Dolphin dorsal fins become marked mainly through natural interactions free of any intentional nick/notch formation, meaning the markings are formed randomly. Even so, we do find “twins” among animals in the wild community.
Dolphins are air-breathing mammals, this means that about 99.9% of the time, when they surface to breathe, their dorsal fin is visible. For our photo-identification efforts, this makes capturing a photo of a fin relatively easy. Let’s consider, however, how one would identify bottlenose dolphins if a dorsal fin was not visible.
One of the most challenging aspects of dorsal identification is positively identifying a fin over time as changed markings to the fin can make a dolphin look, sometimes, significantly different. While some fins are dramatically changed, others are more subtle.