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Bachelor Uncles

Related male peacocks "lek," or gather together and perform their displays, in order to attract mates and ensure that their genes are passed on. Even if it means that an individual bird is unsuccessful, the "bachelor uncles" who are rejected by females have contributed to the perpetuation of the species.

Credits: Photo by David Cavagnaro. Used by permission of Visuals Unlimited, Inc.

Bachelor Uncles

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Topics Covered:
Adaptation and Natural Selection

Backgrounder

Bachelor Uncles:

Anyone who has been rejected in the dating game is familiar with the feeling "Oh, why even bother?" It's totally understandable why, after enough striking out, singles may simply stop going to dances or singles bars.

Yet scientists have long noted that male peacocks continue gathering in communal mating groups called leks even when they are turned down season after season. This never-say-die behavior was puzzling because it seemed to make no sense in evolutionary terms -- and biologists assume that if a behavior persists, it must provide some competitive edge.

The "selfish gene" hypothesis can explain many of the seeming paradoxes in animal behavior. This hypothesis says that underlying an apparently pointless activity there is usually a benefit that is not obvious at first.

That's what happened when researchers studied groups of peacocks and peahens in a park north of London. Every mating season, males would "lek" by gathering in a group and performing their displays to peahens. Year after year, it turned out, the females selected the same few males for mating and producing offspring. Yet many of the unsuccessful males kept returning, some of them performing their displays and others just gathering about.

In 1999, scientists who had been studying the peafowl for years said they had figured out how unchosen males benefited from this arrangement.

Within each lek, the unsuccessful peacocks were relatives of the more successful birds. That means they shared some genes with the go-getters. The "bachelor uncles," by adding their dancing -- or even their mere presence -- to the lek, were boosting the odds that genes related to theirs would be passed on to succeeding generations. The top birds in the biggest, showiest leks mated with more females than the top birds in smaller leks.

In other words, the "selfish" genes were acting through their hosts to perpetuate more of their kind. And the same theory has been used to explain examples of apparently altruistic behavior among birds who expend energy and food taking care of young to whom they are not directly related. In the end, it is not really altruism -- just subtle self-interest at work.

About those peacocks, though, one question remains unanswered: How do the males know which other males they're related to? Even if separated after birth, the males can find their own kind in a lek. What provides those clues is further work for scientists.

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