"invasion"... The Tribbles in Star Trek have been far more numerous and faster breeding than those poor rabbits. I saw how it looks like in M´Hul island and the rabbits looked like they were somewhow stuck between the docks (where only occasionally 1 lonely rabbit hopped over) and the first buildings, so mainly on the ascent from docks to the higher level. Once their number rises to the point that they fill every vacant space in a POT and as a writhing mass are able to block passage of players they are more a little rodent nuisance than an invasion...
Only if they would actually live from the land - 2 more rabbits if 1 eats a Lettuce growing in a field...
