After 5 minutes of googling:

* "Buffalo's brutal revenge: Animal gores lion and tosses it into the air after pride attacks its herd and slaughters one of its companions" http://www.dailymail.co.uk/news/article-3518658/Buffalo-s-br...

* "Rhinos save Buffalo from Hyena Attack" https://www.youtube.com/watch?v=e-cbxLyRN0o

I guess that wolves and crows will also be good examples, but I don't have a link just now.

Also, I live in Argentina and here it's common to have "dogs walkers" that pick a small number of unrelated dogs 5-10 from different owners. I guess that if someone is stupid enough to attack one of the dogs, the other dogs will react.

I've heard tell of ravens attacking humans who had previously attacked other ravens, sometimes quite a while before; at the moment I'm unable to go hunting a cite, but that might be a place to start.

I think it's clear from context that the author meant intra-group aggression. A dispute between a human and a group of ravens isn't really a matter of politics in the way a dispute within a group of humans (or chimps for that matter) is.