Sperm whale

Physeter macrocephalus

LENGTH 11–18 m / 36–59 ft

DORSAL FIN Triangular/rounded hump, followed by knuckles

APPEARANCE Wrinkled dark skin; huge square-shaped head; blowhole very close to front of head

BEHAVIOUR Low, bushy blow, angled to the left; lifts broad triangular tail flukes high in air before diving

Photos by A. Phillips, C. McMillan, J. Towers, J. Ford. Illustrations by A. Denbigh, not to scale.