Here's the sad part: none of this is new. 1992. 1992. Over twenty years ago.
As children they make a best friend for life, they form complicated alliances for mutual benefit, they form political alliances/gangs, they help each other out both tit-for-tat and "pro-bono" while keep score of debts (I help you today, you will owe me at some undefined point in the future), they group together to accomplish tasks (sometimes/often at the expense of other dolphins, for instance a female they are trying to get with).
Another important study was done to research the presence (or lack thereof) of a universal dolphin "language" (EDIT: found source! [http://wakeup-world.com/2011/11/28/the-discovery-of-dolphin-...] but not peer reviewed research). It involved showing dolphins in one aquarium a sequence of objects (red ball, green box, etc.) and recording the sounds made, then travelling to another aquarium with dolphins that have never been in contact with the first and playing back the sounds made, then watching the dolphins "locate" or "identify" the object the sounds were made in response to. They achieved an astonishing (if memory serves!) 86% accuracy rate implying audible descriptions of objects, much in the same manner that a "bee dance" can be universally understood across hives/colonies except it's based on actual sounds rather than movements.</cannot find source>
Regardless of whether or not you feel dolphins deserve the title of "non-human sentient beings" (whatever "sentient" means, it's such a non-word), I think anyone involved in the mass slaughter of dolphins in an attempt to ransom money should be imprisoned for being a killer (Reference: 900 dolphins killed in Solomon Islands as black mail for raise in pay negotiations. Sorry, but f* them [ http://www.nzherald.co.nz/world/news/article.cfm?c_id=2&... ])