By Susan Milius
From Oaxaca, Mexico, at a meeting of the Animal Behavior Society
Male lance-tailed manakins put on a two-guy show when courting females, but only the alpha bird reaps the immediate benefits when the performance succeeds, says a new study.
So, what’s in it for the sidekick? An earlier study in a different species of manakin suggested that courtship cooperation gave the unrequited sidekick a benefit in the form of real estate. If the alpha male disappears, his beta buddy often takes over their habitual display ground.
Emily DuVal of the University of California, Berkeley finds a similar scenario among lance-tailed manakins, but speculates that the betas reap another benefit. Sidekick duty lets the understudy male refine his act, she suggests.
On Panama’s Isla Boca Brava, DuVal set up the first detailed behavioral study of lance-tailed manakins. For 6 years, she has watched male pairs court females with elaborate sequences of acrobatics, such as rapid-fire, flying leapfrogs of male over male on the branch where the female perches.
DuVal’s DNA analysis found no offspring produced by beta males. Nor were the sidekicks laboring on behalf of relatives; an alpha and its beta weren’t closely related. However, beta males in her study rose to alpha status at a rate higher than that of males that rank below betas.
When DuVal removed alphas from some of the display grounds, betas tended to take over at first, but they didn’t consistently hold the spot beyond 10 days.
DuVal is therefore searching for some complicating factor influencing the evolution of cooperation. Perhaps the betas need a lot of practice before they can put on a real alpha show, she suggests. When she watched the betas in her removal experiment, a lot of their displays didn’t look ready for prime time, although they often did recruit their own sidekicks.
