The Jack Rabbit was the weakest of all the beasts here, but what it lacked in strength it made up for with brains. It knew that as soon as the three beasts joined the fight that the surrounding area would become chaotic, so it quickly hopped back into the forest. It would rather wait until all of the individuals here were tired and exhausted their cores until it strikes.
This was how it managed to survive climbing from a species that is only ever seen as food for others, all the way to becoming a blue core ranked beast. It kept that same mentality of 'If you cannot win then retreat and wait to strike from the shadows.' It served the Jack Rabbit well. The Jack Rabbit jumped up a tree and hid its presence as it watched the fight from there.