I don't think there is necessarily any discrepency between the mated pair looking after offspring and the male urge to shag everything in sight. Look at lions, baboons, horses, and others. Generally when a new alpha male takes over, he will kill the very young offspring of the previous alpha, then go about shagging all the females. The male wants only his genes carried on. The females, meanwhile, must deal with this and accept the new alpha, or otherwise they would not be protected by the prode/troop/herd community and the alpha male himself.