The maximum height of the dorsal fin in an adult male killer whale is about 1.8 meters. That is roughly 6 feet, making the mature male orca’s fin one of the most striking examples of sexual dimorphism among cetaceans.
Adult males develop a tall, upright, triangular dorsal fin, while females and immature males usually have shorter, more curved fins. Female fins are commonly around 0.9 meters or less, although size and shape vary among populations and ecotypes. The fin’s profile is therefore useful to researchers identifying individuals and estimating sex from photographs.
Unlike the fins of many fish, a killer whale’s dorsal fin contains no bones or cartilage. It is supported by dense connective tissue, and its great height depends on the fin’s structure and the animal’s maturity. In captivity, adult male fins often bend or collapse, a condition rarely seen in healthy wild animals.
Killer whales are actually the largest members of the dolphin family, Delphinidae, despite their common name. Their dorsal fin is also the tallest among living cetaceans.