I read it years ago and just can't remember what it was called or who wrote it.
It's about blob aliens and nano tech. Humans are a spacefaring species and have met and live along side, on many planets, a blob species of alien. Only the females of the blob species are sentient though and they keep their wild unintelligent males on a preserve for mating purposes.
But there is one male that is intelligent but has to pretend he's female and teams up with a human cop (I think he was a cop) to stop nano tech terror attacks on the settled worlds.