Those would be the footnotes showing that Lockley's Private Life Of The Rabbit (which I read before I read Watership Down btw) demonstrates that rabbits are tool-users, linguists who can communicate and cooperate with other animal and bird species, and have a vibrant oral tradition of tales and poetry, would they?

Because so far as I can recollect, Lockley gets appealed to only when Adams thinks he's coming under fire because the does aren't getting enough sensible airtime. At which point he states that according to Lockley, giving them more airtime would be contrary to the essential nature of the rabbit.

Which really shows the cauldron in which slash was forged, essentially.