"Safety in mumbers"

[El Greco]

I often hear in nature documentaries that preyed animals aggregate because there is safety in numbers. It is natural that if everybody else is in a flock or a herd and you are alone then you are in greater danger. But what if everybody were alone ? Would the hunters have better overall percentages of success ?

 

[MRC_Hans]

Yes. Most predators hunt by singling out a prey and chasing it down. That is more difficult if the potential prey is flocking. Also, there is a question of vigiliance; a single prey cannot be on the lookout constanly, but in a crowd, some will always notice an approaching predator and issue a warning of some kind (if only by taking flight).

Hans

 

[Ziggurat]

Plus, with some potential "prey", the prey can be dangerous to the predator in large numbers. A lion isn't immune to being trampled to death by panicking wildebeasts or whatever, and even an injury such as a broken leg can be life threatening.

Plus, as the old saying goes, "you don't need to outrun the bear, just the other campers". But you can only do that when you're in a group.

 

[chance]

The herd protects the most fit and reproductive from being picked off by a predator, which would be highly likely in a one on one.

The life of a herd animal could be summarised as:

Infant – very venerable low probability of survival,
Reproductive age – very fit high probability of survival,
Aging – less fit, likely food for the predator (but this keeps the most fit isolated from the predator)