It's an anecdote, which I presented very bady :-(

I was actually looking for evidence that white bunny tails signalled to foxes - but people mostly seem to think they signal danger to other rabbits.

Update - abstract of "Do Brown Hares Signal to Foxes?":

"Of a total of 32 sedentary brown hares (Lepus europaeus) approached across open ground by foxes (Vulpes vulpes), 31 reacted when the fox was 50 m or less from them by adopting a bipedal stance directly facing the fox. Of five sedentary hares approached by foxes from nearby cover, none stood, t... (read more)