Testosterone turns male juncos into blustery hunks -- an... (me they can invest in attracting mates a...)

Testosterone turns male juncos into blustery hunks -- and bad dads

Date:10/15/2007

me they can invest in attracting mates and sticking around to parent offspring. Under certain circumstances it may be beneficial for male birds to love 'em and leave 'em, maximizing the number of female partners during a mating season. Under other circumstances, it may be in the male junco's best interests to mate with only one female and stick around until the chick is old enough to fend for itself.

"The results are exciting because they show us how animals that make different choices might differ from each other on a physiological level. On an evolutionary level, they suggest that there may often be more than one right choice, depending on the circumstances," Virginia's McGlothlin said.

Is testosterone calling all the shots" "It is surely more complicated than that," Ketterson said. "The link between testosterone and aggressive and sexual behavior is probably more direct than the link between testosterone and parental behavior. The latter needs much more study."

Diversity in the behavior of male dark-eyed junco is more of a continuum than a dichotomy of Don Juans and Mr. Moms.

"One of the interesting things is that all males stick around and help," Ketterson said. "If they have higher testosterone they help less. If they have lower testosterone they help more."

The situation presents an interesting evolutionary question. Why wouldn't one of the behaviors win out over the other"

"Variation in behavior may persist because the environment varies," Ketterson said. "In cold, wet years, or years when lots of predators are attacking young in the nest, good fathers may be more successful at leaving offspring. When food is plentiful and predators are few, males that focus on mating may be more successful. The balance between the two is probably dynamic."

Another possibility, McGlothlin explained, is that male "quality" is why males divide up their time differently.

"There are only so many eggs
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Contact: David Bricker
brickerd@indiana.edu
812-856-9035
Indiana University
Source:Eurekalert

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Testosterone turns male juncos into blustery hunks -- an...(me they can invest in attracting mates a...)