Why don't male mammals lactate?
D000328:Adult; D000818:Animals; D005075:Biological Evolution; D002118:Calcium / Q000378:metabolism; D002335:Carnivora / Q000502:physiology; D010856:Columbidae / Q000502:physiology; D004734:Energy Metabolism; D005260:Female; D006728:Hormones / Q000502:physiology; D006801:Humans; D006922:Hylobates / Q000502:physiology; D007774:Lactation; D008297:Male; D008322:Mammals / Q000502:physiology*; D008321:Mammary Glands, Animal / Q000254:growth & development; D051379:Mice; D008875:Middle Aged; D011247:Pregnancy; D051381:Rats; D012727:Sex Characteristics; D012733:Sex Differentiation; D012726:Sexual Behavior, Animal
D006728:Hormones; D002118:Calcium