Kogiidae

About the pygmy sperm whales

Kogiids carry a spermaceti organ and the same asymmetric nasal architecture as the sperm whale, scaled down to animals of two and a half to three and a half metres. The resemblance stops at the profile: a blunt, squared head, a strongly underslung jaw and a pale bracket-shaped mark behind the eye give them a shark-like look, and the mark is known as the false gill for that reason.

Startled kogiids release a cloud of reddish-brown fluid from a sac in the lower intestine and dive away behind it — a defence otherwise found in cephalopods, and unique among mammals.

They are rarely observed at sea: undemonstrative, slow at the surface, and living over deep water off the continental slope. In much of the world they are nonetheless among the cetaceans that strand most frequently, and nearly everything known about them comes from those animals. Stomach contents from strandings show them to be badly affected by ingested plastic.