The small size of the Pygmy Sperm Whale means that it is most likely to be mistaken for a dolphin, although its blunt, squarish head, robust body, small dorsal fin and behavior are distinctive. However, it is extremely similar to me Dwarf Sperm Whale. Both species are typically seen travelling slowly or hanging motionless at the surface and on diving, simply sink below the surface rather than rolling forward. Both are also usually shy of boats and, when disturbed, excrete a reddish-brown ink in defence. The Pygmy Sperm Whale is slightly larger but the size and position of the dorsal fin is the key feature, being smaller and positioned further than halfway along the back.