The Cachalot
The sperm whale is the largest and most powerful predator in the sea. It dives deeper than any other whale; locates and zaps its prey with ultrasound; and communicates across a school of up to a hundred animals using individually patterned 'clicks'. Scientists in the Indian and Pacific Oceans are slowly revealing the secret life of the sperm whale, but have yet to record the titanic battles that take place in the deep sea when the sperm whale encounters a giant squid.
Presented by Peter France Producer MICHAEL BRIGHT BBC Bristol
(Re-broadcast next Saturday)