1. Other than what is under consideration or implied
   "where else can we look?"; "ask somebody else"; "I don't know what else to do"
    
2. (usually used with 'or') if not, then
   "watch your step or else you may fall"; "leave or else I'll get angry"
    
3. Additional to or different from this one or place or time or manner
   "I don't know where else to look"; "when else can we have the party?"; "couldn't decide how else it could be done"; "nobody else is here"; "she ignored everything else"

1. Because otherwise
   "the predator would have to find other food, else it would also become extinct"

Encyclopedia: Else, Jean