- The Washington Times - Tuesday, January 31, 2006

Monkey dadsgain weight, too

A new study of two species of male monkeys confirms the tendency noted in many human dads to put on pounds when their mate is pregnant.

The study by scientists at the University of Wisconsin at Madison found that male squirrel-sized marmosets and cotton-top tamarins add roughly 10 percent to their girth when their mate is expecting. The small monkeys are known for being monogamous and for males taking a larger role in parenting than is seen in most primates.

When men gain weight during a partner’s pregnancy, doctors consider it a “sympathetic pregnancy,” also known as Couvades syndrome, from the French word meaning “to hatch or incubate.”

The term covers a variety of me-too pregnancy behaviors among men, from changes in appetite and weight to “nesting” behavior and even nausea and sympathetic labor pains in the more extreme cases. Almost all the time, the symptoms go away when the baby is born.

Most experts have viewed sympathetic pregnancy as a psychological problem mostly having to do with men who have pregnant wives feeling left out or jealous of all the attention the woman’s getting — a situation that resolves when the proud papa gets to hold the infant and start planning his or her sports career.

But the team led by Toni Ziegler, an endocrinologist at the university’s National Primate Research Center, shows the phenomena of weight gain in primate dads-to-be is both real and may have an actual evolutionary purpose behind it.

Miss Ziegler figures that because the papa monkeys are closely involved in infant care to the point they may not have as much time to forage and eat, they may have sound reasons to put on a few extra pounds during pregnancy.

For the study, published Tuesday in the journal Biology Letters, the scientists did monthly weight measures and blood testing of 29 male marmosets and 29 male tamarins, of which 14 marmosets and 11 tamarins had mates who were expecting. Pregnancy lasts about five months for marmosets and six months for tamarins.

“The males somehow cue in to the cascade of hormonal changes going on in their pregnant mates,” Miss Ziegler said.

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