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Monday, March 28, 2005; Page A06

Elephants Are Versatile Mimics

Elephants possess a secret talent -- they can imitate the sounds of other animals and even machines, researchers have found.

An international team of scientists studied unusual sounds being made by two African elephants -- one living in Tsavo, Kenya, and the other that had been living for 18 years with two female Asian elephants at the Basel Zoo in Switzerland.

A new computer-assisted colorizing method permits consistent hues in the whole frame rather than blurry edges. (Yair Weiss -- Hebrew University Of Jerusalem)

Detailed acoustic analysis showed that the first elephant, a 10-year-old female named Mlaika, was mimicking trucks she could hear rumbling down a highway about two miles from her stockade. The second animal, a 23-year-old male named Calimero, was emulating the chirp-like calls of the Asian elephant species she lived with.

Other animals are known to have the ability to mimic sounds, but African elephants are the first example of a non-primate land mammal that can do this -- other than humans.

The discovery supports the idea that vocal learning is an important skill for maintaining relationships among social creatures, the researchers said.

"Many species with similar social systems as elephants use vocal imitation to maintain individual-specific relationships," said Stephanie Watwood of the Woods Hole Oceanographic Institution in Woods Hole, Mass., part of the team that reported the findings in the March 24 journal Nature. "Our study suggests that elephants may be using their vocal abilities in a similar manner."

-- Rob Stein

Add Foxes, Lose Green in Alaska

When the population of Aleutian Islands seals and other furry ocean mammals collapsed because of overhunting in the late 19th century, entrepreneurs came up with a plan to save their fur business -- they would introduce arctic foxes to the islands and then capture and skin them.

More than a century later, researchers returned to look at the effects. They found dramatic, and unexpected, results. Nine islands that did not have foxes were covered with grass and rich soil, while nine islands infested with foxes had evolved into a relatively barren maritime tundra with dwarf shrubs and small, less-productive broadleaf plants.

The cause of the change turned out to be the foxes, which decimated the seabird populations. On foxless islands, large numbers of birds deposited nutrient-rich guano. Where foxes reigned, there were few birds and little guano to fertilize the soil.

To further test their theory, the researchers from the University of California at Santa Cruz and the University of Montana fertilized patches of land on islands that had many foxes and few birds, and they found that the soil quickly began to sprout grass like the guano-fertilized islands.

The results, they wrote in the March 25 journal Science, "show that strong direct effects of introduced predators on their prey can ultimately have dramatic indirect effects on entire ecosystems . . . in this case across an entire archipelago."

-- Marc Kaufman

Taking Color to the Cutting Edge

Automated ways to add color to black-and-white images have been around since the 1970s, but they do a poor job of distinguishing fuzzy or complex boundaries, such as those between a child's bangs and her forehead.

Colorizing the 1938 Marx Brothers movie "Room Service," for example, meant dividing one image into regions, assigning a color to each region and tracing any complex boundary by hand.

"Our premise was that it's easier to point into the interior and say, 'I want this region to have the color.' You don't have to be as precise when you are doing that," said Dani Lischinski, who with his team at the Hebrew University of Jerusalem developed the mathematical idea and then implemented it in software and experimented. The result was a computer-assisted colorization method that saves time and painstaking labor.

The artist makes one scribble for each color he wants in a black-and-white image. The computer then spreads out each color to the appropriate boundaries. Lischinski and his team have tried the method on film clips a few seconds long -- some from home movies, others from TV's "I Love Lucy."

They recently published their research online after presenting it at a conference last summer.

Their method ensures that the regions of color also track to their appropriate places in time and space so that successive frames don't have to be re-scribbled. That way, the flaming red of Lucille Ball's hair stays on the actress's head as Lucy Ricardo skitters across the screen.

-- Susan P. Williams

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