biology zoology blog Fathers milk lactation

Father’s Milk

Father’s Milk – a thing of the future?

In an encyclopaedia of 1909, I found the statement that the only mammal in which males are known to regularly supply milk to their offspring was a snowshoe rabbit in the Rocky mountains by the name of Lepus bairdii. Apparently this claim could not be substantiated later on, for the current view is that in spite of the presence of the nipples in many mammalian males, no male is known to normally lactate on a regular basis (but wait!). A combination of oestrogen treatment and nipple stimulation can, however, provoke lactation in male individuals of a wide range of animal species and spontaneous lactation, even in human males, is known. That male and female breast tissues aren’t terribly different is also borne out by the sad, but little known fact, that men, too, can suffer from breast cancer.

Billy goats have sometimes been seen to suckle a kid (a kid is a baby goat), but one can not call that a regular occurrence. In a steer, for example, an application of oestrogen and progesterone together is known to induce lactation, but the milk yield is low (and whether it tastes the same as cow’s milk I do not know). The same holds true for cases in which the human male was the milk producer. But given then that there are apparently no unsurmountable physiological barriers for males to suckle their young, why has male secretion to assist in rearing their offspring, in evolutionary terms, not “taken off”?

One problem is that because of the mating practices of mammals, there aren’t too many in which the male can be certain that he alone and none other is the father of the young. Although monogamy in mammals isn’t exactly rare and occurs in at least 9 orders of mammals, principally in the Canidae (wolves and kin) and primates (apes and monkeys), it is not exactly common either. The best candidates for male participation in providing the young with milk have for a long time been thought to be the gibbons and siamang monkeys. The babies of these species, in particular, the siamang, would undoubtedly benefit from the occasional sip of some father’s milk, for with them it is mostly the father who carries around the infant postpartum for up to a year. But even in these species fathers apparently have different roles to play in the family than serve as wet nurses: they guard, protect, teach and play with the offspring. Given the fact that primates were the last group of mammals to evolve, perhaps male lactation has not had enough time to develop and is still something to come; perhaps it’s the great “new thing of the future” that so many stressed young mothers can’t wait to see arrive. At least that is what scientists thought until….

… was discovered that at least in some bats like Dyacopterus spadiceus, for example, males do regularly lactate and in this way help their youngster to become independent quickly so that they are no longer in need of having to be carried around by their flying parents (because babies generally and especially baby bats can be a heavy load to be carried around). Thus, there is still some hope for our own species and the aforementioned stressed young human mothers.

© Dr V.B. Meyer-Rochow and, 2018.
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