Animals are usually either male or female and behave in a way that is characteristic of their gender. But in nature there are curious exceptions. Female hyenas look and behave like males, and male seahorses actually get pregnant and give birth. Why have these two animals swapped their sexual identities?

Encoded with permission for digital streaming by Infobase on December 24, 2014. Learn360 is distributed by Infobase for Films for the Humanities & Sciences, Cambridge Educational, Meridian Education, and Shopware.

Hippocampus(2:16) -- Aristotle's Observation (2:53) -- Reproduction Study (3:00) -- Seahorse Birth (2:28) -- Early Perception of Hyenas (2:18) -- William Buckland's Discovery (4:23) -- Dominance and Aggression (3:34) -- Credits: Strange Parents: Attenborough's Natural Curiosities, Series 2 (0:30).