Let species A be prey to another species B. Assume that predators B only attack isolated individuals A (because they are afraid of larger groups of A's). So it is good for species A to be on the way in rather dense herds, flocks, or swarms. But individuals A which find themselves isolated (which happens every now and then) are well adviced to flee when a predator is in sight. So there are two antagonstic tendencies in individuals A: to flee or not to flee when a predator comes into sight. To flee as a herd, flock, or swarm should keep it together, so it's best to flee into the same direction as one's neighbours. Nevertheless single individuals will become isolated and be easier catch for the predator, so for the species (herd, flock, or swarm) it is best not to flee at all.
This can be advanced when the individuals with the least tendency to flee (the most fearless ones) are at the outside border of the herd. So it would be an evolutionary advantage of the species when the most fearless individuals come to be at the border of the herd - by own initiative or being pushed by the others.
I wonder if there have been investigations of this: Are there species of which it is known that (and how) the most fearless individuals are at the border of their herds, flocks, or swarms?
This is how the investigation could go:
- Are there the same individuals at the border of the herd more often than not?
- Do they start fleeing at a smaller rate than other indivuduals which happen to be at the border?
- Why are they at the border? Is it because the others tend to go away from the border, into the center of the herd?
Note that my question is not for the strongest individuals but for the most fearless. (I know the case of the muskox and its typical defense formation.) There may be species with no extraordinally strong, but with extraordinally fearless individuals - which is another case.