"First of all, 'sentient' does not mean 'able to recognize oneself in a mirror.' It means 'able to sense.' Nearly all lifeforms on Earth have at least one sense; certainly all multicellular creatures do. Perhaps the word the researchers are looking for is 'sapient,' which comes from the Latin word for 'wise,' and refers to higher levels of intelligence. If so, I still have a hard time thinking of cetaceans, fellow-primates, and other non-human animals as having that level of ability. Sure, they may be able to learn our ways of communication, but there's more to sapience than that. As just one example -- and the most pertinent to this discussion -- I doubt that any of those creatures could care much about most of the functions the Internet would provide -- information and research, global, social connections, business transactions, and such.
Image credit: With thanks to PBS.org