formalized study. Whale-watching trips conducted on SW, NE, and W coasts of Iceland, (June 2002-September 2013), provided the opportunity to systematically collect a larger body of photographic information from a single area of distribution.

A total of 346 photographs were considered of sufficient quality for body colouration evaluation. Colouration on the flanks, belly area, bridle stripe, rostrum, flipper and around the eyes was described as well as individuals with ‘white helmets’. The colouration components were further described for each age class (e.g. adults, juveniles, calves and newborn) with investigation of ontogenetic patterns. Images and post-mortem report information (e.g. sex, total length, sexual maturity) were used to validate analyses of colouration patterns and group composition. The most variant colour patterns are bridle stripe and blowhole chevrons which are not yet fully visible in juveniles, while calves have two semi-circular orange-coloured patches on either side of the blowholes. Colouration on flanks and peduncle also showed wide variety, especially juveniles with high occurrence of hypo-pigmented areas accompanied with mottled pigmentation. Around 30% of identified animals showed dorsal fin patches (white and grey) observed in adults and juveniles, but not in calves and neonates.