SCIENCE NOTEBOOK

A male lark bunting has to measure up as a mate. (Image Courtesy Of Alexis Chaine)

That's the conclusion of two biologists who reported their work last week in the journal Science.

So-called "secondary sexual traits" -- fancy plumage, rump color, big beaks -- are the product of two forces. One is the competition between males for mates and often for territory. The other is the female's choice of her mate.

Traditionally, biologists believed that females favored male attributes in a predictable and largely unchanging way. But it turns out this isn't true.

Alexis S. Chaine, of France's Laboratory of Evolution and Biological Diversity, and Bruce E. Lyon, of the University of California at Santa Cruz, studied lark buntings, songbirds of the Great Plains. Over the five years they watched the birds, competition was fierce. About 45 percent of males failed to attract a mate; and even when they did, about 25 percent of chicks were fathered by other males.

They found that each year a different constellation of traits was associated with "fitness," allowing the pairs to produce the most offspring. Some traits went out of fashion overnight.

In one example, having a large body and a lot of black rump feathers were marks of reproductive success one year but marks of reproductive failure another year.

Food, predators and weather are constantly in flux in the lark buntings' habitat. The researchers think the female birds somehow discerned which attributes and behaviors were most favorable for each breeding season, and chose their mates accordingly.

-- David Brown

People Infect Chimps With Viruses

Viral infections passed by humans are causing some wild African chimpanzees to get sick and die. Scientists had suspected it for some time, but now German researchers have proven it.

Using evidence gathered about populations of chimps hit by five different respiratory outbreaks between 1999 and 2006 in the Ivory Coast, the researchers found that tissue samples from all that died tested positive for one of two human respiratory viruses.

"Our demographic analyses of chimpanzees suggest that [the infections] started as soon as people got close enough to chimps to transmit diseases," said Fabian Leendertz of Robert Koch-Institut and Max Planck Institute for Evolutionary Anthropology in Germany.

The study, published last week in the journal Current Biology, examined chimps that lived in protected parks where researchers are active but local people don't travel. As a result, researchers concluded, the sources of the viruses were most likely the researchers themselves or possibly poachers.

Despite this, Leendertz said research and ecotourism have had a strong positive effect on the survival of great apes by reducing poaching and giving more "political weight" to apes in protected areas. He said researchers have adopted practices to help minimize the risk of infection by, among other things, maintaining a distance of at least 22 feet, wearing masks and disinfecting their boots regularly.

-- Marc Kaufman