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Testosterone Tradeoff

May 23, 2006

Extra testosterone gives male birds a leg up in the mating game–at a big price.


Feathered Casanovas. I’m Bob Hirshon and this is Science Update.

Would you die younger for a better sex life? That’s what extra testosterone does for birds called dark-eyed juncos. North Dakota State University biologist Wendy Reed and her colleagues found that when young male juncos were treated with extra testosterone, they attracted older, more fertile females, had more extramarital sex, and fathered more offspring than untreated males. But Reed says that attracting more mates also seemed to attract more predators.

WENDY REED (North Dakota State University):
They also had lower immune function than control males, and so they paid a cost of that in actually lower survival rates.

HIRSHON:Reed says that factors like these may keep the junco population’s natural testosterone levels in check. I’m Bob Hirshon, for AAAS, the science society.