Science Digest

Science Digest

Monday, April 6, 2009

Birds Watch, Too

A significant look across a bar or an office can tell us volumes. Humans are so skilled at reading interest, boredom, fear and joy in other people's eyes that we forget how unique this skill appears to be in nature. Most species, including our cousins and best friends -- chimpanzees and dogs, respectively -- seem clueless when it comes to what eyes communicate.

But at Cambridge University in England, researcher Nathan Emery conducted experiments that showed a bird, the jackdaw, gleans information from eye contact and can use that information to discern what's on a person's mind.

When an unfamiliar person looked at a piece of food, jackdaws took much longer to go after it, presumably because they inferred that the person was interested in the same food. But when someone familiar looked at the food, jackdaws quickly went after it, as if they inferred that the person was encouraging them to eat.

Jackdaws, which are close relatives of crows and ravens, were also able to quickly follow a person's pointing finger to find food. When a person stood in front of the bird and alternated her gaze between the bird and the spot where the food was hidden, the jackdaw used that cue, too, to find the food.

The research study was published last week in the journal Current Biology. Emery and other researchers noted that jackdaws are highly social and their eyes have many of the same physical characteristics as human eyes.

-- Shankar Vedantam

Rare Dolphins Pop Up

Wildlife Conservation Society researchers have found a large population of rare dolphins in South Asia, a discovery that provides some hope for the vulnerable species.

The scientists estimate that nearly 6,000 Irrawaddy dolphins are living in freshwater areas of Bangladesh's Sundarbans mangrove forest and adjoining waters of the Bay of Bengal. Until now, the largest-known populations of Irrawaddy dolphins, which are related to killer whales, numbered no more than a few hundred. The team announced its discovery last week at the International Conference of Marine Mammal Protected Areas in Hawaii.

"This discovery gives us great hope that there is a future for Irrawaddy dolphins," said Brian D. Smith, a scientist with the conservation group and the lead author of a recently published journal study of the animals. "Bangladesh clearly serves as a sanctuary for Irrawaddy dolphins, and conservation in this region should be a top priority."

The dolphins are listed as vulnerable to extinction by the International Union for the Conservation of Nature. In Burma's Irrawaddy River they engage in "cooperative fishing," herding the catch into fishermen's nets. The dolphins prey on some of the fish that are trapped, but their involvement can produce a threefold increase in the catch.

-- Juliet Eilperin

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