...the male narwhal's tusk can be up to 3 metres in length and weigh up to 10 kilograms.
...observations of cetaceans date back to at least the classical period in Greece, when fisherpeople made notches on the dorsal fins of dolphins entangled in nets in order to tell them apart years later.
...groups of bottlenose dolphins around the Australian Pacific have displayed basic tool use by wrapping pieces of sponge around their beaks to prevent abrasions. This is a display of a cognitive process similar to that of great apes.
