The colouration of the narwhal consists of a mottled pattern, with blackish-brown markings over a white background. At birth, the skin is light grey, and when sexually mature, white patches grow on the navel and genital slit; such whitening occurs throughout life, resulting in aged narwhals being almost purely white. Unlike most whales, the narwhal has a shallow dorsal ridge, rather than a dorsal fin, possibly an evolutionary adaptation to make swimming under ice easier or to facilitate rolling. The neck vertebrae are also jointed, instead of being fused as in most whales, which allows for a greater range of neck flexibility. These characteristics are shared by the beluga whale. Furthermore, male and female narwhals have differently shaped tail flukes; the former are bent inward, while the latter are swept back on the front margins. This is thought to be an adaptation for reducing drag caused by the tusk.
The colouration of the narwhal consists of a mottled pattern, with blackish-brown markings o!ver a white background. At birth, the skin is light grey, and when sexually mature, white patches grow on the navel and genital slit; such whitening occurs throughout life, resulting in aged narwhals being almost purely white. Unlike most whales, the narwhal has a shallow dorsal ridge, rather than a dorsal fin, possibly an evolutionary adaptation to make swimming under ice easier or to facilitate rolling. The neck vertebrae are also jointed, instead of being fused as in most whales, which allows for a greater range of neck flexibility. These characteristics are shared by the beluga whale. Furthermore, male and female narwhals have differently shaped tail flukes; the former are bent inward, while the latter are swept back on the front margins. This is thought to be an adaptation for reducing drag caused by the tusk.