Contrary to popular belief, apparent
dominance in an animal social hierarchy may not to lead to maximum mate choice or
reproductive potential. Studies in some primates have shown that some female
reproductive strategies, such as
cryptic female mate choice, specifically enable reproduction with males other than the alpha male. The extra strength and energy of the
alpha male may thus go into protecting and feeding progeny that aren't his.
This helps explain the existance of alternate male strategies: evolutionarily speaking, that guy skulking around the outsides of the social group and not jockeying for position wouldn't be there if he didn't get laid occasionally.
(This is one of many reasons the definition and useful domain of "dominance" is still under significant debate.)