Dads eat for baby, too

Monkey fathers-to-be pack on pounds during their mates' pregnancies.

Published February 6, 2006 7:34PM (EST)

Men may never understand morning sickness or the need to urinate every five minutes, but a new study shows that some male monkey species might be able to relate to those strange pregnancy cravings. The report, picked up in New Scientist, found that male common marmosets and cotton-top tamarins gained on average an extra 10 percent of their body weight during their mates' pregnancies.

But it's not a show of solidarity. ("I'm here for you, babe. Pass the chips and guacamole!") The fathers need the extra energy to deal with their new offspring, explain scientists studying the parental weight patterns of the squirrel-size, monogamous primates at the University of Wisconsin at Madison National Primate Research Center. And these dads do pitch in: The male monkeys tote their babies -- which are born in pairs and at about 20 percent of their adult weight -- around on their backs.

Researchers found that the males actually gained more weight than the females and put it on earlier in the pregnancy; the mothers-to-be fattened up during the final weeks of gestation (five months for marmosets and six months for tamarins).

The males didn't get access to extra food, so researchers attribute the extra padding to a surge in their production of prolactin -- the same hormone that makes females produce milk -- about halfway during their mates' pregnancies. And that may kick in all those protective paternal instincts. Apparently, bird fathers with higher levels of the hormone feed their chicks more often.

But since the findings apply only to our monkey brethren, it's too soon to know if male humans experience the same changes. (The article quotes another scientist saying that prolactin doesn't necessarily cause male humans to plump up, and it's hard to compare levels in good and bad fathers.)

In the meantime, future dads of America, have some more Buffalo wings. Your family needs you!

By Sarah Elizabeth Richards

Sarah Elizabeth Richards is a journalist based in New York. She can be reached at

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