Safety in numbers/Mob Rule psychology:
The frustrated grazing/herding creature or pack animal or human will not often wander out of its territory all that often on its own at least not without the company of its pack or herd somewhere around.
When cornered or faced down or threatened by superior force on its own it will not usually put up much of a fight making its demise almost certain and hopefully quick and painless.
However if its faced down by superior force and it is within earshot [and hasnt wandered off on its own or got lost] then it will call out to others who are members of the same pack or herd and they will rush over to help.If the herd or pack is feeling confident then they will attempt to gang up against the lone adversary in an attempt to drive it off by mobbing , bullying , and chanting etc.At this point the creature that was originally faced down on its own will suddenly start to try to fight back and join the other members of its pack or herd in driving off the lone adversary.
At this point the lone adversary has 3 choices:
1:It can either attack and stand its ground and take out the entire pack [depending on the size of pack or herd and potentially risking injury or even defeat[unlikely] to itself] either one at a time or sometimes a few at a time depending on wether it loses its temper or not. [fairly likely depending on the exact circumstance]]
And 2 : It can walk away from it knowing only too well from past experience that the pack or herd will not attack it if they themselves are left alone because the lone adversary is either not interested and sees little point in the confrontation because the end result is a forgone conclusion and isnt a challenge but all the while having the good grace to let the pack or herd think that it itself was successful in driving off the superior force.[very likely]
And last of all 3:The pack or herd can attack the lone adversary all at once in an attempt to drive it off .This doesnt happen very often but it does happen.The lone adversary will have to either take a beating that doesnt usually inflict serious injury which will result in number 1 happening.[100% definate and very messy]