Dolphins have ‘longest social memory’ among non-humans
http://www.bbc.co.uk/news/science-environment-23589041

Forget about elephants – scientists say that dolphins have the longest memories yet found in a non-human species.

Researchers in the US say that even after 20 years of separation, dolphins could recall the whistles of former companions.

The authors believe that these long-term memories are a product of the complex social connections that dolphins have evolved.

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