I don't think they have a way of protecting themselves. They are usually eaten by whales anyways and there isn't much protection from a whale if you are as small as krill. They can protect themselves but not against whales. They protect themselves by traveling in large numbers.
When danger strikes, the cattle protect themselves by running away, by charging themselves and using their horns against the attackers and by kicking with their rear cloven hooves.
their stomach gas
they run away from them or they eat them
strong jaws
Mutually Assured Destuction (M.A.D.)
testifying against themselves
Rockhoppers are very small animals. They cannot protect themselves against predators very well because of this, so they are easy prey.
To protect themselves against nomadic invaders, and against aggressive neighbours.
So to unsure they would not die
democracy
by there wing to fly